Effect of fly-ash application on yield and nutrient composition of rice, wheat and on pH and available nutrient status of soils

A greenhouse experiment was conducted to evaluate the effect of fly-ash application on dry-matter yield and nutrient composition of 60 day-old rice and wheat plants and on pH and available nutrient status of soils. Fly-ash was collected from an old deposit of a thermal power plant and was mixed with seven soils (varying in texture and CaCO3) each at 0, 2, 4 and 8% (w/w) levels. Moderate rates of fly-ash application (2–4% w/w) had a beneficial effect on the dry-matter yield of paddy, but a higher level (8% w/w) had a significant depressing effect. Addition of fly ash resulted in a significant increase in the contents of N, S, Ca, Na and Fe and a significant decrease in P and Zn contents of rice. The residual effect of fly ash on dry-matter yield and nutrient composition of a subsequent wheat crop was non-significant, except for the Fe content of the wheat plants which increased significantly from 138 ppm in the control to 161 ppm at 8% level of fly-ash addition. The pH and available nutrient status of soils after harvest of the rice and wheat crops were not affected by the application of fly-ash. However, the mean DTPA-extractable Fe content in soils increased significantly from 12 ppm in the control to 18•1 ppm in soils amended with 8% fly-ash.