Optimal fertilizer use recommendations in maize production: analysis of experimental data.

Abstract

This study was conducted to enable the determination of economically justifiable fertilizer recommendations for maize farmers in Kisii and Busia Districts of lJIJestern Kenya. The study also sought to indicate the discrepancies between current. recommendations and the economically optimal rates as calculated by the author. The study was conducted within the framework of the Neoclassical Profit Maximization assumption and employed the Production Function Approach to input recommendation. Experimental data from the Fertilizer Use Recommendation Project (FURP) were used. Crop Response Functions were estimated and the marginal products equated to the inverse price ratios. Principally the study showed that there are wide discrepancies between recommendations from the National Agricultural Research Stations (NARS) and the economically optimal rates which the author calculated. In Kisii the optimal recommendation for Nitrogen (N) during the long rains season was 119.3% higher than current NARS recommendation. The corresponding figure for Phosphate (P) was 127.6%. In the short rains season the required increases are for N' and P 36.4% and 81% respectively. Similar results were found in Busia. The study also found that blanket recommendations can be misleading since results from the two districts studied indicated that even locations in the same district may require very different recommendations. Season was found to be a very important factor when optimal recommendations are being made. There were wide differences between the recommendations for the long rains season and those for the short rains for the same locations. In the long rains optimal recommendations were on average 107.9% higher than the current NARS N recommendation and 118.8% higher for P. In the short rains the optimal recommendations were only 54% higher than the current NARS N recommendation. The study thus concluded that current recommendations are not economically justifiable and that Nitrogen and Phosphate recommendations for various locations in Kenya need reassessment. The study recommends that fertilizer trials be conducted with closer involvement of economists so that recommendations are made not only on the basis of agronomic but on economic principles also.