| Ningxia is a primary production and pollution-free and green vegetables base for supplying the north in the winter and supplying the south in the summer.To evaluate the soil quality of protected vegetables in Ningxia,this paper collected seven different planting years and two layers(0-30cm,30-60cm)in 31 different countries which located in 14 cities such as Xingqing Helan,Yongning,Lingwu,Pingluo,and Qingtongxia.Based on grading standards of the national soil census,using the improved Nemerow index the study aim to do the grade evaluation analysis for the soil evaluation factors,soil comprehensive fertility levels,and pollution status.And using Arc GIS Server development technology,the soil database management system of protected vegetable in Ningxia was initially established,which has the basic functions of the soil resource management system.It provides a basis for the hierarchical management and improvement of the protected soil in the district.The main results are as follows:(1)The soil bulk density,specific gravity,total porosity,and solid volume fraction in 0?30 cm soil layer were range from 0.81?1.70 g/cm3,1.75?3.08 g/cm3,17.65-64.62%,and 35.38?93.35%,respectively,while the coefficients of variation(CV)were 11.01%,5.51%,12.81%,and 12.92%,separately.(2)The pH,EC,Na+,and Cl-in 0-30cm soil layer were ranged from 7.61 to 9.32,0.11 to 1.81 mS·cm-1,0.03 to 1.16 g/kg,and 0.06 to 0.79 g/kg,respectively,meanwhile the CV were 3.32%,49.06%,52.09%,and 63.27%,respectively.The pH of 0?30 cm was lower than that of 30?60 cm soil layer,EC was just the opposite,the soil is alkaline,and the surface soil salinization was obvious.As the planting years increase,the pH and EC decreased and increased separately,and the differences in EC,Na+,and Cl-were larger in different regions.(3)The contents of surface soil organic matter,total nitrogen,available nitrogen,available phosphorus,and available potassium were range from 5.44?39.19 g/kg,0.17?1.24 g/kg,28?243.6 g/kg,12.08?426.20 g,and 24.78?479.65 g/kg,and whose CV were 40.82%,40.47%,43.25%,73.81%,and 54.18%,respectively).Compared to the 30?60 cm soil layer,the surface soil nutrient was higher,and the nutrients significantly increased with the increase of planting years.(4)The contents of copper,zinc,lead,chromium,and manganese in the surface soil ranged from 2.74 to 39.09 g/kg,5.74 to 245.86 g/kg?3.28 to 124.59 g/kg,5.23 to 134.30 g/kg,and 165.84 to 986.95 g/kg,and CV were 4737%,47.56%,57.70%,36.91%,and 25.12%,respectively.Compared with the 30?60 cm soil layer,the surface soil had a high content of heavy metals,and there was an obvious aggregation phenomenon,and the content of heavy metal increased significantly with the increase of planting years;(5)The soil organic matter and total nitrogen were overall at a low level,the available nitrogen and available potassium were at a medium level,and the available phosphorus was at an extremely high stand.Heavy metals in the soil such as copper,zinc,and chromium were "clean" levels,and the contents of surface soil lead "clean","neatness" and "excessive" levels account for 62.68%,34.50%,and 2.82%,respectively.The comprehensive quality of soil heavy metals was "clean".Soil comprehensive fertility had obvious regional in spatial distribution.The areas with the highest comprehensive index were Pengyang and Haiyuan in the south and salt pond in the middle located the Yellow River Irrigation District.The comprehensive fertility index of most soils in the central arid zone was relatively low.(6)We had initially established a soil database management system of protected vegetable in Ningxia.It can manage soil information,query information,evaluate quality,render maps and feature maps. |
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