Nitrogen Uptake and Utilization by No-Tillage Rice under Different Soil Moisture Conditions - A Model Study under Simulated Soil Conditions

Most of the existing studies regarding water-saving cultivation on rice are based on tillage rice, rather than no-tillage rice. The purpose of this study was to quantify the effects of nitrogen fertilizer on no-tillage rice cultivation under various soil moisture conditions, in order to determine the suitable soil moisture content for rice production by no-tillage cultivation. Pot experiments were conducted in the early seasons of 2010 and 2011. In each season, a hybrid rice cultivar, Jiyou716, was planted under the soil moisture contents of 95 - 100% (W100), 80 - 85% (W85) and 65 - 70% (W70). N-15 was used as the nitrogen fertilizer. Yield, dry matter accumulation, nitrogen concentration and N-15 abundance of maturity were determined for each sample. The nitrogen loss of basal N-fertilizer (BF) and tillering N-fertilizer (TF) in W70 was 22 - 24% and 18 - 45% larger than in W100, respectively, resulting in reduction in nitrogen uptake and total nitrogen accumulation in plants. The yield of rice by no-tillage in W70 was 47 - 42% lower in 2011 and 2010. There was no significant difference between W85 and W100 in yield, nitrogen uptake and utilization in no-tillage cultivation. It was concluded that the N uptake and yield were decreased by decreasing soil moisture contents to 70% of saturation in no-tillage cultivation. Soil content of around 85% was proposed as a suitable condition without a large reduction in the yield and N use in water-saving cultivation, although a field test is essential for practical use.