Abstract
In western Kenya, severe nutrient depletion, especially that of nitrogen and phosphorus, has drastically reduced crop yields over the past two to three decades. The potential effects of P application, with a single direct application of Minjingu phosphate rock (MPR) at 20, 40 and 60 kg P ha −1 , and fallow biomass in terms of nutrient replenishment on maize and bean yields were investigated on N and P deficient soils of western Kenya for six cropping seasons (three years). The agro-forestry shrubs tested were one season (six months) Crotalaria grahamiana and Tephrosia vogelii followed by maize monocrop. These fallow species were intercropped with beans in the 2000 long rains season to provide a food benefit to the farmer. Soil samples were taken at the end of each season and analyzed for soil pH and extractable P. The results showed that soil available P increased significantly following application of MPR. Significant increases in bean yields were obtained when 60 kg P ha −1 as MPR were applied, and contributed to a 260 % increase above the control. Significant maize grain yield increases were obtained when MPR was applied alone or in combination with fallow biomass as compared with treatments with either no external nutrient addition (control) or with fallow biomass alone in all seasons. The 60 kg P ha −1 MPR rate gave the highest cumulative maize grain yields (9.6 t ha −1 ) over the five consecutive maize growing seasons, followed by 40 kg P ha −1 (8.8 t ha −1 ). The residual benefits of MPR at modest rates of application (60 kg P ha −1 ) were found to persist in the soil for only three cropping seasons. Thereafter, there was a steady decline in soil chemical properties (pH and available P), grain yields and net benefits. The study demonstrated the need for frequent additions of P especially in the fourth consecutive season to ensure sustained availability of P, favorable pH, and increased crop yields and net benefits on the nutrient-depleted soils of western Kenya.
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Claims 9
Claim · model-written summary
MPR significantly increased soil available phosphorus.
- Taxon
- maize and beane1
- Treatment
- application of MPRe0
- Outcome
- soil available Pe0
- Direction
- increasede0
- Setting
- western Kenyae1
Not reportedComparator
Verbatim
e0“soil available P increased significantly following application of MPR”
e1“on maize and bean yields were investigated on N and P deficient soils of western Kenya”
Claim · model-written summary
MPR at 60 kg P ha −1 increased bean yield 260% above control.
Verbatim
e0“Significant increases in bean yields were obtained when 60 kg P ha −1 as MPR were applied, and contributed to a 260 % increase above the control”
e1“on maize and bean yields were investigated on N and P deficient soils of western Kenya”
Claim · model-written summary
MPR alone significantly raised maize grain yield against no nutrient addition or fallow biomass alone across all seasons.
- Treatment
- MPR was applied alonee0
- Outcome
- maize grain yielde0
- Direction
- increasese0
- Qualifier
- in all seasonse0
- Comparator
- no external nutrient addition (control)e0
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Significant maize grain yield increases were obtained when MPR was applied alone or in combination with fallow biomass as compared with treatments with either no external nutrient addition (control) or with fallow biomass alone in all seasons”
Claim · model-written summary
MPR with fallow biomass significantly raised maize grain yield against fallow biomass alone across all seasons.
- Treatment
- MPR was applied alone or in combination with fallow biomasse0
- Outcome
- maize grain yielde0
- Direction
- increasese0
- Qualifier
- in all seasonse0
- Comparator
- fallow biomass alonee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Significant maize grain yield increases were obtained when MPR was applied alone or in combination with fallow biomass as compared with treatments with either no external nutrient addition (control) or with fallow biomass alone in all seasons”
Claim · model-written summary
The 60 kg P ha −1 MPR rate gave the highest five-season cumulative maize grain yield, 9.6 t ha −1.
- Treatment
- 60 kg P ha −1 MPRe0
- Outcome
- cumulative maize grain yieldse0
- Direction
- higheste0
- Value
- 9.6 t ha −1e0
- Comparator
- 40 kg P ha −1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The 60 kg P ha −1 MPR rate gave the highest cumulative maize grain yields (9.6 t ha −1 ) over the five consecutive maize growing seasons, followed by 40 kg P ha −1 (8.8 t ha −1 )”
Claim · model-written summary
The 40 kg P ha −1 MPR rate gave 8.8 t ha −1 cumulative maize grain yield over five seasons.
- Treatment
- 40 kg P ha −1e0
- Outcome
- cumulative maize grain yieldse0
- Direction
- followed bye0
- Value
- 8.8 t ha −1e0
- Comparator
- 60 kg P ha −1 MPRe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The 60 kg P ha −1 MPR rate gave the highest cumulative maize grain yields (9.6 t ha −1 ) over the five consecutive maize growing seasons, followed by 40 kg P ha −1 (8.8 t ha −1 )”
Claim · model-written summary
The residual soil benefit of 60 kg P ha −1 MPR lasted only three cropping seasons.
Verbatim
e0“The residual benefits of MPR at modest rates of application (60 kg P ha −1 ) were found to persist in the soil for only three cropping seasons”
e1“on maize and bean yields were investigated on N and P deficient soils of western Kenya”
Claim · model-written summary
After three cropping seasons, soil pH and available P, grain yields and net benefits steadily declined.
Verbatim
e0“Thereafter, there was a steady decline in soil chemical properties (pH and available P), grain yields and net benefits”
e1“on maize and bean yields were investigated on N and P deficient soils of western Kenya”
Claim · model-written summary
The authors recommend renewed P addition by the fourth consecutive season to sustain soil phosphorus, pH, yields and net benefits.
Verbatim
e0“need for frequent additions of P especially in the fourth consecutive season to ensure sustained availability of P, favorable pH, and increased crop yields and net benefits”
e1“on maize and bean yields were investigated on N and P deficient soils of western Kenya”
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