Study On Lean Soil Improvement For Planting In Baotou Trial Area, Inner Mongolia, China, By Adding Coal Ash, Reservoir Sediments And Sewage Sludge

The researches on soil improvement and environment renovation by utilizing solid wastes as soil additives, are very important, because both environmental and entiroment degeneration. Solid wastes accumulation and soil erosion have led to serious. So the soil improvement trial by adding coal ash, reservoir sediments and sewage sludge (so called 'three kinds of wastes') for lean soil in Beiliang area, Baotou city, were carried out. And the great achievement of the research work was gotten.The soil is arid in Beiliang area, Baotou city. Some nutrients such as organic material, nitrogen, phosphorus and Fe, Mn, Zn, B, S, Cl and so on is lower in the soil than the requirement for plant growth,. The granularity of the soil is coarse, and only few conglutination grains exist in the soil. The soil is poor at water holding and fertilizer-holding. The soil in Beiliang district, therefore, is not only poor in nutrients but also bad in physical properties.The components of the 'three kinds of wastes' collected from Baotou was analyzed, and the results showed that: (1) there are many kinds of nutrients for plant growth in the coal ash. For example, available phosphorus in coal ash is 10.56 - 30.15 times to that in the soil. Dissolving experiments also showed that some of the nutrient elements in coal ash can be released quickly under the strong effect by sewage sludge, (2) The reservoir sediments inherited more nutrients from the soil of upper drainage area, and the contents of the nutrient elements are gradually accumulated in the reservoir. For example, the contents of available nitrogen and organic material in reservoir sediments are respectively 2.6 - 8.85 times and 1.98 - 4.73 times higher to those of the soil from the upper drainage area. (3) There are abundant available nitrogen, phosphorus, potassium, organic material and trace elements in sewage sludge. Some of them are several times to hundreds times higher in content than that of the soil. In addition, sewage sludge generally contains a lot of microbes, which can promote the transformation of nutrients. So the ' three kinds of wastes' mentioned above are able to supply effectively nutrients for soil.In the 'three kinds of wastes', the contents of the harmful elements such as Cd, Cr, Cu, Pb, Zn, Hg, As are lower than the Chinese national standards for agricultural soil. It means that the 'wastes' can be safely used for planting of trees and grasses.Compared with the soil, the granularities of the coal ash and sewage sludge are fine, their densities are low, and the porosity, sop rates and saturated water transmission rates are higher, but their thermal conductivity is lower. The granularity of the reservoir sediments is finer than that of the soil too, and their density is similar with each other, but the porosity and water storage ability of the reservoir sediments are slightly higher than those of the soil. And compared with the soil, thermal conductivity of the reservoir sediments is lower. So the physical properties of the soil can be improved effectively by adding the coal ash and reservoir sediments.Planting trials were carried out with soils mixed with certain proportions of the 'three kinds of wastes'. The results showed: (1) the heights and the haulm diameters of the maize growed on the mixed soils were better than those of the maize growed on the lean soil. And the productivities of the maize on the mixed soils were 1.89 - 2.62 times to those of the maize on the lean soil; (2) The heights and branch numbers of the thorn trees on the mixed soil were better than those on the lean soil; (3) lawn grass planting on the mixed soil were very flourish, but there were few lawn grasses up on the lean soil.Regarding the mechanism that the plant can be promoted by adding the wastes into the soil, following viewpoints can be given in mineralogy, geochemistry and biochemistry. (1) There are much more fine grains in the 'three kinds of wastes'. Being added with the 'wastes', the soil will greatly increase its rates of the fine grains and conglutination...