Effects of Different Nitrogen Dose and Sources as Top-Dressing on Yield and Silage Quality Attributes of Silage Maize

Abstract Effects of different nitrogen doses and sources applied as top-dressing on dry matter yield and quality of maize silage were investigated in this study. Along with 7.5 kg N da-1 application as starter at sowing in the form of 15-15-0+Zn, nitrogen doses of 0, 7.5, 15 and 22.5 kg da-1 were applied as top-dressing at 6-leaf stage of plants in the forms of ammonium nitrate, urea, DMPP blended ammonium sulphate nitrate and urea with NBPT urease inhibitor. Experiments were conducted in randomized blocks-factorial experimental design with 3 replicates in 2013 and 2014. The greatest dry matter yield were obtained from 15 and 22.5 kg N da-1 in 2013 and from 22.5 kg N da-1 in 2014. Nitrogen sources had also significant effects on dry matter yield. According to the average of two years, both DMPP blended ammonium sulphate nitrate and urea with NBPT urease inhibitor increased yield respectively by 7 and 3% as compared to ammonium nitrate and urea fertilizers. Nitrogen doses significantly improved the silage quality attributes. Nitrogen treatments increased silage protein ratio and decreased ADF and NDF ratios of silage samples. The greatest relative feed value was obtained from 15 kg N da-1 treatment. It was concluded based on present findings that besides the nitrogen doses, nitrogen sources also significantly improved yield.

本研究探讨了不同施氮剂量与追施氮源对青贮玉米干物质产量及品质的影响。试验于播种阶段以15-15-0+Zn剂型施用7.5 kg N·ha⁻¹作为种肥，另设置0、7.5、15及22.5 kg N·ha⁻¹四个施氮梯度，于玉米6叶期分别以硝酸铵、尿素、DMPP复配硫硝酸铵及添加NBPT脲酶抑制剂的尿素作为追施氮肥。试验采用随机区组-因子试验设计，于2013年与2014年开展，每组设置3次生物学重复。2013年，15与22.5 kg N·ha⁻¹处理组获得最高干物质产量；2014年，最高干物质产量出自22.5 kg N·ha⁻¹处理组。不同追施氮源对干物质产量同样具有显著影响：以两年试验的平均值计，DMPP复配硫硝酸铵与添加NBPT脲酶抑制剂的尿素较硝酸铵、尿素分别增产7%与3%。施氮剂量可显著改善青贮玉米的品质指标：各施氮处理均提升了青贮样品的粗蛋白占比，同时降低了酸性洗涤纤维（Acid Detergent Fiber, ADF）与中性洗涤纤维（Neutral Detergent Fiber, NDF）占比；15 kg N·ha⁻¹处理组获得了最高的相对饲用价值。综合本研究结果可知，除施氮剂量外，追施氮源同样可显著提升青贮玉米的干物质产量。