INFLUENCE OF TILLAGE SYSTEMS AND OF PULSES AND OILSEEDS SUCCEEDING RICE (ORYZA-SATIVA) ON CHEMICAL-PROPERTIES OF SOIL

An experiment was conducted during the winter season of 1989-90 and 19 90-91 to study the effect of tillage practices on chemical properties of the soil. The tillage practices were: T-1, no tillage; T-2, ploughi ng twice with country plough; T-3, ploughing twice with bullock-drawn mouldboard plough; T-4, ploughing once with tractor-drawn mouldboard p lough; T-5, ploughing twice with cultivator; and T-6, ploughing once w ith tractor-drawn mouldboard plough followed by rotovator twice. The u pland crops grown in sequence with rice (Oryza sativa L.) were blackgr am (Phaseolus mungo L.), groundnut (Arachis hypogaea L.), castor (Rici nus communis L.) and sunflower (Helianthus annuus L.). Land preparatio n in T-6 and T-4 recorded higher values of organic carbon (0.46%) and available N, P and K content of soil during different stages df growth of these upland crops. Organic C (0.55%) and available N (291.4 kg/ha ) were high, whereas available P was low in soils at harvest, especial ly of groundnut, compared with those of other crops.