WWW.DISSERS.RU


...
    !

Pages:     | 1 ||

r t r n r f r r an d r r nlijk ...

-- [ 2 ] --

Chapter 5 Actual and potential salt-related soil degradation in an irrigated rice scheme and radi nt a a f n ti n f t ra h li ht in r a in and t a l r t nt a r d n ar t irri ati n and draina anal h third il it - i art f th l r l and d r i n a in nit lt f h i al and il t t r anal i ar h n in a l il t t r ari d littl t n il it a ra la ilt and and and a la ifi d a ilt l a ilt la l a and la l a h ri n ith a ndant an lar di t ar q art fra nt a f nd rl in th hi t ar nt r k in - and - t thi kn ari d tr n l at h rt di tan n - an fin an lar q art fra nt r f nd in a thin la r at d th j t a th ath r d hi t and r nd d di - i d q art fra nt r r d t n and d th r f fin hard al ar n d l r r d in - at d th and n n in - n th it r i itati n f ar nat in ral a r d in th artl ath r d ar nt r k i in t n th hi t lat l t rth r r il and alt d it in th ath r d ar nt r k had a r tal -lik tr t r n - th r n and i f al ar n d l in r a d ra idl fr d th n ard r n ard al ar n d l r hard in th nt r ith a ft r d r t ri r ntin th n d l t dia t r at d th h il had a d rat t tr n tr t r in an lar l k in - and - and r ri ati in - h latt r it h d rti r rti in th r h ri n h r it thr h t th t q n a n rall di t hi h t a di tin tl l r n ar th il rfa id n f d radati n f th il tr t r di ati n ld f nd i l i al a ti it r d in all it a i rtant ith t r it n t and hann l in th ain f at r h t il f all it h d a t al h dr - r h l i al f at r ith ra i h- r n atri l r and ir n idati n l r ar nd f r r r t hann l - and - d ll drain d ith n a t al h dr r hi f at r l and nl f ir n- an an ttlin and n d l in th d r h ri n f th r fil n - ft ir n- an an n r ti n ld f nd at hall d th and ir n ttlin a a ndantl r nt fr n ard ith th a aran f ra i h- l r d ti n l r at d th n th and t a n thi il a t raril in ndat d d rin fl d f th r l ir ri r lt f th t r nd at r a lin ar i n in a l r nd at r fr all i t r r la ifi d a di -alkalin at r a rdin t all t al t f r i t r hi h a la ifi d l hati alin at rati n indi indi at d r at rati n f th r nd at r ith r t t al it at = at nal i f hi t ri al il data nal ti al th d a lin d th and th n r and l ati n f a lin int ari d tr n l a n t th t di ar f a i tati ti n and and th a lin and tra ti n th d ar i n in a l il and al f th t d did n t diff r i nifi antl fr th il a l tak n in P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes Includes Regular grid, Random Only fields that Random samples outside covering the sampling had been sampling the irrigation initially within the abandoned by within the scheme planned 3600 current 1993 current ha. irrigation irrigation scheme scheme h iti n and han f rfa and r nd at r rri ati n draina and r nd at r a l tak n in l ita r la ifi d a di -alkalin at r a rdin t all t al h r lt f th h i al anal i f all irri ati n draina and r nd at r a l d in th ar ar r nt d in th n ntrati n dia ra f i r l tri al nd ti it a tak n a a tra r f r n ntrati n r a hl rid n ntrati n r r lati l l and h d lar att r h a ra irri ati n at r iti n i i n in a l h han f th l ti n iti n n n ntrati n an r d in i r all a nt f illit r i itat at n ntrati n fa t r = d t i lit i q antitati l th d inant ili at in ral and r i itat fr = n ard d lar art f th i that r i itat ith i r l a d di l ti n f q art hi i ff r aintain i n ntrati n in th il l ti n at l l - al it r i itat fr = d n ard h n nl takin int a nt n ntrati n r th r i itati n f - al it i lit and illit r lt in a d r a f and a n ntrati n in th il l ti n at d lkalinit n ntrati n ntin t in r a hi h i in lin ith th l n t ik i th in r a t data n t h n n n ntrati n n l din han r int th i lati n f n ntrati n r dra ti all alt r d th han f th Chapter 5 Actual and potential salt-related soil degradation in an irrigated rice scheme Mg Ca 0.1 1 10 0. 0. EC (dS m ) EC (dS m ) + Si Na EC (dS m ) EC (dS m ) 100 Alk SO 10 1 0.1 1 10 100 0.1 1 10 0. 0. 0.01 0. EC (dS m ) EC (dS m ) ) ( ( ) ) ( ) ( ) ) ( ( P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes l ti n iti n n q ili ri ith th irri ati n at r th r nta f a and a ad r d at th ar and r ti l in a q i al nt t l dr il th q antit f al i r l a d fr th han l n n ntrati n a i rtant that th l a n ati r ltin in a l hati alin l ti n nl h n th a r d d t th q i al nt f l dr il th alkalinit f th l ti n r ain d ta l at hi h al d and a alan d a a r d in th fi ld data ith in r a in n ntrati n th f th il l ti n initiall in r a t than ta ili ar nd data n t h n i lati n r i ith li htl all r l dr il r hi h r l dr il al l ad t l t l it han f th l ti n iti n i int a tr n alkalin di l ti n and int a l hati alin l ti n r ti l 5.4 Discussion h di tri ti n and ri in f il alinit and alkalinit i h t t il and al r f nd n th hi h t iti n d il in th t q n hi h i in lin ith r ati n in ha t r h r f nd that t il and in r a d h n in fr th ri r ank and l r l t th iddl and r l r and h d tr n h ri ntal ariati n hi h t t that alt di tri ti n thr h h ri ntal r nd at r nt i ini al h r nd at r a l h d a h t r n att rn i ilar t that f th il and h n n th r - ti n a lth h all r nd at r a l t f r i t r r la ifi d a di -alkalin th iti n f th r nd at r ari d di tin tl tin diff r n in h i al ri in h il t t r anal i f th il it a l did n t r al an diff r n in th ri in f th ar nt at rial ndi ati n n th ri in f th ar nt at rial ld tain d fr th q art fra nt r ati n n - and - an lar q art fra nt had a lat d in a h ri n t n lin that ari d tr n l in thi kn rl in th hi t ath rin fr nt h th i d that thi t n lin arat d il at rial fr ll i -all ial d it r th an lar ha f th fra nt and th irr lar thi kn f th h ri n l a t li that that th t n lin i th r lt f a lati n f ar fra nt at th a f th i t r at d h ri n a la i al h n n n nd r r h id li at l t t al hi i li that il at th r art f th t q n ha f r d fr ath rin f th hi t ar nt r k n inati n ith r a ti n that alt di tri ti n thr h h ri ntal r nd at r fl i ini al thi t that alkalin alt in - and - ri inat fr th ar nt r k h r n f r i itat d ar nat in ral in t n th hi t lat l t and in r a in alinit Chapter 5 Actual and potential salt-related soil degradation in an irrigated rice scheme and alkalinit l l n ar th ar nt r k ar in lin ith thi h th i h r n f ar nat in ral in th l r h ri n i al r fl t d in th hi h han a l a al ar d t th r ti ati n f han a l ati n i lar l d t th di l ti n f a- - ar nat alt h n tra tin ith a ni hl rid h i ilariti t n - and - d n t h ld ith r t t alinit and alkalinit l l th th il anal i and th r nd at r a l f i t r h hi h alinit l l n ar - ith lfat a th aj r ani n h trikin diff r n t n - and - an nl lain d diff r n in th h i al iti n f th nd rl in ar nt r k h r n f rit ld a i l lanati n f r th hi h lfat n ntrati n and l r f th r nd at r at i t r h n rth- th ri ntati n r ndi lar t th l and th rti al iti n f th hi t ar nt r k r id th id al nditi n n d d t tain lar h i al h t r n it at h rt di tan h r n f r nd d q art fra nt in - at d th t that thi il artl ha a ll i -all ial ri in nl at a d th f an lar q art fra nt r r d h all ial ri in f th r h ri n f - i al r fl t d in it rti r rti lth h th l ita da r d d ak fl d th il ar r larl fl d d n aft r in tallati n f th irri ati n h h fl d all f r d iti n and n -f r ati n f llin la and th l a hin f a il l l alt fr th r h ri n h ra i h- l r d ti n l r at d th and th r n f a ndant ir n ttlin l t that th r nd at r l l h lar ann al fl t ati n n l d that th a lati n f al ar n d l alt at d th i r lat d t th all ial hara t r f thi il and th alt rnatin ttin -dr in nditi n a lati n r i itati n that r lt fr a i nal fl din and a fl t atin r nd at r ta l h r nt and t ntial han f alkalinit r l in l ita lth h th d t a r and in and ti diff r d il alinit and l l ha n t i nifi antl l d r th la t thirt ar hi i in lin ith r lt f th d tail d t q n t d in that il alinit alkalinit r l ri inat fr th ar nt r k and n t fr th irri ati n at r l ar t f ndar alkalini ati n alini ati n r r d alth h al t nd t li htl in r a n ar irri ati n and draina anal n inati n ith r ati n ad an t n t al ha t r th in r a in r d ti it r l r d in l ita r th r lt f il n tri nt inin ra ti i n n-a li ati n f h h r f rtili r n il that alr ad had a l n tri nt tat than th r lt f r nt il alini ati n r alkalini ati n th il and r nd at r anal h d that in r a d ith alinit l l r at hi h alinit l l al t nd d t ta ili r n d r a hi h i in ntra t t n r al alkalini ati n r h r al ntin t in r a P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes n th n ntrati n dia ra i r alkalinit l l f at r a l initiall in r a d ith t nt all ta ili d r d r a d a al f d lt f i lati n in l ita irri ati n at r d tt d lin in i r h d that th l ita irri ati n at r l t ard a tr n l alkalin di l ti n h n i l n ntrat d hi t f n ntrat d l ti n nt all l ad t h i al and h i al il d radati n h h i al iti n f t r nd at r a l that ha an hi h r than d ann t d ri d i l n ntratin f irri ati n at r i l i n t n r ati t d r a n n ntrati n h d tail d t q n t d r al d that th ntra tin h i al iti n f r nd at r ld ll d t diff r n in h i al a k r nd l a f a fr th ati n han l n n ntrati n an al artl lain th in l ntra tin h i al iti n f r nd at r i lati n r i in l din ati n han r i ld d n ntrati n dia ra that fitt d ll ith fi ld r ati n and that lain a d r a in l ith n ntrati n al i r l a fr th han l n in r a in n ntrati n f th il l ti n a i rtant that alkalinit ld n t f rth r in r a d t th r i itati n f ar nat in ral n l din han r did n t i r i lati n f n ntrati n d t th in r a d l ilit f i lit that r lt d fr th l r h i lati n f - ili at r i itati n n d f rth r t d t i f li it d r l an t th nd r tandin f alkalini ati n r in l ita a ntr l f alkalinit i li it d h n r f at r a l ith an d i t li it d t n l d ith rtaint that d r a in alkalinit at hi h alinit l l i d t han r r th al that i ld d th t fit ith a and alkalinit n ntrati n r d in th fi ld a r all l dr il hi t that th il ati n han a a it ntri t tantiall t th ff rin f alkalini ati n r n th l th il ff rin a a it i ht nt all r n t and th han and rat f alkalini ati n r in l ita an nl d t r in d ith d tail d t di n th il alt and at r alan 5.5 Conclusions il alinit and alkalinit l l ar hi h t n th hall il f th r l r il ha f r d fr th hi t ar nt r k hi h r l a alkalin alt n ath rin il in th l r art f th land a ha a artl ll i all ial ri in h t il ntain l alt d t r lar fl din hi h l d in inati n ith an alt rnatin r nd at r ta l t th a lati n f ar nat in ral l th r t n h diff r n in th ri in f th ar nt at rial and th rti al iti n and n rth- th ri ntati n f th hi t ar nt r k r ndi lar t th a l d t q n l d t lar diff r n in th h i al iti n f th il and r nd at r at h rt di tan h alt di tri ti n att rn Chapter 5 Actual and potential salt-related soil degradation in an irrigated rice scheme did n t h l ar i n f h ri ntal r nd at r fl n r f ndar alini ati n d t irri ati n a ti iti il alinit and alkalinit ar inh rit d fr th ar nt r k ari n f il t di r th la t ar h d n l ar han f l ita alinit and alkalinit l l lkalinit and f r nd at r a l d r a d at hi h r alinit l l d n l ita t alin il tin that th ir h i al ri in diff r fr th aj rit f th il h ir iti n ld n t d ri d fr n ntrati n f th irri ati n at r nl i lati n r i in th h i al d l h d that t r nd at r a l in l ita ar r at rat d ith r t t - al it at = at n ntrati n f l ita irri ati n at r ill l ad t th r i itati n f thi in ral r ltin in a hi hl alkalin and di l ti n that nt all a l ad t th f r ati n f di alkalin il d l i lati n that in r rat d il han r h d dra ti all alt r d han f l ita irri ati n at r n n ntrati n h r l a f han a l a fr a all = l dr il t al i d inat d il l l d t th ntr l f alkalinit in th il l ti n n l i n f han r in th i lati n r lt d in a d fit ith fi ld data han f n ntrati n ld n t d l d ll d t in ffi i nt kn l d n th t f - ili at that la k r l in l ita n l d d that han r ha artl r lt d in th in l ntra tin iti n f l ita t alin r nd at r r r th d l i lati n h that th il han l f r an i rtant ff r a ain t alkalini ati n r h ari n f d l i lati n ith n ntrati n dia ra f fi ld a r nt r at d a d in i ht int th t ntial f r il alkalini ati n in l ita r q antitati t di n th at r and alt alan at fi ld l l ill n d d t d t r in d l nt rat and q ili ri l l f il alinit and alkalinit i n il t and rr nt at r ana nt ra ti r r lt ar in lin ith th r t di f in n alt r lat d il d radati n in ah lian irri ati n h in that n i n r f nd f ndar alini ati n r alkalini ati n in irri at d ri fi ld Chapter 6 The effect of irrigated rice cropping on the alkalinity of alkaline rice soils rri at d ri r in i ra ti d t r lai alkalin - di il in an art f th rld hi ra ti i in a ar nt ntra t ith arli r t di in th ah l hi h t that irri at d ri r in a l ad t th f r ati n f alkalin - di il il l n ri nt r d n ith f th ah l t alkalin - di ri il fr th ffi d i r ali and l ita a ritania il r irri at d in n n- alin ar nat -ri h irri ati n at r t i al f r th ah l and r lati n a aintain d at da ft r n r in a n il had t rn d fr di t n n- di and had dra ati all d r a d t n ta l in th r il la r h han r t i rtant in th ffi d i r il d t it all ff rin a a it all and a lkalinit n d a r nd att r f th ri lant rain and tra q al d r d d alkalinit add d ia irri ati n in a r - r lati n nari n f r a li at and irri ati n at r that ar t i al f r ah l r al f tra and rain r nt f rth r alkalini ati n f th il if r lati n i a nt r in a f r lati n tra an t in r rat d in th t il f al ar il a it a l rat d -alkalini ati n and d - di ati n thr h in r a d di l ti n f al it id n a f nd indi atin that f rr l i alt r d th h rt-t r alkalinit alan f th t di d il t an t nt r r lt ar in lin ith r nt fi ld t di and t a d alkalini ati n f di -alkalin fl d d ri il in th ah l P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes 6.1 Introduction alt-r lat d il d radati n i n id r d n f th t i rtant thr at t th taina ilit f irri ati n h in th ah l rtrand t al i in n t al i in t al t i n id r d t aff t r than f irri at d land rld id h ad a l i z i th t i rtant r in th ah lian irri ati n h and it r q ir lar a nt f at r d t th lar a rati n in th h t and dr li at lth h t irri ati n at r in th ah l ntain littl di l d alt th ft n a iti al it r id al alkalinit l = lkalinit a in l l all t al rtrand t al h r f r if th at r ar n ntrat d in th il r t n thi a l ad t th f r ati n f an alkalin hi h and di hi h di nt nt il h a il i l r d ti a f th -ind d l a aila ilit f ral lant n tri nt n and th r h i al r rti f th di h ri n r l t al r r d ti n r l attri t d t il alkalinit - di it ha n r rt d thr h t th ah lian n f r th r i n ffi d i r in ali rtrand t al r all in rkina a arr t al a in i r arl t t al a and l ita in a ritania ha t r r r nt il t di ha t r arl t a ar i r and an li t- an t that rr nt alkalinit and di it -r lat d r d ti n r l r inh rit d fr th ar nt r k r fr r l n d lti ati n f n n-fl d d r rath r than a d irri at d ri r in n it i lik l that rr nt alkalin - di ri il in t fri a ar n t in q ili ri ith rr nt land h q ti n ri h th r irri at d ri r in ld in r a r d r a th alkalinit and di it f rr nt alkalin - di il in th ah l d id d t t d th r that a aff t th alkalinit and di it f alkalin - di il in irri at d ri h in th ah l ith ha i n i iliti f r r la ati n f h il h r la ati n f di il i a d n th r la nt f han a l di al i i n ral h i al a nd nt h a al i hl rid and a id ha r n t r lai di il ff ti l r l t al r h a r diati n i n i and th hi h initial in t nt n d d i ft n r hi iti adir t al hi a ar iall tr f r irri at d ri r in in th ah l h r r fit ar ft n all n an t al and h i al a nd nt n t r adil a aila l n di il that ntain al it th f r ani a nd nt an d a a l - t alt rnati r l t al h r and n a a f nd that d t th d iti n f r ani att r in r a in th il r tin n and d r a hi h r lt in al it di l ti n and lar r a n ntrati n in th il l ti n han ith r d di th iti n f th ati n han l han fa ra l f r ani a nd nt i iall f l f r th r la ati n f di il h n in d ith irri at d ri r in i i r t l rant t di il nditi n r l and h la t it hall r tin n r t ar l ha r d a di -h ri n rth r r ri r t r l a r ani nd and l n r r r aar hi h in r a artial r r in a ll a d r a il thr h r t n Chapter 6 The effect of irrigated rice cropping on the alkalinity of alkaline rice soils r ti n ll th r in d fa r th in r a d di l ti n f a in th il and th d r a f il alkalinit and di it a a f n ti n f ti r l t al h ad t al hha ra and r l h d that ri lti ati n i r d r lati n rat n in hi hl di il hi h nhan th l a hin f han d di fr th r tin n nd h d that r d r an al infl n th alkalinit alan f alkalin - di irri at d ri il in ali t did n t r id a i-q antitati ti at f th r n th alkalinit alan f th r t n rink an h d that f rr l i a th a idifi ati n f ri il in th- a t ia and a an rr l i r h n ir n-h dr id ar r d d in ana r i il lth h th f an alkalin ri il d r a t ard n tral al n fl din nna r a th alkalinit lk f th il l ti n a t raril in r a d t th r d ti n f ir n-h dr id q ati n [ art f th r d d ir n han ith ati n h a a a and h di la d ati n t th r ith ani n ainl i ar nat that ar r d d i ltan l ith th di l d an r n an tran f rr d int th rfa at r r l a h d t r nd at r ft r di ntin ati n f fl din il idati n r lt in a idifi ati n f th r h ri n and alkalini ati n f rth r d n ard t i nkn n t hat t nt f rr l i al la a r l in th alkalinit alan f irri at d ri il in th ah l and t hat t nt thi r an infl n d th a nd nt f ri tra h j ti f thi t d r i t q antif th ff t f irri at d ri r in n th alkalinit and di it f alkalin - di ri il in th ah l ii t id ntif and a th r lati i rtan f r that ntri t t han in th alkalinit and di it f th il and iii t in ti at th t ntial f ri tra a a l t a nd nt f r th d -alkalini ati n f th il nd t d n- tati n il l n t t in t f t fri a t alkalin - di ri il il l n t t all d tail d and ntr ll d nit rin f th il and ha arli r n d t f ll t d d - alkalini ati n and d - di ati n r l h r in th rld hha ra and r l ha dhr t al r nk l t al adl r t al ah and rh in 6.2 Methods it d ri ti n h alkalin - di ri il d in thi t d ri inat d fr th l ita irri ati n h in a ritania and fr th ffi d i r irri ati n h in ali i r t th it th li at i t i all ah lian ith a h rt t a n r fr l t t r and P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes a l n dr a n ith ini t rat r ar nd in an ar and a i t rat r r larl din in ril a t ntial a tran irati n i r lar r t far r lti at ri in th t a n and a in rit l than ra ti d l r in h l ita h a ta li h d t n and and r a t ha ft r initial d r d ti it far r ri n d i ld r d ti n hi h th attri t d t alt ffl r n f th h land had n a and n d and t a n i ld had d r a d fr n a ra t ha t t ha n ha t r h d that r d ti it r l r a d artiall alkalinit -r lat d n tri nt d fi i n i t n ta l n th hall thi k il at th r l h r il had f r d fr th hi t ar nt at rial ar r la ifi d th il a d rad d n th inland d lta f th i r i r th n tr ti n f th ffi d i r h tart d in th nitiall tt n a th aj r r r n t it lar - al lti ati n a a and n d in th arral rr ntl f th ha ar d f r ri lti ati n h h i th lar t in th ah l r nd at r l l r fr d th t l than d th in a t ar and a d alkalini ati n f th initiall li htl a idi il dia n th arl a lar art f th h a r t r d and draina fa iliti in r a d arl t a a r lt alkalinit f th la il d f r ri r in d r a d li htl t in r a d in th adja nt ar -t t r d il that r tl d f r ta l r in arl t a il l n t t lar t il a l a tak n in l ita and in th ffi d i r th a l r tran rt d t th r ar h tati n in aint i n al h il a l d r j t f arli r r ar h nd an t n t al a th a l r air-dri d r nd a r at i h ni d and th n tran f rr d t l n il t tr at nt r titi n h il a li htl a t d t tain a r l fra ti n f a r i at l and a lk il l f lit r h hi h l n i r r la d in a r nh and ra d in al in f il t r nt h atin th n thin la r f rifi d q art and a fir t la d at th tt f th l n f r draina ri r t irri ati n th il l n r at r- at rat d fr l t r nt air ntra nt h at r d f r at rati n and irri ati n a n n alin and ar nat -ri h hi h i t i al f r th ah l a l th il r j t t th f ll in fi tr at nt in d li at n lant - ri lant - ri lant and n tri nt - ri lant and tra - ri lant n tri nt and tra n a h l n t thirt da ld ri dlin z r tran lant d aft r l t at r- at rati n f th il i tra a in r rat d at Chapter 6 The effect of irrigated rice cropping on the alkalinity of alkaline rice soils an q i al nt f t dr att r ha h rtl f r at rati n rtili ati n ri d a al a li ati n f k ha ri l r h hat - and t -dr in f k ha r a lit a li ati n at and da aft r tran lantin rri ati n tart d i diat l aft r tran lantin fl d at r la r f a r i at l a aintain d dail irri ati n ar in th h i ht f th drain t tl t th h dra li h ad ld adj t d t aintain r lati n rat l da hi h i i k d fi ld nditi n h il l ti n a a l d at and d th in all hi n il i t r a l r ha in a h dr hili r l r ith a all d ad l l and n n- han r rti hi h r ar h r d t a nin n h a l r ll t d nd r a in l a la t at and k aft r th tart f irri ati n n rd r t a id ll ti n fr r i a l a all l a l a tak n in a rin ri r t nn tin th a la t tal alkalinit lk f th il l ti n a l a d t r in d a rdin t ran lth h h h ri a id and th r in r ak a id a l.

