Trichoderma-Inoculation and Mowing Synergistically Altered Soil Available Nutrients, Rhizosphere Chemical Compounds and Soil Microbial Community, Potentially Driving Alfalfa Growth

Fengge Zhang,Yunqian Huo,Xixi Xu,Yan Xiao

doi:10.3389/fmicb.2018.03241

Abstract

Trichoderma spp. are proposed as major plant growth-promoting fungi (PGPF) to increase plants growth and productivity. Mowing can stimulate aboveground regrowth to improve plant biomass and nutritional quality. However, the synergistic effects of Trichoderma and mowing on plants growth, particularly the underlying microbial mechanisms mediated by rhizosphere soil chemical compounds, have rarely been reported. In the present study, we employed Trichoderma harzianum T-63 and conducted a pot experiment to investigate the synergistic effect of Trichoderma-inoculation and mowing on alfalfa growth, and the potential soil microbial ecological mechanisms were also explored. Alfalfa treated with Trichoderma-inoculation and/or mowing (T, M, and TM) had significant (P < 0.05) increases in plant shoot and root dry weights and soil available nutrients (N, P, and K), compared with those of the control (CK). Non-metric multidimensional scaling (NMDS) demonstrated that the rhizosphere chemical compounds and soil bacterial and fungal communities were, respectively, separated according to different treatments. There was a clear significant (P < 0.05) positive correlation between alfalfa biomass and the relative abundance of Trichoderma (R2 = 0.3451, P = 0.045). However, Pseudomonas, Flavobacterium, Arthrobacter, Bacillus, Agrobacterium, and Actinoplanes were not significantly correlated with alfalfa biomass. According to structure equation modeling (SEM), Trichoderma abundance and available P served as primary contributors to alfalfa growth promotion. Additionally, Trichoderma-inoculation and mowing altered rhizosphere soil chemical compounds to drive the soil microbial community, indirectly influencing alfalfa growth. Our research provides a basis for promoting alfalfa growth from a soil microbial ecology perspective and may provide a scientific foundation for guiding the farming of alfalfa.

Highlights

Trichoderma species are important plant growth-promoting fungi (PGPF) in soils that have been reported to significantly facilitate plant growth and development (Singh et al, 2015) through numerous mechanisms: increasing solubilization of soil nutrients (Yadav et al, 2009; Kapri and Tewari, 2010), increasing nutrient efficacy and recycling (Azarmi et al, 2011), releasing plant growth stimulatory agents (Contreras-Cornejo et al, 2009) and inducing systemic resistance (Shoresh et al, 2010)
Alfalfa treated with Trichoderma and/or mowing (T, M, and Trichoderma and mowing (TM)) had significant increases in plant shoot and root dry weights, compared with those of the control (CK)
Alfalfa inoculated with Trichoderma and mowing (TM) had the highest dry weight (1.17 g/plant) among all treatments (Figure 1)

Summary

Introduction

Trichoderma species are important plant growth-promoting fungi (PGPF) in soils that have been reported to significantly facilitate plant growth and development (Singh et al, 2015) through numerous mechanisms: increasing solubilization of soil nutrients (Yadav et al, 2009; Kapri and Tewari, 2010), increasing nutrient efficacy and recycling (Azarmi et al, 2011), releasing plant growth stimulatory agents (Contreras-Cornejo et al, 2009) and inducing systemic resistance (Shoresh et al, 2010). Several studies show that Trichoderma-inoculation has significant promotion effects on the growth of many plant species (Howell et al, 2000; Zhang et al, 2013a), including those of pasture fields (Lee et al, 2015; Zhang et al, 2018b). Alfalfa (Medicago sativa L.) is the most familiar and widely distributed legume in the world, which is characterized by high yields and nutritive value, palatability and digestibility, and plays a important role in animal husbandry development (Radovicet al., 2009). The synergistic effects of Trichoderma and mowing on alfalfa growth, the underlying microbial mechanisms that are mediated by rhizosphere chemical compounds, have rarely been studied

Methods

Results

Conclusion