Soil Enzyme Activities under Agroforestry Systems in Northern Jiangsu Province

The authors presented the enzyme characteristics of catalase, sucrase, urease and alkaline phosphatase under agroforestry systems in northern Jiangsu Province. The results show that soil enzyme activities reduce gradually from top to bottom layer of the soil profile, and the fluctuations of catalase and urease are smaller than those of sucrase and alkaline phosphatase. Soil enzyme activities differe significantly in different samples, and the order is arranged as poplar-crop intercropping segment (A, D) > paulownia-crop intercropping segment (B, C) > CK. Furthermore, soil enzyme activities increase with intercropping age. On the other hand, in the same plot, there are closer relationships between enzymes in the soil samples. Catalase, alkaline phosphatase and urease are negatively related, while alkaline phosphatase and urease are positively related (except in samples B and C). In addition, the enzyme activities have a close relationship with the fertilizers. Catalase is positively correlated with the soil pH value (r = 0.854, 0.804, 0.078 and 0.082, respectively), and is negatively correlated with total N (r = –0.201, –0.529, –0.221 and –0.821, respectively), total P (r = –0.143, –0.213, –0.362 and –0.751, respectively) and available P (r = –0.339, –0.351, –0.576, and –0.676, respectively). Sucrase, urease and alkaline phosphatase are negatively correlated with the pH value, while positively correlated with the other fertilizers (r 1). The authors suggest that enzyme activity will be a great potential as an indicator of soil quality.