• Authors:
    • Hubbs, M. D.
    • Franzluebbers, A. J.
    • Norfleet, M. L.
  • Source: Journal of Soil and Water Conservation
  • Volume: 67
  • Issue: 5
  • Year: 2012
  • Summary: Simulation models that are sensitive to management, edaphic factors, and climate could provide insights into how land owners and producers might be able to sequester soil organic carbon (C) and engage in emerging carbon markets. In this study, the soil conditioning index (SCI) embedded in the Revised Universal Soil Loss Equation (RUSLE2) model was used to predict (1) potential soil organic C sequestration under conventional and conservation management of a diversity of cotton cropping systems throughout the Cotton Belt and (2) relative influences of soil texture, slope, climatic conditions, and management on potential soil organic C sequestration. Across 10 regions of the Cotton Belt, SCI scores ranked in the following order: perennial pasture > no-till cropping systems > conventional tillage cotton. Variations in significance of SCI scores occurred among 5 different no-till cropping systems within regions of the Cotton Belt. For example, 7 of the 10 regions had significantly (p <= 0.05) greater SCI scores (linked to greater soil organic C sequestration) when monoculture cotton was grown with winter cover crop than without.Variation in SCI was dominated by management (46%) and slope (24%) and very little affected by climate (7%) and soil texture (1%). Increasingly wetter climatic conditions (as expressed by increasing precipitation to potential evapotranspiration) had a negative influence on SCI scores for all management systems and land slopes evaluated, but particularly for moldboard-plowed cotton on sloping land, With a linear relationship between SCI and soil organic C sequestration, predicted soil organic C sequestration averaged -0.31 +/- 0.19 Mg C ha(-1) y(--1) (-280 +/- 170 lb ac(-1) yr(-1)) under conventionally tilled cotton, 0.12 +/- 0.06 Mg C ha(-1) y(-1) (103 +/- 52 lb ac(-1) yr(-1)) under various no-till crop rotations, and 0.26 +/- 0.02 Mg C ha(-1) y(-1) (231 +/- 20 lb ac(-1) yr(-1)) under perennial pasture. Cotton production with conventional tillage could only be expected to maintain soil organic C under a best-case scenario and would lose substantial soil organic C under most other scenarios. Simulations showed the strong, positive influence that conservation agricultural management has to sequester soil organic C, irrespective of climate, slope, and texture.
  • Authors:
    • Tsegaye, T. D.
    • Loescher, H. W.
    • Gebremedhin, M. T.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 5
  • Year: 2012
  • Summary: The southeastern United States is an economically important agricultural region, yet its role in the regional C budget is not fully understood. There is concern that climate change, particularly altered precipitation patterns, may induce a shift in how crops exchange CO2 with the atmosphere. This study examined the seasonal and interannual variation in net ecosystem exchange (NEE) of a winter wheat cover crop (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.] using the eddy covariance (EC) method. This was conducted at Winfred Thomas Agricultural Research Station, Hazel Green, AL (2007-2009). Annual C balance ranged from a source in 2007 (NEE = 100 g C m(-2) yr(-1)) to a sink (-20 g C m(-2) yr(-1)) in 2009. Annual ecosystem respiration (Re) ranged between 750 and 1013 g C m(-2) yr(-1), while gross ecosystem productivity was between 650 and 1034 g C m(-2) yr(-1). Seasonal NEE for soybean ranged between 42 and -66 g C m(-2). The uptake rates from the cover crop (NEE = -80.0, -80.4, and -40.0 g C m(-2) for 2007, 2008, and 2009, respectively) suggested the importance of winter C uptake off setting C losses caused by summer droughts. The R-e varied between 286 and 542 g C m(-2) for soybean and between 160 and 313 g C m(-2) for the cover crop. Annual variations in NEE and R-e were primarily due to precipitation and air temperature, respectively, indicating a tight coupling between biophysical factors and C uptake. Our results were compared with those from other reported NEE crop estimates using EC.
  • Authors:
    • Parkin, T.
    • Hatfield, J.
