• Authors:
    • Marland, G.
    • West, T. O.
  • Source: Biogeochemistry
  • Volume: 63
  • Issue: 1
  • Year: 2003
  • Summary: There is a potential to sequester carbon in soil by changing agricultural management practices. These changes in agricultural management can also result in changes in fossil-fuel use, agricultural inputs, and the carbon emissions associated with fossil fuels and other inputs. Management practices that alter crop yields and land productivity can affect the amount of land used for crop production with further significant implications for both emissions and sequestration potential. Data from a 20-year agricultural experiment were used to analyze carbon sequestration, carbon emissions, crop yield, and land-use change and to estimate the impact that carbon sequestration strategies might have on the net flux of carbon to the atmosphere. Results indicate that if changes in management result in decreased crop yields, the net carbon flux can be greater under the new system, assuming that crop demand remains the same and additional lands are brought into production. Conversely, if increasing crop yields lead to land abandonment, the overall carbon savings from changes in management will be greater than when soil carbon sequestration alone is considered.
  • Authors:
    • Prior, S.
    • Torbet, A.
    • Rogers, H.
    • Hendrey, G.
    • Mitra, S.
    • Wielopolski, L.
  • Source: Second Annual Conference on Carbon Sequestration
  • Year: 2003
  • Summary: Global warming is promoted by anthropogenic CO2 emissions into the atmosphere, while at the same time it is partially mitigated by carbon sequestration by terrestrial ecosystems. However, improvement in the understanding and monitoring of belowground carbon processes is essential for evaluating strategies for carbon sequestration including quantification of carbon stores for credits. A system for non-destructive in situ carbon monitoring in soil, based on inelastic neutron scattering (INS), is described. The system can be operated in stationary or scanning mode and measures soil to depth of approximately 30 cm. There is a good agreement between results obtained from INS and standard chemical analysis of soil cores collected from the same study site.
  • Authors:
    • Acosta-Martinez, V.
    • Gill, T. E.
    • Zobeck, T. M.
    • Kennedy, A. C.
  • Source: Biology and Fertility of Soils
  • Volume: 38
  • Issue: 4
  • Year: 2003
  • Summary: Microbes (i.e., fungi and bacteria) are needed to maintain the quality of semiarid soils and crop production. Enzyme (produced by microbes) activities were increased in the soil when cotton was rotated with sorghum or wheat under reduced or no-tillage in comparison to continuous cotton under tillage. Soil bacteria and fungi did not change, according to one analysis conducted, due to crop rotation under reduced or no-tillage in comparison to continuous cotton under tillage. The increases in enzyme activities, however, are indicating that microbes and their enzymes will be increased, and thus nutrients will be more available to plants, more organic matter will be formed, and other soil properties will also positively change if crop rotations with reduced or no-tillage are applied to semiarid soils in comparison to the typical current practice of continuous cotton with tillage.
  • Authors:
    • Hutchinson, R. L.
    • Boquet, D. J.
    • Paxton, K. W.
  • Source: Louisiana Agriculture
  • Volume: 46
  • Issue: 2
  • Year: 2003
  • Summary: Studies were conducted in Louisiana, USA, between 1987 and 2002 to determine the effects of tillage practices (no-till and surface till), cover crops (winter wheat, winter hairy vetch and volunteer winter native (fallow) vegetation) and nitrogen rates (0, 35, 70, 105 and 140 pounds per acre) under rainfed or irrigated conditions on cotton growth and yield. Following a cotton crop and without additional fertilizer, the native, vetch and wheat cover crops produced an average 1054, 2054 and 4045 pounds above-ground biomass per acre, respectively. Nitrogen concentration of the cover crop vegetation averaged 2.0, 4.0 and 1.5% in native, vetch and wheat, respectively. The total nitrogen in the cover crop biomass averaged across year, tillage regime and nitrogen rate was 27, 90 and 38 pounds per acre in native, vetch and wheat, respectively. Initially, lint yields in surface-till and no-till were similar but, after five years, no-till yields were higher. No cover crop + tillage treatment recorded the lowest yield. Savings in equipment and labour costs increased the returns for cotton grown with no-till practices. Cotton following vetch needed no nitrogen fertilizer. Cotton following wheat required high nitrogen rates for optimum yield. At the optimum nitrogen rate, all tillage cover crop regimes produced similar yields. Lint yields were lower in rainfed than irrigated conditions. Wheat cover crop was more beneficial to yield in rainfed than irrigated cotton. No-till + wheat cover crop recorded the highest yields and returns from rainfed cotton. No-till cotton produced yields similar to or higher than cotton planted in surface-till treatments.
  • Authors:
    • Flury, M.
    • Huggins, D. R.
    • Bezdicek, D. F.
