基于旋耕玉米秸秆还田条件下土壤微生物、酶及速效养分的动态特征

为研究旋耕条件下秸秆还田的腐解机理,设置不同数量秸秆还田处理,分别于玉米拔节期、抽雄期、乳熟中期、完熟期测定土壤微生物数量、土壤酶活性和速效养分含量。结果表明:(1)秸秆还田促进土壤微生物繁殖,提高土壤酶活性,增加碱解氮含量,降低速效磷和速效钾含量;秸秆量为11 250kg/hm~2时真菌、细菌、放线菌数量及蔗糖酶、纤维素酶活性增幅最大;秸秆量为7 500kg/hm~2时脲酶、磷酸酶活性和碱解氮增幅最大,速效磷、速效钾降幅最大。(2)部分土壤微生物数量与土壤酶活性之间存在相关性,播种后40天,土壤真菌、细菌、放线菌数量、纤维素酶活性之间存在正相关,真菌与磷酸酶活性呈负相关;播种后67天,放线菌与磷酸酶、蔗糖酶呈正相关;播种后140天,放线菌与蔗糖酶呈正相关。(3)部分土壤酶活性之间存在相关性,播种后67天,脲酶与纤维素酶、磷酸酶与蔗糖酶之间呈正相关;播种后140天,蔗糖酶与纤维素酶呈正相关,脲酶与蔗糖酶、纤维素酶呈负相关。(4)土壤酶活性与速效养分存在相关性,播种后40,112天的脲酶、67天的纤维素酶、112,140天的磷酸酶与碱解氮含量呈正相关;播种后40天,蔗糖酶与速效钾呈正相关,播种后40,67,112天脲酶活性与速效钾含量呈负相关。(5)碱解氮与速效磷含量呈负相关,播种后40,112,140天的碱解氮与速效钾含量呈负相关。

Dynamic Characteristics of Soil Microorganisms, Enzymes and Available Nutrients Under the Conditions of the Corn Straw Returning Based on Rotary Tillage

In order to understand the decomposing mechanism of the straw returning to field under rotary tillage, the different treatments based on amounts of straw returning were set up. Soil microbial biomass, soil enzymes activities and available nutrients contents were measured at maize jointing stage, male stage, middle maturity stage and mature stage respectively. The results showed that: (1) The straw returning could promote the soil microbial reproduction, increase the soil enzymes activities and the content of alkali hydrolyzable nitrogen, but decrease the contents of available phosphorus and available potassium. The number of fungi, bacteria, actinomycetes and sucrase and cellulase activities increased substantially under the straw returning amount of 11 250 kg/hm2. Urease and phosphatase activities and the contents of alkali hydrolyzable nitrogen increased under 7 500 kg/hm2, but the available phosphorus and available potassium decreased. (2) There were positive correlations between the number of soil fungi, bacteria, actinomyces and cellulase activity, but the fungi quantity was negatively related to phosphatase activity after planting for 40 days. Actinomycetes quantity was positively related to phosphatase and sucrase after 60 days, and related to sucrase after 140 days. (3) There were correlations among the soil enzymes activities. Urease was positively related to cellulose, and phosphatase was positively correlated with sucrase in 67 days. Sucrase was positively related to cellulose, and urease was negatively related to sucrase and cellulose in 140 days. (4) There were correlations between the soil enzymes activities and the available nutrients contents. Urease in 40 days and 112 days, cellulase in 67 days, phosphatase in 112 and 140 days had positive correlations with alkali hydrolyzable nitrogen contents.