水旱轮作条件下免耕土壤微生物生物量变化特征及其活性评价

研究长期免耕土壤微生物活性能及时准确反映免耕土壤质量的演变趋势,探求最佳免耕年限。通过野外调查和室内分析,调查了水旱轮作条件下,不同免耕年限土壤微生物量的变化,并采用主成分分析法对土壤微生物活性进行了综合评价。结果表明:①旱作和水作后,免耕土壤微生物量碳、氮均显著高于常规每年翻耕的耕作方式,微生物量磷则相反。随着免耕年限延长,旱作土壤微生物量碳、氮均呈逐渐降低的趋势;水作后,则呈先增加再降低的趋势;而微生物量磷在不同免耕年限间无显著差异。②主成分分析表明,旱作后免耕土壤微生物活性高于常规每年翻耕,水作后则相反。随着免耕年限延长,免耕土壤微生物活性呈先降低再增加的趋势,旱作后免耕7—8 a土壤微生物活性最低,水作后免耕5—6 a土壤微生物活性最低。

Changes of the Microbial Biomass and Microbial Activities Evaluation of Soil under No-tillage and Paddy-upland Rotation

Soil microbial activities can reflect the trend of soil quality evolution quickly and correctly.By field survey,soil sample analysis and principal component analysis,a study was made on the changes of microbial biomass and the activities of soil microorganism under no-tillage and paddy-upland rotation.The results showed that: ① After dry cropping and paddy cropping,the contents of microbial biomass C and N in no-tillage soil were significantly higher than those of conventional tillage soil.The microbial biomass P was just the opposite.After dry cropping,the contents of microbial biomass C and N tended to decrease with the extension of no-tillage years,but they tended to increase first and then decrease after paddy cropping.There were no significant differences in the microbial biomass P between different no-tillage years.② The principal component analysis indicated that themicrobial activities in no-tillage soil was higher than that in conventional tillage after dry farming,which was lowest in no-tillage soil aging 7—8 years.After paddy cropping,the microbial activity also tended to decrease first and then increase in no-tillage soils but lower than that in conventional tillage all the time,and it was lowest in no-tillage soil aging 5—6 years.