.

P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes ntri t t t nt in ra ti nl di l d ar ni a id i f q antitati i rtan f r th a r d alkalinit l and t a ra k t in q ati n d n t t tal n ntrati n in l - har lk [ h r ainin il l ti n a l a a idifi d ith nitri a id and t r d in a l dark la f r anal i f a a and in an at i a r ti n tr t r hl rid a a r d ia l tri titrati n d t ntial h a a r d in latin l tr d at and d th il at and d th a nit r d in n trati n l tr d and l a l i r - i t r h h i al i lati n d l arkh r t and l a d t al lat at rati n indi f r in ral in th il l ti n d fin d in th data a hi all d t a th in ral that ld t ntiall r i itat th r alt rin th il l ti n iti n h f th il l ti n a al al lat d in in th il l ti n alkalinit a a r d in th a t a l and th a a r d ith th n trati n l tr d rri ati n a di ntin d da f r at rit f th ri rain a l f th il a tak n ri r t fillin th l n h rtl aft r har t th il f a h l n a a l d at and d th ll a l r n-dri d r nd and anal d f r and in a and at r- at rat d a t r ti l i and rth r r han a l a f th ri inal il and th a l at and d th r d t r in d in an aft r tra ti n ith a ni hl rid ar t d lant r n-dri d and rain and tra i ht r a r d ati n a a r anal d in an aft r tra ti n ith a l l ti n hida t al n ntrati n f in rain and tra r d t r in d in th i r - j ldahl th d r n r lant h h r n ntrati n r a r d in th th d d ri d hida t al lkalinit alan a in th t ral d l nt f th alkalinit f th il r t n d rin th r in a n k aft r tran lantin alkalinit alan r al lat d f r a h il l n in th dail a r nt f irri at d and r lat d l and f th il l t a r nt at and k aft r ri tran lantin at d th lati r lat d l f r th ti int r al i k aft r tran lantin r lti li d th il l ti n alkalinit f a h rr ndin ti int r al h f th l a h d alkalinit f a h ti int r al q al d th t tal alkalinit l a h d fr th r t n f a h l n lk h alkalinit add d ith irri ati n at r lk a al lat d a th t tal irri at d Chapter 6 The effect of irrigated rice cropping on the alkalinity of alkaline rice soils l lti li d th alkalinit f th irri ati n at r hi al lati n a r at d nl th irri at d l a li it d t th a tran ir d l lk i th alkalinit add d t a h l n if n r lati n r t r h alkalinit that a r d fr th l n thr h har t f th a - r nd att r lk a al lat d a a f n ti n f lant in ral nt nt and i a r d ti n a rdin t an i h in ral n ntrati n f rain and tra r a d n la rat r anal i f a and a and lit rat r al f l and f r d rn z ari ti i in t al atta r ann and airh r t t r t al i l = and = f r tra and l = = f r rain a d that lant a tak n a and lant a h r f tak ri inat d fr r a and f tak ri inat d fr in th tr at nt that r i d f rtili r a f l ha t r rth r r a d that lant n tri nt tak a r tri t d t th la r hi h i n rall n id r d t th ff ti r tin d th f ri h alkalinit add d thr h tra a li ati n lk a al lat d f ll in th a th d and a ti n d f r al lati n f lk h ff t f f rtili r a li ati n i r a and n th alkalinit alan f a h l n lk a al lat d di r ardin tak n a - r nd lant art a d that r a had n ff t n th il l ti n alkalinit h dr l i f r a n r t n r i n t an q i al nt a nt i r l a d n lant tak latili ati n and nitrifi ati n-d nitrifi ati n a d that n di l ti n f a half f th a n rt d t n id rin th a ra il at d th in th il tati ti al anal tati ti al anal r nd t d in th ft ar a ka f r ind r i n r at nt an f r rain i ld lant i a irri at d l r lat d l a tran ir d l and aria l f th alkalinit alan r ar d ithin a h il t in l a t q ar diff r n t t aft r a l in n t t f h n it f arian t th l n r f r li ati n i t th r ad r h ld f r n il q alit han h n ar d t th initial it ati n than n i nifi an f tr at nt diff r n P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes 6.3 Results han in il di it and lt f th anal i f th and il a l r al d that th il r initiall di a rdin t la ifi ati n r l t al h a lar r and all r in th il ar d t th il nlik th il th il ntain d ar nat in ral k h and r fil f th il aft r th ri nt f r th diff r nt tr at nt ar h n in i r n all l n i l r n ar th il rfa n th il lar t d r a a f nd in tr at nt that r i d tra and r n tri nt h d r a a t ta lar in th il h r dr d fr an initial al f t r l n ar th il rfa n th il th a lar t n ar th il rfa ith hi h t al a r d in tr at nt that r i d tra and n tri nt h at a d th f and i h n in i r h lar t d r a in rr d in th il n th il th at d th d r a d th t in tr at nt ith d ri r th pH EC (dS m ) 5.0 6.0 7.0 8.0 0.0 0.1 0.2 0.3 0.4 0.5 0. 0 10 15 O O OR OR 20 ORN ORN ORS ORS ORNS ORNS pH EC (dS m ) 5.0 6.0 7.0 8.0 0.0 0.1 0.2 0.3 0.4 0.5 0. 0 F F FR FR FRN FRN FRS FRS FRNS FRNS p h ( ) p h ( ) p h ( ) p h ( ) Chapter 6 The effect of irrigated rice cropping on the alkalinity of alkaline rice soils at r and alt nt il l n fill d ith il tt d r ra idl da and h n l than l n fill d ith il da h il l ti n a arin at th r rfa f th l n aft r l t at rati n a l ar f r l n t t r id f r l n indi atin la r r ani att r di r i n f r th latt r h alt that had a lat d n ar th il rfa d rin ttin r tran rt d d n ard ith th irri ati n at r and th alt ak at and an r d in i r lth h r lati n rat r an all adj t d ar in th h dra li h ad i h i ht f th tl t diff r n in lati r lati n r r d t n th t il t and diff r nt tr at nt a l ra d f r all tr at nt and ti r lati n rat r da and da f r th and l n r ti l ft r k lati r lati n a lit r f r th l n and lit r f r th l n h lar tandard d iati n f r th lati r lat d l f th l n a ainl d t lar lati r lati n lit r a r d in th tr at nt nlik all th r tr at nt th tr at nt r i d irri ati n f r an th r k a r d l nt a tr n l d la d rri ati n a nl t d aft r k and lati r lat d l at at rit a ra d lit r lati irri ati n and a tran irati n a l r iti l r lat d t r r th tr at nt ith d lant r th had i nifi ant hi h r a tran irati n rat than tr at nt ith n r r lant r th P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes..

