Effects of nitrogen application rate on grain filling characteristics and nutritional quality of summer maize.

Abstract

Suitable nitrogen application rate can significantly increase grain filling rate and yield and improve nutritional quality. Denghai 518 (DH518) and Zhengdan 958 (ZD958) were used as experimental materials in this study. A field experiment with four treatments, no nitrogen treatment (N0), decrement nitrogen application rate (N1, 129 kg N·hm-2), suitable nitrogen rate (N2, 184.5 kg N·hm-2) and excessive nitrogen rate (N3, 300 kg N·hm-2), was conducted to explore the effects of nitrogen fertilization on grain filling parameters and nutritional qualities of summer maize. Results showed that grain filling characteristics, grain dry weight, and yield in N0 treatment was decreased. With increasing nitrogen application rate in the suitable range, average filling rate, grain dry weight, and yield increased. Grain yield of two hybrids in N1 and N2 treatments was higher than that of N0 by 16.4%-57.2% and 35.8%-65.1%, respectively. Grain protein, soluble sugar, starch contents and the ratio of amylopectin and amylase contents were lower and crude fat content was higher in N0 treatment. Grain protein content, soluble sugar content and starch content in N2 of DH518 were higher than that of N0 and N1 by 32.5% and 6.5%, 19.9% and 9.5%, 8.9% and 5.2%, and the ratio of amylopectin and amylose contents was increased. Grain protein, soluble sugar and starch contents in N2 of ZD958 were higher than that of N0 and N1 by 16.9% and 7.8%, 30.5% and 14.8%, 11.5% and 5.7%, and the ratio of amylopectin and amylase contents was increased. Crude fat content in N2 of both hybrids decreased significantly by 4.8%-12.3% than that of N0 and N1. However, yield and nutritional quality was increased in N3 treatment than that of N2. Our results suggested that suitable nitrogen rate could enhance grain filling, grain weight, and grain nutritional quality.