  • Source: Agricultural Sciences
  • Volume: 3
  • Issue: 8
  • Year: 2012
  • Summary: Spatial variation of soil carbon dioxide (CO 2) flux during a growing season within corn and soybean canopies has not been quantified. These cropping systems are the most intense in the United States and the potential for carbon (C) sequestration in these systems through changes in soil management practices create an opportunity for reduction in greenhouse gas emissions; however, the need to understand the variation in fields is critical to evaluating changes in management systems. A study was designed to evaluate the spatial variation in soil CO 2 fluxes along two transects in corn and soybean fields. Samples were collected every 5 m along a 100 m transect between the rows of the crop and also along a transect in which the plants had been removed to reduce the potential of root respiration. Soil CO 2 fluxes were collected at each position with air temperature, soil temperature at 0.05 m, and soil water content (0-0.06 m). At the end of the season, soil samples for the upper 0.1 m were collected for soil organic C content, pH, sand, silt, and clay contents. On each day measurements were made, the observed CO 2 emissions were scaled by dividing the CO 2 flux at each position by the mean CO 2 flux of the entire transect. Observed CO 2 fluxes were signifycantly larger in the row than in the fallow position for both crops. There were no differences between the corn and soybean fallow transects; however, the corn row samples were larger than the soybean row samples. No consistent spatial patterns were observed in the CO 2 fluxes or any of the soil properties over the course of the study. When the CO 2 flux data were combined over the season, there was a significant spatial pattern in the fallow transects for both crops but not for the row transects. Sampling for CO 2 flux values in cropping systems has to consider the presence of a crop canopy and the amount of root respiration.
  • Authors:
    • Barbour, N. W.
    • Archer, D. W.
    • Weyers, S. L.
    • Johnson, J. M. F.
  • Source: Soil Science Society of America Journal
  • Volume: 76
  • Issue: 4
  • Year: 2012
  • Summary: Empirical data on methane (CH4) and nitrous oxide (N2O) emission are needed for management systems from many regions of the United States to evaluate mitigation strategies. The primary objectives of this study were to assess and compare crop productivity, CH4 andN(2)O flux, and yield-scaled emissions between a conventionally and an organically managed system. All phases of a corn (Zea mays L.)-soybean [Glycine max L. (Merr.)]-wheat (Triticum aestivum L.) over alfalfa (Medicago sativa L.)-alfalfa rotation were present each year. Both systems emitted about 4.2 kg N2O-N ha(-1) yr(-1) including growing and nongrowing season emissions, which cumulatively represents 4.74 and 9.26% of 267 kg synthetic-N and 136 kg manure-N applied, respectively. The equivalent of 0.84% of the 78 kg urea-N and 0.76% of the 136 kg manure-N were emitted as N2O ha(-1) within 30-d of fertilizer application in the conventionally managed system and organically managed system, respectively. Following the application of starter fertilizer to the conventionally managed corn, the equivalent of 3.45% of the 11 kg starter N was emitted within 30 d. The largest spring-thaw N2O flux was measured in the conventionally managed system following alfalfa, which had been killed the previous fall. Yield-scaled N2O+CH4 emission (Mg CO2 equivalents Mg-1 yield) was 1.6- to 5-times greater in the organically managed system, which had lower yield but similar emission compared to the conventionally managed system. Thus, viability of organic systems to mitigate greenhouse gas (GHG) emission may be compromised when crop productivity is reduced. Study results highlight the importance of assessing emission and crop production when evaluating GHG mitigation strategies.
  • Authors:
    • Liska, A. J.
    • Archer, D.
    • Karlen, D. L.
    • Meyer, S.
  • Source: Council for Agricultural Science and Technology
  • Issue: 48
  • Year: 2012
  • Summary: Quantifying energy issues associated with agricultural systems, even for a two-crop corn ( Zea mays L.) and soybean ( Glycine max [L.] Merr.) rotation, is not a simple task. It becomes even more complicated if the goal is to include all aspects of sustainability (i.e., economic, environmental, and social). This Issue Paper examines energy issues associated with and affecting corn/soybean rotations by first defining the size of the system from both a U.S. and global perspective and then establishing boundaries based on the Farm Bill definition of sustainability. This structured approach is essential to help quantify energy issues within corn/soybean systems that are themselves best described as "systems of systems" or even "systems within ecosystems" because of their complex linkages to global food, feed, and fuel production. Two key economic challenges at the field and farm scale for decreasing energy use are (1) overcoming adoption barriers that currently limit implementation of energy-conserving production practices and (2) demonstrating the viability of sustainable bioenergy feedstock, production as part of a landscape management plan focused not only on corn/soybean production but on all aspects of soil, water, and air resource management. It is also important to look beyond direct energy consumption to address the complex economics affecting energy issues associated with corn/soybean systems. To help address the complex energy issue, life cycle assessment is used as a tool to evaluate the impact of what many characterize as a simple production system. This approach demonstrates the importance of having accurate greenhouse gas and soil organic carbon information for these analyses to be meaningful. Traditional and emerging market and policy forces affecting energy issues within corn/soybean systems are examined to project the effects of increasing bioenergy demand associated with the Energy Independence and Security Act of 2007. Uncertainty with regard to biofuel policy is a major factor affecting energy issues in all aspects of agriculture. This uncertainty affects investments in biofuel production and energy demand, which together influence commodity prices, price volatility for food and feed, and agricultural energy decisions. The authors conclude by offering an approach, including decreased or more efficient energy use, that can enhance all aspects of sustainability. Their strategy, defined as a "landscape vision," is suggested as an agricultural system approach that could meet increasing global demand for food, feed, fiber, and fuel in a truly sustainable manner.
