Effect Of Covering Soil And Benefit Analysis For Land Reclamation Of The Black Soil Region In Northeast China

At present, soil source of land reclamation and land regulation of soil and water conservation mainly come from topsoil stripping. Land remediation is based on soil covering and tractor pushing. Topsoil stripping is thought as the most convenient and economical method to protect the precious soil resources, added arable land or restored surface landscape.With the gradual improvement of national laws, regulations and policies, the government and enterprises have strengthened the importance of land reclamation. But the thickness of covering soil is related because of suitable of topsoil stripping and limited quantity of topsoil can be stripped. The thickness of covering soil is influenced by climate, landform, vegetation type, slash surface type and other factors. And vegetation requires different thickness of the matrix. Different thickness of covering soil of different soil types are not representative and universal applicability.In order to study the best thickness of topsoil coverage in the black soil region of Northeast China, a deserted quarry and the demolition of village were chosen as the test field for land reclamation. The abandoned mine areas was chosen as Jingyue demonstration zone which with steep slopes, exposed rock and bumpy slope. Three different kinds of topsoil thickness(20 cm、30 cm、50 cm) were tested for the growth of corn. The demolition of village was chosen as Shuangyang demonstration zone which was covered with four thickness(10cm、20 cm、30 cm、50 cm). Corn of Xianyu 335 was chosen as planting variety for both two zones.Then, the yield of corn, soil SOM, pH, nutrients like N, P and K as well as their production were monitored. The suitable thickness of covering soil was determined by plant growth and soil nutrient contents.According to the requirements of "Regulation on compiling land reclamation plan", land reclamation costs included engineering reclamation fee and biological reclamation fee.Engineering reclamation fee consisted of soil transportation fee, land consolidation fee, covering fee of surface soil. Biological reclamation fee meant planting corn fee which consisted of seeds expense, fertilization expense, irrigation expense, machinery expense and labor expense, etc.Without considering the capital time value, calculated the recovery time of net income of the project total investment to indicate the thickness of covering soil from the benefit cost optimal.The comprehensive evaluation determined the optimal thickness of covering soil, which are good for crop growth and fastest to recover cost.The following conclusions can be obtained by the studies above:1) Different thickness of covering soil were designed combined with two types of covering soil from the abandoned mines and demolition of old village. The adaptable thickness of covering soil were confirmed from the content of soil nutrient and crop yield. The results showed that the thickness of 50 cm overlying topsoil was conducive to soil fertility and a higher production.2) Calculating the static investment payback period according to cumulative net cash flow which showed that the 30 cm thickness of overlying topsoil cost the shortest time 3.54 years for cost-recovering.3) The comprehensive evaluation results showed that the 30 cm thickness of overlying topsoil had better nutrition to corn growth and best economy cost while land reclamation.