Aarons Sharon R, Gourley Cameron J P, Powell J Mark
Ellinbank Dairy Centre, Agriculture Victoria Research, 1301 Hazeldean Road, Ellinbank, VIC 3821, Australia.
Centre for Agricultural Innovation, School of Agriculture and Food, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Melbourne, VIC 3010, Australia.
Animals (Basel). 2023 Apr 19;13(8):1404. doi: 10.3390/ani13081404.
Improving nutrient management in grazing system dairy farms requires determining nutrient flows through animals, the placement of cows within farms and potential for collection, and the re-use and loss of nutrients. We applied a model incorporating data collected at a range of temporal and spatial scales to quantify nutrient excretion in all locations that lactating herds visited on five days over a year on 43 conventional and organic grazing system dairy farms. The calculated nutrient loads excreted by cows in different places were highly skewed; while N, P and K deposited loads were consistent across the year, S, Ca and Mg loads varied between sampling times and seasons. The greatest mean and range in nutrient loads were deposited in paddocks, with the smallest amounts deposited in dairy sheds. All excreted nutrient loads increased with farm and herd sizes and milk production. Mean daily loads of 112, 15, 85, 11, 22 and 13 kg of N, P, K, S, Ca and Mg were deposited by the herds which, when standardised to a 305-day lactation, amounted to 24, 4, 20, 3, 5 and 3 t excreted annually, respectively. In addition to routine manure collection in dairy sheds, ensuring collection and recycling of nutrients excreted on feed pads and holding areas would decrease potential nutrient losses by 29% on average. Non-collected, recycled nutrients were disproportionately returned to paddocks in which cows spent time overnight, and except for S and Ca, nutrient loading rates were greater than rates applied as fertilisers. These data demonstrate the extent of excreted nutrients in grazing dairy systems and indicate the need to account for these nutrients in nutrient management plans for Australian dairy farms. We propose incorporating excretion data in current budgeting tools using data currently collected on most Australian grazing system dairy farms.
改善放牧系统奶牛场的养分管理需要确定养分在动物体内的流动、奶牛在农场内的分布以及收集的可能性，以及养分的再利用和损失情况。我们应用了一个模型，该模型整合了在一系列时间和空间尺度上收集的数据，以量化43个传统和有机放牧系统奶牛场中泌乳牛群在一年中的五天内所到访的所有地点的养分排泄量。计算得出的奶牛在不同地点排泄的养分负荷高度不均衡；虽然氮、磷和钾的沉积负荷全年一致，但硫、钙和镁的负荷在采样时间和季节之间有所不同。养分负荷的最大平均值和范围出现在围场，而奶牛舍中的沉积量最小。所有排泄的养分负荷都随着农场和牛群规模以及牛奶产量的增加而增加。牛群平均每天沉积112、15、85、11、22和13千克的氮、磷、钾、硫、钙和镁，按305天的泌乳期标准化后，每年分别排泄24、4、20、3、5和3吨。除了在奶牛舍进行常规粪便收集外，确保收集和回收在饲料垫和待牧区排泄的养分，平均可减少29%的潜在养分损失。未收集和回收的养分不成比例地返回奶牛夜间停留的围场，除了硫和钙外，养分负荷率高于作为肥料施用的比率。这些数据表明了放牧奶牛系统中养分排泄的程度，并表明在澳大利亚奶牛场的养分管理计划中需要考虑这些养分。我们建议使用目前大多数澳大利亚放牧系统奶牛场收集的数据，将排泄数据纳入当前的预算工具中。
