Responses Of Soil Quality To Change In Land Use

Although the total amount of soil resources has been ranked among the first in the world, the per capita possession of arable land is less than forty-five percent of the average level in the world. And degradation of cultivated land is severe and the overall quality is not very high. With the rapid development of urbanization and the implementation of the project of returning farmland to forest in the western China, the national cultivated land will be further reduced. Under the dual pressures of the population's continuous increase and the gradual decrease of the arable land area, land use intensity of soil resources shows a further increase. Consequently improving soil quality is essential for guaranteeing the stable social and economic development.Land use is a comprehensive reflection. It reflects the various activities of human use of land. Changes in land use patterns affect the soil physical structure, chemical reaction process in soil and status of biological activities, then affect soil quality. Reasonable land use improve the structure of soil, and enhance soil quality;unreasonable land use increase soil erosion, and decline in soil quality.Therefore, the relationship between land use and soil quality is a growing focus of attention.The research about the relationship between land use and soil quality at home and abroad are mostly about soil properties under different land use patterns, but the parts of the relationship between changes of land use patterns and soil quality were few,especially that in agricultural system. There is good agricultural climate resources and well properties of soil retention water and fertilizer in Xiema Town, at beibei area of Chongqing. Due to the social and economic conditions, many regions change their farmland into other types of land use, in order to adapt to the changing environment of social and economic. Therefore, this paper studied land use changes of agricultural system on soil physical, chemical and biological properties, to provided the scientific basis for improving soil quality and rational use of land resources in purple hilly area.The main results are as follows:The paddy field changed to the orchard, the physical, chemical and biological properties of soil tended to decrease,except total content of P in 0-20cm soil and total content of K in 0-60cm soil.The paddy field changes to the dry land, physical properties of soil tended to decrease.Total content of P and availability P increased more, but the other chemical properties of soil tended to decrease,and some of biological properties of soil tended to increase,such as fungi in 20-60cm soil, actinomycetes in 40-60cm soil, urease activity in 0-20cm soil, catalase activity in 20-60cm soil, microbial biomass carbon, microbial biomass nitrogen in 0-20cm soil. The paddy field changed to the vegetable land, physical properties of soil tended to decrease, which was different from two former is that chemical properties had been improved on different degrees, especially total content of P, availability P in 0-40cm soil, availability Mn in 0-20cm soil;and quantity of fungi, bacteria, actinomycetes tended to increase in biological properties of soil.The dry land changed to the orchards,the soil physical properties had no obviously change,but there were some obviously changes in the soil chemistry and biological properties.ln the soil chemical properties,the content of total K tended to increase in a narrow range,as well the available nutrition and the minor element had increased.In the soil biological properties,besides the bacterium in 0-20cm soil horizon and fungi and catalase acticities in 20-60cm soil horizon had reduced,the other biological indicators had increased. The dry land changed to the vegetable land; water content in 0-20cm and 40-60cm had been increased,but the other physical properties had no obviously change. In the chemistry properties,the content of organic carbon tended to increase,and the other properties except availability Fe and availability Mn had increased inordinately.In biological properties,the content of actinomycetes and microbial biomass carbon in 0-20cm soil horizon had decreased,the other properties tended to increase.After paddy field transforming into other land use types, soil quality showed a downward trends,except for vegetable land, soil quality of which had been improved. While after dry land changing into other land use patterns, soil physical, chemical and biological properties had been improved on different degrees, and soil structure had been effectively regulated, so that the overall quality of the soil had been improved.