Spatial And Temporal Variability Of Ariable Land Fertility Quality And Its Driving Factors In Typical County

There is a outstanding contradiction between the large population and little arable land. Arable land quality provides a protection for the food safety. The research was carried in Quzhou County (Hebei Province, China)——A typical alluvial regions of Huang Huai Hai Plain. We collected and measured the contents of soil organic matter (SOM), total nitrogen (TN), available phosphorus (AP) and available potassium (AK) in the0-100cm in1980,2000and2010. The geostatistical method combined with GIS technique was used to analyze the spatio-temporal variability of soil attributes. The main influencing factors such as soil type, soil texture, land use type and farming practices were analyzed. At the same time, the change of soil quality has been evaluated applying to the method of soil quality compressive index to dissect the driving force of Soil quality evolvement. The main results were as follows.It showed that the average SOM contents were8.8,12.9, and14.0g kg-1in1980,2000and2010, respectively; the average TN contents were0.6,0.7, and1.0g kg-1in1980,2000and2010, respectively; the average AP contents were5.2,8.8, and23.4mg kg-1in1980,2000and2010, respectively. The results showed the increasing trend with the time for the three soil nutrients. There was the larger increase for SOM in1980-2000and the smaller increase in2000-2010. There were smaller increase for TN and AP and larger increase for them. The average AK contents were167.1,900., and87.7mg kg-1in1980,2000and2010, respectively. It showed the decreasing trend with the time. There was the larger decrease in1980-2000and smaller decrease in2000-2010, meanwhile there was some increase in some regions.For SOM, the largest area which the amplification was4-6g kg-1accounted for52.1%in1980-2010. The area which the amplification was2-4g kg-1and4-6g kg-1accounted for57.0%and43.0%respectively in1980-2000. The increased area accounted for83.4%in2000-2010. For TN, the largest area which the amplification was0.3-0.5g kg-1accounted for63.6%in1980-2010. All of the TN content increased in1980-2000and the lagest area which the amplification was0.1-0.3g kg-1accounted for73.5%. The increased area accounted for64.2%in2000-2010. For AP the largest area which the amplification was10-20mg kg-1accounted for38.2%and the area which the amplification was20-30mg kg-1accounted for33.1%in1980-2010. For AK the largest area which the reduction was-100--60mg kg-1accounted for60.8%in1980-2010. The area which the reduction was-120--60mg kg-1accounted for90.0%in1980-2000. The increased area accounted for80.7%in2000-2010.The distribution of soil nutrients had the rules as follows:SOM and TN had the high similarity. The area that had the most content increase lies in Quzhou and Disitan town. For AP, this kind of area lies in Quzhou, Disitan and Huaiqiao town. For AK, this kind of area lies in Disitan town, the next class lies in Quzhou and Huaiqiao town.The vertical distribution model of SOC was constructed based on negative exponential function. SOC contents showed a gradually decreasing trend with the increase of soil depth, and SOC contents for all layers were belong to moderate degree of variation. The spatial continuity was better for SOC in0- 20cm and20～40cm, and their correlation distances were14km and3km, respectively. However, SOC in subsoil (>40cm) showed a pure nugget effect. The vertical distribution model can well describe the changes of SOC content with the increasing of depth, the root mean squared errors and the coefficients of determination of the predicted and measured SOC contents reached to0.70and0.94, respectively. Spatial distribution of SOC density was similar to the distribution of soil texture, both showed a decreasing trend from northwest to southeast across the county.The contents of soil nutrients for different soil types had the following order:Fluvo-acquic soi1> Drab fluvo-acquic soil> Salined fluvo-acquic soil> Saline soil. That for soil textures had the following order:clay> medium loam> light loam> sandy loam> sand. That for land use thpes, the SOM, TN and AK had the similar order:irrigated land> dryhad> forestland in1980and forestland> irrigated land> dryland in2000and2010. The order of AP content is dryland> irrigated land> forest land in1980and forest land> irrigated land> dryland in2000and2010.According to the distribution and changing of the SQI, the SQI increased with the time gradually. In2000and2010, The area of I-class land occupied6.3%and40.7%, that of Ⅱ-class land occupied64.2%and51.1%, that of the Ⅲ-class land occupied29.5%and8.2%. The SQI increased in1980-2000and there is78.5%increasing land in2000-2010.The change of land use and managing measures had the great effects on soil qualities. The change of SOM and TN had the simililarity in1980-2000:except "irrigated land to forest land" had the greater amplification, had the124.22%and146.94%, other amplification were34.66%-68.38%and19.64%-54.35%respectively. When the land use change occurred in2000-2010, the soil nutrients showed increasing trend except the SOM which had decreased partly in some land use change. AP had the greatest increase.Managing measures such as straw return, fertilizer application based on soil testing technology had the important role in effectively increasing the soil quality.