Current Journal of Applied Science and Technology

The continuous evolvement of dairy industry in countries like New Zealand, with increased dairy conversions and intensification, has resulted in remarkable economic development, though at the cost of environmental degradation. The increasing use of nitrogen fertilizers to sustain increasing number of cows has increased the risk of enhanced nitrate leaching and methane and nitrous oxide emissions. In this study, Compromise Programming (CP) and Weighted Goal Programming (WGP) have been applied to a Waikato dairy farm to reconcile economic goals with environmental and resources management goals. The models are based on Tier 2 methodology, developed specifically for New Zealand, for determining the energy requirements of cattle. The models are first applied with the current farm management practices to analyse the performance of the farm in meeting the two specific objectives of: (i) Attaining the production target of 1320kg MS ha-¹ year-¹, set by the farm management for maximizing profit and (ii) Keeping the nitrogen leaching limit to 26kg N ha-¹ year-¹, as calculated by the agricultural management model OVERSEER nutrient budget. Model results show that with the existing management practices, it is not possible to meet the MS production and nitrogen leaching targets simultaneously. The production target of 1320kg MS ha-¹ year-¹ results in nitrogen leaching loss of 29kg N ha-¹ year-¹ whereas the nitrogen leaching target limits the production to 1195kg MS ha-¹ year-¹. The results further shows that by keeping the number of cows calving in autumn within 150–200, and by putting an optimum area under the maize crop, it is possible to meet the twin objectives of minimizing the nitrogen leaching and maximizing the profit margins, though the production target has to be lowered significantly.