Plantas de cobertura no ecótono Cerrado-Amazônia e seu impacto na física do solo

Abstract

In the Brazilian Cerrado, direct seeding system is most common practice, with one or two crops seasons per agricultural year. Low inputs of organic matter and soil cover in this region, together with soybean harvesting, and corn or cotton crops seeding, carried out in rainy periods, resulting in compaction and degradation of these soils. Thus, it is necessary to use cover plants that provide the continuous supply of organic matter, improving the physical quality of these soils. Given the lack of studies of this nature in the Cerrado-Amazonian ecotone, the present study aimed to evaluate the effect of cover plants on the physical quality of a dystrophic Yellow Latosol. The experiment was carried out in 2016, in an experimental area of the Federal University of Mato Grosso, Sinop. A randomized block design with three replicates and eight treatments was used, with the main factor fallowed by cover plants: T1: Crotalaria espectabilis; T2: Cajanus cajan; T3: Mucuna lands; T4: Fagopyrum esculentum; T5: Urochloa ruziziensis; T6: Urochloa brizantha; T7: Pennisetum glaucum; and T8: Eleusine coracana. Soil samples of preserved and deformed structure were collected in the 0-0.10 and 0.10-0.20 m layers for determination of porosity, bulk density, soil resistance penetration, soil water retention curve, least limiting water range and normal proctor test. The results indicated that the use of cover plants modified the soil structure in the surface and subsurface layers. Cajanus cajan and Urochloa ruziziensis increased macroporosity in the soil superficial layer. The soil cultivated with Pennisetum glaucum had the lowest penetration resistance and lowest bulk density, with values of 1.39 MPa and 1.01 Mg m-3, respectively. In all treatments, the soil presented a degree of compaction limiting the development of crops. The soil least limiting water range was limited mainly by the soil resistance penetration, with critical bulk density of 1.14 Mg m-3, corresponding to 91.20% of the reference density. Among the cover plants, Cajanus cajan and Urochloa ruziziensis were the best options for soil cover in the off-season in the Cerrado-Amazonian ecotone region.