  • Authors:
    • Schwarz, G.
    • Noleppa, S.
    • Kern, M.
  • Source: Pest Management Science
  • Volume: 68
  • Issue: 11
  • Year: 2012
  • Summary: BACKGROUND: A major global challenge is to provide agricultural production systems that are able to sustain growing demands for food, feed, fibre and renewable raw materials without exacerbating climate change. Detailed and reliable data on the CO2 balance of different agricultural management activities and inputs as a basis to quantify carbon footprints of agriculture are still lacking. This study aims to fill this gap further by quantifying the net balance of emitted and assimilated CO2 due to the application of crop protection treatments on the farm, and by assessing their partial contribution to GHG emissions and mitigation in agriculture. The study focuses on key agricultural crops including wheat, corn, oilseeds and sugar crops. RESULTS: The final CO2 balance, considering GHG emissions due to on-farm CPP treatment in comparison with CO2 storage in additional biomass, CO2 protected with respect to agrotechnical inputs and land inputs and CO2 saved with respect to associated global land use changes, is positive and may reach multiples of up to nearly 2000. CONCLUSION: The results highlight the importance of the positive yield effects of the CPP programme applications on the farm, resulting in additional assimilated biomass at the farm level and less land use changes at the global level, and thus lower pressure on environmentally important indicators of overall agricultural sustainability.
  • Authors:
    • De Figueiredo, E. B.
    • La Scala Junior, N.
    • Panosso, A. R.
  • Source: Brazilian Journal of Biology
  • Volume: 72
  • Issue: 3
  • Year: 2012
  • Summary: Agricultural areas deal with enormous CO2 intake fluxes offering an opportunity for greenhouse effect mitigation. In this work we studied the potential of soil carbon sequestration due to the management conversion in major agricultural activities in Brazil. Data from several studies indicate that in soybean/maize, and related rotation systems, a significant soil carbon sequestration was observed over the year of conversion from conventional to no-till practices, with a mean rate of 0.41 Mg C ha(-1) year(-1). The same effect was observed in sugarcane fields, but with a much higher accumulation of carbon in soil stocks, when sugarcane fields are converted from burned to mechanised based harvest, where large amounts of sugarcane residues remain on the soil surface (1.8 Mg C ha(-1) year(-1)). The higher sequestration potential of sugarcane crops, when compared to the others, has a direct relation to the primary production of this crop. Nevertheless, much of this mitigation potential of soil carbon accumulation in sugarcane fields is lost once areas are reformed, or intensive tillage is applied. Pasture lands have shown soil carbon depletion once natural areas are converted to livestock use, while integration of those areas with agriculture use has shown an improvement in soil carbon stocks. Those works have shown that the main crop systems of Brazil have a huge mitigation potential, especially in soil carbon form, being an opportunity for future mitigation strategies.
  • Authors:
    • Williams, S.
    • Easter, M.
    • Paustian, K.
    • Lokupitiya, E.
    • Andren, O.
    • Katterer, T.
  • Source: Biogeochemistry
  • Volume: 107
  • Issue: 1-3
  • Year: 2012
  • Summary: Carbon (C) added to soil as organic matter in crop residues and carbon emitted to the atmosphere as CO(2) in soil respiration are key determinants of the C balance in cropland ecosystems. We used complete and comprehensive county-level yields and area data to estimate and analyze the spatial and temporal variability of regional and national scale residue C inputs, net primary productivity (NPP), and C stocks in US croplands from 1982 to 1997. Annual residue C inputs were highest in the North Central and Central and Northern Plains regions that comprise similar to 70% of US cropland. Average residue C inputs ranged from 1.8 (Delta States) to 3.0 (North Central region) Mg C ha(-1) year(-1), and average NPP ranged from 3.1 (Delta States) to 5.4 (Far West region) Mg C ha(-1) year(-1). Residue C inputs tended to be inversely proportional to the mean growing season temperature. A quadratic relationship incorporating the growing season mean temperature and total precipitation closely predicted the variation in residue C inputs in the North Central region and Central and Northern Plains. We analyzed the soil C balance using the crop residue database and the Introductory Carbon Balance regional Model (ICBMr). Soil C stocks (0-20 cm) on permanent cropland ranged between 3.07 and 3.1 Pg during the study period, with an average increase of similar to 4 Tg C year(-1), during the 1990s. Interannual variability in soil C stocks ranged from 0 to 20 Tg C (across a mean C stock of 3.08 +/- A 0.01 Pg) during the study period; interannual variability in residue C inputs varied between 1 and 43 Tg C (across a mean input of 220 +/- A 19 Tg). Such interannual variation has implications for national estimates of CO(2) emissions from cropland soils needed for implementation of greenhouse gas (GHG) mitigation strategies involving agriculture.
