Abstract
SUMMARY Mineral fertiliser is a scarce input for smallholder maize farmers in Malawi. A recent provision of small amounts of subsidised fertilisers by government programmes to farmers throughout Malawi has increased fertiliser access and raised maize production, but fertiliser management and yield responses frequently remain poor. To seek ways to use the fertiliser more efficiently, we analysed the effects of low rates of N (15 or 30 kg N ha −1 ) and P (9 kg P ha −1 ) fertiliser in combination with improved weed management on maize yields in experiments on 12 smallholder farms in Chisepo, central Malawi. Several indices of N and P use efficiency were computed from the above-ground crop components and nutrient contents. Maize yield simulations were conducted using long-term rainfall records in the APSIM crop-soil system model. NP fertiliser significantly ( p < 0.001) raised maize grain yield from 0.65 to 1.5 t ha −1 , and twice-weeding fertilised maize significantly ( p < 0.001) raised maize yields by 0.4 t ha −1 compared with weeding once (0.9 t ha −1 ). The agronomic efficiency of applied fertiliser N (AE N ) averaged 19.3 kg grain kg N −1 with one weeding but doubled to 38.7 kg with the additional weeding. The physiological efficiency of applied N (PE N ) was 40.7 kg grain kg −1 N uptake. APSIM predicted that similar or larger maize yield responses to 15 or 30 kg N ha −1 can be expected in 8 out of 10 years in areas with similar rainfall patterns to Chisepo. A financial analysis showed that the application of these small amounts of fertiliser was economic even when fertiliser was purchased from the open market, provided the crop was adequately weeded. Participatory assessments helped farmers understand the increased efficiency of fertiliser use possible with additional weeding, although some farmers reported difficulty implementing this recommendation due to competing demands for labour. We conclude that to raise the productivity and sustainability of fertiliser support programmes in Malawi, initiatives should be introduced to help identify and educate farmers on the major drivers of productivity in their systems.
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Claims 9
Claim · model-written summary
NP fertiliser raised maize grain yield from 0.65 to 1.5 t ha −1.
Zea maysNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NP fertiliser significantly ( p < 0.001) raised maize grain yield from 0.65 to 1.5 t ha −1”
t0“MAIZE”
Claim · model-written summary
Twice-weeding fertilised maize raised yield by 0.4 t ha −1 relative to one weeding.
- Treatment
- twice-weedinge0
- Outcome
- maize yieldse0
- Direction
- raisede0
- Value
- 0.4 t ha −1e0
- Qualifier
- 0.9 t ha −1e0
- Comparator
- weeding oncee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“twice-weeding fertilised maize significantly ( p < 0.001) raised maize yields by 0.4 t ha −1 compared with weeding once (0.9 t ha −1 )”
t0“MAIZE”
Claim · model-written summary
An additional weeding doubled agronomic efficiency of applied fertiliser N from 19.3 to 38.7 kg grain kg N −1.
- Treatment
- the additional weedinge0
- Outcome
- agronomic efficiency of applied fertiliser Ne0
- Direction
- doublede0
- Value
- 38.7 kge0
- Qualifier
- 19.3 kg grain kg N −1e0
- Comparator
- one weedinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The agronomic efficiency of applied fertiliser N (AE N ) averaged 19.3 kg grain kg N −1 with one weeding but doubled to 38.7 kg with the additional weeding”
t0“MAIZE”
Claim · model-written summary
Physiological efficiency of applied N was 40.7 kg grain kg −1 N uptake.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The physiological efficiency of applied N (PE N ) was 40.7 kg grain kg −1 N uptake”
t0“MAIZE”
Claim · model-written summary
APSIM predicted similar or larger yield responses to 15 or 30 kg N ha −1 in 8 out of 10 years.
- Treatment
- 15 or 30 kg N ha −1e0
- Outcome
- maize yield responsese0
- Direction
- similar or largere0
- Value
- 8 out of 10 yearse0
- Setting
- Chisepoe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“APSIM predicted that similar or larger maize yield responses to 15 or 30 kg N ha −1 can be expected in 8 out of 10 years in areas with similar rainfall patterns to Chisepo”
t0“MAIZE”
Claim · model-written summary
Applying small fertiliser amounts was economic when the crop was adequately weeded.
- Treatment
- these small amounts of fertilisere0
- Outcome
- was economice0
- Qualifier
- provided the crop was adequately weedede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the application of these small amounts of fertiliser was economic even when fertiliser was purchased from the open market, provided the crop was adequately weeded”
t0“MAIZE”
Claim · model-written summary
Participatory assessments helped farmers understand increased fertiliser-use efficiency with additional weeding.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Participatory assessments helped farmers understand the increased efficiency of fertiliser use possible with additional weeding”
t0“MAIZE”
Claim · model-written summary
Some farmers reported difficulty adding weeding because of competing labour demands.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“some farmers reported difficulty implementing this recommendation due to competing demands for labour”
t0“MAIZE”
Claim · model-written summary
The authors recommend initiatives to identify and educate farmers about major productivity drivers.
- Outcome
- initiatives should be introduced to help identify and educate farmers on the major drivers of productivity in their systemse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“initiatives should be introduced to help identify and educate farmers on the major drivers of productivity in their systems”
t0“MAIZE”
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