A geographical and economic analysis of past nitrogen response trial results for maize in Malawi
1997
Benson, T.D.
In the 1995/96 growing season, the agricultural research and extension services of the Malawi government jointly evaluated provisional area-specific fertilizer recommendations for maize grown by smallholders throughout the country. These recommendations are to replace a blanket recommendation currently in place. To complement that work, in this paper I present the results of a statistical and economic evaluation of historical nitrogen (N) response trial data. Yield results were used from 500 nutrient response trials implemented at close to 300 sites on farmers' fields throughout Malawi by the Department of Agricultural Research from 1970 through 1993. This research involved evaluating and cleaning the data set, assigning trial sites to fertilizer recommendation zones, and calculating through multiple regression the coefficients of both the linear and the quadratic N-response functions at each site. The current provisional area-specific recommendations are evaluated in light of the results of this analysis. The quadratic response curves are used to determine the optimum nitrogen application in each zone under current fertilizer and maize prices. Finally, suggestions are made as to how the recommendations can be extended in scope and content to enable extension agents to offer farmers flexible and appropriate information on inorganic N-fertilizer management.
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