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Agriculture is a source for three primary greenhouse gases (GHGs): CO(2), CH(4), and N(2)O. It can also be a sink for CO(2) through C sequestration into biomass products and soil organic matter. We summarized the literature on GHG emissions and C sequestration, providing a perspective on how agriculture can reduce its GHG burden and how it can help to mitigate GHG emissions through conservation measures. Impacts of agricultural practices and systems on GHG emission are reviewed and potential trade-offs among potential mitigation options are discussed. Conservation practices that help prevent soil erosion, may also sequester soil C and enhance CH(4) consumption. Managing N to match crop needs can reduce N(2)O emission and avoid adverse impacts on water quality. Manipulating animal diet and manure management can reduce CH(4) and N(2)O emission from animal agriculture. All segments of agriculture have management options that can reduce agriculture's environmental footprint.

Contemporary agricultural systems can be generalized as highly specialized operations that are fueled by mechanization; supplied with external nutrients to maximize production; crops protected by petrochemicals to fight against weed, disease, and insect pressures; and livestock protected by therapeutics to ward off virus and bacterial infections when managed in confinement. Such specialized systems have led to low levels of diversity, elevated environmental risks from contamination, loss of soil organic matter, ecological instability, and limited adaptability to climate change. More diversified farming systems are possible, but research required to characterize them in a holistic manner as an alternative to contemporary, specialized systems remains challenging to fund and sustain over time, primarily because they require more labor, management skills, and accessible markets to achieve additional ecological, environmental, and social goals. We share some perspectives as to (1) how specialized systems became the norm and (2) what changes could be made to reverse some ecological risks and environmental declines associated with specialization, acknowledging there is no panacea. Strong evidence exists for perennial forages to restore soil organic carbon (C) and nitrogen, but system‐level analyses of the net balance in greenhouse gas emissions remain to be characterized in the myriad of potential integrated crop–livestock systems that might be deployed across the diversity of edaphic, environmental, and socio‐economic conditions. We suggest there are abundant opportunities for more sustainable agricultural production to sequester soil organic C, reduce greenhouse gas emissions, and develop more climate‐resilient agricultural systems that will be needed in a future dominated by climate change issues. Core Ideas: Forage‐based crop rotations are a proven practice for conserving nutrients and improving soil health.Diversity on farms in the United States is low and could be enhanced with integrated crop–livestock systems.Structural barriers to integrated crop–livestock systems are present but could be overcome. [ABSTRACT FROM AUTHOR]

Highlights: [•] Integrated crop-livestock systems are effectively implemented in every region of the U.S. [•] New technologies facilitate successful adoption of crop-livestock systems. [•] Adoption of crop-livestock systems in the U.S. occurs primarily among livestock managers. [•] Cash crop managers have few current incentives to incorporate livestock into their crop systems. [ABSTRACT FROM AUTHOR]

The article discusses the benefits and barriers of well-managed grazing-based farming system and promotes adoption of this conservation tool in the eastern U.S. It informs that this system provides society-wide environment services, productivity and profit to individual producers. It proposes the local, state and federal programs to support grazing system and encourages development of policy options for adoption of pasture-based livestock production as one of several agroecological approaches.

Surface soil characteristics arc of key importance in assessing the sustainability of agricultural management systems. We evaluated the factorial combination of nutrient source (inorganic, mixed organic + inorganic, and organic as broiler litter) and forage utilization (unharvested, low and high cattle grating pressure, and hayed) on soil organic matter during 12 yr of pasture management on a Typic Kanhapludult in Georgia. Nutrient source had very little effect on bulk density, soil organic C (SOC), and total soil N (TSN). Forage utilization greatly affected all soil properties, more so nearest the surface. For example, SOC at a depth of 0 to 3 cm under low grazing pressure was 47.6 g kg-1 and under haying was 28.8 g kg-1 (P < 0.00 1), while at 3 to 6 cm it was 20.1 and 14.9 g kg-1, respectively (P = 0.04), and at 6 to 12 cm it was 12.7 and 11.0 g kg-1, respectively (P = 0.59). Soil bulk density was inversely related to SOC. Total SOC (0-20 cm) plus surface residue C was 3.6 ± 3.6 Mg C ha-1 greater (mean ± standard deviation among six nutrient source it forage utilization comparisons) in the zone nearest shade and water sources than farther away. Sequestration of TSN in the surface 6 cm averaged 8 ± 8 kg N ha-1 yr-1 (mean ± standard deviation among three nutrient source comparisons) when hayed, 31 ± 15 kg N ha-1 yr-1 when left unharvested, and 74 ± 5 kg N ha-1 yr-1 when grazed by cattle with either low or high grazing pressure. These results indicate the large potential of well-managed grazing systems to improve the quality and functioning of soils in the southeastern United States. [ABSTRACT FROM AUTHOR]

