INFLUENCE OF PADDY AND CORN IN DIFFERENT ROTATIONS ON WHEAT YIELD, NUTRIENT REMOVAL AND SOIL PROPERTIES

In a 3 year field study, the effect of 2 rotations, rice paddy (Oryza sativa L.), wheat (Triticum aestivum L.), mung (Phaseolus aureus L.) and corn (Zea mays L.), wheat (T. aestivum), mung (P. aureus) on wheat yield and chemical, physical and biological properties of soil was evaluated. Grain yield of the wheat sown after paddy during 1972-73, 1973-74 and 1974-75 was lesser by 0, 300 and 390 kg/ha, respectively, than that of the wheat following corn. The reduction in the yield of wheat was attributed to relatively higher NPK removal by paddy, greater immobilization of N applied to wheat and deterioration of soil physical conditions in the paddy field. Total NPK removal by paddy average 131 kg/ha more than that by corn. Sharp increase in bacterial population of soil during early growth of wheat that followed paddy and the concurrent less available N in soil and low N content in wheat plants suggested that the N applied to wheat was immobilized to organic form. The increase in soil bulk density and particle dispersion ratio and decrease in water storage in deeper soil layers in the paddy field probably restricted the root proliferation and growth of wheat.