Variabilidade espacial da fertilidade do solo antes e após aplicação de calcário em taxa variável para o cultivo da soja

Abstract

Precision agriculture tools (PA) enable the management of rural properties, and their application in Brazil has consisted of characterizing soil fertility, being important for allowing the interpretation of the causes of variations and, thus, carrying out interventions in a localized manner. through the application of variable rate inputs. Therefore, the objective was to evaluate the spatial variability of some fertility attributes of an Oxisol, before and after limestone application at a variable rate, such as the Normalized Difference Vegetation Index (NDVI) of the soybean crop. The experiment was carried out in a commercial area of approximately 100 ha during the 2018/2019 soybean harvest, with systematic sampling in a grid with regular spacing for soil collection, and before soil correction, 20 sample points were allocated, with 5 ha grid; and after correction, 50 sample points were allocated, with a 2 ha grid. In both soil samplings, 12 subsamples per point were collected in the 0.00-0.20 m layer. This was carried out before and after application at a variable rate of calcitic and dolomitic limestone, which were later incorporated by a plow harrow. The following chemical attributes were determined: pH, MO, P, K, Ca, S, Mg, Al, H + AL, SB, CTC at pH 7.0 and V%. To obtain data from the Normalized Difference Vegetation Index (NDVI), images from the Sentinel 2A and 2B satellite were used at the R1 stage of the soybean crop cycle. The data were used, analyzed classic descriptors and, later, used or statistically controlled of the process, using as charts of control of individual values, which shows central lines (general average), as well as the calculated quality limits , calculated based on three times the standard deviation, and the spatialization maps using the distance inverse method. A variable rate calculation application reduces the variation of Ca, Mg, K, Al, SB, CTC, V and S, increases the contents of exchangeable bases and efficiency in correcting soil acidity. In general, there was an improvement in soil fertility after the application of lime, evidenced by the increase in macronutrients and pH, in these predominantly larger spatial distributions. The NDVI values in the studied soybean area and its relationship with the chemicals show higher values in relation to the amount of soil with which the nutrients, as some parts of the study area have excess water in the soil , due to the restriction of water subsurface. The attributes of MO, P, K, Ca, Mg and CTC, agree with a correlation analysis between variables, are not considered with NDVI, are well below 75% (correlations above 75% are satisfactory).