Avaliação da qualidade do solo, sob cultivo de tabaco (Nicotiana tabacum L.), em propriedades agrícolas familiares no município de Pelotas - RS

Abstract

Tobacco is a crop of great economic importance in Brazil being this the second largest producer in the world. Rio Grande do Sul is the largest Brazilian producer. The municipality of Pelotas, even though it is not characterized as a major tobacco producer, this crop represents to the municipality a very important source of income. However, the cultivation of tobacco causes several problems related to the soil, since it has been intensively cultivated, which causes many wear to the soil. The objective of this work was, therefore, to construct a soil quality diagnosis in areas submitted to tobacco cultivation, with at least 15 years of continuous production, located in the city of Pelotas, RS. In order to construct this diagnosis, in addition to the areas with tobacco, adjacent areas with native vegetation were evaluated. In order to measure soil quality, a minimum data set of indicators was selected, considering the physical, chemical, biological and microbiological attributes of the soil. Soil density, total porosity, microporosity, macroporosity, penetration resistance, weighted average diameter of the aggregates, pH, organic matter, cation exchange capacity, ontent of Al and Na, macronutrients (K, P, Ca, Mg), micronutrients (Mn, Zn, Cu), mite and collophy (mesofauna) relationship, earthworms (macrofauna), microbial biomass carbon, basal respiration and metabolic quotient. The chemical results showed significant changes when compared to the native vegetation, mainly due to the loss of organic matter and lower cation exchange capacity of the cultivated area with tobacco. On the other hand, the physical indicators presented statistically lower values, mainly to the weighted average diameter and the biological indicators presented values below the recommended one, but without statistical differences between the areas. In turn, the microbiological indicators presented lower values for microbial biomass carbon in the cultivated areas and there was no significant difference in relation to the basal respiration evaluated in the areas. In this sense, it was concluded that the intensive production of tobacco caused losses in the quality of the soil as a whole.