Analysis And Assessment Of Soil Quality In Jinghuiqu Irrigation District, Shaanxi Province

Irrigation district has a pivotal position in China's agricultural development.The construction of the irrigation districts has a close relationship with food security,the harmonious development of economy between urban and rural districts,and sustainable development of socio-economy.But with the growing development of irrigated districts,a large number of agricultural pollutants,municipal solid waste and "three industrial wastes" were released into the environment,which is leading to the serious soil environment problems of irrigation districts.With the correct assessment of the soil quality in the irrigated districts, the soil resources can be used reasonably,which has important theoretical and practical value for the maintenance of agro-ecosystem productivity and achievement of sustainable agricultural development.In this paper,the Jinghuiqu Irrigation District of Shaanxi Province was chosen as the research object.Through the investment,data collection,sample collection and indoor laboratory analysis of the present state of soil quality in Jinghuiqu irrigation district,the soil fertility quality of the irrigation district,environmental quality and the regulation of the dynamic changes of soil salt content have been studied,the comprehensive evaluation index system of the soil quality have been established,the index method has been used to quantitatively evaluate the integrated quality of the soil,the measures of how to use the soil resources in irrigated district reasonably have been put forward.Conclusions are presented as follows:1.The average value of the soil organic matter,total nitrogen,total phosphorus,available Nitrogen,Phosphorus and Potassium of Jinghuiqu Irrigation district were 17.5g/kg,1.1g/kg, 1.13g/kg,73.8mg/kg,19.1mg/kg,213.9mg/kg respectively,and the ratio of the indexes of the samples which meet the gradeâ…¡of the fertility reference standards of green food production could be 83.3%,96%,100%,25%,87.5%,99%respectively.The Kriging interpolation method has been used to analyze the spatial distribution of the content of soil organic matter and available nitrogen.Results showed that the organic matter content of the Jingyang County is lower than other areas in the Jinghuiqu irrigated district,while only the available nitrogen content of the southwest part of Sam won County,the center of Gaoling and the eastern part of Jingyang County is in the level of gradeâ…¡,the others are in the level of lower gradeâ…¢. The analysis of the relevance of Soil fertility indicators showed that the organic matter was significantly positive correlated with the total nitrogen and available nitrogen,total nitrogen was significantly positive correlated with available nitrogen,and total phosphorus was significantly positive correlated with available phosphorus. 2.The results of the determination of heavy metals in the soils of irrigation district showed that the Zn in Zhaojia village of Sanyuan city and Cd in Jianwang village of Yanliang has extend the gradeâ…¡of the national environmental standards for soil,which is 1.02 and 2.48 times of the standards,respectively,and the remaining elements did not exceed the standards,and the individual pollution index is＜1,which are non-contaminated.From the analysis of comprehensive pollution index,91.7 percent of the soil samples of the irrigated district have not been contaminated by the heavy-metals.Through the analysis of Kriging interpolation method,the soil of the Yanliang District is seriously polluted,reaching to the light pollution level.3.The determination results of the soil salt content in the irrigation district showed that 83.3%of the soil samples belong to non-saline soil,and 16.7%of the soil samples were mild salinization.The percentage of ions in the total salt content of the soil is in this order of HCO₃ ^-＞Cl^-＞SO₄^2-＞Na⁺+K⁺＞Ca²⁺＞Mg²⁺,which are 43.14%,16.45%,13.40%,10.89%,10.78% and 5.34%,respectively.The analysis of the relevance of the ions in the soil showed that, Na⁺+K⁺ and Cl^- are significantly positive correlated.Na⁺+K⁺ and Ca²⁺ are significantly negative correlated.Ca²⁺ and HCO₃^-are positive correlated,Mg²⁺ and SO₄^2-are positive correlated.4.Through the principle component analysis,it illuminated that in the assessment system of soil quality in Jinghuiqu irrigation district,the soil fertility is the principle component of the various indices in this irrigation district,which is contributing most to the quality of soil. The heavy-metals factor and salinity factor is the second pollutant and third pollutant in the soil pollutants.This result provided the basis for the confirmation of weight for each assessment factor in the integrated assessment of soil quality5.The comprehensive index of soil quality evaluation results showed that 75.3%of the soil in irrigation district is in good quality,20.8%of the soil is fair,and the soil quality of Yanliang District is poor.The variation coefficient of the comprehensive index of soil quality is 11.81%,which is a low degree of sensitivity.6.The protection counter-measures have been presented from the three aspects: increasing the soil fertility of the irrigated district;prevention of heavy metal contamination in the soil and prevention of soil salinization.