Eficiência de grades amostrais e zonas de manejo na acertividade da correção e fertilização em área de agricultura de precisão consolidada

Abstract

Soil samples from sampling grids is currently the leading precision farming tool used in Brazil. But it still has doubts about the economic feasibility of using grids with high density points. New technologies such as the use of management zones (MZ) to guide soil samples have been studied in order to reduce the number of samples and consequently the sampling costs while maintaining the quality of the information obtained. However, this method lacks scientific information about its efficiency. The aim of this study was to evaluate the technical efficiency (chapter I) mapping chemical attributes of soil and economic viability (chapter II) of the recommendations of fertilizers and from the parameters obtained by conventional sampling, sample grids and MZ delimited by different methodologies. The study was carried out in Boa Vista Missões - RS, on an area of 118,9 ha. The soil sampling was carried out in 2015, using a sample grid of 0.5 ha. From the systematic elimination of sample points simulated the use grids; 1, 2, 3 and 4.5 ha. The MZ were defined based on data altimetry of the area and the yield maps. To Chapter I used the data of P, K and pH which were submitted to descriptive statistical analysis. Data collected in sampling grid was submitted to geostatistical analysis. The accuracy of thematic maps was evaluated from the Pearson correlation and coefficient of relative deviation. For chapter II we used the P, K and SMP index to generate recommendations of P2O5, K2O and lime, respectively. The recommendation of errors were calculated in relation to the reference grid (0.5 ha) in application area (ha) kg of fertilizer and in real (R$), later smpling costs were compared with the total cost of errors recommendation. The increase in the size of the sampling grid resulted in loss of information on the spatial variability of attributes and concenquentemente raised the deviations in both fertilizer and corrective recommendations. For a proper assessment of the spatial variability of soil chemical attributes and an accurate prescription of inputs recommends the use of sampling grid of 0.5 ha.