Soils Salinity Content of Greenhouse in Shanghai Suburb

Salinity content and characteristic of farmland soil in Shanghai suburb was studied.Result indicates that soils in greenhouse in Shanghai suburb are partially salted.Soils of suburb where melons or vegetables grow in Shanghai city,88.52% soil is non-salted while 10.37% mildly salted,0.74% obviously salted and 0.37% badly salted.Anions component of salt salinity in soil are mainly SO~(2-)_4,Cl~-,NO~-_3 and cations component are mainly Ca~(2+),Na~+,Mg~(2+),K~+.These ions are mostly from fertilizer auxiliary component or fertilizer transformation component besides some original deposition in soil.The formation of soil secondary salted in greenhouse cultivation in suburbs of Shanghai has a close relationship with improper fertilization or employing too much fertilizer.Soil salinity is different with different cultivation mode and utilization time.From high to low,sequence of soil salinity content in 0～20 cm cultivation layer of different crop mode is greenhouse vegetable soil,melon soil,vegetable melon rotation soil and hypaethral vegetable soil respectively.In the same region,salinity in greenhouse soil continually increases and accumulates from underlayer to surface along with more utilization years.