Positive Effects on Alfalfa Productivity and Soil Nutrient Status in Coastal Wetlands Driven by Biochar and Microorganisms Mixtures

Qian Cui,Ximei Zhao,Fanzhu Qu,Jiangbao Xia,Ling Peng

doi:10.3389/fevo.2021.798520

Abstract

Biochar application in reclaiming degraded soils and improving plant productivity has been recognized as a promising technology. Yet, the impacts of biochar and mixtures with compound effective microorganisms (CEM) on alfalfa growth and soil quality in coastal wetlands are poorly understood. A greenhouse experiment was set to systematically reveal the impacts of biochar and biochar combined with CEM on alfalfa growth traits, nutrient uptake, biomass, soil quality, and enzyme activities. Eight treatments were included: (1) control (CK−CEM), (2) 10-g/kg biochar (B10−CEM); (3) 20-g/kg biochar (B20−CEM); (4) 30-g/kg biochar (B30−CEM), (5) CEM without biochar (CK + CEM); (6) 10-g/kg biochar with CEM (B10 + CEM), (7) 20-g/kg biochar with CEM (B20 + CEM), (8) 30-g/kg biochar with CEM (B30 + CEM). The utilization of biochar promoted seed germination, height, and tissue nutrient contents of alfalfa, and the combined biochar with CEM showed greater effects. Alfalfa biomass showed the maximum value in the B20 + CEM treatment, and the biomass of root, shoot, leaf in the B20 + CEM treatment increased by 200, 117.3, 144.6%, respectively, relative to the CK−CEM treatment. Alfalfa yield in the CK + CEM, B10 + CEM, B20 + CEM, B30 + CEM treatments was 71.91, 84.11, 138.5, and 120.5% higher than those in the CK−CEM treatment. The use of biochar and CEM decreased soil salinity and elevated soil nutrient content effectively. Biochar elevated soil organic carbon (SOC) and microbial biomass carbon (MBC), NH4+, NO3–, and enzymatic activities, and the positive impacts of biochar combined with CEM were additive. The combined addition of 20-g/kg biochar with CEM showed the pronounced improvement effects on improving soil fertility and nutrient availability as well as soil enzyme activities. Path analysis indicated that the application of biochar mixture with CEM promoted alfalfa biomass by regulating plant nutrient uptake, soil quality (soil nitrogen, SOC, MBC, NH4+, NO3–), and soil enzymatic activities (sucrase, urease, and alkaline phosphatases). Thus, incorporation of suitable biochar and CEM can serve as an effective measure to promote alfalfa productivity and restore coastal wetlands soils.

Highlights

Soil salinization with potentially nutrient deficiency has become a global issue concerning the sustainable development of food security and human livelihoods (Saifullah et al, 2018; Hassani et al, 2020)
Biochar elevated the contents of plant total nitrogen (TN), total phosphorus (TP), and TK in the −compound effective microorganisms (CEM) treatments, while biochar increased the concentrations of plant TN, TP, and TK first and decreased in +CEM treatments
The interactive application of biochar and CEM led to more improved performance on alfalfa growth and nutrient absorption than the individual addition of either biochar or CEM

Summary

Introduction

Soil salinization with potentially nutrient deficiency has become a global issue concerning the sustainable development of food security and human livelihoods (Saifullah et al, 2018; Hassani et al, 2020). Low nutrient deficiency, and poor vegetation coverage occur on coastal wetlands, aggravating plant productivity and unsustainable land use (Huang et al, 2012; Li et al, 2021). Biochar has been proved to increase soil aggregate stability and water retention (Palansooriya et al, 2019; Caban et al, 2020), stimulate nutrient utilization efficiency (Biederman and Harpole, 2013; Chen et al, 2018), boost soil microbial proliferation and activities (Pokharel et al, 2020), and improve plant nutrient uptake and productivity (Lashari et al, 2015). Inappropriate use of biochar to salt-affected soils may increase salinity and alkalinity and inhibit soil nutrient supply, which have an adverse impact on plant performance (Sigua et al, 2016; Luo et al, 2017). The effect of biochar on soil and plant quality under salinity conditions depends on soil type, plant feature, biochar feedstock type, biochar pyrolysis terms, and biochar addition rate

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