Effects Of Monoculture On The Soil Quality In Gravel-mulched Land

The bare land is covered with material of gravel by sand、pebbles、gravel or mixture from alluvial or fluvial deposition. The thickness is 10-20cm.This gravel-covered land is called gravel-mulched land. Gravel-sand can coordinate soil moisture, temperature, air, fertilizer and other conditions effectively,to achieve the physiological coordination between the soil and crops, to activate potential fertility of the soil,to create better environmental conditions and increase crop yields,also has significant ecological protection effect. The gravel-sand mulched field watermelon industry had become the advantageous industry in Zhongwei city. It played a decisive role for local farmers. But with successive planting,sand field soil there had been many problems, soil degradation, pests and diseases frequently, watermelon production declined year by year. These problems made people pay more attention on soil quality and soil quality evaluation. This study analyzed the effects of different continuous cropping of gravel-sand biological, physical and chemical properties by Excel、SPSS,and discussed and analyzed the correlation of three properties, had a comprehensive assessment for soil quality. Designed to investigate the soil quality characteristics on the gravel-land,so as to provide a theoretical basis for soil health. In order to achieve the maintenance of soil fertility, and improve the sustainable use and development.The main findings are as follows:(1)Varieties of biological properties on the gravel-land with succession cropping:with the years of cultivated increasing, soil bacteria, actinomycetes, microbial nitrogen, microbial carbon changed relative consistency, as follows:a downward trend after the first rise,5a is a particularly significant. It had a significant increased in 5a.while the layer 2> layer 1> layer 3.(2) Varieties of physical properties on the gravel-land with succession cropping:with the years of cultivated increasing, soil moisture, saturated water holding capacity, capillary water holding capacity, total porosity, capillary porosity changes showed relative consistency:a downward trend after the first rise,7a is a particularly significant.while the layer 3> layer 2> layer 1. The change of the bulk density is in contrast.while the layer 1>layer 2> layer 3.(3) Varieties of chemical properties on the gravel-land with succession cropping:with the years of cultivated increasing,chemical properties changed relative consistency, as follows:a downward trend after the first rise,7a is a particularly significant. It had a significant increased in 7a.while the layer3> layer 2> layer 1.(4) Correlation analysis showed that:biological and chemical properties, chemical properties and physical properties had strong relation, and physical and biological properties had a weak correlation.Regression analysis and path analysis showed that:moisture content,available potassium, actinomycetes, microbial nitrogen, carbon had large effects on bacteria; available phosphorus and bulk density had large effects on fungi; moisture content, available phosphorus, bacteria, microbial carbon had large effects on actinomycetes; water content, capillary water,available potassium, organic matter, bacteria, actinomycetes, microbial nitrogen had large effects on microbial carbon; total phosphorus and nitrogen had large effects on bacterial.(5) The comprehensive evaluation of monoculture on the soil quality in gravel-mulched land. Select the soil water content, bulk density, capillary water, saturated water holding capacity, total phosphorus, available phosphorus, total nitrogen, available nitrogen, total potassium, potassium, organic matter, bacteria, fungi, actinomycetes to have a principal component analysis, and feature the contribution rate weighting weighted index,obtained composite score.It obtained compositive scores about CK, la,3a,5a,7a,9a, lla, were -0.398,0.185,0.477,0.272,0.388,-0.323,-0.645. The highest score in 3a,the lowest in 11a. It had significant obstacle in 7a.