EFFECT OF GREEN MANURING WITH SESBANIA-ACULEATA ON PHYSICAL-PROPERTIES OF SOIL AND ON GROWTH OF WHEAT IN RICE WHEAT AND MAIZE WHEAT CROPPING SYSTEMS IN A SEMIARID REGION OF INDIA

Cultivation of rice generally has an adverse effect on soil physical properties, which results in low yields of subsequent wheat crops. A field experiment was conducted for a 3-year period on a loamy sand soil to study the effects of green manure (Sesbania aculeata) incorporation in wetland rice and maize on soil physical properties in a semiarid region of India. The residual effect of green manuring was studied on root growth and yield of succeeding wheat crops. Growing wetland rice caused a breakdown of soil structure, formation of a compacted layer at a depth of 5-20 cm, and a decrease in infiltration rate. Application of green manure to wetland rice increased the water-stable aggregates between 0.1 and 0.5 mm size by 62%, reduced the soil bulk density, and increased infiltration rate. The effects of green manure in maize were relatively small. After rice, soil water content in the 15- to 90-cm profile was higher in the green manured plots than in unmanured plots. At maturity, density of wheat roots in the 0- to 60-cm layer was 12.8% higher after cultivation of maize than after rice. Incorporation of green manure increased root density and grain yield of wheat grown after rice. These results showed that green manuring can help to improve physical properties of soil under wetland rice.