Soil fertility quality evolution after land use change from rice-wheat rotation to plastic film covered vegetable

A field survey was conducted in Jiaxing, Zhejiang province at Yangtze River Delta Results indicated that soil fertility quality had been changed dramatically after land use changing from ricewheat rotation to continuous vegetable cultivation and under plastic film covered condition in particular Average soil pH of 153 soil samples was 5.34, about 1 unit lower than the same vegetable soil 20 years ago Acidification varied with soil texture, i.e heavy textured vegetable soil had most severe acidification (pH 5.28), medium textured soil with moderate decrease of soil pH (5.31), and light textured soil with least decrease of soil pH (6.14) As compared with the same type of paddy soils that was still under ricewheat rotation system, the soil pH had no significant change The average salt content was 2.81 g/kg for 84 soil samples, 36.2% of which contained over 3.0 g/kg of soluble salts The high soluble salt contents have caused severe damage to vegetable growth Again the heavier the soil texture, the higher the soluble salt content Overaccumulation of N, P and K has caused unbalanced nutrition supply There were about 31% samples with higher than 300 mg/kg NO3--N and average available P were higher than P2O5 90 mg/kg Very higher fertilization and the higher evaporation coupled with very low leaching under plastic film covered vegetable cultivation caused dramatic change of soil fertility quality This implies that remedy of this degraded soil needs balanced fertilization program and scientific land use management (crop rotation and changing plastic film covered to open field)