Effects of Nitrogen Nutrition on Grain Quality in Upland Rice Zhonghan 3 and Paddy Rice Yangjing 9538 under Different Cultivation Methods

Abstract

Upland rice and dry-cultivated paddy rice have been attracted more and more attention because of limited water re- sources in China. Researches on interaction between water and nitrogen supplies for crop resistance to drought stress has become a hot topic in crop physiology. However, the information linking to the effect of nitrogen nutrition on grain quality of upland rice and paddy rice under different cultivation methods is unavailable. The objective of this study was to evaluate the difference be- tween upland rice and paddy rice and interaction between cultivation methods and N levels. One upland rice cultivar Zhonghan 3 (japonica) and one paddy rice cultivar Yangjing 9538 (japonica) were grown under either moist cultivation (MC, control) or bare dry-cultivation (DC) conditions, with three N levels, low amount of nitrogen (LN, 100 kg ha-1), normal amount of nitrogen (NN, 100 kg ha-1), and high amount of nitrogen (HN, 300 kg ha-1). The results showed that, compared with NN, the grain yield under HN was lower for both upland and paddy rice under DC and for paddy rice under MC, whereas it was higher for upland rice under MC. Under both DC and MC, the percentage of chalky grains and the chalkiness of upland rice were increased under NN and reduced under HN. With the increase in N levels, amylose content was reduced and protein content was increased for both upland and paddy rice. However, the percentage of chalky grains and the chalkiness of paddy rice was decreased under DC and increased under MC. Breakdown viscosity was the highest and setback viscosity was the lowest for upland rice under NN and for paddy rice under LN. The bare dry cultivation can improve appearance quality and nutrient quality for upland rice. There was no significant difference in other rice quality indices between upland rice and paddy rice under DC. Compared with paddy rice, upland rice showed better nutrient quality and poor appearance quality and cooking quality. The correlation coefficient between cooking and nutrient quality and leaf nitrogen content was smaller for upland rice than for paddy rice. The results suggest that the response to cultivation methods and nitrogen levels varies largely between upland rice and paddy rice. The approaches to increase grain yield and grain quality for both paddy and upland rice were discussed.