Effects of nitrogen application rate on maize yield and nitrogen metabolism after anthesis under shallow buried drip irrigation

Objectives The effects of different nitrogen (N) application rates on maize yield and nitrogen metabolism after anthesis under shallow buried drip irrigation were studied.

Methods A three-year field experiment of water and fertilizer integration was carried out in Horqin agricultural high technology demonstration zone, Tongliao City, Inner Mongolia Autonomous Region. The test material was maize, and drip irrigation pipes were buried in shallow soil. The study had four N application rates 0, 150, 210 and 300 kg/hm², and were denoted as N0, N150, N210 and N300, respectively. From anthesis to maturity stage, plant samples were regularly collected for the measurement of the activities of enzymes related to N metabolism, the photosynthetic and N use efficiency, and non-structural carbohydrate content. At maturity, the N content, dry matter accumulation, yield and yield components were determined.

Results The yield of N300 was similar with N210, but significantly higher than that of N150. The grain number per ear and 1000-grain weight in N300 and N210 were significantly higher than N150 treatment, with average increment by 15.70% and 10.85% in grain number per ear , and by 9.78% and 5.82% in 1000-grain weight. The partial productivity, agronomic efficiency, physiological utilization rate of nitrogen fertilizer, and nitrogen absorption efficiency of N210 were averagely 37.01%, 29.84%, 10.10%, and 28.89% higher than those of N300. The N accumulation after anthesis in N300 was higher than in N210, but the N translocation was similar between N300 and N210. The enzyme activity of N metabolism and photosynthetic N-use efficiency of the three N treatments were not different until 10 days after anthesis, and the non-structural carbohydrate content was not significantly different among the treatments until 30 days after anthesis. N210 and N300 elicited similar enzyme activity of N metabolism, photosynthetic N-use efficiency, and non-structural carbohydrate content after anthesis, but they were both significantly higher than those of N150.

Conclusions Under the water and nitrogen integration of shallow buried drip irrigation of Xiliaohe plain, the N application rate of 210–300 kg/hm² could improve the nitrogen absorption and translocation of plant, maize nitrogen use efficiency, enzyme activities related to nitrogen metabolism, yield, and maintain nitrogen photosynthetic production capacity after anthesis. While the aforementioned indices were similar for N rates of 210 kg/hm² and 300 kg/hm², the 210 kg/hm² N rate could be recommended as the economically and environmentally cost effective rate based on its better fertilizer efficiency.