Plantas de cobertura e qualidade do solo na região dos tabuleiros costeiros

Abstract

In the North of Espírito Santo, in the Coastal Tablelands region, in the face of water scarcity in recent years, there have been observations of a migration of previously cultivated areas with papaya and coffee, under central pivot irrigation, to grains in the no-tillage system, particularly beans and corn. In these areas, newly started in the system, the formation and persistence of straw mulch has been one of the major limitations. The use of cover crops, besides the formation of straw mulch, is capable of improving the physical, chemical and biological attributes of the soil, making a more sustainable agricultural system. The objective of this study was to evaluate the soil quality in relation to the cultivation of cover crops and their potential for straw mulch formation aiming at the adoption of no-tillage system in the North of Espírito Santo, under different irrigation water regimes. The experiment was conducted in the field, in a dystrophic Yellow Argisol, experimental design in RBD, in subdivided plots, with four repetitions. The treatments were composed in the plots by two water regimes and in the subplots by six covering crops, four cultivars of Pennisetum glaucum (L.) R. Brown (millet: ADR 300, ADR 500, ADRf 6010 and BRS 1501), a Canavalia Ensiformis (L.) DC. (jack bean) and a Brachiaria ruziziensis Germain & Evrard, cv. Common (brachiaria). The agronomic performance of the cover crops were evaluated (plant height, leaf area, chlorophyll content, root development, cover index, phytomass production, remaining phytomass and decomposition rate) and soil quality under these plants (chemical and biological attributes). The jack bean and ADRf 6010 millet show resistance to water deficiency for most of the agronomic performance variables studied. The jack bean and Brachiaria ruziziensis show the lowest decomposition rates and longer half-life. Among the millets this occurs for the cultivar ADR 300. Considering soil cover index, dry matter production and decomposition rate, ADR 300 millet, in both irrigation regimes, is the most indicated crop for straw formation and soil cover. The water regime interferes in soil chemical attributes, with higher influence on pH, K+ , Na+ , H+Al, V and MO, especially on the 0- xiii 20 cm layer. The use of cover crops promotes the increase of soil chemical attributes. The cultivar of millet ADRf 6010 and Brachiaria ruziziensis promote improvement in the biological quality of the soil, increasing the levels of MBC and qMIC and decreasing qCO2. The accumulation of organic matter on the surface and consequent mineralization results in increases in the biological quality of the soil. In view of the main results, there is potential for consolidation of the no-tillage system in the Coastal Tablelands region, increasing the chemical and biological attributes of the soil with the use of cover crops adapted to the water deficiency condition.