Abstract:
Pot experiments were conducted to study the effects of chicken manure, cow manure and earthworm manure (application rate of 4%) on soil enzyme activities, rape growth and Cadmium (Cd) accumulation in soil added with different concentrations (0, 1, 10 and 50 mg kg
−1) of exogenous Cd. The results showed that the organic matter content and enzyme activities of soil were significantly increased by the application of organic fertilizer. The activities of urease and phosphatase were the highest in the treatments of chicken manure and cow manure, and the activities of catalase were the highest in the treatment of earthworm manure. The effect of organic fertilizers on soil pH value was not significant. The soil enzyme activities were decreased with the concentration of Cd. Compared with the treatment of no organic fertilizer (CK), the proportion of organic-bound Cd in total Cd was increased by 37.6%-117.3% and that of exchangeable Cd was decreased by 14.7%-28.3% in the treatments of organic fertilizers with high concentration (10, 50 mg kg
−1) of Cd addition. Compared with CK, the chlorophyll content and yield of rape were significantly increased by organic fertilizers application with 0, 1 and 10 mg kg
−1 Cd addition, and the effect of chicken manure and cow manure was better than that of earthworm manure. In the soil added with Cd concentration of 50 mg kg
−1, the chlorophyll content and yield of rape was increased by 38.8% and 290% respectively in the treatment of earthworm manure compared with CK. In the soil added with 10 and 50 mg kg
−1 Cd, the Cd concentration of rape plants was decreased by 14.2%-27.7% in the treatments of organic fertilizers compared with CK, and the effect of earthworm manure was better than that of chicken manure and cow manure. In conclusion, chicken manure and cow manure applied to soil with Cd concentration less than 10 mg kg
−1, and earthworm manure applied to soil with Cd concentration up to 50 mg kg
−1 reduce the content of Cd in rape and increase the yield of rape.