Impacts of nitrogen application amounts on grain quality and mineral elements concentrations of Japonica rice in Jianghuai River area

Field experiments on two Japonica rice varieties(Zhendao 88 and Nanjing 44) were conducted to study the impacts of nitrogen(N) application amounts(0 kg/hm2,150 kg/hm2,300 kg/hm2) on grain quality and mineral concentrations.Similar impacts of N application levels were found on the varieties.Grain quality indicators of brown rice rate,milled rate,head rice rate,chalkiness size,chalky grain rate,chalkiness decreased and length-width ratio increased along with the increase of N application amount.The head rice rate,chalky grain rate declined significantly and length-width ratio increased significantly in high-nitrogen-level treatment.The effect of nitrogen fertilization was bigger on appearance quality than on processing quality.Grain amylose content dropped,while protein content rose in the grain as N application amount went up,and protein content increased significantly in high nitrogen level.The contents of most mineral elements(Mg,Ca,P,Fe,Zn,Cu) except Mn in milled rice decreased with N application rates,and the contents of other elements varied among rice cultivars.The results demonstrate that N application may sacrifice the processing quality and mineral nutrition,but improve the appearance quality of Japonica rice in Jianghuai River area.Determining the optimal N application rate for a rice crop requires comprehensive consideration of all the aspects of production,including the integration of high yield and high nitrogen use efficiency,and simutaneous improvement of yield and mineral mutrition.