Effect of organic wastes on the extractability of cadmium, copper, nickel, and zinc in soil

A soil incubation experiment lasting 6 months was carried out to ascertain the effects of tobacco dust, mushroom compost, and grape marc, which contain high organic matter, on the extractable cadmium, copper, nickel, and zinc in soil. The rates of organic wastes in its moist state added were 0%, 2%, 4%, and 8% of the air-dried soil on mass basis. Soil pH was decreased significantly in soils treated with the mushroom compost and grape march during the incubation period. The addition of all three organic wastes caused a significant increase in the organic matter content of soils. The application of tobacco dust significantly increased the DTPA-extractable Cd content in soil, whereas the addition of grape marc and mushroom compost caused a significant decrease in the extractable Cd content of soils. The DTPA-extractable Cu decreased significantly with increasing rates of grape marc amendment and increased with increasing rates of tobacco dust amendment, but there was no consistent effect of mushroom compost. The amount of DTPA-extractable Ni was higher in mushroom compost added to soil than in grape marc added to soil due to higher organic matter content of grape march. The DTPA-extractable Zn increased with increasing rates of all three organic wastes amendments.