Description
In a 2 year experiment, two levels of mineral N fertilization (nil and 225 kg N/ha) on pasture were checked for their effects on pasture yield and quality as well as for performance of dairy cows. Twenty six cows were used in each treatment and the stocking density was adapted to previous results on pasture growth rates. Cows were kept on pasture during summer and grass silages were harvested from the respective experimental areas for winter feeding periods. Digestibility of organic matter in these silages, determined in wether sheep, was always higher in those silages harvested from pasture without mineral N fertilization, probably due to higher proportions of white clover. Consequently, roughage intake in winter was higher in cows receiving silage from these plots. There was no effect of level of fertilizer on milk yield or fat and protein concentration of the milk. N balance calculated as a difference of N input from concentrates and fertilizer and N output from animal products was 235 and -19 kg N/(ha•y) for the treatments with and without mineral N fertilizer, respectively, when N fixing by legumes and N deposition was not included. Mean nitrate concentration in the soil (0 to 150 cm) was 130 kg N/ha when N fertilizer was applied but only 39 kg N/ha when N fertilizer was omitted.
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Performance of Dairy Cows, Feed Quality and N Balance on Pasture Systems with or without Mineral N Fertilizer
In a 2 year experiment, two levels of mineral N fertilization (nil and 225 kg N/ha) on pasture were checked for their effects on pasture yield and quality as well as for performance of dairy cows. Twenty six cows were used in each treatment and the stocking density was adapted to previous results on pasture growth rates. Cows were kept on pasture during summer and grass silages were harvested from the respective experimental areas for winter feeding periods. Digestibility of organic matter in these silages, determined in wether sheep, was always higher in those silages harvested from pasture without mineral N fertilization, probably due to higher proportions of white clover. Consequently, roughage intake in winter was higher in cows receiving silage from these plots. There was no effect of level of fertilizer on milk yield or fat and protein concentration of the milk. N balance calculated as a difference of N input from concentrates and fertilizer and N output from animal products was 235 and -19 kg N/(ha•y) for the treatments with and without mineral N fertilizer, respectively, when N fixing by legumes and N deposition was not included. Mean nitrate concentration in the soil (0 to 150 cm) was 130 kg N/ha when N fertilizer was applied but only 39 kg N/ha when N fertilizer was omitted.
