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.
Highlights
Maize is one of the most significant roughage sources of animals
Variance analyses revealed that fertilizer sources, nitrogen doses and source x dose interactions had significant effects on dry matter yields in 2013 and nitrogen dose and source had significant effects on dry matter yields in 2014
Increasing dry matter yields were observed with increasing nitrogen doses
Summary
Maize is one of the most significant roughage sources of animals. It is used either in fresh forms or as silage in animal feeding. Maize is quite available for machine-culture, has high unit area yields, can be cultured as a second crop in several regions, has high digestibility levels, provides quality and palatable source of silage and is ensiled without any needs for additives. NBPT urease inhibitors control urease enzyme activity transforming urea into ammonium They reduce hydrolysis of the urea, prevent abrupt increases in pH around the fertilizer granules and decrease NH3 volatilization losses (Rozas et al 1999). Various researches have been conducted about the effects of different nitrogen sources and stabilized fertilizers on maize yield and quality (Gagnon et al 2012, Motavalli et al 2013, Abalos et al 2014, Halvorson & Bartolo 2014, Mota et al 2015). Efficiency of increasing doses of different nitrogen sources applied at a certain growth stage with the greatest need for nitrogen was compared
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