..

.

.

.

.

..

.

.

......

......

lant r th i ld r lar t f r tr at nt that r i d f rtili r a l tra a li ati n had a tr n iti ff t n lant r th and i ld f r th il t had n ff t f r th il i lant in th tr at nt h d t nt d r th r n l rati n f th ld r l a and a r l n d tati r th ri d hi h r a l indi at d in d fi i n i lant in th tr at nt h d al t n lant d l nt aft r tran lantin lkalinit alan ll tr at nt h d a n ati alkalinit alan i alkalinit a l t fr th r t n a l ar t alkalinit l r r d f r tr at nt that r i d n tri nt and r tra a li ati n t alkalinit a l t thr h l a hin lant tak a al an i rtant l fa t r in tr at nt that had d rat t d ri r th lk a nt d f r f t tal alkalinit l lk in th l n and f r in th l n n a ra tra a nt d f r a r i at l and rain f r f lk lant in ral n ntrati n h d littl ariati n t n tr at nt and il and an n ntrati n and tandard d iati n r a a f r tra and r a a f r rain li ati n f n tri nt had littl dir t ff t n th alkalinit alan lkalinit add d t th t in th r - r lati n nari lk a q al t r all r than lk tra a li ati n a nt d f r f th t tal alkalinit add d t th r t n in tr at nt - - rain a a a b a b a lant a b a b a b a a h l a a a a a a a a a a rri l c c b b a c b a b ab t l c c b b a c b a b a total percolated volume after 11 weeks;

total irrigated volume after 11 weeks;

total evapotranspired volume after 11 weeks;

the mean above-ground biomass was less than 1 g and not included in the statistical analysis;

within each soil type, means in the same row followed by the same letter are not statistically different (LSD test;

p < 0.05);

prolonged irrigation, resulting in 13.4 0.2 liter percolation after 15 weeks lk b ab a a a c bc bc a ab lk b a b c b c a lk lk lk c c b b a c b a b ab lk c c b b a c b a b a lk b ab a a a b b b a ab ( i alkalinity accumulated in the root zone 020 cm) of each column;

alkalinity taken up by the plant (above-ground matter), assumng that nutrient uptake was restricted to the 020cm horizon;

alkalinity added with the application of 5 t ha of dry straw (97% dry matter);

alkalinity added with the application of nutrients (~326 kg Urea ha ;

~ 60 kg TSP ha );

alkalinity added with the irrigation water;

alkalinity added if no percolation took place ~ evapotranspired volume K alkalinity irrigation water;

alkalinity leached from the root zone (020 cm);

within each soil type, treatment means in the same row followed by the same letter are not statistically different (LSD test;

p < 0.05) P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes han in th il l ti n ft r at rati n f th il l n at d th in th il ta ili d ithin da t al f a t f r tr at nt and f r th th r tr at nt t d th in th il initial t adil d r a d d rin th fir t k aft r at rati n t a ini f f ll d a li ht in r a t f r tr at nt and f r th th r tr at nt n th il d l nt a i ilar at th d th ith t adil d linin fr initial al f a r i at l t al f ith n diff r n t n and n - tr at nt I r d a r nt r al d a ra id r d ti n f th il n ir n nt aft r l t at rati n f th il l n d t ntial at d th in all l n dr d fr t ithin a k t f r th l n ith t h r r a h d thi al nl aft r k t d th initial al ari d ar nd f r l n and f r l n t ta ili d at in th il aft r k and data n t h n di a th d inant ati n in th il l ti n f th il r it r lati i rtan ari d tr n l in ti h a a rati tr n l d r a d a th alt fr nt a d at and d th hi ff t a t r n n d at d th and in th il i r h il l ti n alkalinit al h d i rtant diff r n t n il t and a a f n ti n f ti n th il alkalinit d r a d lin arl ith th il l ti n n ntrati n and i ar nat at lk a th d inant ani n n th il i ar nat a th aj r ani n at l l ti n n ntrati n t alkalinit a h i all ntr ll d h n th f th il l ti n a hi h r than d n th il tra a li ati n had n di tin t ff t n th alkalinit f th il l ti n n th il alkalinit in r a d aft r a li ati n f tra at d th i r t th ff t a n l n r i i l at d th n aft r l t at rati n f th Na:Ca ratio 30 EC 0 Percolated volume (l) - : r ti E (d Chapter 6 The effect of irrigated rice cropping on the alkalinity of alkaline rice soils 10 0 10 Fo um G leita (F) O ffic e du Nige r (O ) 5 c m 5 c m 20 c m 20 cm 10 1 0. 1 1 10 0. 1 1 -1 - E C (d S m ) EC (dS m ) il a at f r th il and at th d th t d th l l d r a d in ti t r a h al ar nd at in th il t f r tr at nt in th il h r a hi h at a aintain d t d th ta ili d in th il at ar nd at h il l ti n f th il at d th h d r at rati n ith r t t al it at th innin f th trial ft r lit r r lati n th alt ak a fl h d d n ard and th at rati n ind f al it ra idl d lin d t al t n and f r tr at nt ith t tra and t al f a t r f r tr at nt ith tra h diff r n r t r d in th il i r t d th - al it al......

......

