Dedicated energy crops and crop residues will meet herbaceous feedstock demands for the new bioeconomy in the Central and Eastern USA. Perennial warm-season grasses and corn stover are well-suited to the eastern half of the USA and provide opportunities for expanding agricultural operations in the region. A suite of warm-season grasses and associated management practices have been developed by researchers from the Agricultural Research Service of the US Department of Agriculture (USDA) and collaborators associated with USDA Regional Biomass Research Centers. Second generation biofuel feedstocks provide an opportunity to increase the production of transportation fuels from recently fixed plant carbon rather than from fossil fuels. Although there is no “one-size-fits-all” bioenergy feedstock, crop residues like corn (Zea maysL.) stover are the most readily available bioenergy feedstocks. However, on marginally productive cropland, perennial grasses provide a feedstock supply while enhancing ecosystem services. Twenty-five years of research has demonstrated that perennial grasses like switchgrass (Panicum virgatumL.) are profitable and environmentally sustainable on marginally productive cropland in the western Corn Belt and Southeastern USA.

Regional Frameworks for the USDA Long-Term Agroecosystem Research Network

Long‐term research is essential for guiding the development of agroecosystems to meet escalating production demands in a manner that is environmentally sound and socially acceptable. Research must integrate biophysical and socioeconomic factors to provide geographically scalable knowledge that involves stakeholders across the research‐education‐extension‐policy spectrum. In response to this need, the Long‐Term Agroecosystem Research (LTAR) network developed a “Common Experiment,” which seeks to develop and disseminate multi‐region, science‐based information to enable implementation of visionary agricultural innovations while simultaneously promoting food security, well‐being, environmental quality, and climate adaptation and mitigation. The core design of the Common Experiment contrasts prevailing and alternative/aspirational production systems, with the latter including novel innovations hypothesized to advance sustainable intensification in locally appropriate ways. Treatments in the Common Experiment represent a diversity of production systems under cropland, grazing land, and integrated crop/grazing land management. Where possible, treatments are evaluated at multiple spatial scales (e.g., from plot to enterprise) and are designed to evolve over the course of the experiment with stakeholder input. A common assessment framework guides data collection for the experiment and is complemented by metric‐specific protocols and an emerging data management infrastructure. Currently, there are large differences among sites in the application of the experimental framework and degree of stakeholder engagement; differences largely grounded in pragmatic issues related to land access, site expertise, and resource availability. The full potential of the LTAR Common Experiment may be realized with strategic investments in network capacity.

Conservation tillage (CsT) involves management that reduces soil erosion by maintaining crop residue cover on farm fields. Typically, both infiltration and soil organic matter increase over time with CsT practices. We compared the impact of a commonly used CsT practice, strip tillage (ST), to conventional tillage (CT) management on soil nitrogen (N) dynamics and leaching and examined associations to soil N availability and microbial biomass. A winter cover crop was used in both tillage treatments. The study was conducted over a five-year period during rotational cotton (Gossypium hirsutum L.) and peanut (Arachis hypogaea L.) production in the Atlantic Coastal Plain region in Georgia, United States. Fertilizer and poultry litter were applied ahead of the cotton crops. Sets of PVC cylinders were filled with soil from each of six plots, three in ST and three in CT, and maintained in situ in their respective plots for 16 intervals of about 90 days. After retrieval, the soil in each cylinder was analyzed for inorganic N (ammonium and nitrates [NH₄⁺ and NO₃⁻]), total N, total carbon (C), and microbial biomass. Leached NO₃⁻-N was captured on anion exchange resin-filled bags attached to the bottom of each cylinder. After the five-year study period, the ST and CT soil C content increased by 22% and 23%, respectively. Total soil N content increased 27% with ST compared to 22% with CT. Temporal patterns in NO₃⁻-N leaching were not different between CT and ST treatments, and a high amount of NO₃⁻-N leaching was observed after the application of poultry litter. The cumulative amount of NO₃⁻-N leached from soils throughout the five-year study was 141 and 122 kg N ha⁻¹ (126 and 109 lb N ac⁻¹) with CT and ST practices, respectively. Results suggest that leaching from the top 15 cm (6 in) of soil may be an important pathway of N loss from both CT and ST cropping systems in the region. Regardless of tillage, soil microbial biomass N was equal to or higher than the total inorganic N, but still represented a small percentage (up to 9%) of the total soil N. Overall, microbial biomass N was higher in ST compared to CT. Minimizing NO₃⁻-N in the soil from reaching ground and surface waters while increasing crop productivity represents a major challenge. The use of ST in conjunction with winter cover crops may improve plant N availability by more than 27 kg ha⁻¹ y⁻¹ (24 lb ac⁻¹ yr⁻¹) in the sandy landscapes of the southeastern Coastal Plain region through microbial cycling of organic N while reducing subsurface NO₃⁻-N losses.