Effect of different rice-based intercropping systems on rice grain yield and residual soil fertility.

In a field study the biological efficiency of intercropping in direct seeded upland rice and its effect on residual soil fertility was determined at the University of Agriculture, Faisalabad for two consecutive years. The intercropping systems comprised rice alone, rice + maize, rice + sesbania, rice + mungbean, rice + ricebean, rice + cowpea and rice + pigeonpea. The rice was seeded in 75 cm spaced 4-row strips (15/75 cm) while the intercrops as forage were seeded on the vacant spaces between the rice strips. The results revealed that rice grain yield decreased to a significant level by forage intercrops compared to monocropped rice which varied from 10.94 to 25.87%, with the maximum (25.87%) by sesbania followed by pigeonpea (16.67) against the minimum (10.94%) by maize intercrop. In terms of total rice grain yield equivalent (TRGYE), the highest TRGYE (6.45 ton ha -1 ) was recorded for rice + forage maize intercropping system followed by rice + cowpea (5.08 ton ha -1 ) and rice + sesbania (4.92 ton ha -1 ) against the minimum (4.02 ton ha -1 ) for monocropped rice clearly indicating yield advantages of intercropping over monocropping of rice. Similarly the net field benefits obtained from different intercropping systems were considerably higher than the sole cropping of rice. The maximum net benefit of Rs.42325 ha -1 was recorded for rice + maize which is 37.32% more than sole rice followed by rice + cowpea (Rs.30885 ha -1 ) which is 14.03% higher than monocropping of rice (Rs.26526 ha -1 ). The results also revealed that residual soil nitrogen and organic matter was improved in all the intercropping systems except rice + maize intercropping system. However, the maximum increase in soil nitrogen (7.14%) was recorded for rice + sesbania intercropping system while the residual soil phosphorus and potassium were depleted in all the intercropping systems as compared to initial soil analysis.