Maximising dairy production by using nitrogen fertiliser and calving early

Abstract

The effects of applying nitrogen (N) fertiliser at 100 kgN/ha as a split application (40 kgN/ha in July/ early August and 60 kgN/ha in October) and of earlier calving (16 July vs 2 August) on milk solids production and farm profitability were evaluated at the Waimate West Demonstration Farm in South Taranaki. Two systems were comparedover 3 years: calving on 2 August with no N (LC) and calving on 16 July with N (ECN). In the second and third year calving on 16 July with no N (EC) was also evaluated. All herds were stocked at 4.0 cows/ ha. Early calving without N (EC) increased the average lactation length/cow by only 2 days because poorer cow condition andless winter supplements required earlier drying off. Milkfat increased by only 13 kg/ha and protein by 1 kg/ha. Early calving with N (ECN) increased the average lactation length/cow by 16 days, milkfat by 57 kg/ha and protein by 27 kg/ha. Nitrogen applied in October was more effective (kg milk solids/kg N) at increasing milk solids production (1.08 kg milk solids/kg N) than N applied in late winter (0.56kg milk solids/kg N). At 4.0 cows/ha and calving on 16 July, the break-even milkfat price for N use was $3.OO/kg fat. Keywords milk solids, production, nitrogen fertiliser, calving date.