A method of nitrogen application for maximizing rice yield in the Nile Delta

In the Nile Delta in 1980's, half of the farmers cultivated rice (Oryza sativa) by the basal application of nitrogen at 10 g m(-2) and the remaining half by split application, half at transplanting and half at panicle initiation stages. However, grain (paddy) yield remained as low as 650 g m(-2) despite the favorable solar radiation; 26 MJ m(-2)d (-1) during the cultivation period. In this study, to establish the most suitable nitrogen application method, we cultivated a cultiva Giza 172 by various nitrogen application methods combined with various application rates. Nitrogen fertilizer was applied at four growth stages (split application); transplanting, seven days after transplanting, the beginning of pollen meiosis and full heading. The proportion (%) of split application was 100 - 0 - 0 - 0 (basal application), 50 - 20 - 20 10 (split application with priority at the early growth stage), 25 - 25 - 25 - 25 (even split application) and 0 - 40 - 40 - 20 (split application with priority at the late growth stage). The rate of nitrogen application was 6, 12 and 18 g m(-2). Under the combination of the split application with priority at the early growth stage and application rate of 1 8 g m(-2), grain (paddy) yield was as high as 1120 g m(-2) with 47,000 grains m(-2) and 93% ripened grains. The crop growth rate (CGR), leaf area index (LAI) and net assimilation rate (NAR) under this combination were high throughout the growth stage. Under the basal application, LAI rapidly decreased and the number of grains per unit field area was low. Under the even split application and under the split application with priority at the late growth stage, grain yield was low because CGR and LAI were low throughout the growth period. In conclusion, split application of nitrogen, 50% at transplanting, 20% at 7 days after transplanting, 20% at the beginning of meiosis of pollens and 10% at the full heading stage, is most appropriate for obtaining a high yield in the Nile Delta.