Hu Xiaojing, Liang Aizhen, Yao Qin, Liu Zhuxiu, Yu Zhenhua, Wang Guanghua, Liu Junjie
Key Laboratory of Mollisols Agroecology, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Harbin, China.
University of Chinese Academy of Sciences, Beijing, China.
Front Microbiol. 2020 Jun 30;11:1333. doi: 10.3389/fmicb.2020.01333. eCollection 2020.
Reduced tillage practices [such as ridge tillage (RT)] have been potential solutions to the weed pressures of long-term no tillage (NT) and the soil-intensive disturbances caused by conventional tillage [such as moldboard plow (MP) tillage]. Although soil diazotrophs are significantly important in global nitrogen (N) cycling and contribute to the pool of plant-available N in agroecosystems, little is currently known about the responses of diazotrophic communities to different long-term tillage practices. In the current study, we investigated the differences among the effects of NT, RT, and MP on soil properties, diazotrophic communities, and co-occurrence network patterns in bulk and rhizosphere soils under soybean grown in clay loam soil of Northeast China. The results showed that RT and MP led to higher contents of total C, N, and available K compared to NT in both bulk and rhizosphere soils, and RT resulted in higher soybean yield than NT and MP. Compared to NT and RT, MP decreased the relative abundances of free-living diazotrophs, while it promoted the growth of copiotrophic diazotrophs. Little differences of diazotrophic community diversity, composition, and community structure were detected between RT and NT, but MP obviously decreased diazotrophic diversity and changed the diazotrophic communities in contrast to NT and RT in bulk soils. Soil nitrogenous nutrients had negative correlations with diazotrophic diversity and significantly influenced the diazotrophic community structure. Across all diazotrophs' networks, the major diazotrophic interactions transformed into a cooperatively dominated network under RT, with more intense and efficient interactions among species than NT and MP. Overall, our study suggested that RT, with minor soil disturbances, could stabilize diazotrophic diversity and communities as NT and possessed highly positive interactions among diazotrophic species relative to NT and MP.
减少耕作措施[如垄作（RT）]一直是解决长期免耕（NT）杂草压力以及传统耕作[如铧式犁（MP）耕作]造成的土壤密集扰动问题的潜在解决方案。尽管土壤固氮微生物在全球氮（N）循环中极为重要，并有助于农业生态系统中植物可利用氮库的形成，但目前对于固氮微生物群落对不同长期耕作措施的响应了解甚少。在本研究中，我们调查了免耕、垄作和铧式犁耕作对中国东北黏壤土种植大豆的耕层土壤和根际土壤的土壤性质、固氮微生物群落及共现网络模式的影响差异。结果表明，与免耕相比，垄作和铧式犁耕作均使耕层土壤和根际土壤中的总碳、氮和有效钾含量更高，且垄作的大豆产量高于免耕和铧式犁耕作。与免耕和垄作相比，铧式犁耕作降低了自生固氮微生物的相对丰度，同时促进了富营养型固氮微生物的生长。垄作和免耕之间在固氮微生物群落多样性、组成和群落结构方面差异不大，但铧式犁耕作明显降低了耕层土壤中的固氮微生物多样性，并与免耕和垄作相比改变了固氮微生物群落。土壤含氮养分与固氮微生物多样性呈负相关，并显著影响固氮微生物群落结构。在所有固氮微生物网络中，主要的固氮微生物相互作用在垄作条件下转变为合作主导型网络，物种间的相互作用比免耕和铧式犁耕作更为强烈和有效。总体而言，我们的研究表明，垄作土壤扰动较小，能像免耕一样稳定固氮微生物多样性和群落，并且相对于免耕和铧式犁耕作，固氮微生物物种之间具有高度积极的相互作用。
