Soil Fertility Evaluation And Soil Physical And Chemical Properties Of Different Land Use Patterns In Guizhou Karst Area

Typical karst geomorphology was distributed in Guizhou,Guangxi and Yunnan Provinces.Fragile ecological environment and human activity's interference made the contradiction between soil and people sharp,land quality deteriorative,the rock desertification severe,therefore ecological reconstruction was urgently needed.The variety of land use would directly affect the soil fertility,on one hand it could cause soil nutrient loss and land desertification,on the other hand it could improve soil fertility and achieve ecological restoration.Analyzing the influence of different land use types on soil physico-chemical properties and evaluating soil fertility were particularly important to realize the treatment about rocky desertification and ecological reconstruction.The upper reaches of the Yangtze River and the Pearl River Basin flowed through the southwestern China,so the sustainable development of its ecological environment was of great significance to the ecological security of China.Guanling-Zhenfeng Huajiang Demonstration Area in Guizhou was located in the upper reaches of the Pearl River Basin—Beipanjiang River valleys,protecting its fragile ecological environment from damage had an important role in ecological construction of the entire southwest region.Thus,this paper selected the bangui Township as experimental subjects,which was located in Guanling-Zhenfeng Huajiang demonstration area in Anshun City,Guizhou Province and researched the changes of soil physical and chemical properties of eight kinds of land use types including the natural forest land,plantations,plum,cultivated land,toon,pepper,plantains and dragon fruits,providing a theoretical reference for understanding the ecological condition of each land use types in the study area.Then the article selected some fertility indexes,and the soil fertility was evaluated by the principal component analysis method,providing an effective way for the ecological restoration and the basis for governance of rocky desertification and the management of land resources in southwest China.The main conclusions were as follows:(1)The soil mechanical composition was mainly silt,followed by clay,and the sand is the least.Bulk density and moisture content of the soil had little difference.PH ranged from 5.5 to 6.5,with the soil belonging to acid soil.The average contents of organic matter,total nitrogen and alkali nitrogen were 43.84 g/kg,3.40g/kg and 199.37mg/kg respectively,which reached the first class national standard.The average content of total phosphorus and available potassium were 0.94 g/kg and 195.05 mg/kg respectively,which belong to the national secondary standard.The average content of available phosphorus was 6.34 mg/kg,which was in the fourth level of national nutrient grading standards.The total potassium mean was 8.85g/kg,only up to the fifth level of national standard.The coefficient of variation of all the indexes was medium variation(10%-100%)except that the bulk density,moisture content and sand content are weak variation.The maximum coefficient of variation in the physical and chemical index was the sand content and available phosphorus respectively.The coefficient of variation of available potassium and available phosphorus is higher than that of total potassium and total phosphorus,because the available nutrients were affected by many factors such as climate,topography and lost feasibly.The soil organic matter,total nitrogen,available nitrogen,available phosphorus,total phosphorus and available potassium decreased with the increase of depth,showing obvious surface enrichment.(2)There was a significant positive correlation between organic matter and totalnitrogen,available nitrogen,available potassium,total phosphorus,available phosphorus,water content and clay,and negative correlation between organic matter and total potassium and bulk density.Soil bulk density was negatively correlated with organic matter,total nitrogen,available potassium,available phosphorus and water content,while the moisture content was opposite.There was a significant positive correlation between clay content and organic matter,available nitrogen,total potassium,available phosphorus and total phosphorus.There was a significant negative correlation between sand content and organic matter,available nitrogen and total phosphorus and no significant correlation between silt and physical and chemical indicators,showing that clay played an important role in the fertility indicators.Therefore it need to take measures to increase the clay content for ecological restoration.(3)The soil texture of different land use types was similar,which was clayey silt and silt.The clay content of the original forest land was the largest,and the cultivated land was the least,primarily because the cultivation was not unfavorable to conducive to the accumulation of soil surface clay content.In the original forest land,the soil was relatively loose,and the bulk density was small,and the water content was large,which were due to its rich floor litter and biodegradation,while the cultivated land was opposite.In addition to quick-acting phosphorus,the content of each chemical indexes in the original forest land was the highest and the cultivated land was the lowest,and the fruit trees as representative of banana,dragon fruit and pepper were higher,which showed that the soil productivity of the study area was restored after taking a series of ecological restoration measures.Soil physical and chemical properties of the cultivated land were poor because of human factors.Research about the physical and chemical indexes of topsoil by one-way analysis of variance showed that they have significant difference.In addition to total potassium,the chemical index content is reduced with the increase of depth.(4)The results of soil fertility comprehensive evaluation based on principal component analysis showed that the four main components were extracted from the original 12 indicators,and the cumulative contribution rate was 79.26%,which could reflect the overall condition of soil fertility.The general factor score of soil fertility range from-1.132 to 2.082,and the order of fertility comprehensive score was as follows: primary forest land> banana> dragon fruit> plantation> pepper> toon> cultivated land> plum,with plum and cultivated land lower,the primary forest land highest.Organic matter,total nitrogen,available nitrogen,total potassium,available potassium,available phosphorus,water content and soil fertility comprehensive score were significantly correlated,indicating that they can be used as an important indicator of evaluating soil fertility.