Moderate Nitrogen Application Synergistically Improved Yield and Quality of Nanjing Series japonica Rice Varieties with Good Taste

Nanjing series japonica rice varieties developed by the Institute of Food Crops, Jiangsu Academy of Agricultural Sciences in China have the characteristics of excellent taste quality, high yield, and good resistance. They are being widely promoted and applied in the lower reaches of the Yangtze River in China's japonica rice planting areas. In response to the problem of the lack of coordination between nitrogen fertilizer management measures and variety characteristics in production, which makes it difficult to synergistically improve yield and quality, this study adopted a split-plot experimental design, with four nitrogen application rates (pure nitrogen) treatments (N1: 0 kg hm-2; N2: 150kg hm-2; N3: 300 kg hm-2; N4: 450 kg hm-2 in 2021, N1: 120 kg hm-2; N2: 180kg hm-2; N3: 240 kg hm-2; N4: 300 kg hm-2 in 2022) as the main plot, and four varieties (2021: Nanjing 46, Nanjing 9108, Nanjing 9308 and Nanjingxiangnuo; 2022: Nanjing 9108, Nanjing 5718, Nanjing 5818 and Nanjing 5758) as the split plot, to study the effect of nitrogen fertilizer application on yield and rice quality. The results showed that the differences between different nitrogen fertilizer treatments were significant at the 5% or 1% level, except for the milled rice rate, head rice rate, peak viscosity, setback viscosity and paste temperature in 2021, panicle number, grain number per panicle, all RVA characteristic values, and amylose content in 2022. With the increase of nitrogen application rate, the number of panicles and grain number per panicle increased, and the yield increased. The rates of brown rice, milled rice, and head rice showed an upward trend, while the rates of chalky grains and chalkiness were increased. The peak viscosity, hot viscosity, final viscosity, and breakdown viscosity decreased, while the setback viscosity increased. For the quality of cocked rice, the hardness increased, appearance, viscosity and balance decreased, protein content increased, and taste value decreased. The interaction between nitrogen application rate and variety only reached a significant level of 5% or 1% in yield components, processing quality, and rice protein content in 2021, and in eating and cooking quality, appearance quality and peak viscosity in 2022, other traits were not significant. The comprehensive results of two years of experiments showed that under the conditions of this experiment, a nitrogen application rate of 240-300 kg hm-2 could improve the quality of rice in the Nanjing series varieties while maintaining a high yield. The results of this experiment have guiding significance for the high-yield and high-quality cultivation of Nanjing series excellent tasting japonica rice.