Can switchgrass increase carbon accrual in marginal soils? The importance of site selection

Abstract

Most soil carbon (C) is in the form of soil organic matter (SOM), the composition of which is controlled by the plant–microbe–soil continuum. The extent to which plant and microbial inputs contribute to persistent SOM has been linked to edaphic properties such as mineralogy and aggregation. However, it is unknown how variation in plant inputs, microbial community structure, and soil physical and chemical attributes interact to influence the chemical classes that comprise SOM pools. We used two long‐term biofuel feedstock field experiments to test the influence of cropping systems (corn and switchgrass) and soil characteristics (sandy and silty loams) on microbial selection and SOM chemistry. Cropping system had a strong influence on water‐extractable organic C chemistry with perennial switchgrass generally having a higher chemical richness than the annual corn cropping system. Nonetheless, cropping system was a less influential driver of soil microbial community structure and overall C chemistry than soil type. Soil type was especially influential on fungal community structure and the chemical composition of the chloroform‐extractable C. Although plant inputs strongly influence the substrates available for decomposition and SOM formation, total C and nitrogen (N) did not differ between cropping systems within either site. We conclude this is likely due to enhanced microbial activity under the perennial cropping system. Silty soils also had a higher activity of phosphate and C liberating enzymes. After 8 years, silty loams still contained twice the total C and N as sandy loams, with no significant response to biofuel cropping system inputs. Together, these results demonstrate that initial site selection is critical to plant–microbe interactions and substantially impacts the potential for long‐term C accrual in soils under biofuel feedstock production.

Site and Bioenergy Cropping System Similarly Affect Distinct Live and Total Soil Microbial Communities

“…Site can encompass many attributes; because pH and climate are similar between our two study sites, soil type and nutrient status are likely the main drivers of community structure. The importance of texture and nutrient status indicates a reliance on habitat niche, a pattern consistent with previous studies ( Girvan et al, 2003 ; Oehl et al, 2010 ; Jesus et al, 2016 ; Jach-Smith and Jackson, 2018 ; Kasanke et al, 2021 ). It is interesting to note that Jesus et al (2016) studied the same field sites and found a strong site effect on DNA communities after 2years of establishment ( Kasanke et al, 2021 ), and after 8years of establishment also found a strong long-term site effect.…”

“…The importance of texture and nutrient status indicates a reliance on habitat niche, a pattern consistent with previous studies ( Girvan et al, 2003 ; Oehl et al, 2010 ; Jesus et al, 2016 ; Jach-Smith and Jackson, 2018 ; Kasanke et al, 2021 ). It is interesting to note that Jesus et al (2016) studied the same field sites and found a strong site effect on DNA communities after 2years of establishment ( Kasanke et al, 2021 ), and after 8years of establishment also found a strong long-term site effect. The novelty of our results come from the inclusion of RNA-based data as well as sampling pre-growing season, which reveal that the strong site effect on microbial community characteristics is consistent for both the time-integrated total community and the contemporary live community.…”

“…The sandy loam has a lower percent total soil C and N than the silty loam (~1% C, 0.1% N compared to 2% C, 0.2% N). Both sites have an average pH of 6.3 ( Kasanke et al, 2021 ).…”

“…Microbial community composition influences nitrogen (N) availability and carbon (C) mineralization, while their biomass and biochemistry influence the production of microbial necromass and the formation of persistent SOM ( Simpson et al, 2007 ; Kallenbach et al, 2016 ; Crowther et al, 2019 ; Liang et al, 2019 ). Therefore, understanding how bioenergy cropping systems influence microbial community composition and necromass production is fundamental to sustainable bioenergy crop production ( Jansson and Hofmockel, 2020 ; Zhu et al, 2020 ; Kasanke et al, 2021 ).…”

Phytomanagement of Metal(loid)-Contaminated Soils: Options, Efficiency and Value

“…LCA studies clearly attested that the sustainable management of contaminated sites can provide positive environmental and socioeconomic outputs (Vigil et al, 2015;O'Connor et al, 2019), bringing meaningful benefits for a country's development. A central and up-to-date environmental benefit of soil rehabilitation encompasses climate change mitigation, through the increase of soil C sequestration (Paustian et al, 2019;Kasanke et al, 2021;Souki et al, 2021), which can help tackling the net-zero carbon targets in urban and sub-urban areas (Olsson et al, 2019;Bardos et al, 2020). Carbon neutrality is a multinational pledge that is gaining momentum and is supporting efforts toward including degraded land conversion actions in decarbonation strategies (Lask et al, 2021).…”