| Walnut is one of the most important woody grain and oil plant in the world.It has high economic value and excellent forest species for soil and water conservation and ecological economy.With the expansion of the policy of returning farmland to forestry,the competition of land between farmland and woodland become stronger.Due to the growth cycle of trees is very long,there is less or even no income in the early stage of woodland.Planting under forest can bring short-term gains,and can solve the problem of early economic benefits and employment of woodland.Furthermore,it can solve the problem of the contradiction between woodland and farmland efficiently.In order to screen suitable planting pattern under the walnut forest in the dry-hot valley of Dadu River,four planting modes of walnut + cabbage + cabbage(HLL),walnut + Chinese cabbage + potato(HLT),walnut + cabbage + soybean(HDD)and walnut control(HCK,without underwood planting)were established,and corn + potato(NCK)farmland control group was established.In order to know the effect of underwood planting of walnut on the physical and biochemical properties of soil,we use membership function to comprehensively evaluate soil improvement effects under different understory planting patterns.Comparison with farmland,The main results are as follows:(1)Planting under walnut forest increased soil non-capillary pore,capillary pore and total pore by 2.4~14.8%,2.8~29.1% and 2.6~23.1%,respectively,and reduced soil bulk density by 4.6~17.6%.(2)Planting under walnut forest increased the natural of soil water content,maximum moisture capacity,capillary moisture capacity,field moisture capacity and drainability by 10.5~46.1% ? 7.6~49.2% ? 7.8~56.8% ? 9.1~68.9% and 1.4~9.1%,respectively.(3)Planting under walnut forest increased the content of soil organic matter,total nitrogen,alkali hydrolysable nitrogen,available phosphorus and rapidly available potassium by 5.1~14.9%?3.9~12.5%?25.1~112.4%?-28.3~21.9% and-17.4~53.0%,respectively.(4)Planting under walnut forest increased the number of soil bacteria,actinomycetes,fungi and total microorganisms by 21.4~54.3%,19.2~58.1%,17.8~58.4% and 21.2~54.6% respectively.(5)Planting under walnut forest increased the activities of soil saccharase,urease,phosphatase,catalase,polyphenol oxidase and peroxidase by 9.3~57.8%,16.9~57.5%,6.4~32.0%,9.7~42.2%,4.1~14.2% and 1.4~38.6% respectively.(6)Planting under walnut forest increased the comprehensive value of soil properties(physical,biological and chemical)by 72.1~491.8%,and the order of each mode is HLL > HLT > HDD > HCK > NCK.In conclusion,all models can reduce the value of soil bulk density,and increase the oil porosity value,water holding capacity,drainage capacity,nutrient content,microbial quantity and enzyme activity.In the dry-hot valley area of Dadu River,the development of planting under walnut forest has a good effect of fertilizing and improving soil properties.Among them,planting cabbage in two seasons under walnut forest is the best,which plays an important role in increasing the total income of walnut forest land and solving the problem of labor and employment. |
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