Agricultural opportunities to mitigate greenhouse gas emissions.

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.

Bermudagrass management in the Southern Piedmont USA: VI. Soil-profile inorganic nitrogen.

Fate of applied N in forage-based agricultural systems is important to long-term production and environmental impacts. We evaluated the factorial combination of N fertilization targeted to supply 20 g N m 2 yr(-1) and harvest strategies on soil-profile inorganic N during the first 5 yr of 'Coastal' bermudagrass [Cynodon dactylon (L.) Pers.] management. Harvest strategy had much larger effects than fertilization strategy, most notably that soil-profile inorganic N was lower when hayed than under other systems. In the upper rooting zone (0- to 0.3-m depth), soil inorganic N (initially at 3.1 g m(-2)) remained unchanged during the 5 yr under unharvested and low and high grazing pressures (0.00 +/- 0.08 g m(-2) yr(-1)), but declined with haying (-0.25 g m(-2) yr(-1)). In the lower rooting zone (0.3- to 0.9-m depth), soil inorganic N (initially at 2.9 g m(-2)) accumulated with unharvested and low and high grazing pressure (0.64 +/- 0.20 g m(-2) yr(-1)), but remained unchanged with haying (-0.06 g m(-2) yr(-1)). Below the rooting zone (0.9- to 1.5-m depth), soil inorganic N (initially at 5.8 g m(-2)) increased with unharvested and high grazing pressure (0.34 +/- 0.03 g m(-2) yr(-1)), was unchanged with low grazing pressure (-0.10 g m(-2) yr(-1)), and declined with haying (-0.50 g m(-2) yr(-1)). Applied N appears to have been efficiently utilized by forage with subsequent sequestration into soil organic matter and little movement of inorganic N below the rooting zone (< 2% of applied N), irrespective of inorganic or organic fertilization strategy designed to supply sufficient N for high animal production from grazing.

Leaching and binding of fumonisins in soil microcosms.

Fumonisin B(1) (FB(1)) is a water-soluble mycotoxin produced by Fusarium verticillioides. Our research objectives were to determine the leaching of FB(1) through soils and FB(1) binding in soil. Leachate columns were used to determine the movement of FB(1) through soil. FB(1)-contaminated corn screenings or water extracts containing FB(1) were placed on the surface of soil columns. In 100% sand columns, FB(1) leaching was only slightly retarded, whereas at 50%, 75%, and 100% Cecil sandy loam, approximately 60%, 50%, and 20% of the FB(1) was recovered in the column leachate, respectively. The FB(1) retained on the 100% Cecil sandy loam column was tightly bound. However, approximately 75% of the bound FB(1) was released with 5% formic acid and 5% formic acid/acetonitrile (1:1), indicating that the nature of the interaction was probably ionic. The results suggest that FB(1) is quite stable in soils and, while tightly bound, under certain environmental conditions could be released.