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Maximizing returns to fertilizer use on maize in

MalawiLessons from on-farm agronomic research

Farm Input Subsidy Program (FISP)National Symposium

14-15 July 2014 Lilongwe, Malawi

Todd BensonIFPRI

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How can farmers derive maximum benefits from using fertilizer on maize? Presentation outline

Nationwide on-farm fertilizer trials on hybrid maize Activity of the Maize Productivity Task Force of the

Ministry of Agriculture in 1995/96 and 1997/98 Results - agronomic response in Malawi

kg maize per kg fertilizer (or kg N) applied Optimal crop management practices

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Area-specific fertilizer recommendations trials, 1995/96 & 1997/98 Single-replicate trials run by extension FAs

Plot treatments were fertilizer packages – bags of fertilizer per ha Six treatments in 95/96;

Four in 97/98 Urea, 23:21:0+4S, &

DAP (DAP in 95/96 only)

Second year trial signboard here MH17 or MH18 hybrid maize

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Area-specific fertilizer recommendations trials, 1995/96 & 1997/98 Planted on farmer’s field Farmer managed, with

supervision by FA Good, consistent crop

management

Site selection protocols to avoid confounding factors Pests, Striga, frequent flooding

Plots not fertilized previous year

Successful - Obtained data for analysis from 83% of sites in first year, 70% in second year

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Agronomic results Strong yield response in

maize to fertilizer Nitrogen is most limiting nutrient

for maize production Yield response to phosphorus

varies from area to area Generally significant responses

to sulphur

National quadratic N-response pattern across the two years shown here In analysis, adjusted trial plot yield

values downward to better reflect likely crop performance on larger fields

0

500

1000

1500

2000

2500

3000

3500

0 25 50 75 100 125

Mai

ze y

ield

(kg/

ha)

Nitrogen (kg/ha)

Y = 1286 + 29.7N – 0.122 N2

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Agronomic results 17.7 kg maize per kg N-

applied National average linear hybrid

maize yield response 7.0 to 9.5 kg grain per kg

fertilizer (urea & 23:21:0+4S)

Highest responses seen in upland areas Lowest response in Lower

Shire Valley But highest yields without fertilizer

Lakeshore – intermediate and more varied

N-response (linear)

kg maize per kgN

Intercept

(no N) kg maize

per ha

National 17.7 1,430

Karonga ADD 14.4 1,620

Mzuzu ADD 19.0 1,110

Kasungu ADD 19.0 1,330

Lilongwe ADD 19.3 1,440

Salima ADD 19.1 1,550

Machinga ADD 17.8 1,290

Blantyre ADD 17.7 1,600

Shire Valley ADD 11.7 1,860

Note: ADD – Agricultural Development Division

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Phosphorus and Sulphur Nitrogen single most

important nutrient limiting maize yields in Malawi

However, response to phosphorus and sulphur over wide areas 1995/96 trial results

provided insights here However, note this is an

agronomic assessment Annual use of P & S

fertilizers may not necessarily make economic sense for farmer

In any case, apply with nitrogen

M zu z u

L i lo n g w e

B la n ty r e

Z o m ba

K a ro n g a

S a l i m a

K a s u n g u

M c h i n j i

C h i t i p a

N s a n je

M an g o c h i

M z i m b a

N o s i g n ifi c a n t re s p o n s e

S i g n i fi c a n t r e s p o n s e

Z o n e s o f r e s p o n s e t o t h e a p p l i c a t i o n o f

i n m a i z e a t m o d e r a t e

l e v e l s o f n i t r o g e n .

,p h o s p h o r u s a n d s u l p h u r

Comparison of 35:10:0+2S (kg N:P 0 :K+S

per ha). 2 5

versus 35:0:0

M zu z u

L i l o n g w e

B la n ty r e

Z o m ba

K a r o n g a

S a l i m a

K a s u n g u

M c h i n j i

C h i t i p a

N s a n je

M an g o c h i

M z i m b a

N o s i g n ifi c a n t re s p o n s e

S i g n i fi c a n t r e s p o n s e

Comparison of 96:40:0 versus 92:21:0+4S.

Z o n e s o f r e s p o n s e t o t h e

a p p l i c a t i o n o f

i n m a i z e w h e n

n i t r o g e n a n d

p h o s p h o r u s a r e

n o t l i m i t e d .

,s u l p h u r

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Optimal crop management practices Agronomic ‘rules of thumb’ for profitable and

efficient fertilizer use on maize Regardless of how much fertilizer is applied,

farmers must do a good job in growing maize Use fresh hybrid seed adapted for local conditions Plant as early as possible Apply fertilizer on time

Basal dressing immediately after emergence Apply top-dressing 3 to 4 weeks later

Any further delay and nitrogen in fertilizer increasingly goes to produce stover, not grain

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Agronomic ‘rules of thumb’ (cont.) Weed well

1996/97 demonstration on this point at 118 sites

Weeding twice with half fertilizer (Trt 2) gives about same yield as weeding once with full rate (Trt 3)

Economically, net benefits of Trt 2 higher than Trt 3 Reflecting cheaper cost of

labour for weeding relative to cost of fertilizer

0

1000

2000

3000

4000

Trt 1 Trt 2 Trt 3 Trt 4

mai

ze y

ield

(kg

/ha)

Trt 1 Weed onceApply half recommended fertilizer

Trt 2 Weed twiceApply half recommended fertilizer

Trt 3 Weed onceApply all recommended fertilizer

Trt 4 Weed twiceApply all recommended fertilizer

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Agronomic ‘rules of thumb’ (cont.) Application methods

1996/97 demonstration at 318 sites to compare methods

Expected to see no difference in yields, but not the case

Dolloping superior No statistical yield difference

between banding and broadcasting

However, labour requirements differ between methods When labour constrained,

economically could make sense to broadcast

0

1000

2000

3000

4000

Bandin

g

Dollopi

ng

Broad

cast

ing

mai

ze y

ield

(kg

/ha)

Banding Sprinkled in groove on side of ridge

Dolloping Two holes 10 cm from planting station

Broadcasting Spread evenly on ridge top; follow with weeding to cover with soil

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Agronomic ‘rules of thumb’ (cont.) Soil and within-field variations

Soil texture useful indicator of fertilizer response Sandy soils typically less fertile, so respond well to

fertilizer when growing conditions are good Medium-textured soils not as responsive to fertilizer as

light-textured soils, but typically less risky Less affected by drought. Fertilizer does not leach from them

as much under heavy rains

“The best and worst parts of a field should not receive fertilizer” Best areas – locally fertile patches – not very responsive Worst areas – other problem than soil fertility limit maize

yields – termites, Striga (kaufiti), waterlogging, etc.

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Organic strategies for soil fertility management

Organic residue use reduces need for inorganic fertilizers Not all organic sources of value

Grain legume crop residues, khola manure, compost, & prunings from N-fixing shrubs and trees generally good

Maize stover generally not recommended Grain legume rotations

At higher N:maize price ratios (>4.5), grain legume-maize rotations (e.g., groundnut, soyabean) often provide better financial returns over 2 years than fertilized maize alone

Best rotation crop with maize for soil fertility and increased maize yield is kalongonda (velvetbean)

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Implications for FISP design Efficient logistics

Timeliness in crop operations is a big part of efficient production

Agronomic information to FISP beneficiaries Extension component to FISP

Many farmers know as much about making effective use of fertilizer as do researchers, but many do not

Targeting Can identify areas where greater returns from applying

fertilizer to hybrid maize can be obtained Can identify beneficiaries who have assets or labour that

will enable higher returns to fertilizer use