Economic feasibility of optical sensors for variable rate nitrogen fertilization in corn

This study aimed to determine the economic feasibility of the chlorophyll meters SPAD-502 and ClorofiLOG CFL1030 for nitrogen fertilization management in corn using deterministic and probabilistic models for small farms. To do so, representative cash flows for corn production were analyzed using three variable rate fertilization systems based on different nitrogen sufficiency indices. Thus, for each system, eight scenarios of different-sized cultivation areas and two sampling methodologies of the chlorophyll meter index (CMI) were simulated as follows: scenarios 1, 2, 3 and 4 used the CMI average obtained from 30 individual samplings in 1, 3, 5 and 7 ha areas; scenarios 5, 6, 7 and 8 used the CMI average in zones (30 individual samplings per zone), with 3, 5, 7 and 9 zones in 1, 3, 5 and 7 ha areas, respectively. The economic feasibility of the sensors was determined using different economic indicators, such as the internal rate of return (IRR) and the net present value (NPV), considering a minimum rate of attractiveness (MRA) of 6% per year with an 8-year project horizon. The risk was assessed by the Monte Carlo simulation. The results showed that regardless of the sampling approach, the SPAD-502 is economically feasible when acquired in Brazil or via importation through the USA in cultivation areas from 7 or 5 ha in size, respectively. Conversely, the ClorofiLOG CFL1030 could result in greater economic feasibility in areas from 3 ha.