Within-field variability of crop yield levels has been extensively investigated, but the spatial variability of crop yield responses to agronomic treatments is less understood. On-farm precision experimentation (OFPE) can be a valuable tool for the estimation of in-field variation of optimal input rates and thus improve agronomic decisions. Therefore, the objectives of this study were to investigate the spatial variability of optimal input rates in OFPE and the potential economic benefit of site-specific input management. Mixed geographically weighted regression (GWR) models were used to estimate local yield response functions. The methodology was applied to investigate the spatial variability in corn response to nitrogen and seed rates in four cornfields in Illinois, USA. The results showed that spatial heterogeneity of model parameters was significant in all four fields evaluated. On average, the RMSE of the fitted yield decreased from 1.2 Mg ha−1 in the non-spatial global model to 0.7 Mg ha−1 in the GWR model, and the r-squared increased from 10 to 68%. The average potential gain of using optimized uniform rates of seed and nitrogen was US$ 65.00 ha−1, while the added potential gain of the site-specific application was US$ 58.00 ha−1. The combination of OFPE and GWR proved to be an effective tool for testing precision agriculture’s central hypothesis of whether optimal input application rates display adequate spatial variability to justify the costs of the variable rate technology itself. The reported results encourage more research on response-based input management recommendations instead of the still widespread focus on yield-based algorithms.

中文翻译：

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农场精确试验中作物对农艺投入反应的空间变异性

作物产量水平的田间变异性已被广泛研究，但对农艺处理的作物产量反应的空间变异性知之甚少。农场精确试验 (OFPE) 可以成为估计最佳投入率的田间变化的有价值的工具，从而改善农艺决策。因此，本研究的目的是调查 OFPE 中最佳投入率的空间变异性以及特定地点投入管理的潜在经济效益。混合地理加权回归 (GWR) 模型用于估计当地产量响应函数。该方法用于调查美国伊利诺伊州四个玉米田中玉米对氮和播种率的响应的空间变异性。结果表明，模型参数的空间异质性在所有四个评估领域中均显着。平均而言，拟合产量的 RMSE 从非空间全局模型中的 1.2 Mg ha-1 降低到 GWR 模型中的 0.7 Mg ha-1，r 平方从 10% 增加到 68%。使用优化的均匀种子和氮肥的平均潜在收益为 65.00 公顷-1 美元，而特定地点应用的附加潜在收益为 58.00 公顷-1 美元。OFPE 和 GWR 的组合被证明是测试精准农业中心假设的有效工具，即最佳投入施用率是否显示足够的空间可变性以证明可变速率技术本身的成本是合理的。