Effects of compound slow-release fertilizer rates on maize growth and fertilizer utilization efficiency

To screen out the optimum rate of controlled-release special fertilizer on corn growth and yield in improving the extension of light and simplified cultivation under plastic sheet mulching, five fertilization treatments including three rates of controlled-release special fertilizer, 900 kg · hm^-2(ZF900), 1 200 kg · hm^-2(ZF1200), and 1 500 kg · hm^-2 (ZF1500), and recommended soil fertilizer treatment (OPT) and no fertilizer treatment (CK), were implemented in a field experiment to investigate their effects on corn yield, yield components, and fertilizer use efficiency.The results showed that the corn grain yield demonstrated a single-peak curve with the increase in the rate of slow-release special fertilizer application.The highest yield was 14 677 kg · hm^-2 with ZF1200 treatment, followed by 14 596 kg · hm^-2 with ZF900 treatment, and the lowest was 13 768 kg · hm^-2 with ZF1500 treatment.Compared with CK treatment, the slow-release fertilizer significantly increased yield by 19.3%~27.2%.Compared with OPT treatment, the yield gain was 2.3%~9.1%, with no significant difference.ZF900 treatment reduced nitrogen and total nutrients by 30.3% and 30.1% respectively compared with OPT treatment, but increased 1000-grain weight by 29.3 g, and yield per plant by 7.5 g.Additionally, the nitrogen utilization efficiency, nitrogen agronomic efficiency, fertilizer partial productivity, and fertilizer economic efficiency was increased by 9.1%, 9.2 kg · kg^-1, 17.1 kg · kg^-1 and 1 859.2 yuan · hm^-2 respectively.The slow-release fertilizer treatments can significantly increase early growth and chlorophyll content in early stage and late stage, leaf area and biological yield at mature stage.The reasonable rate of slow-release fertilizer in corn production in the loess plateau irrigation area is 900~1 200 kg · hm^-2, maximum rate is 1 200 kg · hm^-2, and economic and environmental protection rate is 900 kg · hm^-2.