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.