Soil infertility is one of the major problems contributing to low and stagnated agricultural productivity in sub-Saharan Africa. In Kenya, this problem is manifested in maize where yields have remained low and stagnated over time despite increased use of inorganic fertilizers and improved seed varieties. More effective alternatives and/or complimentary actions to address this problem thus remains germane. This dissertation contributes to that endeavor through two broad objectives: to generate evidence that can support decisions to address the problem of low agricultural productivity in general and of maize in particular in Kenya; and to contribute to the body of knowledge about agricultural intensification in sub-Saharan Africa.The first essay uses household panel survey data from rural Kenya covering a period of 13 years (1997 – 2010) to examine trends and patterns in land and labor productivity of maize, measured as net returns to land and to family labor. Results show declining landholdings and farm sizes but maize occupied over one-half of cultivated land. Land productivity declined by 42% for households with at least 10 acres and by 33% in the most important maize producing regions. Labor productivity increased in areas with smaller landholdings and higher population density because of increase in land productivity, and declined or only marginally increased in areas with larger landholdings and lower population density because of a decline in land productivity. These results demonstrate that increasing maize production and returns to family labor in Kenya will rely on improving yields especially in the major maize growing areas where this has declined.The second essay uses data on maize production in five major maize growing counties in Kenya to compare maize farmers’ perceived soil fertility to measured soil fertility. It also investigates the influence of farmers’ perceptions of soil fertility on their adoption (use) of soil fertility management practices. Results show little agreement between farmers’ perceived and measured soil fertility, and farmers mostly judge the fertility status of soil by crop performance. Farmers apply management practices that may not match the fertility needs of soil on their plots, exemplified by the persistent application of an acidifying fertilizer (diammonium phosphate (DAP)) and low application of organic soil amendments even on plots with soils that are acidic and deficient in organic carbon. Farmers on average are more likely to apply inorganic fertilizer to plots they perceive to be infertile, and they treat manure or compost and inorganic fertilizers as serving substitute roles in soil fertility. These results suggest policy and extension information gaps regarding soil fertility management.The third essay uses the same dataset as in the second essay together with rainfall data to estimate technical efficiency of maize farmers and the effect of farmers’ soil fertility perception on technical efficiency. It also demonstrates the importance of including environmental production conditions and agronomic practices in agricultural productivity and efficiency analysis. Average technical efficiency level is 0.75 and 0.70, respectively, with and without environmental variables and agronomic practices in the model, indicating that scope for increasing maize yield through better management of inputs exits and that omission of environmental variables and agronomic practices underestimates technical efficiency. Farmers’ perception of soil fertility and the consistency of their perception with measured soil fertility both have significant effects on technical efficiency, underscoring the importance of information that can enhance farmers’ accurate understanding about soil fertility conditions on their farms to help them make better production decisions.
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