Response variability and optimal N-rates in irrigated rice [Philippines]
1986
Flinn, J.C. | Velasco, L.E. (International Rice Research Inst., Los Banos, Laguna (Philippines))
This study was undertaken to quantify the relationship between N-response and yield variability and demonstrate the impact of incorporating risk of N-response in the farmer's choice of optimal N-rate applications. The data was obtained from N-response experiments on IR36 by the Agronomy Department of IRRI [International Rice Research Inst., Los Banos, Laguna, Philippines]. The Random Coefficient Model was used to estimate the production function and yield and profit variabilities. The results showed that IR36 was more N-responsive during the dry season than the wet season. Yield variability during the dry season is lower indicating that IR36 is more stable with respect to fertilizer input during this season. The profit maximizing N-levels of risk neutral farmers are 51 and 110 kg N/ha during the wet and dry seasons, respectively. For risk-averse farmers the profit maximizing N levels are 36 kg N/ha during the wet season and 94 kg N/ha during the dry season. There was a decline in N-application by 29% and 16% during the wet and dry seasons, respectively. This reduction in N-application results to about 5% decrease in yield and 2% decrease in profit.
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