Tropical soils under continuous cultivation undergo fast degradation, leading to crop production decline, mainly due to erosion and reduction of soil organic matter levels. Soil protection with live mulching is one of the alternatives to alleviate these effects and to control soil degradation. This study was conducted to evaluate the root distribution and morphology of three perennial herbaceous leguminous species, as well as its effects on soil aggregation and organic carbon content when used as live mulching. The experiment was carried out on a Typic Haplustult soil in the experimental area of EMBRAPA Agrobiologia, Seropédica, State of Rio de Janeiro, Brazil, arranged in a completely randomized block design with three replicates. Treatments consisted of soil-covering with three herbaceous leguminous species (Arachis pintoi, Pueraria phaseoloides and Macroptilium atropurpureum) and a control treatment without live mulching, kept weed-free. Soil was sampled at depths of 0-5 and 5-10 cm for aggregate stability analysis and at depths of 0-5; 5-10; 10-20 and 20-40 cm for root distribution and morphology. A higher percentage of aggregates in the > 2.0 mm class was observed under A. pintoi and P. phaseoloides covers, 38 % above the control treatment mean. The values of mean weigth diameter aggregates of soil for leguminous treatments were also higher than in the weeded area for both depths, demonstrating the favorable effect of live mulch on soil aggregate stability. An increase in the organic soil carbon level was observed for the treatment with A. pintoi. Root morphology analysis showed that A. pintoi presented an intermediate root radius and higher root mass and area compared to other species, which may explain its positive effect on soil aggregation.
green manure; organic matter; aggregate stability