Soil Quality Impacts of Perennial Bioenergy Crops on Marginally-Productive Lands.

Dedicated perennial energy crops grown on marginally-productive croplands can provide a sustainable bioenergy feedstock supply while improving soil quality and enhancing ecosystem services. Because marginally-productive croplands typically are at higher risk of degradation, growing highly productive perennial grasses and short rotation woody crops that require less intensive management than row-crops can benefit soil physical, chemical, and biological properties. Improvements in soil organic carbon (SOC) can be used as a primary indicator to evaluate overall soil quality changes due to its links to numerous soil properties. Multiple studies have demonstrated the positive effect of perennial energy crops on SOC stocks compared to annual row-crops, with subsequent improvements in soil bulk density, soil aggregation and stability, water retention, and reduced erosion risk. Changes in microbial communities in soils planted with perennial bioenergy crops also indicate changes in C and nitrogen (N) cycling functions, including increases in microbial groups associated with decomposition (i.e. saprophytic fungi), N fixation, and denitrification. In addition to perennial crop production, agronomic use of co-products from bioenergy production processes (i.e. biochar, lignin co-products) also can improve soil quality. Properly managed perennial bioenergy crop systems have been shown to have positive C and energy balances, emphasizing the importance management impacts on the overall sustainability and climate change mitigation potential of these agroecosystems. While challenges to adopting perennial bioenergy crop production include feasibility and profitability concerns for producers, current research indicates that perennial bioenergy crop production could provide unique opportunities for diversifying farming enterprises while also benefitting soils and the environment.