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 and nutrient supplement during a field study on the growth of rice, Oryza sativa. Generally, pH and organic carbon (OC) content did not increase significantly (P > 0.05) in flyash amended soil, but significant increases (P < 0.05) in soil conductivity (32%), available phosphorus (48%) and organic matter (OM, 29%) were observed during harvest at the 20 t ha-1 flyash application rate. Amylase, invertase, dehydrogenase and protease activities, and CO2 evolution increased in flyash amended soil over the control. The pigment (chl-a, chl-b, and carotenoid) content in rice plants did not vary significantly (P > 0.05) between different flyash amendments. Total plants biomass and aboveground biomass increased (P < 0.05) significantly (17% and 25%, respectively) at the 20 t ha-1 flyash application. However, there was a retarded growth of underground biomass. Grain and straw yield increased by 21% and 18%, respectively, at 17.5 t ha-1 flyash amendment when compared to 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 waste disposal and management, elucidation of reasons for retarded growth in underground biomass will require additional research based on long-term studies.