Effect of frequency of application of inorganic nitrogen fertilizer within a rotational paddock‐grazing system on the performance of dairy cows and inputs of labour

Abstract

AbstractAs herd sizes and labour costs increase, and the availability of skilled labour decreases, efficient use of available labour becomes more important in dairy cow systems. Two experiments were conducted to examine the effect of reducing the frequency of application of inorganic nitrogen (N) fertilizer on inputs of labour and performance of dairy cows. Experiments 1 (duration of 169 d) and 2 (duration of 179 d) involved fifty‐eight and forty multiparous Holstein–Friesian dairy cows, respectively, in mid‐lactation. In each experiment, in the ‘infrequent’ treatment fertilizer was applied to all paddocks on a single occasion at the start of each grazing cycle, while in treatment ‘frequent’, fertilizer was applied on three occasions each week, within 2 or 3 d of each paddock having been grazed. The experimental treatments were started from 30 March and 29 March in Experiments 1 and 2 respectively. Total N application rates were approximately 360 and 250 kg N ha−1 in Experiments 1 and 2 respectively. Concentrate feed (4·0 kg per cow) was offered daily in both experiments. With the ‘infrequent’ treatment, highest concentrations of crude protein and nitrate in herbage were observed in swards grazed approximately 10 d after N fertilizer was applied. Treatment had no significant effect on milk yield, milk fat and protein concentrations, and final live weight and body condition score of cows in either experiment. Milk urea and plasma urea concentrations were not significantly affected by treatment. Calculated application times of fertilizer for a herd of 100 dairy cows were 107 and 83 min week−1 for the ‘frequent’ and ‘infrequent’ treatments respectively.