Atributos físicos do solo e crescimento de raízes do milho no sistema de plantio direto sobre palha de leguminosas

Abstract

In Maranhão state (Brazil) most of the production of food crops is done by shifting cultivation in soils predominantly of low natural fertility and susceptible to cohesion. The objective of this study was to determine selected soil physical indicators and their relation with corn root development in an alley cropping system with mixtures of four leguminous trees, Leucaena leucocephala, Gliricidia sepium, Acacia mangium and Clitoria fairchildiana. The experimental design was a randomized block with four replications. Samples for assessment of bulk density and porosity of the soil were collected with 100cm³ sized rings. The rate of water infiltration was determined using a Guelph permeameter. Samples for determination of root length density and root mass of maize were collected with the aid of an auger. I also collected three maize plants per plot to calculate dry matter production. Results indicate that maize shoot dry mass in plots without legume residues was considerably lower than in plots covered by mulch. Estimates of soil density and penetration resistance, as well as maize root density and root mass differed significantly between plots with or without mulch cover. The larger macropore volume associated with soil cover resulted in higher water infiltration into the topsoil and lower soil bulk density.