Nitrogen (N) losses from agricultural land is a major environmental concern, as N leaching can cause eutrophication and nitrous oxide (N₂O) is a greenhouse gas. A lysimeter experiment was undertaken to investigate the effects of cattle diet and winter plant growth on N losses from cattle urine patches. The experiment was conducted using intact soil monolith lysimeters, beneath two different pasture or cropping systems: (i) perennial ryegrass/white clover pasture, and (ii) bare fallow after simulated grazing of fodder beet (beet fallow). Two different cow urine treatments (700 kg N ha⁻¹) were applied to each of the crop treatments in June 2017, using freshly collected urine from herds on a diet of either pasture or fodder beet (beet) (supplemented with lucerne silage). Winter plant growth was found to have a large effect on N leaching losses. There were high N leaching losses beneath the beet fallow (335–345 kg N ha⁻¹) compared to the significantly lower leaching loss beneath the pasture (55–121 kg N ha⁻¹). Urine treatment had a significant effect on N losses/transformations beneath the pasture. The pasture with beet urine treatment had 36% lower average ammonia oxidising bacteria (AOB) population abundance, 31% lower soil NO₃⁻–N concentration and subsequently 64% lower NO₃⁻–N leaching losses than the pasture with pasture urine treatment. The lower AOB population and lower average soil NO₃⁻–N suggest a biological nitrification inhibitor effect was present in the beet urine. This study shows the potential of winter plant growth and manipulation of cattle diet in reducing farm N losses.

中文翻译：

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牛饮食和冬季植物生长对牛尿斑中氮素流失的影响

农田中的氮（N）损失是主要的环境问题，因为氮的淋溶会引起富营养化，而一氧化二氮（N ₂ O）是一种温室气体。进行了溶渗仪实验，研究了牛饮食和冬季植物生长对牛尿斑中氮损失的影响。该实验是在两个不同的牧场或耕作系统下使用完整的土壤整体测渗仪进行的：（i）多年生黑麦草/白三叶草牧场，以及（ii）模拟饲用甜菜（甜菜休耕）后的裸露休耕地。两种不同的牛尿处理方法（700 kg N ha ^-1）在2017年6月应用于每种作物处理，使用从牧群中新鲜收集的尿液（以牧草或饲料甜菜（甜菜）（补充了卢塞恩青贮饲料）的饮食）。发现冬季植物的生长对氮的淋失有很大影响。甜菜休耕地的氮素淋失损失较高（335-345 kg N ha ^-1），而牧场下的氮素淋失损失显着较低（55-121 kg N ha ^-1）。尿液处理对牧场下的N损失/转化有显着影响。用甜菜尿治疗牧场具有36％较低的平均氨氧化细菌（AOB）种群数量，低31％的土壤NO ₃ ^- -N浓度，随后64％降低NO ₃ ^--N的损失比牧场用牧场尿液处理的牧场要多。较低的AOB种群和较低的平均土壤NO ₃ ^-- N表示甜菜尿液中存在生物硝化抑制剂作用。这项研究显示了冬季植物生长和控制牛日粮在减少农场氮素损失方面的潜力。