- - l li it ( lc l l li it ( lc l - l A P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes d r a d fr an initial ak t n ar- r al aft r a r i at l lit r f r lati n n th il ith n diff r n t n tr at nt ith and ith t tra r n n ntrati n in th il l ti n ar h n in i r r n n ntrati n f r th il r di tin tl lar r than f r th il r th ri d f k till n ntrati n in th il at d th r ta l a ra in l l f r tr at nt and l l f r n tr at nt t d th in th il th ff t f tra a l id nt nl fr k t tr at nt had lar r n ntrati n i ilar t th at d th n th l n n ntrati n r n rall all l l nl in tr at nt at d th n ntrati n t adil in r a d thr h t th a n t r a h an a ra a i f l l at k aft r tran lantin i lati n r al d that n at all n ntrati n f l l th l ti n a r at rat d ith r t t id rit f r th il 10 without straw 1 with straw 0. 0. without straw 0. with straw 0. 0. 0. -0.5 1.5 3.5 5.5 7.5 9.5 11. -0.5 1.5 3.5 5.5 7.5 9.5 11. Weeks after transplanting Weeks after transplanting without straw with straw 0. 0. without straw 0. 0. with straw 0. 0. -0.5 1.5 3.5 5.5 7.5 9.5 11. -0.5 1.5 3.5 5.5 7.5 9.5 11. Weeks after transplanting Weeks after transplanting ( ) + ( ) ( ) ( ) Chapter 6 The effect of irrigated rice cropping on the alkalinity of alkaline rice soils 6.4 Discussion ran rt and l a hin r ra r lati n rat da rr nd t a i fi ld rat f r th il nd an t n n li h d r r lati n rat in th fi ld ar ft n tain d nl d rin th fir t k aft r fl din and an d r a t n li i l al n r nd at r l l ha r a h d th rfa nd h il h d i n f la di r i n and ha d in a r h t r n a than th il i h n ar d t th il th initial at rati n f th il r q ir d r ti th ttin att rn a r irr lar and l irri ati n at r a n d d lit r r lit r t fl h th alt ak fr t d th i r hi h rr nd t a l r a ti r l r rth r r th alt ak in th il h d tr n r tailin hi h a r ith lar r di r i n and i l a fl in thi il ar d t th il n th il di it a hat l r and alinit f th il l ti n hi h r hi h and in thi a r nt d la di r i n ith th ti n f tr at nt and th lati r lat d l f tr at nt f th a il t did n t diff r h hi h all th int r r tati n f tr at nt ff t n il di it and alkalinit han in il di it alkalinit and alinit th il h d a r arka l d r a in il alinit di it and ft r n r in a n th il han d fr di t n n- di ith t dra ati han in th il and n ar th il rfa h tr nd r d in th alkalinit alan a l rr nd d t th r d in th and r fil aft r th ri nt i r and n n l d that th il l ti n and at r alan a r nt an n rall n id r d r lia l and r r ntati h tr nd f d r a in alkalinit rr nd t fi ld r ati n arl t h f nd that that il had li htl d r a d n th la il in th ffi d i r irri ati n h d rin r nt ar f ri r in h alkalinit alan al lati n l arl r al d that l a hin ntri t d t t th l f il alkalinit idifi ati n f th il r t n r ti n f th ri r a al an i rtant fa t r a ntin f r t f th alkalinit l h r t n r ti n in r a d in tr at nt that r i d f rtili r n f rtili r a li ati n d n t nl in r a i ld and r fit ar in n an t al t al nhan a idifi ati n thr h lant r t n r ti n h n lant alkalinit tak i n rt d t a idifi ati n rat r rfa ar a r findin l r q it i ilar t th l r rt d ar i r t al h lti at d th f dd r r r i nd r fl d d ri -lik nditi n ith th ai t r lai alkalin di il in th a irri ati n h in i r n a f r - r lati n i n l a hin tr at nt ith r r ri r th P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes ld till ha had a n tral t n ati alkalinit alan in lk lk rain i ld a nt d f r a r i at l f lk and r al f rain nl ld n t n at th alkalinit add d irri ati n in a r - r lati n t in th rr nt trial t r alkalinit and l f th irri ati n at r d in thi trial ar ti lar r than al r rt d rtrand t al arl t t al and i in t al f r th i r and n al i r n r al f rain nl ld n at t a lar t nt f r th alkalinit add d d rin irri ati n in a il ith t nat ral r artifi ial draina in t ah lian irri ati n h h th r r al f tra h ld r nd d t far r i q ti na l in tra a nd nt h l i r i ld and l n -t r il f rtilit nna r a li ati n f tra initiall in r a d th il alkalinit ith l r l n t thi in r a a l t l n at d in r a d lk a l iall in th l n n th l n tra a li ati n al in r a d lant r th and th th a idif in ff t f lant lk h i r d lant r th a attri t d t in r a d a aila ilit and in r a d n a aila ilit thin that a arli r r d in fi ld trial in ah lian irri ati n h an t n n li h d h hi h r lk and lk a d t tr at nt t ha a l r lk than th ir q i al nt tr at nt ith t hi i in a r nt ith th r fil i r that h d l t t il in tr at nt that r i d tra t th nd f th trial th a hi h r in th rfa h ri n f r all tr at nt d t a illar ri that rr d t n th nt that irri ati n a di ntin d and har t hi ff t a tr n t in tr at nt ith d lant r th han r and r i itati n-di l ti n f al it d r a in il di it i li a d r ti n f han a l a hi h i ll r d in i r h a a rati in th il l ti n ra idl in r a d aft r th a a f th alt ak hi h indi at th d r ti n f a fr th han l lr ad in a n r d th d nd n f han f n al nt and di al nt ati n n th i ni tr n th f th il l ti n hi ff t lain that il di it d r a if th il i l a h d ith a l i ni tr n th l ti n that ha a a a rati i ilar t r l r than that f th ri inal il l ti n a a th a in r trial h dr in a r r n n d and n ti a l at r at r d th in th than in th il d t it all r di il ith a all ill th a i r t r lai than il ith a lar n r l il ith a all ill r r n t di ati n a illar ri fr alin r nd at r r f r q alit irri ati n at r n th il th a li ati n f tra l d t an in r a in il l ti n alkalinit i r a n ntrati n data n t h n and at d th hi ff t an attri t d t th di l ti n f nati al it k hi i i ali d in i r Chapter 6 The effect of irrigated rice cropping on the alkalinity of alkaline rice soils h r th al it f th il l ti n f tr at nt r ain l t r i at rati n n h n alinit l l dr h h th i that a li ati n f tra ld in r a th r di l in nati a th r f r rr t h il ntain d r littl a k tra had littl ff t n th alkalinit f th il l ti n r i itati n and di l ti n f al it a ntr llin alkalinit f th il l ti n f l n t n t in th l n hi i ll ill trat d in i r h r r h i al ntr l f alkalinit at lar n ntrati n in th t n t in th il h il l ti n had a iti l r lt n t h n at all n ntrati n d t a n ati l and a l rin f l ti n alkalinit at lar r n ntrati n r lt n t h n hi an lain d d r ti n f han a l a ith in r a in l ti n n ntrati n hi h l ad t al it r i itati n and a q nt l rin f th il l ti n alkalinit d r h ra id d r a in il h rtl aft r in ndati n a a ani d an in r a f in th il l ti n h r d al r in th ran that i nl f nd f r ri il nna r a n th il l ar diff r n in n ntrati n t n and n - tr at nt at r d fr k n ard a ar d at d th n t arli r than k aft r tran lantin h d la in tran rt i ht attri t d t i ad r ti n f at th ati n han l hi h ld l ad t f rr l i rink an r ii r i itati n f ndar in ral h a id rit id rit r i itati n ld l ad t an q i al nt l rin f and alkalinit in th il l ti n it r i itati n ld d r a th t ntial a idif in ff t f f rr l i in an fi ld t di r n t al th il l ti n f th il and at th d th ra idl a r at rat d ith r t t id rit h rr nt trial t d n t all t diff r ntiat h th r th d la in d n ard tran rt an attri t d t ad r ti n at th han l f rr l i r r i itati n f ndar ir n in ral n th il ir n n ntrati n r di tin tl hi h r l l h n tra a a li d i r t r ain d l ar d t th il l ti n alkalinit l l hi t that th t ntial ff t f f rr l i n th il alkalinit alan in th rr nt trial t a r li it d r n ntrati n ar till hi h n h t t i nifi ant l n -t r ff t f f rr l i n th alkalinit alan f th il 6.5 Conclusions rri at d ri r in an t ntiall d f r th r la ati n f t f t fri a t alkalin - di il in n r in a n th il in th l n ri nt han d fr di t n n- di and d r a d i nifi antl h l f alkalinit and di it a r d inantl th r lt f l a hin ith n n- alin ar nat -ri h irri ati n at r h ff t f l a hin a l dra ati in fi ld P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes nditi n h r r lati n rat an l r d il nditi n and in r a in r nd at r l l thr h t th r in a n rth l th tr nd f d alkalini ati n r d in th il l n rr nd t fi ld r ati n f il d f r fl d d r l h r in th ah l arl t ar i r t al r t n r ti n lant i an i rtant fa t r r n i l f r f th r d il alkalinit d r a lant a idifi ati n rat r rfa ar a rr nd t fi ld r ati n in i r ar i r t al and q al d r d d alkalinit add d ia th irri ati n at r in a r - r lati n nari lth h initiall il alkalinit in r a d li htl ith ri tra a li ati n it d iti n in r a d and a d di l ti n f nati al it in th il hi r lt d in in r a d l a hin f alkalinit and a f rth r l rin f th il di iti nt all thi r a l ad t a d al ifi ati n f th il li ati n f tra i nifi antl in r a d ir n r d ti n in th t la r f th il r f rr l i a f littl i rtan t th h rt t r han f th il alkalinit alan t i ht i rtan f r th l n -t r han rall n l d that tra a li ati n a l rat a d r a f t il alkalinit and di it r id d that th il ntain al it and that d n ard r lati n i a r d n n n- al ar alkalin di il ith r l r lati n rat r al f tra a th tt r ti n if d r a in th il alkalinit i th ri ar j ti rtili r a li ati n in r a lant r th and nhan il a idifi ati n thr h lant r t n r ti n ar d t il ith a lar and a nt nt il ith a all and a nt nt ha l ff r a a it and an r lai d ra idl nd r tandard nditi n f lti ati n far r in l ita and th ffi d i r d n t ha t f ar ra id alkalini ati n f th ir ri fi ld r id d that a illar ri d rin th fall a n i li it d Chapter 7 Conclusions n th id- d linin ri i ld and th r ati n f alt ffl r n at th il rfa rri d th far r and i nti t and l d t th n ral li f that th a ri lt ral t ntial f ah lian irri ati n h a j ardi d ra id alini ati n and alkalini ati n hi d nari a f rth r f l d t di that h d that t ah lian irri ati n at r ar r lati l ar nat ri h and i ht n t a af a t d l and al n n al ali and i r ral t di r nd t d t q antif alini ati n and alkalini ati n r t f i nti t f d n th r lati n hi t n l and d linin ri r d ti it and th d alt-r lat d il d radati n r l n alt-r lat d il d radati n a an i rtant i in ah l irri ati n h ith t kn in h a t hat i a t it ld i l ha n ri r d ti it t k a l l k at ri r d ti it r l in th irri ati n h f l ita and th r all and n l d d that l i ld r a d n tri nt d fi i n i and d fi i n r id ntifi d a aj r r in n traint in l ita hil n d fi i n r ail d in th r all h lar aj rit f th r l il at th it ntain d littl alt and littl han a l di n th il ld n ith r la ifi d alin n r di a rdin t la ifi ati n i hard and f r n ith r di it n r alinit it i r a l that th ntri t d t th r d n tri nt d fi i n r l r in l ita and th r all all il h r ri ri r d ti it r l r r d had an alkalin - al ar hara t r - h r n f alkalin alt a ll ha ntri t d t th l a aila ilit f and n thr h a l and ad r ti n nt r r i itati n in th f r f ar nat in ral n n th il ld n t la ifi d d rad d f ll in int rnati nal la ifi ati n t th alkalinit -ind d il f rtilit r l th far r r fa in r r r al h far r in th h r rr t in r latin alkalin alt ffl r n t th r d ti it r l t ah lian far r had n ri n ith ri r in ri r t th n tr ti n f th irri ati n h - ar a h r f r it d littl r ri in that t t di n ri r d ti it r l in ah lian irri ati n h id ntifi d ti al r ana nt a ri ar r a n f r th l i ld nit r d far r ra ti in l ita and th r all and f nd that far r r ana nt in th l ita and in th r all n rall d iat d hat fr l al r ndati n r n t th n n- lian t l al r ndati n t th inad q a f l al f rtili r r ndati n a th ain r a n f r th lar i ld a i th all d and r f rtili r d r ndati n in l ita and r n f rtili r d r ndati n in th r all th in l ita and in th r all i ld ld a il in r a d fr ar nd t ha t t ha thr h a li ati n f a l and n f rtili r n l ita h r and f rtili r r q ir nt n th alkalin P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes d rad d il r h lar r than n th n tral n n-d rad d il r t far r in th r all and n th d rad d il in l ita th r nd d f rtili r d ar ith r r n i r n t a aila l n th l al ark t n t t d th f r ani a nd nt a an alt rnati l ti n t i r n tri nt a aila ilit hil aintainin r d ti n t at an a ta l l l h f r ani a nd nt r d r n fi ial at th irri ati n h n l ita a li ati n f t ri tra ha in r a d i ld t ha n a ra ind nd nt f il t and f rtili r d tra a li ati n i r d a aila ilit t f nd n l ar id n f i r d a aila ilit h i r d a aila ilit a attri t d t in rali d fr th tra fr in r a d in rali ati n f il r ani att r ith a l rati and fr in r a d r r ffi i n f a li d in ral f rtili r r a h th i d that i r d f rtili r r r n tra a li ati n a d t r d d nitrifi ati n d nitrifi ati n l n th r all th a li ati n f t ha d d ri tra t r attl an r in r a d i ld t t ha h f r ani a nd nt i r d n tak t did n t radi at n d fi i n ntir l rall th f d d tra a nd nt r d r n fi ial at th it t ian t di n th f ri tra in irri at d ri h littl t n h rt-t r i ld in r a - t ha lth h tri d t lain h tra a nd nt infl n d and a aila ilit in l ita ha t r r r ar h i n d d t f ll nd r tand and q antif th l n -t r r l f r ani att r a nd nt n th an ti far r an a l d d ri tra t i r th ir i ld tra i r adil a aila l alth h it i a i nall d a attl f dd r in l ita n th r all r ani a nd nt ar al d f r ta l r in r th ain n traint f r lar - al ad ti n f r ani att r a nd nt far r a th lar la r r q ir nt that ar n d d t in r rat r ani a nd nt int th t il f nd n id n t rt th h th i that alkalini ati n thr h i a tran irati n f l iti irri ati n at r i an n in r in l ita and th r all th in l ita and in th r all t fi ld and r nd at r a nl ti r n ntrat d than irri ati n at r h all n ntrati n fa t r indi at th a n f i n ntrati n f irri ati n at r at thi int in ti n l ita th alkalin alt in th - all d d rad d il ri inat d fr th hi t ar nt r k at hall d th ari n f hi t ri al il data r al d n i nifi ant han f il and r th la t ar lth h l ita irri ati n at r i a n t th t alkalin in th ah l th il a ar t ha a tantial ff r a a it a ain t alkalini ati n d it th iti l f th il and irri ati n at r th d n t d l int hi hl alkalin - di l ti n n n ntrati n d t r l a f a fr th han l rth r r r t n r ti n lant lar l n at f r th alkalinit that i add d d rin irri ati n h n r lati n i a nt hi an that n in h ith li it d draina fa iliti irri at d ri r in i nlik l t Chapter 7 Conclusions ntri t t a tantial ild f alkalin alt in th r t n d rin th r in a n lth h f nd n id n f n in alkalini ati n in th ah lian h alkalini ati n an till r h n irri ati n i halt d and tantial a illar ri fr a hall r nd at r ta l r r r tantial a illar ri an r in fi ld that ar l ft n lti at d r in ar a rd rin an irri at d ri h r r ar h ill n d d t f rth r a in ndar alini ati n and alkalini ati n ff t f irri at d ri r in n n n-fl d d n i h rin ar a land d f r ta l r in r fall h i tin alkalin - di il in th ah l an r lai d thr h irri at d ri r in r id d draina t r alkalin alt i i l t ah lian irri ati n at r ntain littl alt and th r n f a nd d at r la r nhan d n ard l a hin f alt h ri r f rth r nhan th r la ati n f alkalin di il thr h r t n r ti n r r lt rr nd t findin in ia h r ri i ft n d t nhan r la ati n f alkalin - di il f nat ral draina r and th il ntain al it th n tra an t in r rat d in th il a it ana r i d iti n in r a and a in th il l ti n h latt r nhan d r ti n and l a hin f han a l a and fa r d di ati n and d -alkalini ati n f th il h th a li ati n f r ani a nd nt did n t nl i r n tri nt a aila ilit in l ita t al ntri t d t th r la ati n f al ar alkalin - di ri il n n n- al ar alkalin il r al f tra ld th tt r ti n if th l j ti i t d r a il alkalinit t a a i f nd n id n that f rr l i aff t d th h rt t r alkalinit alan f alkalin ri il t an t nt rall n l d that th r i littl id n that rt th h th i that alkalini ati n i an n in r in irri at d ri fi ld in th ah l n th ntrar irri at d ri r in a ll d r a th alkalinit and di it f alkalin - di ri il in th ah l n th l alkalinit -ind d n tri nt d fi i n r l ha n f nd t r in ral f th ah lian irri ati n h h alkalinit an a r al r in n traint ar r r r i t nt in indi atin that l i ld r r lat d t a alt-r lat d r l d it r ri ar int r r tati n that il and r n thin t rr a t a rdin t int rnati nal la ifi ati n r ft n far r n t nl r d ri ht intin t alkalin alt t th ir arti i ati n in th r ar h a in tr ntal f r th id ntifi ati n f r r d ti n n traint and t ntial l ti n h d in far r fi ld and r ar h- ana d trial that alkalinit -ind d n tri nt d fi i n i an r th a li ati n f in ral f rtili r r th in ral f rtili r d n d d ar lar r ar n t a aila l n th l al ark t n th a far r ill n t a l t ad t n f rtili r r ndati n rth r r if d n t tt r nd r tand th hani that r d n tri nt a aila ilit f rtili r r ndati n i ht ha t in r a r r ain hi h in ti h d that r d ti it r l an artiall r a li ati n f r ani a nd nt t littl i kn n a t th l n t r ff t f r ani att r a li ati n in inati n ith t l in ral P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes f rtili r d h f rth r r ar h n r that r lat a aila ilit f and n n alkalin - al ar ri il i r nd d n additi n l n t r alt-r lat d r l till d r r att nti n in ar a h r r nd at r i in nta t ith th r t n in inati n ith li it d nat ral i iliti t l a h a lat d alt References r l h la r r n t diff r ntial a li ati n in a hi hl di il and th t l ran f ral r t han a l di nd r fi ld nditi n il i n r l ada a d alt-aff t d il and th ir ana nt d and ri lt ral r ani ati n f th nit d ati n il ll tin dh a atnaik a th nanthan itrifi ati n f a ni in diff r nt n nt f a fl d d ri il t i l rtil il h ad r hi adir li rati n f a al ar alin - di il and f ra lant and radati n and ha ilitati n l t a h i tr r nd at r and ll ti n alk a tt rda h th rland lakh h ra ran r n n nitrifi ati n and fl in ri - h at r in t a aff t d r r id f rtili r and l r n an r i l rtil il ar i r l al alini r l dan la all d fl i r ri in d l al alini ati n t l ti n d l irri ati n ra a t nt i r dit h ari ar i r an li t- an h alkali il f th iddl i r all ri in f r ati n and r nt han d r a ar i r all ard h rr id al lkalinit a a tra r t ti at th han ind d a f ra lti ati n in a n n alin di il ri lt ral at r ana nt arral han d l irri ati n l ffi d i r la ti n d l a l ffi d i r a rt d a ti it ra a t t d i n ali arr an t n i r i hi i ak dra i an radati n d l ar n n l nt n tritif dan l ri tr ri i l d la all d r nf r n r din - ril a ad t d d l iq d ri tr d r l ir l ita a rt d t d t art ini t r d d l nt r ral ak h tt liq la iq d a ritani li r a ara r i r it t d nir d r ltat t hni - n iq d la r d ti n ri i l irri d l itati n a ri l d d lta d fl n al n i an r i in k hn k r and l h d rri at d ri in th ah l r t f r taina l d l nt t fri a i l nt iati n ak r a t P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes rtrand ita dia a d radati n d l d ri tr irri d rand all d- ahari nn a d l ffi d i r a ali ahi r ri lt r i in il d radati n in irri ati n h in th n al i r iddl all hani hara t ri ati n th d and a t al it ati n n i an r i in k hn k r and l h d rri at d ri in th ah l r t f r taina l d l nt ak i in a r a k r a ht lari i r in r i r dri in il l ti n h i tr in a fl d d ri - r d rti l anal i f l n -ti nit rin data d r a ldin n ra n inda atri k r a tran f r a ti n in fl d d il l n d ri ati n f d l and i li ati n t a nia latili ati n il i n i t f ri a rnal l t nda ll lfi n al ati n d la it d l a lati n rfi i ll d la ati r ar la fa n d l artir d la datati n d har n t d l h in d l a l d lat l d r ant d la a tr alitr ina rai r il ad i ari r ia r n r itr n-t tal n ark d th d f il nal i art h i al th d k ri adi n rink an rr l i a h dr r hi il f r in r d r a r k lk ff rld d l f il ar n di id arth rf r r kl r radati n d l rin i a r ltat t r ti d r h r h n il an tt d n a a dia d r n l nt ra l d l ri lt r rri dan la n dan - ah li nn l t rri - akar r n t r in rand r n th infl n f ar nat in in ral di l ti n h th r d na i and kin ti f h atit di l ti n in i ar nat l ti n at = hi hi ta arit l i n a ritani ini tr d l d ati n nati nal n tit t da iq nati nal di d i - n- r n ran a an a driaan a a i ld a anal i in r lati n t il r rti in dir t- d d fl d d ri d r a n a arr r ltat d r j t ti n d l a dan l ri i r d d lta d fl n al n il an tt d n a a dia d r n l nt References ra l d l ri lt r rri dan la n dan - ah li nn l t rri - akar - n r i i an il alini ati n r in ri irri ati n h in th n al i r d lta il i n i t f ri a rnal n r i a t f n n-drain d irri at d ri r in n il alini ati n in th n al i r d lta d r a ha r in kl t alf lin ndar lin anal i and d l f l af nd tan f r f r ak-hi k r f r t i r t i n ha r a hr d ar r ir t ar r nn ati n and ri lt ral ar h nt r diat hn l li ati n nd n ha an ati n han a a it n la k t al d th d f il anal r n r n adi n hatt rj in h al aiti r ani an r a tit t f r h i al f rtili r f r hi h- i ldin ri ari ti ndian rnal f ri lt ral i n ha dhr h ad had la ati n f alin di il a aff t d h i rnal f raina and la ati n h n halk r n itr n tran f r ati n in a fl d d il in th r n and a n f ri lant itrifi ati n tr l r hha ra r l lai in ff t f ri r n in di il il i n hir n t d l iq d la han d a ritanid ntr l arall l d dj ria t l fl n al h ni r it la d rnard d n ran h r n a a ar nat h i tr and h i al r rti f an alkalin di il a aff t d ari a nd nt la in r nd nal t d li ati n l d r h dr - hi iq d la alini ati n d l a li ati n a l ri i l irri d l ffi d i r ali h l ati nal r n iq d nt lli r ran nd r arl t all ijn alini ati n alkalini ati n and difi ati n in nja aki tan hara t ri ati n f th h i al and h i al r f d radati n and rad alal ahra at r n l i n f nitrat and nitrit in th j ldahl nitr n d t r inati n f il and lant at rial in di thi l hat ni ati n in il i n and lant nal i an tt rin i a t d ri i lt r irri d la n d'int r nti n d ti it d r h r h nd it t r ltat n il P.

