The success of Variable Rate Application (VRA) techniques is closely linked to the algorithm used to calculate the different fertilizer rates. In this study, we proposed an algorithm based on the integration between some estimated agronomic inputs and crop radiometric data acquired by using a multispectral sensor. Generally, VRA algorithms are evaluated by comparing the yields, but they can often be affected by factors acting in the final phase of the crop cycle and not dependent on the fertilization treatments. Therefore, we decided to compare our algorithm (ALG) versus the traditional application of fertilizer (TRD) by evaluating the crop growth 1.5 months after the fertilization time. The algorithm was tested on a sorghum crop under organic farming, managed with or without manure. The saving of N obtained with ALG was equal to 14 and 5 kg ha^− 1 (-14 and − 10% for the non-manure and fertilized treatments, respectively). The NDVI values acquired after fertilization showed a remarkable reduction of relative standard deviation for ALG system (from 22 to 9% and from 34 to 14% for manured and not manured, respectively), which was not found for TRD system (from 16 to 17% and from 29 to 18% for manured and not manured, respectively). The above ground biomass produced was statistically equivalent for the two systems in the manured plots and significant higher for ALG in not-manured plots (+ 0.74 t ha^− 1 of dm, equal to + 23%). Finally, the indices calculated to evaluate the Nitrogen Use Efficiency (NUE) were consistently better in the ALG theses.

可变施肥量（VRA）技术的成功与计算不同施肥量的算法密切相关。在本研究中，我们提出了一种基于一些估计的农艺输入与使用多光谱传感器获取的作物辐射数据之间的集成的算法。一般来说，VRA 算法是通过比较产量来评估的，但它们通常会受到作物周期最后阶段因素的影响，而不依赖于施肥处理。因此，我们决定通过评估施肥时间后 1.5 个月的作物生长情况来比较我们的算法 (ALG) 与传统施肥 (TRD)。该算法在有机农业下的高粱作物上进行了测试，无论是否施肥。 ALG 节省的氮量分别为 14 和 5 kg ha ^{− 1} （无粪肥和施肥处理分别为 -14 和 − 10%）。施肥后获得的 NDVI 值显示 ALG 系统的相对标准差显着降低（施肥和未施肥分别从 22% 降低到 9%，从 34% 降低到 14%），而 TRD 系统则没有发现这种情况（从 16% 降低到 17%）。 %，施肥和未施肥分别为 29% 至 18%）。施肥地块中两个系统产生的地上生物量在统计上相当，而未施肥地块中 ALG 的地上生物量显着更高（+ 0.74 t ha ^{- 1} dm，等于+ 23%）。最后，ALG 论文中计算出的用于评估氮利用效率 (NUE) 的指数始终更好。