The effects of crop residues and green manure on the physical properties of a red-yellow latosol in the "Cerrado"

Abstract

The Latosols of the Cerrados of the Central highlands of Brazil are chemically poor and therefore require large applications of lime and phosphorus to become productive. They also have physical problems as low clay activity and low water availability for most crops. Although soil organic matter content is reasonable and ranges from 2.5 to 3.0%, soil management practices are needed to counteract the rapid decline in organic matter content and the negative effects on the chemical and physical properties of the soil that are observed soon after the soil is cultivated. Therefore an study was conducted to test the effects of incorporation of "mucuna preta" (Styzolobium atterimum, Piper & Tracy); "mucuna preta" + sorghum; corn: soybean and sorghum at two fertility levels on some properties of the soil like: water holding-capacity, water availability, bulk density and total porosity. Also the effects of the incorporation of the materials on corn production planted in the following cropping season were evaluated. Results indicated that soon after incorporation of the crop residues, water holding-capacity and availability decreased. The effects was inversaly proportional to the quantity of dry matter added and to its C/N ratio. Soil organic matter levels decreased in all treatments after incorporation of the materials. It was observed a declining tendency of the bulk density and total porosity values which may be caused by the decomposition and rearrengement of the soil organic matter. The incorporation of "mucuna preta" and soybean at the highest fertilizer level resulted in the largest corn production.