Correlations between indexes of soil nitrogen availability and nitrogen percent in plant, nitrogen uptake, and dry-matter yield of rice grown in the greenhouse

Abstract

Relationships between available nitrogen determined by two anaerobic incubation methods (30°C for 2 weeks: 40°C for 1 week) and seven chemical indexes (Organic C, total N, ammonium released by acid dichromate, acid permanganate, alkaline permanganate, hydrogen peroxide and dilute sulfuric acid) and nitrogen percent in rice plant, nitrogen uptake and dry-matter yield of IR 26 rice grown under submerged conditions in pots were investigated using 39 Philippine wetland rice soils differing markedly in their capacities to supply nitrogen. It was found that all the availability indexes were best correlated with nitrogen uptake of rice followed by N% in rice plants at 55 days after seeding. Dry-matter yield of rice was also significantly correlated with the available nitrogen status but the correlation coefficients were the lowest. It is concluded that for unfertilized soils, nitrogen uptake provides a better criterion for evaluating the performance of nitrogen availability indexes for wetland rice.