水稻-油菜周年耕作方式对土壤微生态的影响

为探索土壤微生态对稻-油系统周年耕作方式的响应机制,利用湘北洞庭湖区长期免耕直播土壤,设置稻-油轮作试验,通过比较双免耕双直播和旋耕抛栽土壤中酶活性、微生物数量、群落多样性和菌群功能等指标的差异,研究不同耕作方式对土壤微生态的影响。宏基因组测序表明,细菌群落在2种耕作方式下组成相似,双免耕双直播下细菌多样性更高;真菌群落在不同耕作方式下有不同的真菌类型,但旋耕抛栽下真菌多样性更高。菌群功能分析显示,需氧和兼性厌氧原核微生物相对丰度在双免耕双直播中较高;与氮代谢相关的原核微生物相对丰度在双免耕双直播中较高,而与碳代谢相关的原核微生物的相对丰度在旋耕抛栽中较高。可培养微生物数量测定表明,免耕土壤中可培养细菌、真菌、放线菌和硝化细菌的数量都较旋耕极显著降低,而氨化细菌数量极显著增加。酶活性分析表明,双免耕双直播土壤中的脲酶活性比旋耕抛栽提高了58.12%,而转化酶、磷酸酶和纤维素酶的活性分别降低了28.57%、11.00%和57.73%。本研究表明稻-油轮作双免耕双直播的耕作方式有利于提高土壤中细菌的多样性、需氧和兼性厌氧原核微生物的相对丰度,有利于土壤中氮的转化和利用,为洞庭湖区稻-油系统合理耕作方式的选择提供依据。

Effect of Rice-rapeseed Annual Tillage Patterns on Soil Microecology

To explore the response mechanism of soil microecology to rice-rapeseed system annual tillage patterns, a rice-rapeseed rotation experiment was conducted on the long-term no-tillage direct seeding soil of Dongting Lake area of north Hunan. The differences of soil enzyme activity, microorganism quantity, diversity and microbial community function between the double no-tillage direct seeding (DNT) and double rotary-tillage transplantation (DT) were compared to illustrate the effects of different tillage patterns on soil microecology. The metagenomic sequencing showed that there were similar bacterial types under the two patterns, the bacterial diversity was higher under DNT, but the fungal diversity under DT was higher. Function analysis illustrated that the relative abundance of aerobic and facultative anaerobic prokaryotes was higher in DNT; the relative abundance of prokaryotes related to nitrogen metabolism was higher in DNT, while the relative abundance of prokaryotes related to carbon metabolism was higher in DT. The number of culturable bacteria, fungi, actinomycetes and nitrifying bacteria in DNT soil was significantly lower than that in DT, while the number of ammonifying bacteria was significantly increased. Enzyme activity analysis showed that urease activity of DNT was 58.12% higher than that of DT, while the activities of invertase, phosphatase and cellulase decreased by 28.57%, 11.00% and 57.73%, respectively. The results indicated that the DNT rice-rapeseed rotation system was beneficial to improve the bacteria diversity, and the relative abundance of aerobic and facultative anaerobic prokaryotes, and was conductive to the transformation and utilization of nitrogen in the soil. The study provides a basis for the selection of reasonable tillage patterns of rice-rapeseed system in Dongting Lake area.