DIVERSIFICATION OF RICE-BASED CROPPING SYSTEMS TO IMPROVE SOIL FERTILITY, SUSTAINABLE PRODUCTIVITY AND ECONOMICS

Experiment on rice based cropping systems to improve soil fertility and sustainable crop productivity was conducted at Rice Research Institute, Kala Shah Kaku, Sheilchupura, Pakistan during 2007-08 in Randomized Complete Block Design with three replications. Seven cropping patterns viz; rice-berseem, rice-lentil, rice-canola, rice-wheat-mungbean, rice-wheat-cowpeas, rice-sunflower and rice-wheat-sesbania (rostrata) were compared with commonly practiced rice-wheat cropping pattern. Three crops viz; sesbania (dhancha), mungbean and cowpeas were sown in the 4th week of April just one week after the harvest of succeeding wheat crop and their crop residues incorporated into the soil by rotavator before puddling for transplanting of rice crop. Berseem, lentil and canola were sown in the 3rd week of November after the harvest of rice crop (super basmati) while sunflower was sown in the 3rd week of February. The cropping systems were evaluated for their productivity & to assess their effect on the soil organic carbon contents and available soil NPK. The results revealed that the green manuring and leguminous cropping patterns gave higher paddy yield as compared to commonly practiced rice-wheat cropping pattern. The maximum paddy yield of rice (3.73 t/ha) was obtained from rice-wheat-sesbania cropping pattern where sesbania was sown and incorporated in the soil as green manuring crop just before rice transplanting. This increase in paddy yield was statistically at par with the paddy yields received from rice-wheat-mungbean (3.57 t/ha) and rice-berseem (3.52 t/ha) cropping pattern. The yield of succeeding wheat crop was also higher in case of green manuring (sesbania) and leguminous crops (mungbean and cowpeas) which yielded 2.81, 2.69 and 2.63 t/ha respectively. The yield in case of rice-wheat cropping pattern was only 2.59 t/ha. As regards cost benefit ratio, the highest ratio was received in case of rice-lentil (1:2.38) cropping system followed by rice-canola (1:1.96) and rice-wheat-mungbean (1:1.78) as against the existing cropping pattern (rice-wheat) which gave the ratio (1:1.56). The results further indicated that introduction of green manuring or leguminous crops in the existing rice-wheat system not only increased grain yields but also improved the physio-chemical properties, organic matter contents and nutrients availability in the soil. Increase of NPK over initial soil fertility was N (0.12 %), P (2.8 ppm), and K (52 ppm). Soil pH lowered from 8.2 to 7.8 and organic carbon increased from 0.67 % to 0.72 %.