Yield and Appearence Quality of Rice Cultivated with Basal Dressing with Lime Nitrogen on Clayey Gley Soil

Abstract

Basal dressing with lime nitrogen can inhibit the occurrence of rice false smut. However, how it affects rice yield and appearance quality has not been fully revealed. We compared the yield and grain appearence quality of Koshihikari that received basal dressing of lime nitrogen (LN) with those that received split application of ammonium sulphate (CTL) in 2010 and 2011. Total amounts of nitrogen were 4 g m^-2 in both LN and CTL. We investigated the uptake of 15N labelled fertilizer of lime nitrogen, and proved that rice continued to absorb lime nitrogen until the panicle formation stage. The recovery rate of lime nitrogen given as basal dressing was estimated to be 9.1-17％ at full heading stage. Ripening ratios were significantly lower in LN than in CTL in both years. The rice appearance quality in LN was inferior to that in CTL in 2011, a year with small biomass production in the ripening period due to low irradiance. The low ripening ratio and poor grain appearance quality were associated with less nitrogen absorption after panicle formation. These results indicate that additional nitrogen application to improve the plant nitrogen status at heading is required for LN to have biomass production and grain appearance quality equivalent to CTL.