Objective  Effects of peanut/maize intercropping on crop yield, rhizosphere enzyme activity, and nutrients in soil were studied.

  Method  In a field experiment, Quanhua 557 peanut and Xuetian 7401 maize plants were cultivated either separately or under intercropping. The resulting crop yields as well as the nutrient content and enzyme activity in the rhizosphere soils were monitored at different growth stages of peanut monoculture, maize monoculture and peanut/maize intercropping for a correlation analysis.

  Result  (1) In comparison with monoculture, peanut intercropped with maize raised the rhizosphere urease activity by 4.7% at peanut flowering stage, and by 5.0% at pod setting stage. For maize, the increases at the stages were 2.6% and 4.3%, respectively. (2) During seedling, flowering/needle setting, and maturation of the peanut plants, the acid phosphatase activities in soil were 8.0%, 13.0%, and 34.7%, respectively, higher under intercropping than monoculture. For maize, the activities rose by 11.1%, 19.6%, and 6.4%, respectively. (3) In the seedling, flowering/needle setting, pod setting, and maturation of peanut plants, the invertase activity in soil increased 1.5%, 21.5%, 11.2%, and 6.4%, respectively, by the intercropping. In those stages of maize plants, the increases were 46.4%, 33.8%, 27.3%, and 11.1%, respectively. (4) At peanut maturation, the contents of alkali hydrolyzable nitrogen and available potassium in the intercropped rhizosphere soil were 15.11% and 5.66%, respectively, higher than those of maize monoculture, while the contents of alkali hydrolyzable nitrogen, available phosphorus, and available potassium 3.42%, 13.17%, and 11.39%, respectively, higher than those of monoculture. (5) A significant correlation existed between the alkali hydrolyzable nitrogen and the activities of acid phosphatase and sucrase, as well as between the available phosphorus and the activities of acid phosphatase and sucrase, in soil when the peanut plants were flowering and needle setting (P＜0.05). At the pod setting stage, it was one between the alkali hydrolyzable nitrogen and the invertase activity (P＜0.05), and another between the available potassium and the acid phosphatase (P＜0.05). At maturity of peanut, available potassium in the rhizosphere soil correlated significantly with catalase activity (P＜0.05). (6) The intercropping generated 48 217.50 yuan·hm⁻² in revenue, which was 8 842.50 yuan·hm⁻² more than the peanut monoculture or 3 157.50 yuan·hm⁻² more than the maize monoculture.

  Conclusion   The peanut/maize intercropping significantly increased the enzyme activity and nutrient contents in the rhizosphere soil as well as the economic return over monoculture of either crop.