Evaluating Soil Microbial Communities and Cropping Systems for Biomass Feedstock Production on Degraded Lands

NOTE: GRANT PROJECT TERMINATED 2/2/2021 DUE TO NON-COMPLIANCE OF USDA SUBAWARD AGREEMENT. FINAL REPORT NOT SUBMITTED.

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Commodities

• Agronomic: grass (misc. perennial)

Practices

• Crop Production: cropping systems
• Energy: biofuel feedstocks
• Soil Management: soil microbiology, soil quality/health

Cellulosic biomass production on degraded soil modulates land competition for food versus bioenergy crops. Due to little or no agricultural value of degraded soil, improved land management coupled with fortification of soil with an organic amendment or inoculum will bio-stimulate or bio-augment respectively, the existing soil microbial community (SMC) which will, in turn, improve soil and water quality. The goal of this study is to evaluate the effects of intercropping, soil amendment and inoculation strategies on SMCs while assessing its potential to rejuvenate the soil health for enhancement of switchgrass (SG) and eastern gamagrass (GG) production in degraded soil. This study will be conducted at two different degraded land sites in Eastern and Middle Tennessee. After land preparation, SG and GG will be seeded in plots designated for the following treatments: intercropping with hairy vetch, soil amendment with paper mill sludge (PMS) and inoculation with a commercial preparation of mycorrhizae (BioVam). Treatments will assess SMC diversity in degraded land and evaluate their abilities to rejuvenate soils with simultaneous enhancement of bioenergy feedstock production. Since sustainable biomass production on arable land has been a major challenge both nationwide and in the south-west region, the results from this study will provide essential knowledge on the sustainable production of biomass feedstock on degraded land using cellulosic (non-food based) perennial crops. Our findings will also be beneficial to Tennessee farmers, who are currently confronted with degraded land, on how to rejuvenate their land while restoring and maintaining good soil health.

Two selected sites that share a common biomass production lower than 0.5 kilograms per hectare were identified for this research through collaboration with Tennessee NRSC. This study proposed to test the following hypotheses that:

First, biostimulation with an organic substrate, bioaugmentation with a competent microbial agent and legume intercropping will enhance biomass productivities GG and SG above current <0. 5kg.ha-1 in selected soils.

Second, that combinations of biostimulation, bioaugmentation and intercropping will enhance the functional and structural diversity of soil microbial communities under GG and SG cultivation, which in turn drive biomass productivity and soil quality including nutrient geochemical cycling.

Based on these two hypotheses, specific objectives were determined as:
1) Conduct field studies to evaluate sustainable biomass production systems for switchgrass (SG) and eastern gamagrass (GG), two selected native warm-season perennial grass that will be grown in degraded soil of two sites with or without organic substrate amendment, legume intercropping and/or microbial inoculation;

2) Characterize microbial structural and functional diversity in soils under GG and SG production in Objective 1 and correlate with enhanced bioenergy biomass production,

3) Assess effects of soil treatments in Objective 1 on nutrient cycling and soil quality.