Integrated agronomic management practices improve nitrogen absorption, grain filling and nutritional qualities of summer maize

Objectives Summer maize production is generally low in efficiency due to low planting density, unreasonable fertilization and early harvest. In order to improve yield, nitrogen use efficiency and grain quality, we studied an integrated agronomic management practice suitable for Huang-Huai-Hai region.

Methods A summer maize cultivar of Zhengdan 958 was used as experimental material in a field experiment carried in Shandong Agricultural University. Four integrated agronomic practices managements were setup, including T1 (conventional management), T2 (increasing plant density, decreasing fertilizer input, optimizing application period of NPK fertilizers, and postponing the harvest dates), T3 for super high yield treatment (based on T2, further increasing fertilizer input and planting density), T4 for optimum high yield and high efficiency management (based on T3, reducing planting density and fertilizer input, and applying 30 kg/hm² of ZnSO₄). The dry matter accumulation and water contents of grains were measured at a five-day-interval from initial tasseling to the complete of grain filling stage, the filling and dehydrate rate of grains were calculated, and the yields were weighed at harvest.

Results The three integrated managements increased grain filling rate, yield and economic benefits, and improved grain nutritional quality significantly. In the two years, the highest grain yield was in T3, with a significant increase of 46.0%–47.8% compared with that in T1 treatment, and followed by T2 and T4, with a significant increase of 14.9%–31.6% and 25.9%–33.6% respectively compared with that in T1 treatment. The N partial factor productivities (PFPNs) of T2 and T4 treatments were higher than those of T1 by 61.1%–84.5% and 53.6%–62.9%. The grain filling rate from the date reaching maximum grain water content to harvest was significantly increased under T2 and T4, and the dehydration rate and grain dry weight were increased significantly at harvest stage as well. The grain quality was improved through integrated managements. The best processing quality was obtained in T4, in which the contents of amylopectin, protein and soluble sugar were significantly higher than those in T3, and the crude fat content was significantly reduced, and the total starch and amylopectin content was 4.5% and 10.1% higher than those of T1 treatment, and amylose content decreased significantly by 7.6%, and the ratio of amylopectin to amylose increased by 0.4. The economic benefit of T4 treatment was also the highest, which was 613 and 1084 yuan more than those of T2 and T3 treatments in two years.

Conclusions Through relatively decreasing plant density and fertilizer rate, the optimized high yield and high efficiency management (T4) can effectively increase the nitrogen fertilizer efficiency, improve grain nutritional quality and the maize production profit compared with the super high yield management (T3), and significantly increase maize yield than the general double-high management (T2).