Integrated Phosphorus Management in Soybean-Wheat Cropping System in Southern Rajasthan

摘要

Phosphorus plays a pivotal role in improving the productivity of soybean - wheat cropping system which has become prominent in Southern Rajasthan. Keeping in view the high phosphorus requirement of the system and availability of alternate P source like low grade rock phosphate, an attempt has been made to develop a strategy of integrated phosphorus management in soybean - wheat cropping system in this region. A field experiment was conducted during 1999-00 and 2000-01 on clay loam, medium fertility soils of Udaipur. The result of the same revealed that phosphorus fertilisation through inorganic fertilisers was a determining factor in achieving higher productivity of the system. Sole FYM @ 10 tonnes/ha did not fulfill phosphorus needs of soybean and succeeding wheat crop. Single superphosphate as a phosphorus source significantly improved the yield attributes, yield and nutrient content of soybean crop over URP+SSP (1:1). The available P status of soil at 60 DAS of soybean was higher under SSP over URP+SSP. While at harvest of soybean, the increase became insignificant and during the wheat crop, significantly higher P status of soil was maintained due to residual effect of URP+SSP over SSP. This resulted in higher P absorption, improved tillering and ultimately higher yield of the succeeding wheat crop. Application of 90 kg P_2O_5/ha increased the yield attributes and the yield of soybean by 13.3 %, 5.4 % of wheat, and net returns of system by Rs. 4200 over 30 kg P_2O_5/ha with a higher B:C ratio (2.63). Incorporation of FYM with and without PSB significantly improved the yield attributes, yield and net returns of the system (Rs.3429) over PSB inoculation alone. Direct P application to succeeding wheat @ 60 kg P_2O_5/ha proved highly remunerative and left higher soil P after the harvest of the crop.Thus, on the basis of experiment conducted it can be inferred that the indigenously available low grade rock phosphate may be substituted for SSP safely upto 50 % in soybean. Application of 90 kg P_2O_5/ha to soybean and 60 kg P_2O_5/ha to wheat, incorporation of FYM @ 10 tonnes/ha at the beginning of system and seed inoculation of soybean with PSB seems to be the viable phosphorus management strategy for soybean- wheat cropping system in southern Rajasthan.