J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes an tt d n a a dia d r n l nt ra l d l ri lt r rri dan la n dan ah li nn l t rri - akar - q in k i kh l irri ati n ad ini tr n ti n n rt d t rrit ir irri a l l n d ar h r n l ti n d d d ri d d i i n n il an tt d n a a dia d r n l nt ra l d l ri lt r rri dan la n dan - ah li nn l t rri akar - atta rin i l and ra ti f ri r d ti n hn il and n in a r f r d l an l in art r ildin n kn l d t k f r arti i at r arnin and ti n ar h n f r d l an d ana in il rtilit in th tr i r id f r arti i at r arnin and ti n ar h al r i al n tit t t rda iall il ad aid in id n li rati n d rf r an d tit ri tr irri illa i ar la i n la d n t d inf r ati n t d i i d ratiq a ri l n il an tt d n a a dia d r n l nt ra l d l ri lt r rri dan la n dan ah li nn l t rri - akar - in k hn hara t ri in irri at d ri n ir n nt in th ri h n l d l n i an r i in k hn k r and l h d rri at d ri in th ah l r t f r taina l d l nt ak in k hn t ntial i ld f irri at d ri in th ah l n i an r i in k hn k r and l h d rri at d ri in th ah l r t f r taina l d l nt ak in k hn a l ia k h li ati d t r inant f irri at d ri rf r an in th ah l h t th r al and i r - li ati r n f fl rin ri lt ral t i ia n dia ra al ar ai t n d l n iq r al r la r nnit d l a ri lt r irri dan la nn all d fl n al rid r th atiq rri ati n t l nt r ann a t r a in fi ld ariati n f dir t- d d fl d d ri d r a r ann a lin d i nt in a l f r n- it a nt f il n tri nt l in l land ri fi ld il i r ann airh t i tri nt di rd r and n tri nt ana nt nt rnati nal i ar h n tit t a References n an r i ind i il f rtilit ana nt in irri at d ri t in th ah l and a anna r i n f t fri a r fita ilit and ri k anal i i ld r ar h r aar ff t f lant r t n h i al and i h i al r rti f rr ndin di r t il n an il i ri n dal h aj r il f th rld t r t n th ir ra h r ati n r rti and ri lt ral ni r it a nin n and ath li k ni r it it n a nin n an l il and lant ali rati n f r r r n in th id tlanti a tal lain ni ati n in il i n and lant nal i an l r tili ati n f th ndar lin a r a h in th d l nt f il n tri nt n r f r an r d ti n ni ati n in il i n and lant nal i a - n il a f th rld i d nd il ll tin d and ri lt r r ani ati n f th nit d ati n id lin f r il d ri ti n rd diti n r i d il r ana nt and n r ati n r i and and at r l nt i i i n dit alan data a htt a fa r i n ld r an nnin hl rid t t n nd d h i al il t t r d r f r th rth ntral i n rth ak ta ri tn rth ntral l i n r tin il f r h h r n t r an d il t tin and lant anal i k ri nr adi n i n in ht r tra t i h i al l f nitrifi ati n and d nitrifi ati n n l and r d d an in il i r i l l n rk ra r at n li ati n f i ld n nt anal i t r r ar h i ld r tra t r nk l r tl l r it h han -ind d di l ti n f and th r la ati n f di il il i a hi i d a in d la had ra a t d nt d l ari ran a r i rtrand ard h i al ha i r f ili a and a n i d rin th a rati n f at r in had h i al l a n h r f han ad r ti n in il n h n l tran l ill ija - in h hind ad ind r- in h ffi i n f - n- t l thi h h ri tria id in r tardin h dr l i f r a and a nia latili ati n l in a fl d d and l a il a nd d ith r ani at rial tri nt lin in r t P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes ran t r inati n f th q i al n int in t nti tri titrati n art nal t ddari h i t th r nd na iq d a rit ntin ntal t d d la atr n n an ani t d h tt l rid n ni i i n l iq ir ni r it d tra r ran a f l r d and taina l n tri nt ana nt f r irri at d ri - a d r in t in t- fri a h -th i a r ni r it a r r d nk ndli h r it n a r a f l hn n iall r i anin r d il f rtilit and d ana nt i r fita l f r irri at d ri far r in ah lian t fri a i ld r ar h a f l r i n an a i n r in th r d ti it and r fita ilit f irri at d ri r d ti n in a ritania r an rnal f r n a f l r i n an ar r r ti n ra ti and rf r an in a ah lian irri at d ri h rnal f ri ntal ri lt r l a t r na nt h dr -a ri l d r l ir t d r d l iq ini t r d tat har d d l nt r ral ak h tt liq la iq d a ritani n r h r ili n n ark d th d f il nal i art h i al th d il i n t d f ri a k ri adi n anar a riti al n ntrati n f nitr n h h r and ta i in ri lant ff t f f rtili r at art rnal f at ral i n ari ian a r i r di ti n f r id al ff t f in lfat n r th and in tak f rn lant in thr in il t t ni ati n in il i n and lant nal i h i an -ant al ati n f int rat d r ana nt ti n f r irri at d ri r d ti n in th n al i r all i ld r ar h l d la n a han and tland lant r n t il r d int n it and a a it il i il ntr d ti n n ral n il an tt d n a a dia d r n l nt ra l d l ri lt r rri dan la n dan - ah li nn l t rri - akar - il id n ad in an ara ai a n r h r h n a a n nt la r f i nnali ati n d la ti n a ann d a na nt h dr -a ri l n il an tt d n a a dia d r n l nt ra l d l ri lt r rri dan la n dan - ah li nn l t rri - akar - References r n art d l iq d r nnai an a d la a t lta t d r li inair in t d la r i n d r akar n al ind a r ll l nt f a il t t f r in ir n an an and r il i n i t f ri a rnal r l al d la a all d fl n al ll ti n t d t h ari ran ar hal n ri tr a ri l n a t - lta i d - all d r ahi r ri i n h ain arl t a han d l irri ati n n il an tt d n a a dia d r n l nt ra l d l ri lt r rri dan la n dan - ah li nn l t rri - akar - arl t ti n n r at ir d la f rtilit d l irri ati n n il an tt d n a a dia d r n l nt ra l d l ri lt r rri dan la n dan ah li nn l t rri - akar - arl t ar i r all a il alkalini ati n and irri ati n in th ah lian n f i r r n i n q n f alkalinit and di it rid il ar h and ha ilitati n arl t an ara r ilan d a t d l l h ll d ri tr l ffi d i r t -r nd d ri ntati n t d t tra a l t rri a ak atl n and l h i a t f ri r ar h in t fri a nt rnati nal nf r n n th i a t f ri r ar h an k k n t fri a i l nt iati n ak at h dd lati n f r ani att r d iti n and n tri nt r l a in a tland il n alit al ar n at h r r ff t f ri lt r n th r la ati n f di il r n rnal ikk l n itr n d t in fl d d il d f r ri r d ti n lant and il ll r- i l n rij - i l n al ati n and ntr l f th n triti nal tat f r al r ff t f a n tri nt lant and il ra han i i ith in in h at rain a aff t d nitr n f rtili ati n and a aila l il in rnal f lant triti n adl r r n i n r di al ar il r la ati n a aff t d at r h i al iti n and fl rat il i dia a n ti nn nt d na hr atiq dan l ri tr irri n il an tt d n a a dia d r n l nt ra l d l ri lt r rri dan la n dan - ah li nn l t rri - akar - P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes dia nth d tra a d la ant tt ntr la d radati n d l irri n il an tt d n a a dia d r n l nt ra l d l ri lt r rri dan la n dan - ah li nn l t rri - akar - i a rt r la ti n d la f rtilit d l r n ri i lt r irri rf r ant t d ra l a ah l n tit t d t d t d h r h ri l a ad l n t r inati n f a ni in l tra t f il th ali lat th d n il i lant nal l n r tal ar n r ani ar n and r ani att r n ark d th d f il nal i art h i al th d il i n i t f ri a k ri adi n ijan nadhira tt r trat i f r d alin ith i r n tri nt di rd r and alinit in l land ri t i ld r ar h lk an l r n n ana in in ri and n nri il a r n i q ti n n irk lk d ar n and nitr n d na i in fl d d il nf r n r din ril a hili in attnaik alli k a akri hnan dh a th nathan r a a ti it and r a h dr l i in tr i al fl d d il n lant d r lant d t ri i d ri arkh r t l r id t r i n - t r r ra f r iati n at h r a ti n n -di n i nal tran rt and in r h i al al lati n at r-r r in ti ati n r rt l i al r ar n l ran f r t han a l di nit d tat art nt f ri lt r nf r ati n ll tin nna r a h h i tr f r d il d r n nna r a r th li itin fa t r f a r i il n aj r ar h in land i nt rnati nal i ar h n tit t a hili in nna r a tra a a r f n tri nt f r tland ri n r ani att r and ri nt rnati nal i ar h n tit t a hili in nna r a artin nfl n f r d t ntial and artial r r f ar n di id n al and th n i n ff t f fl d d il il i n in i in rf r an d t ri i l irri ah li n ahi r ri lt r References in r i i a ht t r inant f irri at d ri i ld in th n al i r all r an rnal f r n adir r hi h ad l a alt-t l rant f ra lti ati n n a alin - di fi ld f r i a r d ti n and il r la ati n and radati n and l nt adir h rt haf r rta a li rati n trat i f r di il a r i and radati n and l nt an ah r h l ir nk i ant - n ah ar r r ti n and ana nt f il r ani att r - a a t d fr t fri a tri nt lin in r t a dd i lati n f nitr n d na i in fl d d il il i n ard n i n d ina fft i in t fri a f r and aft r fran d al ati n n ntri n i an r i in k hn k r and l h d rri at d ri in th ah l r t f r taina l d l nt t fri a i l nt iati n ak t d ir dd atri k itr n tran f r ati n and l in fl d d il and di nt riti al i in n ir n ntal ntr l dd n l inda atri k r a l in fl d d il ith ta li h d idi d and r d d il la r i l rtil il i hardt n hi i dj i r ial r in and d na i in irk lk d ar n and itr n na i in l d d il nt rnati nal i ar h n tit t a - t r in n tki i lant anal i n int r r tati n an al - nd diti n tralia h ad taina ilit f irri ati n n r i f alinit r l and ntr l trat i t rint f anit fl ti n n ar f at r r r d l nt nn nf an at th rid l rta anada i hard d ia n i and r nt f alin and lkali il and k a hin t n i rd r it a d ill ar a idal a ri i lt r irri n friq ah li nn r a l i i ahi r ri lt r in di al ar il r la ati n a aff t d diff r nt a nd nt and r r n rnal h t r n ta l nitrifi ati n and i ili ati n in fl d irri at d alkalin r la a aff t d nitrifi ati n inhi it r h at tra and il t t r t il ahra at lati n hi t n il r a a ti it and th r r rti f tr i al tland ri il rt P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes a adi ilk h h r tran f r ati n and th ir r lati n hi ith al ar il r rti f th rn t rn tralia il i n i t f ri a rnal a ithri r al a arajan il and r ana nt t hn l i f r nhan in ri r d ti n nd r i r n tri nt n traint tri nt lin in r t h idt h ni a nj hann in a ndar lin a r a h t anal fl data fr a ri lt ral il tri nt lin in r t n h n d nd ar r ir t ral l kn l d a ri lt ral r ar h and t n i n ra ti nt rnati nal n tit t f r n ir n nt and l nt nd n han at ari n f in il t t adj t d f r il and f rtili r h h r rtili r ar h in h d l f a nia latili ati n fr a li d r a n iti it anal i hani and a li ati n rnal f il i n i tan t hniq a r j t d r l ir ti n d r a h dra liq i i n d i nr anq ndial n l a rt r l al alinit d l d ri tr d l ita r ntati n l at li r d n i ili ati n r l r l d d radati n d l l ita i t ati nal r l l nt ral ak h tt a ritania n l t in r in far r kn l d f il in akin r ar h r lt r r l ant t fi ld ra ti ri n fr anda ri lt r t and n ir n nt ar h ad h a ar nt l ilit f al i ar nat in il il i a l r t f il alinit f r th t nt r th rld n r f il i n a l l ian ai a i a t r aff tin a nia latili ati n fr a ri - h at r tati n t h h r ra r ri n d l n arr d li r r l r d ti it t r d ti n n ri i lt r irri dan la all d r rkina a alt rnati t r ti a rt d nth r l at li r t n ia an d a ar n tit t ati nal d h r h ri l a ad rkina a t d d l iq d la all d r l ir ntr i a t l nt a- a t d r la i n al r d a in d r l a rt t hniq r ak h tt all dia rnada ard h i tr f at r in th r ari i n ali l i and in at r n ntrat d a rati n l nt f a d l rid il ar h and ha ilitati n References all a h k n k n ariant rit ria f r irri ati n at r q alit a nt in arid and i-arid r i n n n i and ntr l f rtilit f alt ff t d il i i n n alt ff t d il i n k ha il n it t an i h n-i ni nitr n n triti n f lant n tri nt tak and a i ilati n and r t n tr i n d rin tili ati n f r a r i ti all fi d nitr n h -th i a nin n ni r it h th rland an r n ff t f r d r n il a idit th ri i ldh i n at r - a r a ir hn n h n ar r r ar h in ra ti n fr th fi ld diat hn l li ati n nd n ill a - an a lar fr a r nt f d iti n and a iat d n tri nt r l a fr tra z f diff r nt ri ari ti in a rf i n t lant and il alkl la k n a inati n f th tjar ff th d f r d t r inin il r ani att r and a r d difi ati n f th hr i a id titrati n th d il i n al rth t h r f ndar lin in ta li hin dia n ti n r il i n i t f ri a rnal nn al rt t fri a i l nt iati n ak r a t f th ndar lin in th anal i f i l i al data rnal f rti lt ral i n itt r ann d lra h an in an h a arajan ata atanan nt ran h n ha an an i i ahan lk nt rnal n tri nt ffi i n i f irri at d l land ri in tr i al and tr i al ia i ld r ar h itt ik r ali ia tt na i f il i r ial i a and nitr n a aila ilit in a fl d d ri il a nd d ith diff r nt and r i l rtil il r i n i in ia an r r in il q alit nd r irri ati n in th n al i r all th ri i r i n an i ind ia il f rtilit ana nt in irri at d ri t in th ah l and a anna r i n f t fri a art r n i anal i i ld r ar h n a a hida iti n f ri r id