Efeito de diferentes plantas de cobertura sobre atributos físicos de um latossolo sob preparo convencional e na produtividade da soja

Abstract

The use of cover crops is essential to improve the physical, chemical and biological characteristics of the soil. Soil cover species, allied to management and conservation practices recover or maintain soil physical characteristics such as aggregation. In this context, the present study we had as objective to verify the effect of the annual cover plants, grasses and legumes, preceding the soybean crop in no-tillage, under the distribution of aggregate size in water in layers 0,0 - 0, 1m and 0.1 - 0.2m, the influence of cover crops on macroporosity, microporosity, total soil porosity, soil density, 0.0 - 0.05m, 0.05 - 0.1m, 0, 1 - 0.2m and 0.2 - 0.3m, dry matter of cover crops and soybean, soybean yield. For that, a field study was conducted in 2016/17, in the experimental area of the Universidade Federal da Fronteira Sul, campus Cerro Largo, and the laboratory analyzes for the determination of the physical attributes under analysis were carried out in the Laboratory of Soil Physics. The treatments implanted were the following: sudan grass, forage turnip, white oat consortium with rye and fallow. The experimental design was a completely randomized block design with four replications and the means were compared by the Tukey test at 5% probability. Based on the results obtained, it can be concluded that the cover plants on the physical attributes of the soil, the soil density did not differ statistically. Comparing the effect of the cover plants on the distribution of aggregate size in water in the layers 0.0 - 0.1 m and 0.1 - 0.2 m, there was no significant difference between the treatments. The same happened when comparing the effect of the soybean crop succeeding the cover plants, in the 0.0-0.1 m layer. However, the Oat/Rye treatment in the 0.1 - 0.2 m layer was the one that best answered the evaluation on soil aggregation in Classes 1 and 2, and the Fallow treatment had the highest aggregate index in Classes 3, which together with the Sudan Grass treatment, obtained the highest rates of aggregates in Classes 4 and 5. The Oat/Rye treatment presented higher value of mean wight diameter (MWD) and mean geometric diameter (MGD) in the 0.1-0.2 m layer after soybean cultivation, thus presenting a positive effect on soil aggregation. The dry matter of the soybean crop showed no difference between the treatments. Forage turnip produced the largest amount of dry matter. The soybean yield did not differ from the other evaluated treatments.