Study On Soil Enzyme And Soil Physical- Chemical Nature Of Continuous Cotton Cropping Feild In Ebinur Lake Basin

Xinjiang is the maximal production base of excellent quality cotton in our country. The area of cotton field is 40% of the total arable land in Xinjiang, and the proportion will be more than 80% in central cropping cotton region. Because cotton is the dominating crop, continuous cropping is very widespread. Long-term continuous cropping causes great latent danger for continual agriculture development. The dangers are such as decreasing of natural resource quality, great harmful of plant diseases and insect pests, imbalance of soil nutrient content, destroying of farmland eubiosis, decreasing of cotton quality and so on. Additionally, ever since a long time ago, using large quantity of fertilizer, agricultural chemical and membrane, which makes environmental bearing capacity increasingly go to worst. The effect to soil ecosystem function which caused by continuous cropping is the focal point for people. Soil enzymes are the central factors to be concerned. Choose Ebinur lake wetland nature reserve and cotton field in Tuotuo country as the object of study. Study the change of soil enzyme activities, soil physical-chemical natures and correlation between each other in cotton fields which have been continuous cropped for 5years, 10years, 15years, 20years, 30years.The aim is to study the influence to cotton soil micro-environment that caused by continuous cropping. We hope to uncover the quality character of cotton fields and to provide some useful basal research for cotton sustainable development in Xinjiang.The main study results as follows:(1) The change of soil enzyme activities in cotton field, natural field and semi- natural field: In 0⁵0cm soil layer, the variation tendency of catalase, phosphatase, urease and invertase register as cotton field>semi-natural field>natural field. On vertical direction, all register as upper layer>middle-layer>lower layer, that is the activities of the four enzymes decreased with the increased depth of soil.(2) The change of soil physical-chemical natures in cotton field, natural field and semi- natural field: soil water content and organic matter both register as cotton field>semi-natural field>natural field. On vertical direction, soil water content increased with the increased depth of soil, and the organic matter decreased with the increased depth of soil in cotton field and semi-natural field. Total salt content registers as natural field>semi-natural field>cotton field. Natural field and semi-natural field belong to extremely saltiness and cotton field belongs to moderate saltiness. The pH in three kinds of fields is more the 8.0. Natural field and semi-natural field belong to intensity basic soil and cotton field belongs to basic soil. The content of soil ions decreased with the increased depth of soil and SO₄^2-> Ca²⁺>Cl^->Mg²⁺>HCO₃^-> CO₃^2-. In research region, it is almost the type of sulphate, and the move tendency of salinity ions is almost accumulate with seldom elution. On the process of going up, sulphate shows the strongest surface gathering.(3) The change of soil enzymes in continuous cropping cotton field of different growth years: In 0⁵0cm soil layer, with the increase of growth years, the change of catalase activity registers as 30years>10years>20years>15years>5years and decreased with the increased depth of soil. The change of urease activity registers as 20years>10years>30years>15years>5years and it shows the increased tendency from 5 years to 30years. The change of invertase activity registers as 30years>20years>10years>5years>15years and it decreased with the increased depth of soil all other years except the 5 years. The change of phosphatase activity registers as 20years>10years>5years>30years>15years and it decreased with the increased depth of soil all other growth years except the 10 years.(4) Correlation analysis between activities of soil enzymes in continuous cropping cotton field of different growth years: Activities of phosphatase has extremely marked positive correlation with invertase and marked positive correlation with urease. Activities of catalase has extremely marked positive correlation with urease and marked positive correlation with invertase. There is no significantly correlation between urease and invertase.(5) The change of soil physical-chemical natures in continuous cropping cotton field of different growth years: In 0⁵0cm soil layer, with the increase of growth years, the change of soil water content registers as 10years>5years>20years>30years >15years and increased with the increased depth of soil. The change of total salt registers as 5years>10years>15years>20years>30years and decreased with the increase of growth years. The fields of continuous cropping for 5 years and 10 years belong to extremely saltiness, the fields of continuous cropping for 15 years and 20 years belong to great moderate saltiness and the field of continuous cropping for 30 years belongs to moderate saltiness. The change of pH registers as 15years>5years>10years>20years>30years. The change of organic matter registers as 10years>20years>30years>5years>15years and increased with the increase of growth years. In soil section it is decreased with the increased depth of soil. All the ions except the CO32- are decreased with the increase of growth years, and the ions content registers as SO₄^2->Ca²⁺>Mg²⁺>Cl^->HCO₃^->CO₃^2-.(6) The results of canonical correlation analysis, Pearson Correlation analysis and progressively regression analysis show that the organic matter is the best index to predict the activities of soil enzymes all over the soil physical-chemical factors introduced. The organic matter is able to predict the activities of soil enzymes.(7) The result of saltalization evaluation of cotton field in different growth years indicates that, in 0⁵0cm soil layer, Sequence of total Score level is 5years>20 years >10years>15years>30years. From this, it can be seen that, with the increase of growth years, the harm of soil saltalization has been improved greatly.