Pasture Management Strategies for Sequestering Soil Carbon - Final Report

Pasturelands account for 51 of the 212 Mha of privately held grazing land in the USA. Tall fescue is the most important cool-season perennial forage for many beef cattle producers in the humid region of the USA. A fungal endophyte, Neotyphodium coenophialum, infects the majority of tall fescue stands with a mutualistic association. Ergot alkaloids produced by the endophyte have negative impacts on cattle performance. However, there are indications that endophyte infection of tall fescue is a necessary component of productive and persistent pasture ecology. The objectives of this research were to characterize and quantify changes in soil organic carbon and associated soil properties under tall fescue pastures with and without endophyte infection of grass. Pastures with high endophyte infection had greater concentration of soil organic carbon, but lower concentration of biologically active soil carbon than pastures with low endophyte infection. A controlled experiment suggested that endophyte-infected leaf tissue may directly inhibit the activity of soil microorganisms. Carbon forms of soil organic matter were negatively affected and nitrogen forms were positively affected by endophyte addition to soil. The chemical compounds in endophyte-infected tall fescue (ergot alkaloids) that are responsible for animal health disorders were found in soil, suggesting that these chemicals might be persistent in the environment. Future research is needed to determine whether ergot alkaloids or some other chemicals are responsible for increases in soil organic matter. Scientists will be able to use this information to better understand the ecological impacts of animals grazing tall fescue, and possibly to identify and cultivate other similar associations for improving soil organic matter storage. Another experiment suggested that both dry matter production and soil microbial activity could be affected by the endophyte. Sampling of the cumulative effects of 20 years of tall fescue management indicated that soil organic carbon and nitrogen storage were greater with than without endophyte only under high soil fertility. This extra carbon and nitrogen in soil due to the presence of the endophyte was further found to be located in intermediately sized soil aggregates, which are important for reducing water runoff and improving water quality. These results suggest that well-fertilized tall fescue pastures with a high percentage of plants infected with the endophyte have the potential to help offset the rising carbon dioxide in the atmosphere. This research has also shown positive ecological implications of tall fescue-endophyte association

Tall Fescue (\u3cem\u3eFestuca arundinacea\u3c/em\u3e) Stockpiling Response to N Fertilizer in Southern Virginia as Affected by Biological Soil Quality

Cattlemen in the eastern USA profitably utilize endophyte-infected tall fescue (Festuca arundinacea) for fall-stockpiled winter grazing. Ergot alkaloid concentration in fescue tends to decline in winter. This improves the quality of fescue for grazing when the supply of other forage becomes limited on most farms. Tall fescue dry matter yields generally respond favorably to nitrogen (N) inputs, but response can be limited with summer application due to accumulation of biologically available N in soil. Research is needed to characterize a diversity of pastures for response to N fertilizer during fall stockpiling. Biological soil quality can be estimated with a simple measure of soil respiration following rewetting of dried soil (Franzluebbers et al., 2000). The flush of CO2 following rewetting of dried soil has been related to the quantity of N mineralized during longer term incubations (Franzluebbers and Haney, 2006) and to N uptake in field studies of forage growth (Haney et al., 2001). Soil was collected from a set of pastures in southern Virginia to characterize biological soil quality and determine dry matter yield response to fertilizer N inputs

Surface-Soil Aggregation and Organic C and N Fractions Under Paired Grassland and Cropland Sites in the Southeastern USA

Grasslands are expected to deliver ecosystem services by sequestering soil organic C, improving soil health and water quality, and minimizing soil erosion. Data to support these ecosystem services from contemporary managed grasslands are relatively scant, and so on-farm measurements would help bolster assessment across more diverse environmental settings. This study was conducted to compare soil properties from paired landuse of croplands and grasslands in a diversity of Major Land Resource Areas – the Piedmont, Blue Ridge, and Blackland Prairie of the southeastern USA. Four separate pastures on three collaborating farms were sampled at depth of 0-10 cm. Four samples from a neighboring cropland field were paired with these pastures. A variety of soil chemical, physical, and biological properties were determined. Soil chemical properties were occasionally different between land management systems on one of the three farms, but few consistent differences occurred across farms. Dry-stable mean-weight diameter (MWD) was not different between paired land management systems, but water-stable MWD was dramatically reduced at all three locations with cropland compared with pasture. Soil stability index (water-stable MWD divided by dry-stable MWD) averaged 0.64 mm mm-1 under cropland and 0.91 mm mm-1 under pasture, suggesting that pastures had a highly stable soil surface that was resistant to erosion and likely contributed to high water infiltration. Soil organic C and N fractions (i.e., total, particulate, and mineralizable) were all significantly greater under pasture than under cropland, indicating that these pastures were indeed storing more C and N, and contributing to greater soil biological activity. This study provides evidence that well-managed grasslands can sequester soil organic C and N, improve soil surface stability conditions to foster water infiltration and reduced runoff, and may have important implications for habit development for soil-dwelling organisms