  • Authors:
    • Morrison, M. J.
    • Biswas, D. K.
    • Liang, B. C.
    • Ma, B. L.
    • McLaughlin, N. B.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 94
  • Issue: 1
  • Year: 2012
  • Summary: Studies on the sustainability of crop production systems should consider both the carbon (C) footprint and the crop yield. Knowledge is urgently needed to estimate the C cost of maize (Zea mays L.) production in a continuous monoculture or in rotation with a leguminous crop, the popular rotation system in North America. In this study, we used a 19-year field experiment with maize under different levels of synthetic N treatments in a continuous culture or rotation with forage legume (Alfalfa or red clover; Medicago sativa L./Trifolium pratense L.) or soybean (Glycine max L. Merr) to assess the sustainability of maize production systems by estimating total greenhouse gas (GHG) emissions (kg CO2 eq ha(-1)) and the equivalent C cost of yield or C footprint (kg CO2 eq kg(-1) grain). High N application increased both total GHG emissions and the C footprint across all the rotation systems. Compared to continuous maize monoculture (MM), maize following forage (alfalfa or red clover; FM) or grain (soybean; SM) legumes was estimated to generate greater total GHG emissions, however both FM and SM had a lower C footprint across all N levels due to increased productivity. When compared to MM treated with 100 kg N ha(-1), maize treated with 100 kg N ha(-1), following a forage legume resulted in a 5 % increase in total GHG emissions while reducing the C footprint by 17 %. Similarly, in 18 out of the 19-year period, maize treated with 100 kg N ha(-1), following soybean (SM) had a minimal effect on total GHG emissions (1 %), but reduced the C footprint by 8 %. Compared to the conventional MM with the 200 kg N ha(-1) treatment, FM with the 100 kg N ha(-1) treatment had 40 % lower total GHG emissions and 46 % lower C footprint. Maize with 100 kg N ha(-1) following soybean had a 42 % lower total GHG emissions and 41 % lower C footprint than MM treated with 200 kg N ha(-1). Clearly, there was a trade-off among total GHG emissions, C footprint and yield, and yield and GHG emissions or C footprint not linearly related. Our data indicate that maize production with 100 kg N ha(-1) in rotation with forage or grain legumes can maintain high productivity while reducing GHG emissions and the C footprint when compared to a continuous maize cropping system with 200 kg N ha(-1).
  • Authors:
    • Mauli, M. M.
    • Machado Coelho, S. R.
    • Pereira Nobrega, L. H.
    • de Lima, G. P.
    • Rosa, D. M.
  • Source: Journal of Food Agriculture and Environment (JFAE)
  • Volume: 10
  • Issue: 2
  • Year: 2012
  • Summary: It is known that cover crops can influence on seed quality, as well as on yield cropping. This trial analyzed possible allelopathic interferences of black oat (Avena strigosa Schreb.) remains and a consortium of black oat, forage turnip (Raphanus sativus L.) and vetch (Vicia sativa L.) on cropped seeds quality and soybean yield according to different intervals between the drying of some cover crops with Glyphosate 480 (3 L had) herbicide and seeding with BRS 232 cultivar. Plots of 5.0 m x 2.5 m were established, plus 1 m of edge between each of them. The cover crop was sown in August, 2006, with 0.15 m of width among rows: the parcels were dried in intervals of one, ten, twenty and thirty days before the soybean seedling. Four treatments were arranged for black oat cover, four for consortium and one control for each cover, all randomized, with five replications. The soybean was seeded in November, 2006, with 0.45 m width among seeding rows. Data as yield, adjusted to 13% of moisture content on cropped seeds; seedling rate; weight of 100 seeds; moisture content and seeds vigor were recorded by the accelerated aging test. All the tests were submitted to an experimental design, with subdivided plots (split plot), completely randomized; the averages were also compared using Scott-Knott test at 5% of probability. The data showed a possible allelopathic interference of cover crops on soybean seed quality. The greatest weight of 100 seeds was obtained when soybean was sown under black oat cover compared to the consortium. On the other hand, when it was sown under consortium, it showed the best vigor, evaluated by the accelerated aging test. The yield did not differ between both covers. The intervals between drying and sowing interfered on weight of 100 seeds and soybean yield. The interval between drying and sowing of one day had a positive effect on weight of 100 seeds, but soybean yield decreased. Hence, it is not well recommended to sow soybean next to the drying management of a cover crop.