    • Fuentes, J. P.
  • Source: Soil & Tillage Research
  • Volume: 71
  • Issue: 1
  • Year: 2003
  • Summary: Understanding the fate of soil water and nitrogen (N) is essential for improving crop yield and optimizing the management of water and N in dryland cropping systems. The objective of this study was to evaluate how conventional (CT) and no-till (NT) cropping systems affect soil water and N dynamics. Soil water and N were monitored in 30 cm increments to a depth of 1.5 m for 2 years at growers' fields in two different agroclimatic zones of Washington State (USA): (1) the annual cropping region with a mean annual precipitation of more than 500 rum (Palouse site) and (2) the grain-fallow cropping region with mean precipitation below 350 mm (Touchet site). In each zone, a CT and a NT cropping system were chosen. All sites had an annual cropping system, except for the CT site in the drier area, which was under a traditional winter wheat/fallow rotation previous to the study. At Palouse, the volumetric water content in the top 1.5 m of the soil throughout the year was about 0.05-0.1 m(3) m(-3) less under CT as compared to NT, indicating improved seasonal accumulation and distribution of soil water under NT. Cropping systems modeling indicated, that during winter, surface runoff occurred in the CT system, but not under NT. The differences in soil water dynamics between CT and NT were mainly caused by differences in surface residues. Dynamics of NO3--N at Palouse were similar for NT and CT. At Touchet, differences in soil moisture between NT and CT were less than 0.05 m(3) m(-3). Under NT, high levels of NO3--N, up to 92 kg NO3-N ha(-1), were found after harvest below the root zone between 1.5 and 2.5 m, and were attributed to inefficient use or over-application of fertilizer. In both climatic zones, grain yield was positively correlated with evapotranspiration.
  • Authors:
    • Nair, V. D.
    • Nair, P. K. R.
  • Source: The Potential of U.S. Forest Soils to Sequester Carbon and Mitigate the Greenhouse Effect
  • Year: 2003
  • Summary: Agroforestry is a new concept of land management, especially in North America; therefore quantitative data are rare if not nonexistent on most aspects of it. Carbon sequestration potential of agroforestry systems is one such little-studied area. In the discussion on C storage potential of any land-use system, it is important that the system characteristics and processes governing their functioning are understood adequately. Since such basic information about agroforestry systems is not widely known, in this chapter we will first present background information on the key concepts of agroforestry and major types of agroforestry systems in North America. We then examine the C sequestration potential of agroforestry systems and discuss management considerations and research needs for exploiting the potential.
  • Authors:
    • Wu, J. J.
    • Plantinga, A. J.
  • Source: Land Economics
  • Volume: 79
  • Issue: 1
  • Year: 2003
  • Summary: Besides climate change mitigation, policies encouraging the conversion of agricultural land to forest may generate additional environmental benefits. We estimate the reductions in agricultural externalities (soil erosion, nitrogen, and atrazine pollution) from an afforestation program in Wisconsin. Existing benefits estimates are used to quantify the value of reduced soil erosion and some benefits from enhanced wildlife habitat. These values are the same order of magnitude as the costs of the carbon sequestration policy, indicating that the co-benefits of forest carbon sinks are an important factor for countries to consider in designing a portfolio of climate mitigation strategies.
  • Authors:
    • Ahuja, L. R.
    • Westfall, D. G.
    • Peterson, G. A.
    • Sherrod, L. A.
  • Source: Soil Science Society of America Journal
  • Volume: 67
  • Issue: 5
  • Year: 2003
  • Summary: Soil organic C (SOC) has decreased under cultivated wheat (Triticum aestivum)-fallow (WF) in the central Great Plains.We evaluated the effect of no-till systems of WF, wheat-corn (Zea Mays)-fallow (WCF), wheat-corn-millet (Panicum miliaceum)-fallow, continuous cropping (CC) without monoculture, and perennial grass (G) on SOC and total N (TN) levels after 12 yr at three eastern Colorado locations. Locations have long-term precipitation averages of 420 mm but increase in potential evapotranspiration (PET) going from north to south. Within each PET location, cropping systems were imposed across a topographic sequence of summit, sideslope, and toeslope. Cropping intensity, slope position, and PET gradient (location) independently impacted SOC and TN to a 5-cm soil depth. Continuous cropping had 35 and 17% more SOC and TN, respectively, than the WF system. Cropping intensity still impacted SOC and TN when summed to 10 cm with CC > than WF. Soil organic C and TN 20% in the CC system compared with WF in the 0- to 10-cm depth. The greatest impact was found in the 0- to 2.5-cm layer, and decreased with depth. Soil organic C and TN levels at the high PET site were 50% less than at the low and medium PET sites, and toeslope soils were 30% greater than summit and sideslopes. Annualized stover biomass explained 80% of the variation in SOC and TN in the 0- to 10-cm soil profile. Cropping systems that eliminate summer fallowing are maximizing the amount of SOC and TN sequestered.
