Spatial And Temporal Changes Of Soil Quality And Sustainable Utilization Evaluation In The Yellow River Delta

On the basis of collecting the datum of soil, topography, current land utilization and social economy extensively, appraised the background value of soil quality based on materials of the second overall survey of soil in 1986, chose the suit soil quality indexes of Yellow River Delta, and set up the soil quality automation appraise procedure based on 3S. Utilizing the soil field investigation and analyses data in Dec 2003, appraised the current situation of soil quality in study district of 2003, through the comparison with the background value of soil quality in 1986, and investigated the space-time changed regulation of soil nutrient, salt and quality. Abstract the information of land utilize /cover in 1987 and 2002 by utilizing remote sensing image, found out the regulation of the land use /cover change, got the influence of the change of land use /cover to soil quality, furthermore, and established the soil quality model and warning model. Appraise the soil sustainable utilization of the studying area with 34 indexes choosing from the materials such as land utilizing, social economy, etc during 1986-2004. Analyzed the obstacle factor of sustainable utilization in detail, and put forward the sustainable countermeasure of soil resource of studying area. We chose 10 indexes such as soil organic matter, the total nutrient and available nutrient, soil salt content, soil profile patterns from the materials of the second overall survey of soil in 1986 to evaluated soil quality with traditional method. We confirmed their weight with coefficient correlation, calculated the function value according to membership function curve, and evaluated soil quantity with IQI (Integrated Quality Index). The result indicated that middle quality soil (â…£, â…¤, and â…¥grade) which suit to forest and grassland use occupied 48.95%. The best soil (â… ,â…¡and â…¢grade) which suit to the cultivated land only took 21. 93%. The area that difficult to utilize accounts 23.39%. This proved that whole soil quality in the studying area was relatively lower. We established procedure of automatic soil quality evaluation based on 3S. Position were determined by use GPS, land use current situation were abstracted by use RS, soil indexes were vectorized under MAPGIS, then turn into the type of ARCGIS, made use of membership function curve form distribution maps of every index function value, adopt IQI formula to form soil quality map automatically based on the space analyses function of ARCGIS. In accordance with the result of soil quality evaluation, we set up two kinds of index systems, which were simple and suitable for the Yellow River Delta. The evaluation result based on soil organic matter, salt content and available nutrient was as same as that based on soil organic matter, salt content and the whole nutrient, so we could select one group to evaluated soil quality. The evaluation result based on soil organic matter and salt content was as same as that based on 10 indexes by 90%, which prove that soil quality in Yellow River Delta can evaluated by organic matter and salt content. Comparing and assaying the soil quality of 1986 and 2003, we found that, as a whole, the quality of the area was dropped. Over half-of-the-whole-area's soil quality had dropped. (56.36%), which mainly distributed in the Northeast and dropped by one grade; Only 17. 65% regional soil quality improved, and also mainly improved by one grade which concentrated on western plough area; The area that kept unchanged accounted for 25. 98% of the whole area, but mainly concentrated on plough area and the southeast mud flat area. Soil organic matter had the tendency to reduce, and the reduced area accounted for 39. 49% of the whole area which mainly dropped by 4.0g/kg and distributed on the forest and meadow in the Northeast and salt wasteland; 25. 32% of the whole area increased, distributed in western plough the area mainly, and the increasing degree was generally in 0.49-2.73g/kg; the unchanged area basically accounted for 30. 61% and distributed in western plough and the salt wasteland in southeast mainly. The soil hydrolysable N hadn't changed on 48.81% of the areas, but mainly was salt wasteland and mud flat; 31. 28% of the areas increased in various degrees and the increasing degree was between 5.8-16mg/kg, and mainly distributed on western cultivated land and forest and meadow in the southeast; The drought of both sides of the Yellow River of Northeast (19. 89%) reduced in various degrees, and the increasing degree was between 4.5-15mg/kg. To Soil available P, the areas that increased, reduced and changed were basicallysame. The unchanged area distributed on middle part and forest meadow and salt wasteland of east mainly, reduced area on mud flat in east, and increased area on the area of western cultivated land. The soil available K on over half of the whole area (55. 07%) declined in various degrees, expected forest land of the Northeast and mud flat, other areas were all distributed; The area not changed only accounted for 20.48%, and mainly distributed on the salt wasteland; The area increased accounted for 24. 45%, and mainly distributed on the forest and meadow. Soil available K mainly declined between 10-42mg/kg and increased between 20-52mg/kg. The soil salt declined on nearly 1/3 of the area (35. 55%), which distributed on coastal mud flat and salt wasteland mainly; Along the line of the Yellow River, the soil and salt increased, and took 37. 81% of the whole area; in the area of cultivated land, the soil salt had not great change basically. The range of decline of the soil salt relies mainly on more 6g/kg, and the increase between 1.8-5.7g/kg. Soil quality is variry on different type of land use/ cover. Soil organic matter, hydrolysable N, available P and soil quality is the best on cultivated land, in which soil salt is the lowest, the forest and meadow and salt wasteland is second, mud flat is worst. The land use / cover change influents soil quality change directly. The soil quality mainly improved on not-changed region (75.48%). For wasteland region, the soil quality improved greatly where transfer to cultivated land, did not change or slightly dropped to the forest and meadow, improved slightly to the sand land while declined slightly to the construction land; For the cultivated land that transfer to other areas, including forest and meadow, construction land, salt wasteland and sandy ground, soil quality has a downward trend. Soil quality on forest meadow where transfer to salt of wasteland dropped slightly while did not change or improved slightly to cultivated land. There are two tendency for soil quality where sandy ground transfer to cultivated land. It dropped on no irrigated farmland along the Yellow River in the east while obviously improved on irrigated field in the west. At the same time, it dropped where transfer to forest and meadow while slightly improved or did not change to salt wasteland. We established warning model of soil quality with the warning index of soil quality.