Optimizing variable rate nitrogen fertilization (VRNF) is required to minimize inputs, maximize outputs, and reduce environmental footprints. However, this is not possible in commercial farms, since it would require to intervene in regular agricultural practices with potential economic and environmental consequences and would take years of costly experiments. This study aims at the evaluation of different VRNF scenarios based on simulations that include the crop nitrogen need, soil variability, nitrogen limits set by legislations and the technical specification of variable-rate machinery. A simulation software was designed and developed to allow automatic prediction and mapping of soil and crop properties, and calculate recommendations for VRNF. The software was used to compare traditional uniform rates nitrogen (N) fertilization (URNF) against three VRNF treatments [e.g., map-based (MB), sensor-based (SB) and map-sensor-based (MSB)] in four commercial fields. Under each of the three treatments two different application schemes were evaluated, e.g., applying more N fertilizer to the more fertile zones (Kings scheme - KS) and more N fertilizer to the least fertile zone (Robin Hood scheme - RHS). Simulations were made after imposing N legislation limits and without imposing them. Finally, VRNF application was evaluated for a full boom sprayer, a section control sprayer and a nozzle control sprayer. Results indicated that the VRNF did not exceed the traditional URNF treatment, but only if the N limit by legislation is imposed. The RHS consumed 16.4–118.1 % less N fertilizer than the KS and 33.3–56.2 % than URNF treatment. However, the KS without N limit always exceeded the applied N fertilizer compared to the URNF treatment, generating high risk of N leaching. When imposing the N limit, both KS and RHS consumed less N than the traditional URNF treatment, except for the MSB under the KS, which used the same N as the URNF treatment. Spatial variability can be observed in the MB treatment, temporal variability in the SB treatment and both variabilities in the MSB treatment. Regarding the spatial variability, no significant differences between section and nozzle control options could be observed, whereas variability was minimized when using the full boom control. We concluded that the optimal fertilization scheme is VRNF based on a combination of RHS and section control, which is expected to result in reducing N fertilizer application cost, minimising risk of N leaching, and ensuring N applied is under the set legislation limits. Future work should include the crop response in the analysis to provide a comprehensive evaluation of the optimal VRNF treatment.

需要优化可变速率氮肥 (VRNF) 以最小化输入、最大化输出并减少环境足迹。然而，这在商业农场中是不可能的，因为它需要干预具有潜在经济和环境后果的常规农业实践，并且需要数年的昂贵实验。本研究旨在基于模拟评估不同的 VRNF 情景，包括作物氮需求、土壤变异性、立法规定的氮限制和变速机械的技术规范。设计和开发了一种模拟软件，可以自动预测和绘制土壤和作物特性，并计算 VRNF 的建议。该软件用于比较传统均匀施氮 (N) 施肥 (URNF) 与三种 VRNF 处理 [例如，基于地图 (MB)、基于传感器 (SB) 和基于地图传感器 (MSB)] 在四个商业领域。在三种处理中的每一种下，评估了两种不同的施用方案，例如，向更肥沃的区域（Kings 方案-KS）施用更多的氮肥，向最不肥沃的区域（罗宾汉方案-RHS）施用更多的氮肥。模拟是在施加 N 个立法限制之后进行的，并且没有施加它们。最后，对全喷杆喷雾器、截面控制喷雾器和喷嘴控制喷雾器的 VRNF 应用进行了评估。结果表明，VRNF 没有超过传统的 URNF 处理，但只有在立法强制实施 N 限制的情况下。RHS 消耗了 16.4-118。氮肥比 KS 少 1%，比 URNF 处理少 33.3-56.2%。然而，与 URNF 处理相比，没有 N 限制的 KS 总是超过施氮肥，产生高 N 浸出风险。在施加 N 限制时，KS 和 RHS 消耗的 N 都比传统 URNF 处理少，除了 KS 下的 MSB 使用与 URNF 处理相同的 N。在 MB 处理中可以观察到空间变异性，在 SB 处理中可以观察到时间变异性，在 MSB 处理中可以观察到这两种变异性。关于空间可变性，可以观察到截面和喷嘴控制选项之间没有显着差异，而使用全喷杆控制时，可变性被最小化。我们得出的结论是，最佳施肥方案是基于 RHS 和节段控制相结合的 VRNF，预计这将导致降低氮肥施用成本，最大限度地降低氮浸出的风险，并确保施氮量低于既定的立法限制。未来的工作应该在分析中包括作物反应，以提供对最佳 VRNF 处理的综合评估。