in tr i al il il i n and lant triti n hida nda ntal f ri r i n nt rnati nal i ar h n tit t a P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes hida rn k a rat r an al f r h i l i al t di f ri diti n nt rnati nal i ar h n tit t a hili in ah rh in la ati n f alin di il in nth ti l r and il i Summary n th ah l irri at d ri r in ha n intr d d n a lar - al in th and aft r dr ht d a tat d r and li t k h a i in t nt in irri ati n infra tr t r r ant t i r f d rit hil n ratin in f r th l al far r rth r r ri d and in th ah l a ra idl r in d t a t ad in r a f th r an lati n h r d ti n f ri in ah lian ntri ld d r a th n d f r n i i rt h irri ati n h r n tr t d al n th aj r ah lian ri r and th ir tri tari n n ral irri ati n at r i a ndantl a aila l al n th ri r and th dr and nn li at all hi h t ntial i ld in th dr and t a n i t n and t ha ith ak t t ha r a t al i ld ar t n - t ha and r in int n it i ft n l ral r ar h r h d that a ri f i - n i n traint l d t - ti al r - and land ana nt ith l f rtili r d and lat ti in f f rtili r a li ati n and din a aj r i ld li itin fa t r n irri ati n h i ld tart d t d lin t l l l t ha nl a f ar aft r n tr ti n f th h th far r and r ar h r f ar d that thi i ld d lin a d t an a lati n f alkalin alt lth h t ah lian irri ati n at r ntain littl alt th ntain r lati lar a nt f i ar nat l i and ntin n ntrati n f h at r an l ad t th f r ati n f an alkalin hi h and di hi h di nt nt il h a il ha a l a ri lt ral t ntial and r la ati n f alkalin - di il i ft n ti - n in and n i n th arl th fir t i n f alkalini ati n r r rt d fr th ah l ld t irri ati n h in ali and alt ffl r n r r d in th r ah lian h n th id th d nari f h an-ind d d radati n f th ah l t r i land ra idl ain d larit a n t i nti t and t n i n rk r a ti in th r i n n thi nt t initiat d r ar h t in ti at th a f d linin i ld and th t ntial dan r f il alkalini ati n h r lt f thi r ar h f r th a i f thi th i n ha t r and in ti at d th a f d linin i ld in th irri ati n h f l ita in a ritania and th r all in rkina a n th h i ld had dr d fr ar nd - t ha t ar nd - t ha - ar aft r n tr ti n t th it r ani d tin ith far r t di i l a and l ti n f r th ri r d ti it r l lt f th tin r d t t far r r far r- ana d trial and r ar h r ana d trial n l ita l i ld r a d and d fi i n i ld r l t n th r and iddl l h r il ar hall ar r la ifi d th il a d rad d lth h th d rad d il r r alkalin and alin than il f rth r d n l and al r n rall t l t la if th il a alin r di f ll in int rnati nal la ifi ati n and d fi i n n th d rad d il r a d l il l l il l a i nal l P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes f rtili r d and n t a l in f f rtili r h alkalin - al ar nat r f th d rad d il lik l ntri t d t l a aila ilit thr h latili ati n and l a aila ilit thr h ad r ti n n r r i itati n f ar nat in ral n th r all i ld d lin in id d ith th a aran f l r d ti t h t r a d n d fi i n d t th il l tra ta l n nt nt th alkalin - al ar hara t r f th il and th n n a li ati n f n f rtili r in inati n ith a r lati l lar f rtili r d n d fi i n i a kn n r l n alkalin - al ar ri il d t th il hi h ar nat n ntrati n n th ah l an ri il ha an alkalin - al ar hara t r and thi t d i n f th fir t t h that n d fi i n an a ri r in n traint in ah lian irri ati n h ar r r ana nt in th l ita and in th r all n rall d iat d hat fr l al r ndati n r n t l in t th l al r ndati n a n t th ain a f r l i ld ath r th inad q a f th l al r ndati n i all f rtili r d and r f rtili r d r ndati n in l ita and r n f rtili r d r ndati n in th r all ntri t d t t th r d r d ti it r l th in l ita and in th r all i ld ld a il in r a d fr ar nd - t ha t - t ha thr h a li ati n f a l and n f rtili r r th r nd d f rtili r d ar ith r r tl r th f rtili r i n t ffi i ntl a aila l n th l al ark t h r f r t t d th a li ati n f r ani a nd nt at a rat f t ha dr att r a a an t i r il f rtilit n th r all d d r ani a nd nt in r a d i ld - t ha f nd that th a li ati n f d d ri tra in far r fi ld in r a d th i ld and lant n tak t n n ntrati n r ain d r l hi indi at that n d fi i n a n t f ll radi at d h iti ff t f r ani att r a li ati n n n tak i ht r lat d t in r a d di l ti n f ar nat - nd n n r a d di l ti n f nati ar nat alt n a li ati n f r ani att r a r d in a al ar alkalin il f l ita ha t r r r r ar h ill n d d n th hani that ntr l n a aila ilit a t tal n nt nt f th - r t n i r ti lar r than th q antit a li d ith k n f rtili r ha and r ti lar r than th - tra ta l n nt nt n ha t r l r a in d th ff t f fr h tra a nd nt n i ld and and a aila ilit in l ita li ati n f t fr h tra ha in r a d i ld n a ra t ha ind nd nt f il t r a li d in ral f rtili r nl if i ld r l t t ntial tra did n t ha an ff t n i ld h iti ff t f tra a attri t d t i r d a aila ilit t f nd n id n f i r d a aila ilit a d n a fi ld and t trial n l d d that th i r d a aila ilit a d t in rali d fr th tra t in r a d in rali ati n f il r ani att r ith a l rati and t in r a d r r ffi i n f Summary a li d in ral f rtili r r a h th i d that i r d f rtili r r r n tra a li ati n a d t r d d nitrifi ati n-d nitrifi ati n l n n ral n l d that i r d r ani att r ana nt an tantiall i r i ld hil aintainin f rtili r t at an a ta l l l r i r d in ral f rtili r ana nt ill r ain n ar f r an far r in l ita and th r all a i n tri nt l n a till f rth r d l t d d it r ani att r a nd nt ii far r a find th in r rati n f r ani a nd nt t la r int n i and iii r ani att r r fr h tra a d a attl f dd r r ill d t f rtili th r r ta l n ha t r in ti at d a t al and t ntial alt-r lat d il d radati n in l ita h irri ati n at r in l ita i n f th t alkalin n d in th ah l n if alkalini ati n in ah lian irri at d ri h i an n in r ld t th hi h t alkalini ati n rat in l ita h th l ita irri ati n h ld a t a an arl arnin t f r hat i ht ha n in th r ah lian h at a lat r ta n ha t r alr ad n l d d that hi h r n ntrati n f alkalin alt n th d rad d il lik l ntri t d t l a aila ilit f and n ha t r tri d t lain h th alt r di tri t d and h r th ri inat d fr tail d a lin f il in a l n t q n in d ith il it and r nd at r anal i r al d that th d rad d il hi h ar f nd n th r ti n f th t q n ri inat fr th hi t ar nt r k that an f nd at hall d th il f rth r d n l ar thi k r and n i t artl f all ial d it nn al fl d l a h th l r l in il and r nt a ild f alkalin alt ithin th t q n lar ariati n in il alinit and alkalinit r at h rt di tan indi atin ini h ri ntal r nd at r fl and a tr n ariati n in th h i al iti n f th rti all iti n d dr k h di tri ti n f th alt did n t t r lat d t th r n f irri ati n and draina anal n f nd n id n that rt th h th i that irri ati n a ti iti in r a d il alkalinit rth r r a ari n f hi t ri al data r al d n i nifi ant han f t il alinit and r th la t ar n l d d that rr nt alkalinit r l in l ita r inh rit d fr th ar nt r k and r n t th r lt f h an-ind d alkalini ati n d th d l t i lat i n ntratin f th irri ati n at r a tran irati n h d l nt r ti int a tr n l di -alkalin l ti n did n t a r ith fi ld data hi h h d h i al ntr l f alkalinit at hi h l ti n n ntrati n nl h n ati n han r r in l d d i lat d han ith r ard t a and lkalinit f th il l ti n a r d ith fi ld data h t a r nt ith fi ld data a tain d h n d lin ith a all l dr il t al i at rat d h d l i lati n r al d that th il a a it t nt ra t alkalini ati n i r lar th h n t infinit h ari n f hi t ri al il data th d tail d t q n t d and th i lati n d lin r i all t that ra id alkalini ati n i n t t t d in irri at d ri fi ld in l ita P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes n ha t r t di d th ff t f irri at d ri r in and r ani att r ana nt n t f th t alkalin - di ri il in th ah l a d rad d il fr l ita and an alkalin - di il fr th ffi d i r ali h il r d t fill il l n ith tr at nt ith and ith t ri in ral f rtili r and ri tra a nd nt h l n t t r nd t d at th r ar h tati n in n al in n n- alin ar nat -ri h irri ati n at r t i al f r th ah l r lati n a artifi iall aintain d at da l t at r and alkalinit alan r ta li h d f r all l n and ar d t il anal i f r and aft r n ri r in a n r all tr at nt il had t rn d fr di t n n- di and had dra ati all d r a d t n ta l n ar th il rfa h han r lar t in th ffi d i r il d t it all ff rin a a it littl a and all h lar d r a in di it and alkalinit a ainl th r lt f l a hin ith n n- alin at r r t n r ti n lant a nt d f r - f th alkalinit l r r r t n r ti n q al d r d d alkalinit add d ia irri ati n in a r - r lati n nari hi an that r al f tra and rain ld r nt f rth r alkalini ati n f th il if r lati n i a nt r r al f tra i tl n t r nd d a a h n in ha t r and rth r r in th l ita il tra a li ati n l d t th di l ti n f nati al it d t an in r a in h di l ti n f al it in r a d a f th il l ti n and nhan d d r ti n f han a l a hi r r lt d in an a l rat d d -alkalini ati n and d - di ati n f th il h r d ti n f ir n h dr id ld th r ti all a l rat d -alkalini ati n f th r il la r r f nd n id n t indi at that f rr l i alt r d th h rt-t r alkalinit alan f th t di d il t an t nt r r lt ar in lin ith r nt fi ld t di and t a d -alkalini ati n f di -alkalin fl d d ri il in th ah l h d that th all i ld r d in f th ah lian irri ati n h r r lat d t inad q at r itt d a li ati n f in ral f rtili r n l r r f a li d f rtili r and l lant a aila l n tri nt nt nt in th il n in ral f rtili r ar tl r n t a aila l n th l al ark t an far r ill n t a l t ad t i r d in ral f rtili r r ndati n r d r ani att r ana nt i n f th f an f r far r t i r th ir i ld ith t tantiall in r a in t r ani a nd nt f t ha an in r a i ld - t ha lant a aila l n tri nt nt nt in th il n r ft n r lat d t th r n f ar nat alt r t il ld n ith r la ifi d alin n r di rth r r th alkalin alt r in th t di d il f r irri at d ri a intr d d nd r tandard nditi n f lti ati n irri at d ri far r in th ah l d n t ha t anti i at ra id alkalini ati n f th ir ri fi ld n th ntrar r id d th r i nat ral draina ri r in an d t r lai th rr nt alkalin - di il in th ah l r ani att r a nd nt an a l rat th r la ati n f alkalin - di il that ntain nati al it Samenvatting rri rd rij t i r t haal ntr d rd in d ah l in d jar n nti n ta hti al r a ti d dr t di ta l n t n hadd n r t r t in t rin n in irri ati -infra tr t r hadd n al d l d d l k rh id t rh n n d r n ink t lijkh d n t i d n rd r na d raa naar n i rt an rij t taa t d r d r i an d t d lijk lkin inn nland r d ti an rij t d d r i rt an rij t d n r ind r n irri ati h a rd n t na aan l d lan d r t ri i r n n h n ijar n i r i ld nd at r n h t dr nni kli aat arand rt h t ntil r n t n - t ha t it hi t r t t t ha in h t dr n natt i n h idi rij t t n dra n ht r n t t t ha n l land in d irri ati h a rdt ni t f ini n t r h id n nd r k r h n aan t nd dat d t n all nd r n t n h t l ijn an ti aal land- n a h r t na r kki tin - n nkr id trijdin t hni k n n n ti iaal n i h tandi h d n li n ht r aan d a i an d r l ati k n r hill nd irri ati h a daald d a r n t lf t t nd r d t ha nk l jar n na in r ikna l r n al nd r k r r d n dat d afna h t l a an n h in an alkali h t n lh l h t t irri ati at r in d ah l ini t at i dit at r r lati f rijk aan i ar naat l rtd r nd inda in n ntrati an lk at r kan l id n t t d r in an n alkali h natri d i n d t n it i l aar natri halt an n d n t n a i h it t d h ft n laa land t nti l n h t h r t ll n r an i ka itaalint n i f n tijdr nd n h t in an d jar n n nti rd n in ali d r t t k n n an d r in an alkali h natri d i alkalini ati aar n n in h t d t r t hali irri ati h a an d ah l d r nd d idd n jar n n nti raakt n r n r nd r k r n land rli ht r r an rt i d dat d d r n n r r aakt r an d d radati n r ijd lijk a t a in dit kad r dat h t t frikaan ij t nd r k in tit t nd r k rri htt naar d r ak n an d t r l n n d lijk ar n an d nh in an alkali h t n in d d r ltat n an dit nd r k r n d a i an dit r f hrift n fd t k n rd n d r ak n an d afn nd rij t r n t n in t irri ati h a in d ah l d r all i in rkina a n l ita in a ritani t d rd n ijf t t ti n jaar na d aanl an id irri ati h a daald n d a r n t n an t ha naar t ha lijk r ak n an d la a r n t t id ntifi r n r ani rd n ij nk t n t d tr kk n r n r ltat n an d ij nk t n r ikt n al l idraad r h t tt n an nq t n r n in r n ld n i an d r n rd n d r r n h rd n and r n d r nd r k r P.
