Soil Quality with Various Planting Patterns in Yangtze River Delta Area

In recent years, the problem that soil quality degradation results in reducing vegetable yield is very serious. In order to solve this problem, the difference of soil quality and formative factors among four patterns of cultivations including paddy field, greenhouse vegetable cultivation, open-field vegetable cultivation and vegetable-paddy rotation were studied by investigations in Yangtze River Delta area. The results showed that in contrast to paddy field, fertilization in vegetable cultivation was higher and greenhouse vegetable cultivation was the most of the three patterns of vegetable cultivation with fertilization of 1 826.2 kg·hm-2. And salinization in the greenhouse under vegetable cultivation was the most, too. Soil EC for 10-year and 3-year greenhouse cultivation increased as high as 450% and 138%, more than that of paddy field, while soil pH decreased 0.78 and 0.33 units, respectively, and soil NO3--N increased 24.76 and 13.03 times, respectively. Soil available P of 10 years planting greenhouse vegetable cultivation increased 9.12 times significantly compared with paddy field. Soil microflora of greenhouse culture soil also changed mostly, i.e. the amount of bacteria and actinomyces in the 3 year greenhouse increased 2.54 and 5.66 times more than that of paddy field. On the other hand, biomasses for bacteria and actinomyces in 10 year greenhouse culture decreased dramatically. Furthermore, fungi amount is the most in 10 year greenhouse soil with 9.04 times more than that in paddy soil. Fungi amounts increasing in soil will imperil soil quality because it was prone to result in some soil-borne diseases such as epidemic disease of melon, blight of tomato, and so on. Soil property of open-field vegetable cultivation changed as the same trend as greenhouse cultivation. There were no evident soil property difference between vegetable-rice rotation and paddy field except that fungi increased obviously. It is suggested that large quantity of fertilization result in deterioration of soil physical and chemical characters such as soil EC, NO3-N, Olsen-P and pH, that further adversely affect soil microflora and then the crop. It seems that bacteria and actinomyces were affected by soil nutrients levels while fungi perhaps were affected not only by nutrients but also by the continuous vegetable planting period.