Abstract
Optical crop sensors for variable rate nitrogen application (VRNA) are described as an optimal solution to increase yield while minimizing fertilizer costs, although their operation and acquisition costs could be high. In this study, a partial budgeting approach was used to assess the net income of buying and operating a crop sensor for VRNA for optimizing fertilizer application to winter wheat. Two VRNA scenarios-stimulus, where crops with lower yield expectations received more fertilizer, and compensatory, where crops with higher yield expectations received less fertilizer-were assessed and compared to a conventional way of fertilizer application. Both scenarios showed negative results. The stimulus scenario showed a yearly negative change in income of-227.3 ha/year on 25 ha of fertilized area and-38.9 ha/year on 250 ha of fertilized area. In the case of the compensatory scenario, a yearly change in income of-271.8 ha/year on 25 ha of fertilized area and-83.3 ha/year on 250 ha of fertilized area was achieved. Results also showed that bigger farms had lower losses than smaller farms due to the economy of scale. Farmers may opt for sharing or leasing the use of the crop sensor to reduce costs. © 2021 Francisco Medel-Jiménez et al., published by Sciendo.