Department of Plant Sciences

Abstract Greenhouse pot experiment was conducted to evaluate the changes in soil fertility and nutrient and heavy metal uptake by radish grown in calcareous soil amended with sewage sludge (SS). SS was applied at zero (control), 20, 40 and 80 ton ha-1. Additional treatments were also included (160 ton Cd-enriched SS ha-1; and 80 kg diammonium phosphate ha-1 . Three radish seedlings per pot were planted in a seven-liter pots and were grown for 12 weeks. Radish tuber weight increased with increasing SS rates where the response followed a quadratic relationship and where the rate of 40 ton ha-1 was enough to reach the highest fresh weight. However, doubling the rate of the Cd-enriched SS resulted in a drastic decrease in tuber fresh weight. Addition of 20 ton SS ha-1 was as effective as the addition of the recommended DAP fertilizer. Shoot and tuber Cd concentrations increased with both rates of Cd-enriched SS. However, only the highest rate of original SS slightly increased Cd concentration. Soil pH decreased similarly by all rates and soil salinity increased with increasing SS rates. Soil organic mater, available P and micronutrients and DTPA-Extractable Pb increased by all SS rates. However, Cd sharply increased with application of Cd-enriched SS. Plant Cd concentration was significantly related to the DTPA-extractable soil Cd. It was concluded that SS can be applied to improve plant growth and soil fertility, however, high rates and SS rich in Cd should be avoided.