Effect of interaction between nitrogen rate and irrigation regime on grain quality of japonica rice in Northeast China
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Chinese Journal of Rice Science. [Objective]The objective of this study is to elucidate the effects of nitrogen rates and irrigation regimes and their interactions on grain quality of rice. [Method]Two rice cultivars, Shendao 47 (an inbred japonica cultivar) and Jingyou 586 (a hybrid japonica combination), were grown in pots. Four irrigation regimes, continuous flooded (CF), shallow-wet irrigation (SWI), alternate wetting and moderate drying (WMD) and alternate wetting and severe drying (WSD), and two nitrogen (N) rates, normal amount of N (NN, 180 kg/hm 2 ), and high amount of N (HN, 220 kg/hm 2 ), were designed during the whole growing season. [Result]The interactions between N rates and irrigation regimes significantly affected grain quality of rice. The milling quality, appearance quality, nutrition quality and cooking and eating quality were better under WMD regime regardless of N rate. Under the NN treatment, the WSD regime decreased head rice rate, gel consistency, the peak viscosity and breakdown but increased the percentage of chalky grain and chalkiness, amylose content and setback as compared with the CF regime. Under the HN treatment, the grain quality of rice was slightly better under the WSD regime than under the CF regime, however, the differences in grain quality between the two irrigation regimes were not significant. The effects of irrigation regimes on total amino acid concentrations varied with N rates and cultivars. Under the NN rate, the WMD regime increased the total amino acid concentrations of both rice cultivars; under the HN rate, the WSD regime significantly increased the total amino acid concentrations of Shendao 47, while Jingyou 586 had higher total amino acid concentrations, and the concentrations of essential and non-essential amino acids followed the same trend as those of total amino acids. [Conclusion]The WMD improved grain quality of the rice cultivars. T o achieve high rice quality, the combinations between WMD and NN, and between WMD and HN were recommended for inbred rice Shendao 47 and hybrid rice Jingyou 586, respectively .
