Impact on Crop Yield: All fertilizer treatments led to increases in yield, though in different amounts. Interventions A, B, and C led to yield increases of 28 percent, 48 percent and 63 percent respectively, relative to comparison plots. Intervention D, the Ministry of Agriculture recommended package, led to an average 91 percent increase in yield relative to comparison plots. These increases in yield are generally consistent with the results obtained in experimental farm trials.
Rates of Return: Rate-of-return calculations suggest that Intervention B is highly profitable, with mean returns of 36 percent over a season and 69.5 percent annualized. Implementing Intervention B on a 0.93 acre area of maize cultivation (the average acreage under maize cultivation in this sample) would increase agricultural income net of fertilizer cost by about 1,100 Kenyan shillings (US$33 PPP) compared to traditional methods—this represents a 15 percent increase in net income and more than a month’s agricultural wages. This evidence demonstrates that fertilizer use can have substantial returns, even in the absence of any changes in other farming practices, on real-world farms. However, other levels of fertilizer use, including the official recommendations of the Ministry of Agriculture, are unprofitable for the average farmer in this sample. Thus, while fertilizer can be very profitable when used correctly, one reason why farmers may not use fertilizer is that the official recommendations are not adapted to their specific context. This also suggests that fertilizer is not necessarily easy to use correctly, and may not be profitable for many farmers who do not use the right quantity.
1 Shahua Chen and Martin Ravallion (2008). “The Developing World Is Poorer Than We Thought, But No Less Successful in the Fight against Poverty,” World Bank Policy Research Working Paper #4703.
2 National Coordinating Agency for Population and Development (NCAPD) [Kenya], Ministry of Health (MOH), Central Bureau of Statistics (CBS), ORC Macro. 2005. “Kenya Service Provision Assessment Survey 2004”. Nairobi, Kenya: National Coordinating Agency for Population and Development.
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