| With the adjustment of industrial structure of agriculture,the cultivation area of protected horticulture is increasing. The soil salinization problem in protected horticulture has become more serious, due to the high multiple cropping index and fertilizer inputment in the process of facility horticulture cultivation. The soil salinization problem resulted in the deterioration of soil properties, low crop yield and quality, and threats on human health. Therefore, it is urgent to solve the problem.This research focused on typical soil salinization in horticulture cultivation area of central and southern Jiangsu Province as research subjects, stratified sampling of0-40cm soil layer in this area with10cm as a unit, and putting the adjacent exposed soil outside the greenhouse as control, analyzed the soil properties and the vertical distribution of them in the soil. On the base, the research studied the effect of paddy-upland rotation on soil properties in salinization of facility soil, and the effect of the time of flooding cultivation and the number of paddy-upland rotation on soil properties in salinization of facility soil. The followings are the major findings:1. The results showed that the EC value and salt ions of facility vegetable soil were much higher than those in the corresponding open field soil. NO3-was the major anion in different soil layers of this area and SO42-was also high; while Ca2+was the main cation. Soil EC value and the salt ions content were both higher in0-10cm soil layer, indicating topsoil accumulation for them. Soil salinization had an even development in deeper layers in some bases. Soil nutrients of facilities were significantly higher than outdoor soil. The content of organic matter and available P were at medium level, the content of available K was medium or over medium level, the content of NO3-N was high level, other forms of nitrogen were insignificant. The soil sucrase and phosphatase activities were higher than those in open field soil, except for urease. So the influence of salinization on soil urease was significantly greater than that on sucrose and acid phosphatase.2. The results showed that:after waterlogging of water spinach for one month, the value of soil EC in0-10cm and10-20cm soil layer were significantly decreased, but the value of soil EC in30-40cm soil layer was increased. With two months’ waterlogged cultivation, the decreasing range of the value of soil EC in0-40cm was60.27-81.84%. The content of main salt ions also had corresponding change. The content of NO3-decreased from2193.76mg·kg-1to326.88mg·kg-1, the content of SO42-decreased from809.54mg·kg-1to273.45mg·kg-1. Through water cut-off one month, the value of soil EC and the content of major salt ions in all levels were a small recovery. Due to the basic fertilizer and soil water evaporation, the value of soil EC and the salt ions from fertilizer were significantly rally, with planting chrysanthemum one month. Only the surface and deep soil EC value and the content of salt ions increased, after planting chrysanthemum two months. However, compared with control the value of soil EC in0-20cm cultivated horizon was decreased by52.71%-67.27%and the contents of main salt ions except HCO3-were decreased by22.24%-68.63%. The soil nutrients were reduced by waterlogged water spinach, and the effect on available K was the largest. After dry farming, they would recover by fertilization. The activity of soil soil sucrase, urease and phosphatase were reduced by flooding. But after paddy-upland rotation, the activity of soil soil sucrose, urease and phosphatase were higher than untreated sample.3. With the extension of the waterlogged time, the value of soil EC showed a decreasing trend. Except HCO3-other salt ions have the corresponding change. After two months’ waterlogged cultivation, the value of soil EC was decreased greater than continue waterlogged cultivation, and the decline of soil EC of other layer was significantly bigger than10-20cm. The content of NO3-, SO42-, Ca2+and Mg2+had the same change. But the content of Cl-,Na+and K+showed a decreasing trend. With the extension of the waterlogged time, the content of soil organic matter had increased, but other nutrients showed a trend of decreas but haven’t changed much. With prolonged flooding soil invertase and urease activity showed a decreasing trend, while the acid phosphatase activity showed an increase trend.4. After twice Paddy-upland Rotation, the content of soil salt and soil ion of20-40cm soil layer was further reduced, and the vertical distribution of soil salt was significantly improved. The time of the Paddy-upland Rotation had little effect on soil nutrients soil invertase and urease, but had singnificantly improved the activity of the acid phosphatase. |
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