Soil biochemical activity and growth response of rice Oryza sativa in flyash amended soil

Soil amended with different proportions of flyash, a solid waste generated from coal-fired thermal power plants, was evaluated as a soil conditioner a nd nutrient supplement during a field study on the growth of rice, Oryza sa tiva. Generally, pH and organic carbon (OC) content did not increase signif icantly (P > 0.05) in flyash amended soil, but significant increases (P < 0 .05) in soil conductivity (32%), available phosphorus (48%) and organic mat ter (OM, 29%) were observed during harvest at the 20 t ha(-1) flyash applic ation rate. Amylase, invertase, dehydrogenase and protease activities, and CO2 evolution increased in flyash amended soil over the control. The pigmen t (chl-a, chl-b, and carotenoid) content in rice plants did not vary signif icantly (P > 0.05) between different flyash amendments. Total plants biomas s and aboveground biomass increased (P < 0.05) significantly (17% and 25%, respectively) at the 20 t ha(-1) flyash application. However, there was a r etarded growth of underground biomass. Grain and straw yield increased by 2 1% and 18%, respectively, at 17.5 t ha(-1) flyash amendment when compared t o the control. Although, a significant increase (P < 0.05) in plant biomass and grain yield in flyash amended soil is encouraging from the point of wa ste disposal and management, elucidation of reasons for retarded growth in underground biomass will require additional research based on long-term stu dies. (C) 2000 Elsevier Science Ltd. All rights reserved.