Resumo: O objetivo deste trabalho foi avaliar a qualidade do solo e sua relação com a produtividade de soja (Glycine max) em sistema de integração lavoura-pecuária (ILP), com consórcio entre gramíneas e leguminosas na fase pastagem. O experimento foi realizado no Estado de Mato Grosso, em um Latossolo Vermelho distrófico, em que gramíneas (Megathyrsus maximus 'BRS Tamani' e Urochloa brizantha 'BRS Piatã'), consorciadas com feijão-caupi (Vigna unguiculata 'BRS Tumucumaque') e feijão-guandu (Cajanus cajan 'BRS Mandarim'), foram cultivadas após a colheita da soja. Um delineamento experimental de blocos ao acaso foi utilizado com três repetições, em arranjo de parcelas subdivididas, em que as gramíneas foram consideradas como parcelas, e as leguminosas, como subparcelas. Os consórcios com leguminosas proporcionaram incrementos dos estoques de C e N total. Os consórcios causaram o aumento de C e N da biomassa microbiana, enquanto os cultivos solteiros contribuíram para o estresse da microbiota do solo. A atividade da enzima urease foi sensível às alterações de manejo em curto prazo, porém a fosfatase ácida e a β-glucosidase foram indicadores pouco sensíveis. A qualidade do solo é elevada com os consórcios entre gramíneas e leguminosas, com efeitos positivos sobre a produtividade de grãos de soja.

Abstract: The objective of this work was to evaluate the quality of the soil and its relation with soybean (Glycine max) yield in an integrated crop-livestock system (ICLS), with intercropping between grasses and legumes in the pasture phase. The experiment was carried out in the state of Mato Grosso, Brazil, on a dystrophic Oxisol, in which grasses (Megathyrsus maximus 'BRS Tamani' and Urochloa brizantha 'BRS Piatã'), intercropped with cowpea (Vigna unguiculata 'BRS Tumucumaque') and pigeon pea (Cajanus cajan 'BRS Mandarim'), were cultivated after soybean harvest. A randomized complete block design was used, with three replicates, in a split-plot arrangement, in which grasses were considered as plots, and legumes as subplots. Legume intercrops provided increases of C and total N stocks. The intercrops caused the increase of C and N of the microbial biomass, whereas the single cultures contributed to stress in the soil microbiota. The activity of the urease enzyme was sensitive to management changes in the short term, but acid phosphatase and β-glucosidase were poorly sensitive indicators. Soil quality is high with intercropping between grasses and legumes, with positive effects on soybean grain yield.

ABSTRACT Under integrated crop-livestock production systems (ICLS), plant and animal residues are important nutrient stocks for plant growth. Grazing management, by affecting the numbers of both plants and animals and the quality of residues, will influence nutrient release rates. The objective of this study was to evaluate the impact of grazing intensity on Ca and Mg release from pasture, dung, and soybean residues in a long-term no-till integrated soybean-cattle system. The experiment was established in May 2001 in a Latossolo Vermelho Distroférrico (Rhodic Hapludox). Treatments were a gradient of grazing intensity, determined by managing a black oat + Italian ryegrass pasture at 10, 20, 30, and 40 cm grazing height and no-grazing (NG), followed by soybean cropping. Ca and Mg release rates were determined in two entire cycles (2009/11). Moderate grazing (20 and 30 cm sward height) led to greater Ca and Mg release rates from pasture and dung residues, with low average half-life values (13 and 3 days for Ca and 16 and 6 days for Mg for pasture and dung, respectively). Grazing compared with NG resulted in greater Ca and Mg release from pasture and dung residues. Grazing intensity did not affect Ca and Mg release rates or amounts from soybean residues, but Ca and Mg release rates were greater from soybean leaves than from stems. Although moderate grazing intensities produce higher quality residues and higher calcium and magnesium release rates, a higher total nutrient amount is released by light grazing intensity and no-grazing, determined by higher residue production. Grazing intensity is, then, important for nutrient dynamics in the soil-plant-animal continuum.

RESUMO A seleção de espécies de plantas de cobertura com potencial para elevado crescimento radicular, em camadas adensadas no solo, pode contribuir para o manejo de sistemas agrícolas, por meio da descompactação biológica do solo. Objetivou-se avaliar o desempenho de espécies de crotalária (Crotalaria juncea, C. spectabilis e C. ochroleuca) como agentes de descompactação, em um Latossolo Vermelho distrófico submetido a diferentes níveis de densidade (1,0 Mg m-3; 1,2 Mg m-3; 1,4 Mg m-3; 1,6 Mg m-3; e 1,8 Mg m-3). Todas as espécies apresentaram redução no crescimento da parte aérea e radicular a partir de 1,4 Mg m-3 de densidade do solo. Crotalaria juncea apresentou os melhores resultados, quanto à produção de fitomassa aérea e de raízes, em níveis de compactação do solo de até 1,4 Mg m-3. O crescimento radicular das plantas é maior nas camadas acima e abaixo da camada compactada.

ABSTRACT The selection of cover crop species with high potential for root growth in dense layers of soil can help in the management of agricultural systems through biological soil unpacking. This study aimed at evaluating the performance of crotalaria species (Crotalaria juncea, C. spectabilis and C. ochroleuca) as unpacking agents, in a dystrophic Oxisol under different bulk densities (1.0 Mg m-3, 1.2 Mg m-3, 1.4 Mg m-3, 1.6 Mg m-3 and 1.8 Mg m-3). All species showed reduction in the growth of shoots and roots, when cultivated in soil with bulk density higher than 1.4 Mg m-3. Crotalaria juncea showed the best results for shoot and root biomass production with bulk density up to 1.4 Mg m-3. The root growth of plants is higher in layers above and below the compacted layer.