Switchgrass cropping systems affect soil carbon and nitrogen and microbial diversity and activity on marginal lands

Abstract

Switchgrass (Panicum virgatum L.), as a dedicated bioenergy crop, can provide cellulosic feedstock for biofuel production while improving or maintaining soil quality. However, comprehensive evaluations of how switchgrass cultivation and nitrogen (N) management impact soil and plant parameters remain incomplete. We conducted field trials in three years (2016–2018) at six locations in the North Central Great Lakes Region to evaluate the effects of cropping systems (switchgrass, restored prairie, undisturbed control) and N rates (0, 56 kg N ha−1 year−1) on biomass yield and soil physicochemical, microbial, and enzymatic parameters. Switchgrass cropping system yielded an aboveground biomass 2.9–3.3 times higher than the other two systems (Jayawardena et al., unpublished data) but our study found that this biomass accumulation did not reduce soil dissolved organic C, total dissolved N (TDN), or bacterial diversity. The annual aboveground biomass removal for bioenergy feedstock, however, reduced soil microbial biomass C (MBC) and microbial biomass N (MBN) and bacterial richness in the second and third years; despite this, continuous monocropping of switchgrass improved soil TDN, inorganic N, bacterial diversity, and shoot biomass in the second and/or third years compared with the first year. N fertilization increased aboveground biomass yield by 1.2 times and significantly increased soil TDN, MBN, and the shoot biomass of switchgrass compared with the unfertilized control. Locations with higher C and N contents and lower C:N ratio had higher aboveground biomass, MBC, MBN, and the activity of BG, CBH, and UREA enzymes; by contrast, locations with higher pH had higher soil TDN and activity of NAG and LAP enzymes. Our research demonstrates that switchgrass cultivation could improve or maintain soil N content and N fertilization can increase plant biomass yield. The comprehensive data also can inform future biogeochemical models to successfully implement switchgrass for bioenergy production.

Comparative productivity of six bioenergy cropping systems on marginal lands in the Great Lakes Region, United States

“…Although miscanthus and switchgrass were the two most productive cropping systems in this study, additional factors remain important when selecting candidate bioenergy crops for sustainable use. These include (1) ecosystem services such as soil carbon sequestration and reduced greenhouse gas emissions (Gelfand et al., 2013), (2) pollination and other biodiversity benefits (Werling et al., 2014), and (3) soil N and microbial diversity improvement (Li et al., 2022) as well as agronomically relevant considerations such as (1) resilience to pests (Bradshaw et al., 2010; Parrish & Fike, 2005) and pathogens (Falter & Voigt, 2014; Parrish & Fike, 2005; Sykes et al., 2016), (2) cold tolerance (Lewandowski et al., 2000), and (3) crops potential to become invasive (Pittman et al., 2015; Raghu et al., 2006). Miscanthus in particular may be disadvantaged by biodiversity concerns (Pittman et al., 2015; Williams & Feest, 2019) and high establishment cost (Lewandowski et al., 2000).…”

Regional biogeography versus intra-annual dynamics of the root and soil microbiome

“…For a full description of its establishment and ongoing treatments see https://data.sustainability.glbrc.org/pages/1.html#marginal . For a description of soil health, and other site level characteristics, see Li et al [ 25 ] and Table S1 & S2 . We sampled switchgrass monocultures (G5 treatment), which were established in 2013 by sowing 0.78 g/m 2 of Cave-in-Rock variety seeds with four plot replicates at each site.…”

“…After long-term N additions to a successional grassland at a site adjacent to the current study, N addition didn’t change microbial community diversity, but excess N addition, > 10.1 g N/m 2 , did affect community structure [ 24 ]. Previous research at our sites found that year to year variation in bacterial richness and microbial biomass outweighed the effects of N addition [ 25 ]. It has also been shown that excessive N in agricultural soils can increase the sensitivity of the microbial communities to seasonal dynamics and alter the interactions within microbial communities [ 26 ].…”

Early production of switchgrass (Panicum virgatum L.) and willow (Salix spp.) indicates carbon accumulation potential in Appalachian reclaimed mine and agriculture soil

“…However, diverting farmland dedicated to the supply of food for human and other animal consumption toward producing feedstock for bioproducts is of potential ethical concern (Barnard, 1983; Hasegawa et al., 2018; Stoy et al., 2018). Marginal lands, that is, land with soils that have physical, chemical, and biological properties that make them less suitable for intensive agricultural production, provide an attractive option for bioproduct crop production as they do not compete with land normally used for food production and can support high bioproduct crop yields (Blanco‐Canqui, 2016; Li et al., 2022; Mehmood et al., 2017).…”

“…are particularly promising for production on marginal lands due to their high water and nutrient use efficiencies, robust root systems, and ability to produce viable yields in marginal soil (Kuzovkina & Volk, 2009; Marra et al., 2013; Scalgline‐Mellor et al., 2018). Switchgrass production can result in favorable changes to soil, for example, soil C accumulation, soil N maintenance, and increased microbial diversity, biomass, and activities (Dirks & Jackson, 2020; Jesus et al., 2016; Li et al., 2022; Liebig et al., 2005). Willow production generally boasts similar benefits, and its production has often been used to control soil erosion and N leaching (Ferrarini et al., 2017; Volk et al., 2006; Zumpf et al., 2021).…”