J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes la r n t n in l ita lijk n h t l t ijn an tik t f n f f r r k laa t r n t n rd n t n ndi d nin d t q nti r n la ifi rd n d d al d rad rd lh l d d rad rd d r alkali h t n lijk n t att n dan la r l n r nd n k nn n ni t al t - f natri d rd n la ifi rd l n int rnati nal tandaard n t n tat rd r k aan n in d lant rdt r r aakt d rdat d d ini n l rt d k n t t ift laa i n r n k n t t rdt t di nd kalkrijk alkali h aard an d d rad rd d draa t aar hijnlijk ij aan n la hik aarh id d r latili ati n n la hik aarh id d r ad r ti aan f r i itati an ar naat t n n d r all i rd n d afn nd t n r r aakt d r d nt ikk lin an l kk n an l ht rij t r i in d ld n n nd r k t nt aan dat d l kk n h t l ijn an ink n r k in d rij t lant r aak an h t n r k h dt r and t h t rin halt aan - trah r aar n n d kalkrijk alkali h aard an d d in inati t h t nt r k n an n k n t t ift n n r lati f r t k n t t ift n n r k in rij tt lt kalkrijk d i n k nd r hijn l n i h t l an d h ar naat n ntrati in d d l an d aar rij t rdt t ld in d ah l ijn kalkrijk it i d r t t di di aant nt dat n r k n ri l rin r d rij tt lt in d ah l kan r n t a h r d r d r n in l ita n in d r all i k tal ni in af an d ad i n an d l kal land rli ht r it a ht r ni t d lan rijk t r aak an d rin a r n t n rd n t na r r aakt d r d n hikth id an d l kal ad i n al t la ad i n n n nt r k nd ad i in l ita n d af i h id an n n ad i in d r all i l in l ita al in d r all i na d a r n t t an t ha naar t ha ann r ld nd n f n k n t t rd t di nd aan l n k n t th lh d n ijn ht r d r f ni t hik aar d l kal arkt n aar h n tra ht d d r ht aarh id t r t r n t h l an r ani h t f ift n an t dr t f ha n d r all i r lt rd d t di nin an d t rd r ani h at riaal in n r n t rh in an t ha ltat n an r n ld n t n n aan dat hi r ij d n na d r d lant t na aar dat n n ntrati in d lant r laa l n at t k nt dat h t n r k ni t ll di rd h n t iti ff t an r ani h t f ift n n na i aar hijnlijk r lat rd aan h t rijk n an ar naat- nd n n t l n an ar naat t n al l an r ani h t f t di nin rdt nad r r k n in fd t k r i ht r r nd r k n di naar d hani n di d n hik aarh id in d d al n aan i n d t tal h lh id n in d rt l n - r Samenvatting dan k r r t r i dan d h lh id n t di nd in n k ha n k n t t ift n r dan k r r t r i dan h t - trah r ar n halt di nin an t r tr ha d rad rd n ni t- d rad rd d in l ita rh d d rij t r n t idd ld t t ha nafhank lijk an d a n t llin n d r tt an d k n t t ift fd t k l ht ann r d a r n t ijn t nti l nad rd had tr t di nin n r n t rh nd ff t t iti ff t an tr rdt t di ht aan n r t rd hik aarh id nd n n d id lijk aan ij in n dat tr t di nin d hik aarh id rh t it d r ltat n an ld- n t r n n l d r n dat d r t rd hik aarh id h t l a an in rali ati an tr - in rali ati an d - d r n la rh din in d d n n r t rd na an k n t t- d r d lant r nd r t ll n dat d r t rd k n t t- na rd r r aakt d r n afna an nitrifi ati d nitrifi ati rli n n n al nh id n l d r n dat n r t rd h r an r ani h t f kan l id n t t n d id lijk rh in an d a r n t t r ijl d k t n r k n t t n aan aard aar ni a k nn n lij n n r t rin an h t k n t t h r lijft ht r n d ak lijk r r n in l ita n d r all i dat i i n trint n rrad n n in d d ndank t di nin an r ani h t f rd r k nn n rd n it t ii h t t di n n an r ani h t f t ar id int n i f i n iii r ani h t f r nn n k r and r d l ind n rd n in t tr al di r d r f t al t t f in d t in n fd t k h n d a t l n t ntil d d radati d r alkali h t n t d rd in l ita t irri ati at r an l ita h rt t t h t t alkali h an d ah l ndi n r rak i an h in an alkali h t n in d rij t-irri ati h a an d ah l dan i h t t r a ht n dat dit r r lati f n l rl t in l ita t l ita irri ati h a kan d f n r n al alar t r alkalini ati aar ld r in d ah l n fd t k n l d rd n al dat d rin n hik aarh id r d lant d d rad rd d d rd r r aakt d r h n ntrati alkali h t n n fd t k r k n d r r n n rafi h di tri ti an d t n it d - n r nd at r n t r an n lan t q nti lijkt dat d alkali h t n in d d rad rd d nin d t q nti afk ti ijn an h t hi t d r at riaal t hi t indt i h rin di t a r l n d ijn di r n taan it d l all ial af ttin n aarlijk r tr in an d d r d aanl an h t irri ati h a rk a n a lati an alkali h t n all nd ijn d r t r hill n in t halt n alkalinit it an d d k rt af tand in d t q nti it d idt n rin h ri ntal r nd at r tr in n n r t ariati in d a n t llin an h t rti aal t ld d r at riaal rafi h rd lin an d t n lijkt ni t r lat rd t ijn aan d aan i h id an irri ati - f draina kanal n nd n d n ij r d h th dat irri ati l idt t t n h in an alkali h P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes t n in d d n l i rdt nd r t nd d r n hi t ri h r lijkin an d t di in l ita d n h t t halt in d rt l n ijn in d af l n jaar ni t i nifi ant t n n i r it n l d r n dat d h idi alkalinit it - r l n in l ita rd n r r aakt d r h t d r at riaal n ni t d r t h in al l an irri ati a ti it it n n it raak t k nn n d n r h t t ntil aar an alkalini ati in d t k t h n r ik aakt an h t h i h d l i r i l rd n d i rda in an irri ati at r d r d i lati r ld l ti t t n t rk alkali h n natri rijk at r k a ni t r n t ld n aar alkalinit it ij h t n ntrati h i h rdt ntr l rd t in an kati n- i l r n in h t d l l idd t t n l t r r n t in t n i lati n ld n t r n t in rd haald t n kl in l dr d aar al i r adi d kati n- i l l d l i lati t n n aan dat d d in l ita n r r t aar ni t n indi ff r a a it it h n t n alkalini ati r ltat n an fd t k n aan dat n n ll alkalini ati an rri rd rij t ld n in l ita ni t aar hijnlijk i n fd t k t d r n h t ff t an rri rd rij t n r ani h t f h r d alkalinit it an t an d t alkali h natri d in d ah l l n t hand lin n arir nd t f nd r rij t k n t t ift n f tr t di nin rd n af i l nd ld t r nd an n d rad rd d it l ita n n alkali h natri d it d ffi d i r in ali k l r n nd n laat h t nd r k tati n in n al t irri ati at r dat rd r ikt r d r n a t i h r d ah l h t att ini t aar a r lati f ar naatrijk r lati n lh id rd handhaafd - da l t at r- n alkalinit it alan n rd n t ld r all k l n n r l k n t d n t r an r n na h t r i i n n all hand lin n na d n h t it i l aar natri r nta r t rk af t na nin d k l n r t t rand rin n nd n laat in d ffi d i r d d r ijn rin ff r a a it it ini a n la r t afna in n alkalinit it rd t na r r aakt d r h t l n an d d t at r t n laa t halt r t n it h idin d r lant n dr ij aan h t alkalinit it rli r rin a lijk aan f r t r dan d alkalinit it di d r irri ati at r rd t d in n nari nd r r lati it t k nt dat ann r rij t raan n - tr an d ld n rdt r ijd rt d h in an alkali h t n in d d d r inda in an irri ati at r rdt rk n lf ann r r n r lati laat indt ht r i n d iti ff t n d a r n t rdt r ijd rin an tr ni t aan rad n i fd t kk n n k l r n t n n rd r aan dat in l ita tr t di nin r lt rd in n t na an d i k l r a dr k at l idd t t n r t rkt l in an kalk i rd r na d a n ntrati in d d l in t it r t rkt d ad r ti an a aan h t kati n i l l t n k t an it i l aar a it r draa t ij aan n Samenvatting r n ld afna an d d alkalinit it n n th ri kan d r d ti an ij rh dr id l id n t t f rr l aard r d r rin an d n t d la n rdt r n ld n d h idi r f t nd n ht r n ij dat f rr l d alkalinit it alan k rt t r ijn kan n l d n n r ltat n ijn in r n t in t r nt ld t di n r r n dat d rri rd rij tt lt l idt t t n rla in an d d alkalinit it n an alkali h natri d in d ah l n n nd r k h n aan t nd dat la rij t r n t n in d ah l t ijt n ijn aan inad q at k n t t ift n n n r lati f rin na d r d lant an n tri nt n it k n t t n n r d lant n rin hik aarh id an n trint n n in d d l r n ll n d h r i n k n t tad i n ni t k nn n l n dat d n di d k n t t t d r f ni t in ld nd at hik aar i d l kal arkt n n t r r ani h t f h r i daar n an d ini lijkh d n d a r n t n t rh n nd r n r t rh in an d k n t tk t n r ani h t f ift n an t ha rh n d rij t t t - t ha rin hik aarh id an n tri nt n in d d lijkt aak r lat rd t ijn aan d aan i h id an ar naat t n t d in d t di k nn n ht r ni t al t - f natri d rd n la ifi rd ar naat t n ar n r d in d d aan i rdat d rri rd rij tt lt rd ntr d rd ij t r n in d ah l h n nd r tandaard t lt tandi h d n dan k n n ll alkalini ati an h n d t r a ht n n t nd l d rij tt lt kan rd n r ikt r h t r t r n an alkali h natri r nd n in d ah l aan n n dat ni nat rlijk draina lijk i n d di an ri in al i t att n k nn n r ani h t f ift n dit r n r n ll n Rsum a lt r irri d ri f t intr d it rand h ll a ah l dan l ann t a r q d h r r r nt d a t l lt r t l tail in ti nt a if dan l infra tr t r d'irri ati n a ai nt r t l'a li rati n d la rit ali ntair t t n n rant n r n r l f r i r l al nt l la d and d ri a ntait ti l ar la r i an r li r d la lati n r ain a r d ti n d ri dan l a ah li n tait n r d ir l r r d i rtati n t ri tr irri f r nt n tr it l l n d rin i a r d a ah li n t d l r affl nt ani r n ral l' a n air l'irri ati n t a ndant l l n d ri i r t l li at t n l ill r t d t nir d ha t r nd nt t nti l a i i n n ai n h q ' n ai n h id allant d t ha a d r rd allant j q ' t ha ndant l r nd nt r l ari nt ntr t t ha t l int n it lt ral t nt fai l l i r r h r h nt r l q d n r ntraint i n iq ntranai nt n ti n n n ti al d la lt r t d la t rr d fai l d d f rtili ant t n r tard d'a li ati n d n rai t d ar la tant l rin i al ntraint liq ant d r nd nt li it r rtain ri tr irri l r nd nt nt n ai r d ni a inf ri r t ha q lq ann l nt a r la n tr ti n d ri tr ri lt r t h r h r rai nai nt q tt ai n it d n a lati n d l al alin i n q l a d'irri ati n a ah l nti nn nt d l ll r nt nt d q antit r lati nt i rtant d i ar nat l n n ntrati n i t ntin d t ll a t ntran r la f r ati n d l al alin l t diq ha t t n r n di t l l nt n fai l t nti l a ri l t l r r ha ilitati n t nt t t d and a d t d t d ann l r i r i n d'al alini ati n tai nt ra rt r l l an i n ri tr irri d ah l a ali t d ffl r n d l tai nt r r d'a tr ri tr irri ah li n ili d ann l nari ata tr h d la d radati n d la t rr la l r i d ah l r q ar l a ti n d l'h d int ra id nt lair ar i l i ntifiq t l a nt d l ari ati n a ri l n a ti it dan la r i n ' t dan nt t q l' n an lai a lan n r h r h dan l t d' t di r l a d ai d r nd nt t l dan r t nti l d l'al alini ati n d l r ltat d tt r h r h n tit nt la tan d tt th an l ha itr t n a n t di l a d ai d r nd nt r l ri tr irri d l ita n a ritani t d la all d r a rkina a r l d ri tr l r nd nt nt h t d' n ir n - t ha - t ha inq di an a r l r r ati n r l d it n a n r ani d r ni n a l a ri lt r r di t r d a i l t d l ti n a r l d r d ti it d ri r ltat d r ni n f r nt tili r ta lir n i i d a ri lt r t n r d ai rtain r ar l lti at r rtain ar l h r h r P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes l ita l fai l r nd nt tai nt d n d fi it n l nt t r nd nt l l fai l tr ai nt n ha t d nt i- nt l l nt r f nd a ri lt r nt la l d rad i n q l d rad f nt l al alin t alin q d l it l a l al r d nd ti it l triq t r nta d di han a l tai nt n ral nt tr fai l r n id r r l alin diq l n la la ifi ati n int rnati nal 'in ffi an d t dan l l d rad tait a ar n fai l a r i i nn nt d l n t n n fai l a li ati n d n rai t n a n d a li ati n d n rai a nat r al alin al air d l d rad ntri ait r a l nt n fai l di ni ilit n ar latili ati n t n fai l di ni ilit n ar ad r ti n r i itati n d in ra ar nat an la all d r l d lin d r nd nt a n id a l'a ariti n d n d fai l r d ti it i r ltait d n in ffi an d n ll - d la fai l t n r d l n tra ti l a ara t r al alin- al air d l t la n n a li ati n d n rai n in a n d r lati nt f rt d n rai a ar n n n t n r l nn r l l ri i l al alin - al air a d f rt n ntrati n n ar nat d l ah l n tr fr q nt d l ri i l r ntant n ara t r al alin - al air ai tt t d t l' n d r i r ntr r q l anq d n t n tit r n i rtant ntraint lt ral r l ri tr irri ah li n l ita dan la all d r la ti n d lt r ar l lti at r a q lq d i d r andati n l al ndant l fait d n a nf r r a r andati n l al n n tit ait a la a rin i al d fai l r nd nt ' t a ntrair l fait q l r andati n l al n tai nt a ada t d tit d d f rtili ant t a n d d l ita t a n a li ati n d n dan la all d r q i ntri ai nt l l a r l d r d ti it r l ita t dan la all d r l r nd nt rrai nt ai nt a r d - t ha t ha r n a li ati n ffi ant d f rtili ant t n ndant it l d r and d f rtili ant nt tr t it l f rtili ant n' t a r ll nt di ni l r l ar h l a ar n q nt n a n t t l'a li ati n d a nd nt r aniq n ta d t ha d ati r h r t nt r d'a li r r la f rtilit d l an la all d r l a li ati n d a nd nt r aniq d a ntran n a ntati n d r nd nt d l rdr d - t ha a n tr q l'a li ati n d aill d ri d dan ha a a nt l r nd nt ain i q l a i ilati n d n ar l lant ai l n ntrati n n n r tai nt fai l i indiq