Modelagem geoestatística de nematoides, argila e atributos químicos do solo em área irrigada no município de Paracatu-MG

Abstract

This study evaluated the spatial distribution of nematodes, clay content and soil chemical properties with the aid of geostatistics in an area mostly cultivated with soybeans. For this, georeferenced samples of soil and roots, from a rural property in Paracatu MG, were collected and subjected to chemical, physical and nematode analyses. Sampling was conducted in the form of a mesh, collecting approximately one sample per hectare, in nine areas with central pivot in a property with 831.01 ha. Subsequently, the semivariograms and spatial distribution maps were made, using kriging technique, for each factor evaluated. There was a predominance of spherical and exponential models in semivariograms adjusted for soil chemical properties, of exponential models for nematodes, and clay could not be identified by any of the models. There was spatial independence for various soil chemical properties, which can be associated to the application of precision agriculture to the area, both in correction and fertilization in previous years, which provided adequate or near adequate fertilization levels for soybean cultivation and the main crops used in rotation on the property. The data for total clay were biased, thus modeling of the semivariograms was done with the residues. Similarly, some of the soil chemical attributes were modeled from the residues, and in these cases, the semivariograms showed pure nugget effect, indicating that trend surface is the best spatial representation for them. Due to the low number of samples with nematodes, it was not possible to fit semivariograms adjusted for most trophic groups of nematodes of primary importance for the cultures used in the area. However, the most abundant nematode groups in the trophic structure were the parasites of plants (PP) and the Bacteriophage (B). The nematodes of primary importance found were Pratylenchus brachyurus in greater numbers, followed by Rotylenchulus reniformis and Meloidogyne sp. In soybean and Pratylenchus zeae and Pratylenchus brachyurus in maize and millet. The analyses of chemical soil properties, indicated a tendency for P-rem at pivot 07, V (%), SB, P-rem, Mg2 +, CTC (T) and CTC (t) in the area of pivot 05, P-rem in the area of pivot 04, H+Al and pH in water in the area of pivot 03 and CTC (T), CTC (t) and P-rem in the area of pivot 02. Also, pure nugget effect was observed for H+Al, Al3+ , P, SB and V (%) in pivot area 02; K+, m (%) and P and V (%) in pivot area 03; Al3+, K+, m (%) P and the area of pivot 04; phosphorus in pivot area 06; Al3+ and m ( %) in pivot area 07; Al3+, Ca2+, CTC (T) CTC (t), K+, m (%), Mg2+, SB and V (%) in the area of pivot 08 and phosphorus (P) in the area of pivot 09. In pivot 05, Al3+, Ca2+, H+Al, K+, m (%) and P had spatial independence and the data did not adjust to any of the models.