Conservation management of degraded land has the potential to build soil fertility, restore soil functions, and mitigate greenhouse gas emissions as a consequence of surface soil organic matter accumulation. Literature from the southeastern United States was reviewed and synthesized to: (i) quantitatively evaluate the magnitude and rate of soil organic C (SOC) sequestration with conservation agricultural management; (ii) evaluate how conservation management affects surface SOC accumulation and its implications on ecosystem services; and (iii) recommend practical soil sampling strategies based on spatial and temporal issues to improve the detection of statistically significant SOC sequestration. Soil organic C sequestration was 0.45 ± 0.04 Mg C ha-1 yr-1 (mean ± standard error, n = 147, 20 ± 1 cm depth, 11 ± 1 yr) with conservation tillage compared with conventional tillage cropland. Establishment of perennial pastures sequestered 0.84 ± 0.11 Mg C ha-1 yr-1 (n = 35, 25 ± 2 cm depth, 17 ± 1 yr). Stratification of SOC with depth was common under conservation agricultural management and appears to be integrally linked to abatement of soil erosion, improvement in water quality, and SOC sequestration. Sampling of conservation management systems should ideally occur repeatedly with time in controlled and replicated experiments, but there is also an urgent need for chronosequence and paired-field surveys of SOC on working farms in the region to validate and expand the scope of inference of experimental results. Landowners in the southeastern United States have great potential to restore soil fertility and mitigate greenhouse gas emissions with the adoption of and improvement in conservation agricultural systems (e.g., continuous no-till, high-residue crop rotations, high organic matter inputs). [ABSTRACT FROM AUTHOR]

Tillage, cropping system, and cover cropping are important management variables that control the quantity, quality, and placement of organic matter inputs to soil. How soil organic matter and its different fractions respond to management has not been comprehensively studied in integrated crop-livestock systems. We conducted a 3-yr field experiment on a Typic Kanhapludult in Georgia in which long-term pasture was terminated and converted to annual crops. Tillage systems were conventional (CT, moldboard plowed initially and disked thereafter) and no-till (NT). Cropping systems were summer grain with winter cover crop and winter grain with summer cover crop. Cover crops were either grazed by cattle or left unharvested. Total organic C was highly stratified with depth under NT and relatively uniformly distributed with depth under CT. All soil C and N fractions were greater under NT than under CT at a depth of 0 to 6 cm. Tillage system had the most dominant influence on all soil C and N fractions, and cropping system the least. At the end of 3 yr, total organic C at a depth of 0 to 30 cm was lower under CT than under NT (42.6 vs. 47.4 Mg ha-1 [P < 0.001]). Potential C mineralization was also lower under CT than under NT (1240 vs. 1371 kg ha-1 during 24 d [P = 0.02]). At a depth of 0 to 30 cm, cover crop management had no effect on soil C and N fractions, but within the surface 6 cm some changes occurred with grazing of cover crops by cattle, the most dramatic of which were 1 ± 9% increase in soil microbial biomass C and 3 ± 16% decrease in potential C mineralization. To preserve high surface-soil C and N fractions and total plow-layer contents, NT cropping following termination of perennial pasture is recommended. In addition, since cattle grazing cover crops did not consistently negatively influence soil C and N fractions, integrated crop-livestock systems are recommended as a viable conservation approach while intensifying agricultural land use. [ABSTRACT FROM AUTHOR]

Abstract: A 3-year experiment was conducted to determine pasture and cattle responses to tall fescue–endophyte association (free, novel, and wild endophyte associated with ‘Jesup’ cultivar) and fertilization source (inorganic and broiler litter). Fertilization source had only minor or no effects on botanical composition, forage mass, cattle stocking rate, and yearly cattle performance and productivity. However, cattle performance and production were greater with broiler litter than with inorganic fertilization during summer, but lower in autumn and winter, suggesting a difference in timing of nutrient availability to forage due to mineralization of organic nutrients in broiler litter. Pastures with wild endophyte association either had higher forage mass during some periods or were able to carry more cattle than other endophyte associations. Cattle performance was lower with wild than with other endophyte associations at all times of the year, except in summer. Cattle gain in winter was not different among endophyte associations (64kgha−1; p =0.43), was lower in spring with wild endophyte than with other endophyte associations (244kgha−1 versus 302kgha−1; p =0.04), was higher in summer with wild endophyte (147kgha−1 versus 117kgha−1; p <0.001), and was lower in autumn with wild endophyte (97kgha−1 versus 129kgha−1; p =0.10). Seasonal differences in pasture responses to fertilization and endophyte association suggested that management options could be developed to avoid or limit toxic cattle responses to wild endophyte. [Copyright &y& Elsevier]

An introduction is presented in which the editor discusses various articles within the issue on topics including agricultural systems, ecosystem services and nutrient cycle.