ABSTRACT Future development pathways for irrigated dairy farms in Canterbury operating under stricter nitrogen (N) loss limits were compared in two farmlets over four years. One represented the traditional pathway of intensification via higher inputs of N fertiliser and supplementary feed (‘higher input-high efficiency’, HI-HE), while the other represented a lower input pathway using half the amount of N fertiliser and one quarter the amount of supplementary feed (‘lower input-high efficiency’, LI-HE). The stocking rate of both systems was matched to feed supply to achieve high utilisation (∼90%) of the pasture grown. Mean total annual N surplus and estimated nitrate-N leaching were lower in LI-HE than HI-HE, by 46% and 25% respectively. Milk production was lower for LI-HE (1,700 kg versus 2,240 kg milk fat + protein per ha/year). Estimated profit was the same for both systems at a milk price of $6.46/kg fat + protein, below which LI-HE was more profitable than HI-HE and vice-versa. Compared with the benchmark high-performing Lincoln University Demonstration Dairy Farm (LUDF) through the same period, LI-HE was 2% less profitable, but estimated N leaching was ∼30% lower. Subsequent adoption of the LI-HE system by LUDF demonstrated that the system is scalable, and profitable.

中文翻译：

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代表不同行业发展路径的灌溉乳品系统的产量、利润和氮流量：坎特伯雷的 Pastoral 21 经验

摘要 对坎特伯雷灌溉奶牛场在更严格的氮 (N) 损失限制下运行的未来发展途径在两个农场进行了四年的比较。一个代表通过增加氮肥和补充饲料投入的传统集约化途径（'高投入-高效率'，HI-HE），而另一个代表使用一半氮肥和四分之一氮肥的低投入途径补充饲料（“低投入-高效率”，LI-HE）。两种系统的放养率都与饲料供应相匹配，以实现牧草的高利用率（~90%）。LI-HE 中的年平均总氮过剩量和估计的硝酸盐-N 浸出量比 HI-HE 低，分别为 46% 和 25%。LI-HE 的牛奶产量较低（1,700 公斤与 2,240 公斤乳脂 + 蛋白质/公顷/年）。两种系统的估计利润相同，牛奶价格为 6.46 美元/公斤脂肪 + 蛋白质，低于该价格时，LI-HE 比 HI-HE 更有利可图，反之亦然。与同期基准的高性能林肯大学示范奶牛场 (LUDF) 相比，LI-HE 的利润降低了 2%，但估计氮浸出率降低了约 30%。LUDF 随后采用的 LI-HE 系统表明该系统具有可扩展性和盈利性。