Residual soil fertility as influenced by diverse rice-based inter/relay cropping systems

A field experimented was conducted to study different direct seeded rice-based inter/relay cropping systems and their effect on residual soil fertility at the University of Agriculture, Faisalabad for two consecutive years (1998-1999 & 1999-2000). The intercropping systems comprised rice alone, rice + maize, rice + sesbania, rice + mungbean, rice + ricebean, rice + cowpea and rice + pigeonpea while wheat, lentil and Egyptian clover were sown as relay crops on residual soil moisture just after the harvest of rice previously intercropped with forage legumes and non-legumes at zero tillage. The results revealed that among the three sets of rice based inter/relay cropping systems; the overall production level of total rice grain yield equivalent (TRGYE) was higher for rice-based Egyptian clover set followed by lentil oriented to the lowest for wheat oriented set. Production level of TRGYE was highest (10.95 t per ha) for rice + maize - Egyptian clover inter/relay cropping system followed by rice + sesbania - Egyptian clover inter/relay cropping system (10.29 t per ha) compared to lowest (6.48 t per ha) for rice alone - wheat cropping system. However, rest of the cropping systems gave TRGYE ranging between 7.18 to 10.17 t per ha. Regarding residual soil fertility, residual soil nitrogen was improved in all leguminous inter/relay cropping systems as compared to sole rice as well as non-legume inter/relay cropping systems. Similarly residual soil organic matter was also improved in all inter/relay cropping systems. However, Egyptian clover oriented inter/relay cropping systems increased more residual nitrogen and organic matter as compared to lentil oriented inter/relay cropping systems, while wheat oriented inter/relay cropping systems either decreased or did not add nitrogen and organic matter in the soil. Residual soil phosphorus and potassium were depleted in all inter/relay cropping systems compared with the initial soil analysis. Similarly, as compared to rice alone, all intercropping systems showed similar trend in both years. Since rice-based leguminous inter/relay cropping systems proved to be more remunerative and sustainable than wheat-oriented inter/relay cropping systems, so some leguminous crop like lentil and Egyptian clover should be added in rice-based cropping system in place of wheat to sustain the yield of component crops of the cropping system and maintain the fertility status of the soil for long duration.