q l'in ffi an n n n' tait a t tal nt r l ' ff t itif d l'a li ati n d ati r r aniq r l a i ilati n d n rrait a ir n Rsum li n a l'a ntati n d la di l ti n d n a i a l ar nat 'a ntati n d la di l ti n d l ar nat nat r l ar a li ati n d ati r r aniq f t r r n l al air d l ita ha itr t d l ntair nt n air r ara t ri r l ani q i liq nt rq i la art d n di ni l r la t n r t tal n n d la n ra inair - t l d f i ri r la q antit a liq a k d f rtili ant n ar ha t l d f i ri r la t n r n n tra ti l ha itr n a n a in l n d tail l' ff t d a nd nt d aill fra h r l r nd nt ain i q la r n d t d l ita 'a li ati n d t nn d aill fra h ar ha a r i n a r i nt d r nd nt d t ha n nn ind nda nt d t d l d l n rai in ral tili ff t d la aill tait n l niq nt l r q l r nd nt tai nt r h d t nti l ' ff t itif d la aill f t attri l'a li rati n d la di ni ilit d ai n n'a n tr a n r d'a li rati n d la di ni ilit d artir d n ai n ha t n t n a n n l q l'a li rati n d la r n d tait d la in rali ati n d nt n dan la aill l'a ntati n d la in rali ati n d la ati r r aniq d l a n fai l ta t l'a ntati n d ta d r r nt d l n rai a t r a n i l'h th l n laq ll l'a li rati n d ta d r r nt d l n rai a t ar a li ati n d aill tait d la di in ti n d rt ar nitrifi ati n-d nitrifi ati n n n ral n n l n q ' n ill r ti n d la ati r r aniq t a li r r l r nd nt d fa n n i l t t n aint nant l t d n rai n ni a a ta l ndant n ill r ti n d n rai in ra ra t j r n air r d n r a an l ita t dan la all d r ar i d r r d rtain l nt n tritif n nt ntin r i r n d it d a nd nt d ati r r aniq ii l a an nt n id r r q l a li ati n d a nd nt r aniq l r d and tr d tra ail t iii rtain r d ati r r aniq la aill fra h nt tr tili f rra r l tail r r la f rtili ati n d'a tr lt r t ll q l l ha itr n a n t di la d radati n ff ti t t nti ll d l ar alini ati n l ita ' a d'irri ati n l ita t l' n d a l l al alin tili a ah l ar n q nt i l'al alini ati n d ri tr ri i l d ah l t n r ntin n d ri n n att ndr a ta d'al alini ati n l l l l ita i nf r rait a ri tr irri d l ita n f n ti n d t d r -al rt a r ard d q i rrait arri r l a nir a a tr ri tr ah li n ha itr n a i n d j n l q d l f rt n ntrati n d l al alin r l l d rad ntri ai nt tr r a l nt la fai l di ni ilit d t d ha itr n a n a d' liq r nt l tai nt r arti t q ll tait l r ri in hantill n d taill d l l l n d n t q n d tr l a d f d l iq t d anal d l' a t rrain nt r l q l l d rad q i ai nt la P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes arti ri r d la t q n r nai nt d la r h r n hi t it d fai l r f nd r l it l a dan la t q n nt l ai t f r n arti d d t d'all i n r ann ll l i nt l l l l a t h nt l a lati n d l al alin a t q n tait arq ar d'i rtant ariati n d alinit t d'al alinit d l r d int r h q i r l la fai l d l nt h ri nta d a t rrain t n f rt ariati n dan la iti n hi iq d trat r h di rti al nt a r n d l n lait a tr li ll d ana d'irri ati n t d draina ar n q nt n n'a n a tr d r q i rr r l'h th l n laq ll la ratiq d l irri ati n a nt rait l'al alinit d l l n arai n d n d nn a d d nn an i nn n'a r l a n han nt i nifi atif d la alinit d la n ra inair - t d a r d d rni r ann n a n n l q l r l a t l d'al alinit l ita r nai nt d la r h - r t n n d n al alini ati n r q ar l'h a n tili l d l r i l r n n ntrati n i d l' a d'irri ati n ar a tran irati n a tran f r ati n a l t n n l ti n f rt nt diq t al alin n' tait a nf r a d nn d t rrain q i r lai nt n ntr l hi iq d l'al alinit dan d l ti n f rt n ntrati n n t q n fai ant int r nir d r d han d ati n q l r ltat d d l n rnant l i n a t l'al alinit d la l ti n d l f r nt ati l a l d nn d t rrain a ill r rr ndan a l d nn d t rrain f t t n a n fai l l d l ai at r n al i i lati n ff t r a d l nt ntr q la a a it d l ntr r l'al alini ati n tait tr f rt i n q n n infini a arai n a l d nn d l iq l' t d d taill d la t q n t l i lati n r nt t q n al alini ati n ra id d l irri d l ita n t a r a l ha itr n a n t di l' ff t d la lt r d ri irri t d la ti n d la ati r r aniq r d d l l l al alin - diq d ah l n l d rad d l ita t n l al alin - diq d l' ffi d i r ali l f r nt tili r nf ti nn r d l nn d l a d trait nt diff r n i a an ri a an n rai in ral t a an a nd nt d aill d ri t t n l nn f r nt nd it la tati n d r h r h d l' a n al ' a tili tait a r n l t ri h n ar nat q i t t iq d a d'irri ati n a ah l a r lati n tait aint n d fa n artifi i ll - ar j r ilan l t d l' a t d'al alinit f r nt ta li r t t l l nn ilan d al alinit f r nt ar a d anal d l a ant t a r l ai r t l trait nt l l diq nt d n n n diq t l a ait n id ra l nt di in arti li r nt r d la rfa han nt tai nt l i rtant r l l d l' ffi d i r a d a fai l a a it ta n d a t fai l a f rt ai d di it t d al alinit tait rin i al nt d a l i a ar n a n n alin a ntri ti n d l' r ti n d r t n ar l lant dan la Rsum di in ti n d l'al alinit ' l ait - n tr l' r ti n d r t n n ait a ini ai tait nt ri r n al r a l a r r t d'al alinit a rt ar l a d'irri ati n dan n nari an r lati n la i nifi q l r trait d la aill t d rain h rait la r it d l al alini ati n d l n a d'a n d r lati n t f i l r trait d la aill t d n ill il a t ntr a ha itr t l l'a li ati n d aill a ntran la di l ti n d la al it nat r ll d n a ntati n d dan l l d l ita a di l ti n d la al it a ntran n a ntati n d la t n r n a d la l ti n d l t a r la d r ti n d a han a l r ltat d r f t n in r i n a l r d l al alini ati n t d la difi ati n a l r d l a r d ti n d'h dr d d f r rrait n th ri a l r r la d al alini ati n d la h ri r d l ndant n n'a n tr a n r indiq ant q la f rr l a ait difi rt t r l' q ili r al alin d l t di r ltat nt n a rd a d t d d t rrain r nt t r nt n d al alini ati n d l ri i l diq t al alin d ah l a n ntr q l fai l r nd nt r n ntr r rtain ri tr irri d ah l tai nt li n a li ati n inad q at n ll d n rai in ra n n fai l a i ilati n d n rai a liq t n fai l t n r n l nt n tritif d l ili a l ar l lant n n rai in ra nt t n n di ni l r l ar h l a d n d n r a an n nt a n r d'ad t r l r andati n r n ill r a li ati n d n rai in ra 'a li rati n d la ti n d la ati r r aniq t l' n d q lq n ant tr tili ar l a an r a li r r l r r nd nt an a nt r l t d fa n tanti ll a nd nt r aniq d t ha nt ntran r n a ntati n d r nd nt d - t ha fai l t n r n n tri nt di ni l dan l l n tai nt nt li la r n d l ar nat ndant la aj rit d l n ait tr n id r alin diq l l l al alin tai nt r nt dan l l t di a ant l intr d ti n d ri irri an d nditi n la iq d ri i lt r a ah l l a an n nt a n rai n d r ir n al alini ati n ra id d l r ha ntrair nditi n q 'il ait n draina nat r l la lt r d ri t ntri r r ha ilit r l l al alin diq d ah l a nd nt d ati r r aniq nt a l r r l a li rati n d ara t ri tiq d l al alin diq q i nti nn nt d la al it nat r l P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes h r ar h in thi th i a nd t d ithin th rri at d i r ra f th t fri a i l nt iati n in aint i n al h f th r ar h r nt d in thi th i a f nd d th ir t rat f r l nt rati n f th th rland ini tr f r i n ffair and th riti h art nt f r nt rnati nal l nt Acknowledgements n ar a h n r i d di l a at a nin n ni r it iall thank d th r i r f nd th i h r n rt f r t a hin th f i n and r h n fir t a r a h d hi in h a k d hat ant d th i t a t a affl d a n r all r i r d t r in th r ar h j t nt a k h and a r a h d h da lat r ith a ld lan hi h n i t d f th f ll in t a t q antif il alkalinit and di it n traint in a rtain r i n t id ntif th ri in f th alt and t q antif th alkalini ati n di ati n r in rd r t d r alt rnati ana nt ti n h th ht it a a r at lan t far t a iti f r an th i i - ar ri n and r at t a hin a iliti h l d t rit a d t t h a r iat d th i a r rat f l t hi and till a t littl ld kn that h ld a a a j t a f ar lat r ft r rad ati n nn k and ant d t l a a nin n and n f nd r l rkin in a tif l a n t f r l a in t th fri a th th rland ir t rat f r nt rnati nal rati n ad rti d a a an f r an a iat i nti t at th t fri a i l nt iati n h i nti t ld ha t rk n alkalinit di it r l in irri at d ri h in t fri a h r ar h j ti d i d fr th a iti lan arli r r d t h h r n t t th r n h had f r lat d th j d ri ti n t rn d t t ar r i h had a a nin n a k r nd a ll ft r a ar trad d th fri a f r t fri a and n f nd lf a id t and d n and a l drinkin t a ith far r f diff r nt thni r h r a a fr th n ar t l tri it l r t l h n lin lth h t rat r r k r k tin n r ali d that a in a r f rt nat iti n h rtl f r arri al ar ana d t t a r ar h r j t f nd d th riti h art nt f r nt rnati nal l nt h r ar h r j t r d t th fra rk f a ti iti and all d t lla rat ith artn r in a ritania and rkina a ar did n t nl r t a r ni t al a r ti atin r i r an ll nt i nti t and a f l ana r ith t ar thi th i ld n t ha tart d in th fir t la t t han a f l a ffi at a a r at di i n artn r in i n and ind rfin hank t han f r r fri nd hi and rt n an f fi ld rk nt r a a ani d dia k all and alif ia k h t a h d all a t ri it far r and it i nti t ita ha iatta fr h adq art r al j in d r i i n ral ti a k h in n al ld lik t i ial thank t ji i a na i d di ati n and kill in th la rat r r f r at al ld rit an th r a a t fanta ti ll a at t all j t t t ll that it a a r at ri il t art f th - t i fa il f r f r ar f r ann t f r t th h ad f thi fa il r a i an d n t nl ha r at kn l d f fri an P.J.A. van Asten Soil quality and rice productivity problems in Sahelian irrigation schemes r r t al ana d t ild th h r nt t a f hi h nj d th n fit ial thank al t rjan an t lfd and inda ld r h a all th a fr th th rland t n al t rk n th ir th i nj d rkin ith th and th ir trial r id d r f l data n th th rland inda a r i d t r an d h a t h l f l in takin d kr nt n t f inda a nd tin fi ld rk in l ita a ritania a n t a t half f r trial fail d t thin ld ha n a l t r if tar ld l and f hi ll a f th a ritanian ri lt ral t n i n r i ld n t ha n th r art fr in r n ir n ntal nt d t t r fl din t rat r q it in a i n r ta in l ita r f rta l thank t a a h r ar d ta t f l i di nn ri and fi h ith a ini f t n il n rkina a it a a ti nn arr f th nati nal r ar h in tit t h r i d th a ti iti hank t hi r ran tain d an d r lt ld al lik t thank hi ll a in arti lar i a r and a hi a and l rt a a rth r r ld lik t thank th r a ri lt ral t n i n r i f r rtin r r ar h a ti iti h d r ar h n alkalini ati n a nd t d th i nti t f th ffi d i r in ali ld lik t thank a ir dia ha d i k and i la nd f r th ir h italit and f r harin th ir r ar h findin ith ld al lik t thank a ir dia f r in itin t i n t arti i at in th h i al i lati n r r ani d in nt all in r ar n akar lla rat d ith i nti t fr th r n h n tit t d h r h r l l nt - nd t d fi ld rk t th r in l ita and r id d ffi a and a t r f r in r h n nn k and ta d in akar a aitin th irth f r da ht r a ld lik t i ial thank t la d a k r an- a th and a r nt ar i r f r harin th ir kn l d and fri nd hi ith if in t- fri a ld ha n h l f n ith t all r fri nd r th r i rid ra ha d a i r l n li i r ildr d d i ri at i k al all r fri nd at t i nki rank arij ri i k a l arja and an r hank all f r akin li in and tra lin in t- fri a f n and ra l r ial thank t l r n and i rri k ra al f r th tran lati n f th r n h ar and f r r fri nd hi hi h h ri h a k in th th rland ld fir t lik t i ial thank t r t r j rd an d r and artin r ff j rd ha n r rti ill n r f r t r tri t l ita j t arri d fr th th rland and h r Acknowledgements r atin d t and a lin il at hil till aintainin n h rain a a it t ith a l t f d id a artin thank f r th ni di i n had th in th th rland a ll a in n al and rkina a hank al t n an aar h h l d ith th dit rial art f th th i rin ta in a nin n al a nj d di in ith hri an ff l n hank hri f r all r ad i f r r rk i it t n al and f r h l in h n r n d d t rt thin t in far-a a a nin n r a t r nj d rkin at th d art nt f il alit ial thank t rt an n h har d f hi a t kn l d n il f rtilit ith n d ld r r all nj d ti ith th f ll h t d nt a in n fi d ffi f r a l n ti had an diff r nt r at t n k and rt ana d t k ith l n t t fini h ith thankin fa il ir t f all ld lik t thank ar nt r th r ar nt in la and i t r in la ha al a n r rti f hat did n th h it ant that ld n t a h th r f r l n ri d a t t n t l a t ld lik t thank if nn k ar t th r f r al t t n ar n in a il i nti t r lf ha n t nl rt d rall t al i ntifi all t j t r at that an di a t th i rtan f - l n and il t it i far r at r that an har th j f fa il lif ith r a tif l da ht r a hank f r all r l and rt Curriculum Vitae tr hann nt ni an t n i t a rn in k n nk.
Pages:     | 1 ||



2011 www.dissers.ru -

, .
, , , , 1-2 .