不同耕法对麦田土壤微生物区系影响的研究

A COMPARISON OF CONVENTIONAL AND ZERO TILLAGE EFFECTS ON SOIL MICROFLORA

在砂壤土上设常耕和免耕处理,每一处理又设施肥和不施肥处理。持续实施6年以后比较常耕和免耕法对土壤微生物区系的影响。结果表明:免耕上表层土壤(0-7cm)中微生物数量明显高于常耕;不施肥处理的耕层土壤(0-21cm)中细菌、放线菌、真菌、固氮菌和纤维分解菌的数量分别是常耕的1.27、1.33、1.11、1.91和1.74倍,施肥处理亦呈相同趋势。不施肥条件下小麦对自生固氮菌有明显的根际效应。R/S比在分蘖期达16。根际效应和根系分布特点使固氮菌数量在底层(21-28cm)土壤中总是以免耕大于常耕,耕法对硝化菌和反硝化菌数量的影响是:常耕的硝化和反硝化菌数随小麦生育进程的进行而逐渐增多,免耕处理的则逐渐减少。微生物数量与土壤含水量呈正相关。土壤含水量从19.7％自然失水降至4.4％,细菌、放线菌和真菌数量分别下降了35％、54％和37％;恢复其含水量但不添加营养物质不能恢复微生物到原有的数量。

Under the condition of fertilizcr and no fertilizer applications, the effects of conventional and zero tillage on soil microflora are compared on sandy soil after 6 years of practice of proctice. Results indicate that soil microbial populations (0-7cm layer) are obviously larger than that under conventional tillage treatment. Under the condition of no fertilizer application in soil (0-21 cm layer) of zero tillage treatment, the soil bacteria, actinomycetes, fungi, azotobacter and cellulose-decomposing microbes are more than those of conventional tillage by 1.27, 1.33, 1.11, 1.91 and 1.74 times respectively. Results of fertilizer treatment are similarly to no fertilizer treatment. Under condition of no fertilizer treatment the rhizosphere effect of winter wheat on azotobacter is obvious, R/S ratio is 16 in the tillering stage. The fact that the population of azotobacter in soil of 21-28 cm layer under zero tillage treatment is always larger than that under conventional tillage is attributed to the combination of rhizosphere effect and root distribution. The population of both nitrifers and denitrifers under conventional tillage treatment increases as winter wheat growth proceeds; on the contrary, that under zero tillage treatment decreases. Microbial population is positively correlated to soil moisture content. Under air drying, soil moisture content is decreased from 19.7％ to 4.4％, the soil bacteria, actinomycetes and fungi are decreased by 35％,54％ and 37％ respectively. Without the addition of nutrient material, rewatering of air-dried soil has not recovered the amount of soil microbes.