Production and profit of current and future dairy systems using differing nitrogen leaching mitigation methods: the Pastoral 21 experience in Waikato

Benefits and Trade-Offs of Dairy System Changes Aimed at Reducing Nitrate Leaching

“…The 'Improved' farmlets were designed by applying a suite of strategic changes to the Current for each region to reduce nitrate leaching (Table 1). Farm, animal, and feed management practices for the farmlets in each region are described by Clark et al [8] for Waikato, Chapman et al [9] for Canterbury, and Van der Weerden et al [11] for Otago. A summary of the main features is given in Table 2.…”

“…Individual milk yields (kg milk/cow) were measured for all cows at each milking. Milk component concentrations (MS − milksolids = fat + protein) of both morning and afternoon composite milk samples for each cow were determined weekly for the Waikato farmlets [8] and fortnightly for Canterbury and Otago farmlets [9]. Nitrate leaching from the Waikato farmlets was determined from measurements of nitrate-N concentration in the soil solution below plant rooting depth (collected in porous ceramic cup samplers at a vertical depth of 60 cm).…”

“…Average milk prices for the monitored years in NZ$/kg MS were Waikato 6.59, Canterbury 7.40, and Otago 7.16. The economic calculations included the cost of rearing replacement stock off-farm [8]. For the Waikato Improved farmlet, the base depreciation rate for capital invested in the off-paddock infrastructure was $350/ha, with an additional $61/ha for maintenance of the infrastructure [8].…”

“…Although water quality was the focus of much of the environmental research in NZ in recent decades, many of the management practices to improve water quality were also expected to result in reductions in GHG emissions [7]. For example, the Pastoral 21 (P21) research programme [8] included farmlet (small farm) studies in three regions throughout NZ (Waikato, Canterbury, and Otago) that compared systems typical of that region ('Current') with 'Improved' systems in which strategic changes were made to the Current system. The five key changes used to design the P21 Improved farmlets were using lower nitrogen (N) fertiliser inputs; fewer, but higher producing cows; lower herd replacement rate; greater use of high-energy/low-N feeds; and using off-paddock facilities to reduce the time cows spend on pasture (or on forage crops).…”

“…The five key changes used to design the P21 Improved farmlets were using lower nitrogen (N) fertiliser inputs; fewer, but higher producing cows; lower herd replacement rate; greater use of high-energy/low-N feeds; and using off-paddock facilities to reduce the time cows spend on pasture (or on forage crops). In all regions, the Improved systems could reduce nutrient losses to water [8][9][10][11] while GHG emissions were estimated to be reduced in most of the Improved systems [11]. The total annual GHG emissions were strongly related to total feed eaten, and the lower feed supplies and associated lower stocking rates of the Improved systems were the key drivers of lower total GHG emissions in all three regions [11].…”