Ridge Tillage Improves Soil Properties, Sustains Diazotrophic Communities, and Enhances Extensively Cooperative Interactions Among Diazotrophs in a Clay Loam Soil

Xiaojing Hu,Junjie Liu,Guanghua Wang,Aizhen Liang,Qin Yao,Zhenhua Yu,Zhuxiu Liu

doi:10.3389/fmicb.2020.01333

Abstract

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.

Highlights

Tillage practices, i.e., conventional tillage and conservational tillage, are defined by the degree of soil inversion and the amount of crop residues remaining on the ground for the purposes of crop production and sustainable agricultural environments (Sengupta and Dick, 2015; Zuber and Villamil, 2016)
Soil total carbon (TC), total nitrogen (TN), and AK were significantly higher in ridge tillage (RT) and moldboard plow (MP) than in no tillage (NT) of both bulk and rhizosphere soils
total phosphorus (TP) and available phosphorus (AP) were significantly higher in RT than in MP and NT of bulk soils, while they were remarkably higher in MP and RT than in NT of rhizosphere soils

Summary

Introduction

I.e., conventional tillage and conservational tillage, are defined by the degree of soil inversion and the amount of crop residues remaining on the ground for the purposes of crop production and sustainable agricultural environments (Sengupta and Dick, 2015; Zuber and Villamil, 2016). A variety of “reduced tillage” practices [such as ridge tillage (RT)] that served as conservational tillage can maximize the positive effects on soil quality to improve and sustain productivity and increase food security and profits (Kuntz et al, 2013). These reduced-pass practices can break the compacted soil surface associated with NT, avoid the intense soil perturbations that occur under moldboard tillage, and largely maintain soil health and increase soil resiliency compared with other tillage practices (Busari and Salako, 2015)

Objectives

Methods

Results

Discussion

Conclusion