Atributos físicos do solo de sistemas produtivos e sustentáveis com gesso e nitrogênio

Abstract

The degradation of pastures and the sustainable increase in agricultural productivity drive the search for practices that improve soil quality and the efficiency of natural resources. Given this context, our objective was to evaluate the physical attributes of the soil in a monoculture and integrated system with and without gypsum application, in the Humid Tropic of Maranhão. The experiment was conducted in the experimental area of UNIPAZ/UEMA, in São Luís – MA, in a Distrophic Red-Yellow Argisol with a sandy loam texture and hardening characteristics, common in the region. The experimental design was in randomized blocks, with five treatments and three replications. The treatments consisted of different combinations of grass (Ipyporã), legume (Estilosantes), urea and gypsum: I - Ipyporã (IPY), II–Ipyporã + Urea (I+U), III-Ipyporã + Urea + Gypsum (I+U+G), IV– Estilosantes + Ipyporã (E+I), V–Estilosantes + Gypsum + Ipyporã (E+G+I). Nitrogen fertilization was carried out with urea (46% N) applied at 100 kg N ha-1 year-1. The amount of gypsum applied in a single dose was 4 tons ha-1 year-1. Soil samples were collected at three points within the plots, with undisturbed samples to determine physical attributes (soil density, microporosity, macroporosity and total porosity) and deformed samples for analysis of Total Organic Carbon (TOC). The results indicated that the systems with gypsum and urea with a combination of grass and/or legume had an average of 5.16% TOC, compared to the area with grass (2.87 g/Kg-1). Soil density was lower in systems with legume and grass (1.56 g/cm-3), while microporosity was lower only in the area with grass (25.50%). Macroporosity with an average of 3.56% and total porosity with an average of 33.71%, that is, there were no significant differences between treatments. It is concluded that the combination of legumes and the use of gypsum and urea promote improvements in the physical attributes of the soil, with a positive impact on carbon stock and soil quality, representing viable alternatives to promote the sustainability of production systems in the Humid Tropic of Maranhão