Search

Bioenergy production often focuses on the aboveground feedstock production for conversion to fuel and other materials. However, the belowground component is crucial for soil carbon sequestration, greenhouse gas fluxes, and ecosystem function. Roots maximize feedstock production on marginal lands by acquiring soil resources and mediating soil ecosystem processes through interactions with the microbial community. This belowground world is challenging to observe and quantify; however, there are unprecedented opportunities using current methodologies to bring roots, microbes, and soil into focus. These opportunities allow not only breeding for increased feedstock production but breeding for increased soil health and carbon sequestration as well. A recent workshop hosted by the USDOE Bioenergy Research Centers highlighted these challenges and opportunities while creating a roadmap for increased collaboration and data interoperability through standardization of methodologies and data using F.A.I.R. principles. This article provides a background on the need for belowground research in bioenergy cropping systems, a primer on root system properties of major U.S. bioenergy crops, and an overview of the roles of root chemistry, exudation, and microbial interactions on sustainability. Crucially, we outline how to adopt standardized measures and databases to meet the most pressing methodological needs to accelerate root, soil, and microbial research to meet the pressing societal challenges of the century.

Biofuel feedstocks grown on marginal lands, such as those that experience ephemeral waterlogging, reduce interference with food agriculture. As early‐season extreme precipitation events in the U.S. Midwest continue to increase, waterlogging tolerance may play an important role in the productivity of annual biofuel cropping systems. We assessed the establishment and yield of photoperiod‐sensitive sorghum [Sorghum bicolor (L.) Moench] and maize (Zea mays L.) after extreme early‐season rainfall events in central Illinois. We used paired sorghum and maize transects, spanning from low‐lying poorly drained areas to higher better drained areas, to evaluate the response of both cropping systems throughout the 2020 growing season. Sorghum maintained 25% mean emergence rates in areas that experienced the most severe waterlogging, but maize failed to establish under the same conditions. Despite the low establishment, sorghum yields in the poorly drained areas were upwards of 50% of those found in the better drained, whereas maize yields were zero areas in the poorly drained locations. The yield compensation in sorghum resulted from increased tillering, higher productivity per stem, and subsequently higher productivity per plant, which illustrates the greater phenotypic plasticity of sorghum compared to maize. Land managers who are currently seeking to grow annual cellulosic feedstocks on soils that are vulnerable to transient soil waterlogging will likely have more success with photoperiod‐sensitive bioenergy sorghum than maize. Core Ideas: Sorghum emergence was greater than maize in poorly drained, wet locations.Sorghum yields in the wet areas were greater than expected based on emergence.Greater tillering and leaf area explained sorghum yield compensation in wet areas.Sorghum may be more resilient to early‐season soil waterlogging than maize. [ABSTRACT FROM AUTHOR]

Tallgrass prairie restorations can quickly accrue organic C in soil and biomass, but the rate of C accumulation diminishes through time and is highly variable among more mature prairies. Long-term soil organic carbon ( SOC) accumulation in prairies has been linked to edaphic factors such as soil texture, soil moisture, and SOC content, but it is unclear how these factors affect the ecosystem processes that are responsible for observed differences in C accumulation rates in older prairies. We measured belowground plant and SOC pools and fluxes within 27-36-year-old restored tallgrass prairies in order to quantify total C storage, determine the net ecosystem production of C ( NEP-C), and explore which edaphic factors influence the ecosystem processes responsible for divergent NEP-C. We found that 11% of organic C was stored in biomass, and we estimate that one-third of post-restoration C sequestration has occurred in biomass, thereby highlighting biomass as a large but often overlooked C pool. Belowground biomass and soil C pools were notably smaller than those reported for remnant prairie, suggesting that future belowground C accumulation could still occur. During this study, the prairies appeared to be a net source of C, although the range of NEP-C values encompassed zero. Sand content positively affected NEP-C via increased belowground biomass production-C inputs, and SOC negatively affected NEP-C due to increased soil respiration C outputs. However, soil moisture had a smaller negative effect on soil respiration, indicating that both SOC and soil moisture play important roles in determining prairie C balance. [ABSTRACT FROM AUTHOR]

Quantifying changes in soil organic carbon (SOC) stocks and other soil properties is essential for understanding how soils will respond to land management practices and global change. Although they are widely used, comparisons of SOC stocks at fixed depth (FD) intervals are subject to errors when changes in bulk density or soil organic matter occur. The equivalent soil mass (ESM) method has been recommended in lieu of FD for assessing changes in SOC stocks in mineral soils, but ESM remains underutilized for SOC stocks and has rarely been used for other soil properties. In this paper, we draw attention to the limitations of the FD method and demonstrate the advantages of the ESM approach. We provide illustrations to show that the FD approach is susceptible to errors not only for quantifying SOC stocks but also for soil mass-based properties such as SOC mass percent, C:N mass ratio, and δ 13 C. We describe the ESM approach and show how it mitigates the FD method limitations. Using bulk density change simulations applied to an empirical dataset from bioenergy cropping systems, we show that the ESM method provides consistently lower errors than FD when quantifying changes in SOC stocks and other soil properties. To simplify the use of ESM, we detail how the method can be integrated into sampling schemes, and we provide an example R computer script that can perform ESM calculations on large datasets. We encourage future studies, whether temporal or comparative, to utilize sampling methods that are amenable to the ESM approach. Overall, we agree with previous recommendations that ESM should be the standard method for evaluating SOC stock changes in mineral soils, but we further suggest that ESM may also be preferred for comparisons of other soil properties including mass percentages, elemental mass ratios, and stable isotope composition., (© 2020 John Wiley & Sons Ltd.)