Abstract Application of mineral nitrogen (N) fertilizer is not uniform at the field scale when applied with disc spreaders. Some of the distribution variation is due to potentially predictable mechanisms, but the variation is also influenced by stochastic events and multiple interactions, making each combination of field, spreader and application event a unique case. This may be one of the reasons why the agronomic, economic and environmental consequences of uneven fertilizer distribution at the field scale remains poorly understood and insufficiently quantified. Previous studies have addressed the problem statistically or empirically in regularly shaped experimental plots or a subsection of a field. While these efforts provide valuable contributions to our understanding, they neglect critical areas of the field with regards to fertilizer application: Wedges, interfaces between the in-field and the headland and in-field obstacles. In this modelling study, we present an attempt to describe the variation in fertilizer application at the field scale and assess the consequences on winter wheat grain yields, grain N yields and N losses to the environment. By combining GIS and agroecosystem modelling, we assess yield and environmental effects of two spreaders with different working widths (24 and 48 m) in four field polygons selected to represent a relevant span with regard to size and geometry for Danish conditions. The effects of the combinations were assessed for two soils, a coarse sandy soil and a sandy loam. Both accuracy (average N input rate relative to target) and precision (evenness of distribution) was found to decrease in small (4−6 ha) and geometrically irregular fields compared to large (40−50 ha) and regular fields. Increasing the working width from 24 to 48 m increased the variation in small fields, but not in large. Grain yields were negatively affected by distribution variation, while there was a poor correlation with average applied N rate. In contrast, grain N yields were insensitive to distribution variation, but showed strong correlation with average N input rate. N leaching was affected by both the amount and distribution of applied N. Across all field x spreader x soil scenarios, field scale grain yields decreased between 0–877 kg DM/ha and annual N leaching increased by up to 9 kg N/ha when fertilizer application was simulated with a spreader rather than even application. In general, the agronomic results from the large and regular field resembled the results from previous studies much better than results from the smaller and/or irregular fields. If not accounting for the impact of field size and shape distribution in the landscape, the effects of uneven N application, and thereby the potential gains by improving spreader performance, may therefore be underestimated.

中文翻译：

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圆盘撒布机重叠施氮肥的田间规模农艺和环境后果

摘要 使用圆盘撒播机时，在田间施用矿质氮 (N) 肥料并不均匀。一些分布变化是由于潜在的可预测机制造成的，但这种变化也受到随机事件和多重相互作用的影响，使得场、吊具和应用事件的每个组合都是一个独特的案例。这可能是为什么对田间肥料分布不均所造成的农艺、经济和环境影响仍然知之甚少和量化不足的原因之一。以前的研究已经在规则形状的实验地块或田地的一个子部分中以统计或经验的方式解决了这个问题。虽然这些努力为我们的理解做出了宝贵贡献，他们忽视了田间施肥方面的关键区域：楔子、田间和岬角之间的界面以及田间障碍物。在这项建模研究中，我们试图描述田间施肥的变化，并评估对冬小麦粮食产量、粮食氮产量和环境氮损失的影响。通过结合 GIS 和农业生态系统建模，我们评估了两个具有不同工作宽度（24 和 48 m）的吊具在四个选定的田地多边形中的产量和环境影响，以代表丹麦条件下尺寸和几何形状的相关跨度。对两种土壤（粗砂质土壤和砂质壤土）评估了组合的效果。与大（40-50 公顷）和规则的田地相比，在小（4-6 公顷）和几何不规则的田地中，精度（相对于目标的平均 N 输入率）和精度（分布均匀度）都降低。将工作宽度从 24 m 增加到 48 m 会增加小场地的变化，但不会增加大场地的变化。粮食产量受到分布变化的负面影响，而与平均施氮量的相关性较差。相比之下，谷物 N 产量对分布变化不敏感，但与平均 N 输入率显示出很强的相关性。氮浸出受施氮量和分布的影响。 在所有田地 x 撒布机 x 土壤场景中，当用撒肥机模拟施肥而不是均匀施肥时，田间规模的谷物产量下降了 0-877 kg DM/ha，每年的 N 浸出量增加了 9 kg N/ha。一般来说，大而规则的田地的农艺结果与先前研究的结果相比，比较小和/或不规则的田地的结果要好得多。如果不考虑景观中田地大小和形状分布的影响，不均匀施氮的影响以及由此提高撒布机性能的潜在收益可能因此被低估。