ENSO effect on simulated maize yields at Akatsi under varying planting dates and nitrogen fertilizer application rates is shown in Table 20.2. As noted for peanut, maximum mean maize yields (in boldface) occurred at varying planting dates for the various treatments. Also, at any given planting date and fertilizer rate, yields varied according to the ENSO phases. Fertilizer application generally resulted in increased output under all ENSO phases and at all planting dates. However, in all cases, increasing applied nitrogen rate from 0 to 60 kgNha-1 resulted in higher percent yield increases than for 60 to 120 kgNha-1. For example at PD1, a yield increase of 305.6% resulted from 0 to 60 kgNha-1 increment compared with only 3.2% for 60 to 120 kgNha-1 under El Niño conditions. For La Niña, the yield increase was 384.9% compared with 22.1%, and for neutral 367.7% compared with 23.4%. Thus for fertilized maize production at Akatsi, early planting with a nitrogen fertilizer rate of 60 kg N ha-1 gave the most profitable yield returns for all ENSO phases. Without fertilizer application, late planting showed best yield for El Niño years, early planting for La Niña and intermediate planting date for neutral seasons.
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