Avaliação da fertilidade, aptidão agrícola e ambiental do solo no município de Lagoa Bonita do Sul - RS / Brasil com a utilização de métodos estatísticos multivariados.

Abstract

Food production in agro ecosystems is closely linked to the availability of nutrients in the growing and to the absence of toxic elements. Therefore, it is necessary to make an evaluation of the fertility in the agricultural areas, seeking the interpretation of the nutritional needs of the plantations, aiming at maintaining and increasing of the productivity, as well as the preservation of natural resources. Thus, this dissertation was developed in Lagoa Bonita do Sul, a town in the State of Rio Grande do Sul, Brazil, with the objective of evaluating the soil fertility of the study site, using multivariate statistical methods, using the principal component analysis (PCA) and hierarchical cluster analysis (HCA), seeking to identify the constraints of agricultural production. In addition, the study aims at the elaboration of a geo referenced map of the collection points of the samples, as well as the mapping of the type of current use of the soil, comparing with its agricultural and environmental suitability, in order to identify possible areas of conflict. For this purpose, the evaluation of organic matter (OM), pH, phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), cation exchange capacity (CEC), CEC saturation by bases, CEC saturation by aluminum (Al), sulfur (S), boron (B) and manganese (Mn) of forty-four soil samples analysis, which were collected in conventional and direct planting systems and minimal cultivation systems. The application of PCA and HCA identified the presence of four distinct groups of soils in the study region, which were divided according to their chemical characteristics. In addition, low values of pH, CEC, P and OM, present in a good part of the studied samples were identified, demonstrating that these components are limiting the fertility of some soils. The high percentage of CEC saturated with Al, as well as the excess Mn present in a large part of the samples, cause toxicity to the plants, which can lead to a decrease in productivity. The values of K, Ca, Mg, S and B are present in significant quantities in most soils and are not considered production limitation. The PCA and HCA can be used as an important management tool for the use of chemical soil fertility evaluation.