Soil Displacement Method To Eliminate A Long Effect Of Residual Herbicide And Continuous Cropping Stress Of Soybean

The area of soybean were large in Heilongjiang province, and were planted concentrated, continuous cropping stress, as well as using herbicide for long-term time, which leading to the accumulation of long-term residual herbicide in soil, the phenomenon that herbicide phytotoxicity harmed the second crop were seriously. The influence of crop construction adjustment and sustainable utilization of soil resources were seriously, which had a big influence on agricultural production and farm income. Adopt the unit methods of pot experiment and biological assay, study on the law of spatial distribution of long-term residual herbicide in soil, the natural leaching depth of chlorimuron-ethyl in farmland and the drug resistance to long-term residual herbicide in different growing periods. Confirm the effect of spatial distribution of long-term residual herbicide in soil on beet growth through the simulation experiment in the field. In order to prove the harming degrees of long-term residual herbicide done to plants, Using reversing soil horizon Plow which developed by ourselves to reverse the soil that containing residual herbicide, The objective was to provide theoretical and practical supports for sustainable utilization of long-term residual herbicide in northeast of subnival belt .The conclusions obtained were as follows:1. The residual herbicide in soybean field was mainly distributed in 0²0 cm, below 20cm was the safty production depth of beet. The biggest natural leaching depth of chlorimuron-ethyl was 25cm, which forther proved that the smallest amount of residual herbicide which harmed the beet growth was mainly distributed in 0²5cm.2. The photosynthetic rate, stomatal conductance, and yield of beet were increased with the buried depths of chlorimuron-ethyl. There was significant differences between 0¹0cm, 10²0cm and CK, and the the buried depths of herbicide in 30⁴0cm had little effect on the other index of beet.3. The resistence to chlorimuron-ethyl of potato and beet were different at different growth stages. Potato yield decreased by 20% as the critical concentration of herbicide, for potato during potato seedling was 0.09 mg·kg^-1, and was 0.5mg·kg^-1 before flowering-period in soil; during beet foliage period of rapid growth was 0.05 mg·kg^-1, the plant will die when critical concentration was 0.025 mg·kg^-1 in seedling period.4. Using reversing soil horizon plow relatively complete to transit soil position between "soil fatigue layer" (plow layer) and "good layer" (subsoil layer), to avoid mixing the two layers overlap, could achieve to leisure "soil fatigue layer", to reduce the harmful to the following crops by turned the herbicide residues soil layer to the lower soil layer.5. Compare with subsoil tillage and shallow subsoiling, treatment of the replacement 0 20cm and 20 ⁴0cm soil layers could decreased soil bulk density, hardness and solid fraction, and increased gas rate in soil, which soil replacement could provide good soil physical environment for the growth of plant roots.6. Replacing soil layer in herbicide residues soil could achieve beet yield of 46650kg.hm-2. Compared with subsoil tillage and shallow subsoiling, beet yield was increased significantly by 137.2%, 368.9%, respectively. No herbicides residues soil, beet yield of soil replacement treatment was slightly lower than the other two treaments but the difference was not significant.7. Replacing soil layer could achieve potato yield of 23709.5kg?hm-2 in herbicide residues soil. Compared with subsoil tillage and shallow subsoiling, potato yield was increased significantly by 31.3%,177.1%; starch content increased by 2.56%, 2.43%; victoria C content also increased. No herbicides residues soil, potato yield of soil replacement treatment was slightly lower, the difference was not significant, but the potato commodity rate was higher than the other two treatments.8. The type of weed and quantity in soybean field were reduced by soil replacement treatment, so it was beneficial to control rank grass.