Study on the Effect of Cassava Leaf Allelopathy on Soil Nutrient and Enzyme Activity

【Objective】 The experiment was conducted to explore the effect of cassava leaf allelopathy on nutrients and enzyme activities in the rhizosphere soil of cassava. 【Method】The field experiment was designed by using edible cassava variety“SC9” as tested variety and treating cassava leaf extracts with different concentration to explore the nutrients and enzyme activities of cassava rhizosphere soil in different treatment periods. 【Result】The cassava leaf allelopathy showed little effect on pH larger. The organic matter content was hardly affected by treatment time. However, it increased first and then decreased with the increase of treatment concentration and reached the highest value when the treatment concentration was 0.05 g/mL, with the organic matter contents of 41.14 g/kg (one month treatment), 52.20 g/kg (two month treatment) and 36.22 g/kg (four month treatment), respectively. Soil available nitrogen and available phosphorus content showed a similar trend with organic matter content. The available nitrogen content reached the highest value when the treatment concentration was 0.05 g/mL, with the contents of 143.21 mg/kg (one month treatment), 204.83 mg/ kg(two months treatment) and 127.88 mg/kg (four months treatment) , respectively. The available phosphorus content got the highest value when the treatment concentration was 0.05 g/mL, with the contents of 229.03 mg/kg (one month treatment), 316.40 mg/kg (two months treatment) and 235.99 mg/kg (four months treatment), respectively. The highest effective potassium content was 675.16 mg/kg (one month treatment) when treated at the concentration of 0.1 g/mL, while its highest contents were 819.35 mg/kg (two months treatment) and 665.38 mg/kg (four months treatment) respectively when treated at the concentration of 0.05 g/mL. Generally, allelopathy could increase soil enzyme activities. The highest urease activity was obtained at the treatment concentration of 0.1 g/mL, and the urease NH4 +-N were 467 mg/kg (one month treatment), 503 mg/kg (two months treatment) and 408 mg/kg (four months treatment), respectively. The activities of soil acid phosphatase P2O5 and catalase reached the highest at the concentration of 0.05 g/mL. The acid phosphatase activities were 106 mg/kg (one month treatment), 143 mg/kg (two months treatment) and 134 mg/kg (four months treatment), respectively. The activities of catalase were 6.53 mg/kg (one month treatment), 6.71 mg/kg (two months treatment) and 5.24 mg/kg (four months treatment), respectively. 【Conclusion】 The cassava leaf allelopathy had effect on the soil nutrition and the enzyme activities, and allelopathy could be used as a measure for weed control in the cassava field.