Well-managed grazing systems: A forgotten hero of conservation

Ecologically sound grazing management is an underused and underappreciated conservation tool in the eastern United States. We contend that significant policy and educational barriers stand in the way of expanding the use of this conservation tool. Well-managed pasture systems combine vigorous perennial vegetation cover, reduced pesticide and fertilizer inputs, and lower costs of production using ecological approaches to generate ecosystem services for society, as well as economic sustainability for the producer. The majority of currently available conservation policy tools were designed to address either rangeland grazing situations in the western United States or conservation cropping in the eastern United States. To promote well-managed pastures in the eastern United States, resource managers and government agencies struggle to adapt programs that are really designed for annual row crop systems. Additional educational and technical assistance resources are needed for promoting well-managed pasture-based farming in the region. This paper summarizes the potential of well-managed pasture systems to provide ecosystem services, provides thoughts for discussion on the barriers to adoption of such systems in the eastern United States, and offers some solutions to move such systems forward through policy and educational efforts. These ideas were first presented at a symposium as part of the 2011 Annual Conference of the Soil and Water Conservation Society in Washington, DC

PRODUCTION AND QUALITY OF SORGHUM SILAGE INTERCROPPED WITH MARANDU GRASS AND PIGEONPEA

Lack of forage in the winter dry season is a concern for cattle production in tropical Brazil. Pasture renovation with silage production might solve an immediate concern for forage production and help develop an improved pasture condition after cropping. The objective was to compare the production and quality of monocropped sorghum and sorghum intercropped with Marandu grass and/or pigeonpea in two row spacings. The experiment was carried out on a sandy Oxisol in São Paulo state in Brazil with an experimental design of a 2 x 4 factorial arrangement with four replications. Treatments were: monocropped sorghum, sorghum intercropped with U. brizantha, sorghum intercropped with C. cajan (cv. BRS Mandarim), and sorghum intercropped with Urochloa+ pigeonpea with 0.45 and 0.90 m row spacings. Greatest forage production was with 0.45-m spacing for monocropped sorghum and dual-species intercropping. With 0.90-m spacing, greatest production was for Sorghum+Urochloa. Sorghum+Urochloa+Cajanus intercropping provided the highest concentrations of crude protein in silage, regardless of row spacing. An increase in ensiling time reduced quality of the silage due to a decline in crude protein and TDN and an increase in fibers. However, the reduced spacing between lines with the inclusion of legumes resulted in a greater amount of silage with a higher concentration of protein. Successful short-term production of high-quality silage could be obtained when sorghum is integrated with Cajanus, and impacts on pasture renovation continue to be evaluated

Editorial: Introduction to themed section— supporting ecosystem services with conservation agricultural approaches

Ecosystem services are the properties and processes of the natural world that contribute to the well-being of plants, animals and humans in a holistic and global context. For too long, members of the agricultural community have been solely focused on the provision of food, feed and fiber. Of course, this essential human innovation has provided hugely important products engineered for mass production that serves all of human society. However, agriculture and the ecosystems in which it is practiced provide numerous other services that are becoming increasingly relevant to its very survival and the survival of humans that it supports. Several recent reviews have expressed the need to balance production and environmental goals to create a sustainable future1–3. Ecosystem services have been categorized into four key components, including supporting, regulating, provisioning and cultural services (Fig. 1). Agricultural landscapes have a large and sometimes dominating influence on several essential ecosystem services, including biomass production (i.e., food, feed, fiber and fuel production), air purification and climate regulation through greenhouse gas exchange, soil formation and retention, water cycling, nutrient cycling, wildlife habitat provision and aesthetic experience

Exploring integrated crop–livestock systems in different ecoregions ofthe United States

Large-scale, energy-intensive, specialized production systems have dominated agricultural production inthe United States for the past half-century. Although highly productive and economically successful, thereis increasing concern with unintended negative environmental impacts of current agricultural systems.Production systems integrating crops and livestock have potential for providing additional ecosystem ser-vices from agriculture by capturing positive ecological interactions and avoiding negative environmentaloutcomes, while sustaining profitability. A diversity of ecologically sound integrated crop-livestock sys-tems have been and can be employed in different ecoregions: sod-based crop rotations, grazing covercrops in cash-crop rotations, crop residue grazing, sod intercropping, dual-purpose cereal crops, and agro-forestry/silvopasture. Improved technologies in conservation tillage, weed control, fertilization, fencing,and planting, as well as improved plant genetics offer opportunities to facilitate successful adoptionof integrated systems. This paper explores the use and potential of integrated crop-livestock systemsin achieving environmental stewardship and maintaining profitability under a diversity of ecologicalconditions in the United States