Variation Characteristics of Soil Carbon and Nitrogen after Conversion of Wheat-Maize to Vegetable Cropping Systems

Variation of soil organic carbon(C) and total nitrogen(N) in vegetable fields had a great impact on soil quality and productivity.However,up to now,the variation characteristics of soil carbon and nitrogen in vegetable fields have not yet been clarified.Analysis of the data of soil carbon and nitrogen in vegetable fields and corresponding crop lands collected from major vegetable producing areas in China indicated that soil C to N ratio significantly declined in the vegetable fields,1.7 units lower than that in the crop lands.The total nitrogen content was significantly higher in the vegetable fields than that in the crop lands,with the average difference of 0.330 g·kg-1 between them.However,the difference in soil organic matter content between the vegetable fields and the crop lands was not significant.Decrease in soil C to N ratio in vegetable fields was accompanied by either increase in both soil total nitrogen and organic matter content or decrease in soil organic matter content but increase in total nitrogen content.Soil total nitrogen and organic matter content increased by 91 % and 52 % while decreased by 9 % and 48 % of the vegetable fields,respectively.