Study On The Soil Ecological Effects And-Physiological Response-in Different Groundcover Pear Tree

Clean cultivated is the main soil management system in arid hilly pear orchard in Western Liaoning, which leads to intensification of soil erosionthe and declining of soil fertility. It has severely restricted the healthy development of pear industry. Mulching system has become one of the effective measures to solve this problem. However, the study of the different mulching way on the ecological effects and biological response in orchards were rarely investigated. Within Zaosu pear orchard as test materials, the dynamic variation rule of soil physical and chemical properties, soil enzyme activity, organic carbon and its components and microbial community structure were systematically studied under different mulching system. The response mechanism of tree growth and development, fruit yield and quality on the different mulching system were determined. The main results were as follows:1. The effects of different mulching on soil physical and chaemical characteristic showed that for plastic film mulching, the soil temperature was increased by8.3%, soil water content increased by37.2%and soil bulk density increased by1.65%. The soil temperature increased significantly in early spring. The highest increasing period of soil water content is branch growing rapidly stage and fruit swelling stage while it is a drought and rainless season in western Liaoning. Therefor, it alleviated effectively the water supply and demand contradiction in pear tree. For straw mulch, the soil temperature was lower12.3%, which alleviated injury of extreme high temperature on the surface roots. The water content increased by13.6%.The soil porosity increased by8.8%. Straw mulching speeded up the formation of aggregates. The percentage of aggregates greater than5mm was53.76%～68.73%.The soil physical and chaemical characteristic were improved.2. The effects of different mulching on soil mineral nutrient contents showed that for manure-straw mulching, soil available nitrogen, phosphorus, manganese and zinc contents were respectively increased by43.5%,146.5%,11.9%and68.4%. For straw mulching, soil available K, iron and copper content increased by50.29%,42.89%and13.51%. The increasing of soil mineral nutrient contents dued to enrichment and accumulation of available nutrients in near-surface soil by the decomposition of stalk mulching residues, and the increasing of mineral available contents by the secretion of roots, decomposition of microorganism, soil slight acidification and detention function of stalk mulching residues. For plastic film mulching, the soil available nitrogen, potassium and copper contents were respectively lower1.7%,2.3%and20.9%than the control.3. The effects of different mulching on soil enzyme activity showed that the activities of urease, protease, invertase, neutral phosphatase and catalase increased by37.5%,25.5%,47.3%,16.9%and4.6%respectively after atraw mulching treatment, plus bacterial manure treatment compared with control. With plastic film mulching, the activities of soil urease and protease were decreased by14.5%and6.9%respectively compared with control. The soil enzyme activities were high between0-40cm soil layers. The soil enzyme activities were lower in spring and autumn and higher in summer. The activity peak period of urease, protease, neutral phosphatase in July, and that of invertase, and hydrogen peroxide were in August.Due to the change of soil C/N ratio after organic matter mulching, which provide the substance for enzymatic reaction.4. The effects of different mulching on soil organic carbon and their components showed that for bacterial manure-straw mulching, the soil organic carbon content, easily oxidized organic carbon, microbial biomass carbon and its percentage of total organic carbon were very significantly increased by47.4%,177.6%,59.6%,327.7%and52.6%respectively. The maximum of soil organic carbon content were within0-30cm soil layer.The application of stalk provided more carbon source for the activity of microorganism and increased the soil organic carbon reserves.5. The effects of different mulching on soil microorganism and their population structure showed that for straw mulching plus bacterial manure, the number of soil bacteria, fungi and cellulose-decomposing bacteria respectively increased47.5%,95.85%,107.4%respectively compared with control, and the number of actinomyces were lower10.1%than control. The maximum of soil bacteria and cellulose decomposing bacteria number were occurred in July, the peak of soil fungi number were in June, the number of soil actinomycetes reached the highest value in August. The ranking of single colony of bacteria and fungi were bacterial manure-straw mulching, straw mulching, plastic film-straw mulching, plastic mulching and control from high to low. The mulching very significantly increased the population’s diversity and richness of the bacterial and fungi.So the application of straw provided more carbon source and mineral nutrient and stimulated the increasing of soil microorganism.6. The effects of different mulching on the growth and development of tree, production and fruit quality showed that for bacterial manure-straw mulching, the amount of tree growth, root activity, nutrient contents, production and fruit quality significantly increased. The production was very significantly higher20.78%than that of control. For straw mulching, the production was significant higher18.28%than control. The straw mulching effected the moisture, fertility, gas and temperature factors, improved the soil physical and chemical characteristic, increased the soil organic carbon and microbial biomass, changed the microbial population structure, increased the roots activities, promoted the increasing of tree growth amount and nutrients accumulations. So the production and fruit quality were improved.In conclusions, the bacterial manure-straw mulching is the best for water preserving and soil fertilizing, and plastic film-straw mulching is the best for increasing temperature. In the practical application, the principle should be followed such as adjusting measures to local conditions, obtaining raw materials locally, decreasing the mulching costs. Thereby, the double efficiency of increasing of production and fruit quality and effective utilization of waste resources would be realized.