Soil Physical And Chemical Properties Of Agroforestry In Black Soil Region In Northeast China

To prevent soil erosion, improve soil fertility and enhance soybean yield in Black Soil Region in northeast China, soil physical characteristics, dynamic change in nutrients were compared through field experiment in three agroforestry systems:poplar-soybean, larch-soybean and spruce-soybean. By test and analysis of factors such as soil moisture content, soil density, soil porosity and soil nutrient, effect of different agroforestry systems on physical characteristics of soil moisture were studied. Dynamic changes of fixed-point soil nutrient were studied in the three agroforestry systems, variation of soil nutrients were discussed, differences were compared in effect of agroforestry systems and soybean monoculture on soil nutrients in the Black Soil Region, and agroforestry systems were searched which could improve soil fertility, soil structure and nutrient status. The research results can provide theoretical basis for agroforestry broadcast and application in rolling hills with black soil. The results show:Through test and analysis of the factors, such as physical characteristics of soil moisture, organic matters and content of N, P and K, effect of different agroforestry systems were compared on physical characteristics and nutrient environment of soil in Black Soil Region. Agroforestry eco-system can significantly improve soil structure, enhance the content of soil nutrient, and increase the organic matter and C/N in surface soil. Among all the agroforestry systems, poplar-soybean system had the best effect, with soil moisture content 41.2%, total porosity 60.60% and soil density 1.02g/cm3; its CP/NCP was much higher than soybean monoculture; it had most significant effect on improving the content of soil organic matter, catalyzed N and available P. Larch-soybean system and spruce-soybean system had more available K.In agroforestry systems, pH value was highest in August and comparatively low in April and October; organic matter and catalyzed N were lowest in June and comparatively high in October; dynamic change of available P is not significant; available K was comparatively low in June and August and highest in October. Poplar-soybean system had accumulation of soil organic matter, catalyzed N and available K; larch-soybean system had realized the recycle and accumulation of soil organic matter and catalyzed N; spruce-soybean system had high content of available P and available K. The content of soil organic matter, catalyzed N, available P and available K in agroforestry systems was all higher than that in soybean monoculture, which proved that agroforestry could improve soil and accelerate the recycle and accumulation of soil nutrient. The results can provide significant reference for research on soil nutrient in the program of returning cultivated land to forest.