  • Authors:
    • Paustian, K.
    • Eve, M.
    • Sperow, M.
  • Source: Climatic Change
  • Volume: 57
  • Issue: 3
  • Year: 2003
  • Summary: Soil carbon sequestration has been suggested as a means to help mitigate atmospheric CO2 increases, however there is limited knowledge aboutthe magnitude of the mitigation potential. Field studies across the U.S. provide information on soil C stock changes that result from changes in agricultural management. However, data from such studies are not readily extrapolated to changes at a national scale because soils, climate, and management regimes vary locally and regionally. We used a modified version of the Intergovernmental Panel on Climate Change (IPCC) soil organic C inventory method, together with the National Resources Inventory (NRI) and other data, to estimate agricultural soil C sequestration potential in the conterminous U.S. The IPCC method estimates soil C stock changes associated with changes in land use and/or land management practices. In the U.S., the NRI provides a detailed record of land use and management activities on agricultural land that can be used to implement the IPCC method. We analyzed potential soil C storage from increased adoption of no-till, decreased fallow operations, conversion of highly erodible land to grassland, and increased use of cover crops in annual cropping systems. The results represent potentials that do not explicitly consider the economic feasibility of proposed agricultural production changes, but provide an indication of the biophysical potential of soil C sequestration as a guide to policy makers. Our analysis suggests that U.S. cropland soils have the potential to increase sequestered soil C by an additional 60–70 Tg (1012g) C yr-1, over present rates of 17 Tg C yr-1 (estimated using the IPCC method), with widespread adoption of soil C sequestering management practices. Adoption of no-till on all currently annually cropped area (129 Mha) would increase soil C sequestration by 47 Tg C yr-1. Alternatively, use of no-till on 50% of annual cropland, with reduced tillage practices on the other 50%, would sequester less – about 37 Tg C yr-1. Elimination of summer fallow practices and conversion of highly erodible cropland to perennial grass cover could sequester around 20 and 28 Tg C yr-1, respectively. The soil C sequestration potential from including a winter cover crop on annual cropping systems was estimated at 40 Tg C yr-1. All rates were estimated for a fifteen-year projection period, and annual rates of soil C accumulations would be expected to decrease substantially over longer time periods. The total sequestration potential we have estimated for the projection period (83 Tg C yr-1) represents about 5% of 1999 total U.S. CO2 emissions or nearly double estimated CO2 emissions from agricultural production (43 Tg C yr-1). For purposes of stabilizing or reducing CO2 emissions, e.g., by 7% of 1990 levels asoriginally called for in the Kyoto Protocol, total potential soil C sequestration would represent 15% of that reduction level from projected 2008 emissions (2008 total greenhouse gas emissions less 93% of 1990 greenhouse gasemissions). Thus, our analysis suggests that agricultural soil C sequestration could play a meaningful, but not predominant, role in helping mitigate greenhouse gas increases.
  • Authors:
    • Lal, R.
  • Source: Critical Reviews in Plant Sciences
  • Volume: 22
  • Issue: 2
  • Year: 2003
  • Summary: An increase in atmospheric concentration of CO2 from 280 ppmv in 1750 to 367 ppmv in 1999 is attributed to emissions from fossil fuel combustion estimated at 270 +/- 30 Pg C and land use change at 136 +/- 55 Pg. Of the emissions from land use change, 78 +/- 12 Pg is estimated from depletion of soil organic carbon (SOC) pool. Most agricultural soils have lost 50 to 70% of their original SOC pool, and the depletion is exacerbated by further soil degradation and desertification. The restoration of degraded soils, conversion of agriculturally marginal lands to appropriate land use, and the adoption of recommended management practices on agricultural soils can reverse degradative trends and lead to SOC sequestration. Technological options for SOC sequestration on agricultural soils include adoption of conservation tillage, use of manures, and compost as per integrated nutrient management and precision fanning strategies, conversion of monoculture to complex diverse cropping systems, meadow-based rotations and winter cover crops, and establishing perennial vegetation on contours and steep slopes. The global potential of SOC sequestration and restoration of degraded/desertified soils is estimated at 0.6 to 1.2 Pg C/y for about 50 years with a cumulative sink capacity of 30 to 60 Pg. The SOC sequestration is a cost-effective strategy of mitigating the climate change during the first 2 to 3 decades of the 21(st) century. While improving soil quality, biomass productivity and enhanced environment quality, the strategy of SOC sequestration also buys us time during which the non-carbon fuel alternatives can take effect.