Nitrogen (N) fertiliser inputs represent one of the largest variable costs in dryland cropping systems, and a key determinant of water-limited yield. Despite extensive research into microbial N losses via intermediate denitrification products such as N₂O, limited research exists on total N losses, and the effect of increasing soil N surplus has on fertiliser use-efficiency is not clear. In this study, the fate of banded urea fertiliser N across crop uptake, soil residual N and N losses was determined using the ¹⁵N recovery technique over nine trials with four N rates (0, plus low, medium and high industry rates) across N responsive and non-N responsive sites over 3 years in dryland sorghum (Sorghum bicolor). On average, crop uptake efficiency ranged from 50% at the low and medium N rate (80 kg N ha⁻¹) to < 38% at the highest N rate, and was as low as 5%. Nitrogen losses averaged 26.5% across all rates and trials. At the medium N rate, losses exceeded 18% in all trials, despite relatively dry seasons, and in some trials exceeded 34%. Losses of N were driven by large cumulative rain events and high early-season rainfall. In dryland systems, the inability of crops to acquire banded N fertiliser can potentially leave fertiliser stranded in the topsoil, leaving it vulnerable to losses.

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氮 (N) 肥料投入是旱地种植系统中最大的可变成本之一，也是限水产量的关键决定因素。_{尽管对通过 N 2} O等中间反硝化产物造成的微生物氮损失进行了广泛的研究，但对总氮损失的研究有限，并且增加土壤氮过剩对肥料利用效率的影响尚不清楚。在这项研究中，使用¹⁵ N 回收技术在 9 次试验中确定了带状尿素肥料 N 在作物吸收、土壤残留 N 和 N 损失方面的命运，其中 N 有四种 N 比率（0，加上低、中和高工业比率）旱地高粱（ Sorghum bicolor）3 年以上的响应和非氮响应站点）。平均而言，作物吸收效率从低氮和中等氮（80 kg N ha ^-1）的50%到最高氮的<38%，低至5%。在所有速率和试验中，氮损失平均为 26.5%。在中等 N 速率下，尽管季节相对干燥，但在所有试验中损失超过 18%，在一些试验中超过 34%。N 的损失是由大的累积降雨事件和早期的高降雨量驱动的。在旱地系统中，作物无法获得带状氮肥可能会使肥料滞留在表土中，使其容易遭受损失。

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