Abstract: For the purpose of resolving the continuous cropping obstacle in greenhouse soil, the present study investigated the effects of two types of straws (corn straw and peanut straw) returning on the soil enzyme activities, soil microbial abundance and root growth of melon by preparing the straws in the furrowing and riding ways for continuous two years. The results indicated that straw returning markedly improved the soil pH and content of soil organic matter of continuously cropped soil. The content of soil organic matter was up to 17.08 g·kg^-1 under the corn straw returning condition, with an increase of 12.8% compared to the control. Meanwhile, straw returning enhanced the activities of some soil enzymes, such as urease, sucrase and catalase. Straw application led to the increase of available potassium and available phosphorus, in spite of the decrease of available N. Additionally, straw returning led to the enriched soil microbial biomass, especially the soil microbial biomass under corn straw returning increased by 30.1% compared to the control. Straw returning increased the number of bacteria and actinomycetes, while decreased the number of fungi. Also, straw returning resulted in wellconditioned soil environment and thus promoted root growth, enhancing the root fresh weight and the root activity of melon. Notably, the fresh weight and the activity of melon root were 8.3 g·plant^-1 and 70.4 μg·g^-1 FW respectively under corn straw returning. The results suggested that the application of straws in the furrowing and ridging manners contributes to modifying the properties of continuously cropped greenhouse soil and promoting the root growth of melon, and corn straw returning exhibits better effects than peanut straw returning.

Key words: winter wheat-summer maize, tillage method, leaf area, senescence enzyme activity.