Abstract:
Abstract: Black soil is one of the most important cultivated land resources in Northeast China. Black soil has high soil fertility, and brings about high and stable yield. According to the survey, the humus layer of black soil is generally 30-70 cm. But black soil is on high terrain and the cultivation time is long, coupled with the neglect of enhancing soil fertility management, which lead to serious soil erosion, soil layer thinning, and soil fertility decline. Especially in the past 10 years, in order to save costs, farmers have widely used simplified technology, and the basic soil tillage method has changed from plowing to rotary tillage and stubble cleaning, which has resulted in shallow tillage layer and increased the bottom thickness. The depth of the plough bottom moves from 18-22 to 12-15 cm, and the potential productivity of black soil is restricted. People try to stop the decline of soil fertility and soil thinning by improving the application of organic fertilizer, straw returning and subsoiling technology. Our research group found that the straw deep buried and organic fertilizer application have effectively improved soil fertility. In view of removing the obstacle of continuous cropping, the existing technologies including the nutritional therapy, soil disinfection, and crop rotation technology had the problem of high cost and were difficult in the rotation of crops. Therefore, these techniques were limited to solve the problem of soil continuous cropping obstacles. According to the principle of land fallow for leisure, the technology of improving soil by stereo leisure was presented in this paper, which was aimed at continuous cropping obstacles in soils. Through making full use of the characteristics of black soil with deep humus layer, continuous cropping soil was regularly turned to lower leisure. By alternate use of upper and lower soil, the objectives of soil leisure and agricultural sustainable development would be achieved. In this paper, a machine developed to turn the top soil to the lower layer was operated in the black soil field for breaking its hard plough pan. As the depth of top black soil is more than 40 cm, it has good homogeneity from up part to low part, which can provide a choice for developing soil layer up-down fallow technology. Two test fields were selected. One was operated by above mentioned machine, and the other was operated by conventional machine. The results showed that in the up-down fallow field the soil bulk density was decreased by 0.05, 0.11 g/cm3 respectively compared with that in the conventional field. The soil aeration coefficient was increased by 14.97×10-2, 16.69×10-2 cm/s respectively in the first year and second year. The soil saturated hydraulic conductivity was reduced by 3.14×10-3 in the first year, increased by 10.95×10-3 cm/s in the second year. The soil shearing strength was reduced by 0.72 in the first year, increased by 0.82 kPa in the second year, and the soil moisture content was increased by 4.07%, 4.95% respectively in the first year and second year. It was also found that in the up-down fallow field, soil chemical index including soil organic matter, alkali-hydrolysable nitrogen, available phosphorus and available potassium tended to be lower in the upper layer but higher in the down layer. Under the rotation conditions, the yield of potato and beet in the up-down fallow field was decreased by 5.63% and 3.06% respectively in the first year, but the yield of corn and potato increased by 5.20% and 27.00% respectively in the second year. Under the soybean continuous cropping conditions, soybean grew well in the up-down fallow field, dry weight and root dry weight of soybean were increased by 7.63%-7.82% and 7.61%-13.41% respectively, root length was increased by 4.42%-6.26%, pod number and grain number per plant were increased by 18.83%-20.71% and 32.43%-37.21% respectively, and nodule number was increased by 1.46-5.15. During the 2 tested years, soybean yield in the up-down fallow field was 3.09%-22.38% higher than that in the conventional field.