• Authors:
    • Kohei, U.
    • Ebel, R.
    • Horowitz, J.
  • Source: Economic Information Bulletin
  • Volume: 70
  • Year: 2010
  • Summary: Most U.S. farmers prepare their soil for seeding and weed and pest control through tillage-plowing operations that disturb the soil. Tillage practices affect soil carbon, water pollution, and farmers' energy and pesticide use, and therefore data on tillage can be valuable for understanding the practice's role in reaching climate and other environmental goals. In order to help policymakers and other interested parties better understand U.S. tillage practices and, especially, those practices' potential contribution to climate-change efforts, ERS researchers compiled data from the Agricultural Resource Management Survey and the National Resources Inventory-Conservation Effects Assessment Project's Cropland Survey. The data show that approximately 35.5 percent of U.S. cropland planted to eight major crops, or 88 million acres, had no tillage operations in 2009.
  • Authors:
    • Mikha,M. M.
    • Nielsen,D. C.
    • Halvorson,A. D.
    • Benjamin,J. G.
  • Source: Agronomy Journal
  • Volume: 102
  • Issue: 3
  • Year: 2010
  • Summary: Crop biomass has been proposed as a source stock for bioethanol production. Levels of crop residue removal must be determined to prevent degradation of soil physical and chemical properties resulting from soil organic carbon (SOC) loss. Carbon inputs from crop residues and an estimate of inputs from roots and rhizodeposition (C return) were calculated and compared with changes in SOC after seven cropping seasons at Akron, CO. Tillage treatments included a chisel plow (CP) and a no-till (NT) treatment. A crop rotation alternating grasses and broadleaf crops was compared with continuous corn ( Zea mays L.). Irrigation treatments included water application to meet evapotranspiration demand or application only during the reproductive stage of each crop. Total C return varied from 25 Mg ha -1 for the delayed irrigation, crop rotation plots to 63 Mg ha -1 for the fully irrigated, continuous corn plots. The change in SOC in the surface 30 cm of soil varied from -0.8 Mg SOC ha -1 for the rotation plots to a gain of 2.8 Mg ha -1 for the continuous corn plots after 7 yr. Correlating crop residue input with change in SOC showed that about 4.6 Mg ha -1 yr -1 C return is needed to maintain SOC levels for NT cropping systems and an average of 7.4 Mg ha -1 yr -1 C return is needed to maintain SOC levels under chisel tillage. Continuous corn was the only system that consistently provided sufficient crop residue to maintain SOC levels. Residue removal for off-farm use should consider only amounts that can be harvested without decreasing SOC levels.
  • Authors:
    • Barfoot, P.
    • Brookes, G.
  • Source: AgBioForum
  • Volume: 13
  • Issue: 1
  • Year: 2010
  • Summary: This article updates the assessment of the impact commercialized agricultural biotechnology is having on global agriculture from an environmental perspective. It focuses on the impact of changes in pesticide use and greenhouse gas emissions arising from the use of biotech crops. The technology has reduced pesticide spraying by 352 million kg (-8.4%) and, as a result, decreased the environmental impact associated with herbicide and insecticide use on these crops (as measured by the indicator the environmental impact quotient) by 16.3%. The technology has also significantly reduced the release of greenhouse gas emissions from this cropping area, which, in 2008, was equivalent to removing 6.9 million cars from the roads.
  • Authors:
    • Sohngen, B.
    • Choi, S. W.
  • Source: Climatic Change
  • Volume: 99
  • Issue: 1-2
  • Year: 2010
  • Summary: This study investigates the cost of soil carbon sequestration in the Midwest US. The model addresses several missing components in earlier analyses: the link between the residue level choice and carbon payments, crop rotations, carbon loss when shifting from conservation to conventional tillage and the spatial pattern of carbon sequestration across different soil types. The results suggest that for $100 per metric ton of carbon, 1.5 million metric tons of carbon could be sequestered per year on the 19.9 million hectares of cropland in the study region. These estimates suggest less carbon potential than existing studies because the opportunity costs associated with conservation tillage are fairly high. Annual carbon rental payments are found to be more efficient, as expected, but for smaller programs, per hectare rental payments are not substantially more costly.
  • Authors:
    • Pedersen, P.
    • Janssen, M. R.
    • Nafziger, E. D.
    • Coulter, J. A.
  • Source: Agronomy Journal
  • Volume: 102
  • Issue: 1
  • Year: 2010
  • Summary: Transgenic Bt corn hybrids with resistance to corn rootworm or European corn borer can have greater tolerance to water and nutrient stress, and thus may have higher optimum plant densities. Experiments were conducted following soybean over nine site-years in Illinois to determine whether the response to plant density for corn grain yield and net return to seed cost differ among near-isoline hybrids with no insect resistance, Bt resistance to CRW, or Bt resistance to CRW plus ECB. Similar experiments were conducted over three site-years in Iowa following both soybean and corn for near-isoline hybrids with Bt resistance to ECB or ECB plus CRW. Larval CRW injury was low in Iowa and stalk lodging was minimal in all experiments. Across site-years in Illinois and in both crop sequences in Iowa, grain yield and net return to seed cost were not af ected by hybrid. Net return to seed cost within $2.50 ha-1 of the maximum occurred with densities of 76,300 to >98,600 plants following soybean in Illinois, 87,100 to 93,400 plants following soybean in Iowa, and 87,400 to 95,700 plants following corn in Iowa. Yields within these optimum plant densities were 15.9, 16.1, and 15.4 Mg ha-1, respectively. When CRW and ECB are managed or are at low levels, optimum plant density is similar between hybrids with or without resistance to these pests.
  • Authors:
    • Grignani, C.
    • Zavattaro, L.
    • Bertora, C.
    • Alluvione, F.
  • Source: Soil Science Society of America Journal
  • Volume: 74
  • Issue: 2
  • Year: 2010
  • Summary: Alternative N fertilizers that stimulate low greenhouse gas emissions from soil are needed to reduce the impact of agriculture on global warming. Corn (Zea mays L.) grown in a calcareous silt loam soil in northwestern Italy was fertilized with a municipal solid waste compost and vetch (Vicia villosa Roth.) green manure. Their potential to reduce N2O and CO2 emissions was compared with that of urea (130 kg N ha-1). Gaseous fluxes were measured for 2 yr in the spring (after soil incorporation of fertilizers) and in summer. In spring, the slow mineralization of compost reduced N2O emissions (0.11% of supplied N) relative to urea (3.4% of applied N), without an increase in CO2 fluxes. Nitrous oxide (2.31% of fixed N) and CO2 emissions from rapid vetch decomposition did not differ from urea. When N2O and CO2 fluxes were combined, compost reduced by 49% the CO2 equivalent emitted following urea application. Vetch did not show such an effect. In summer, no fertilizer effect was found on N2O and CO2 emissions. Compost proved to be potentially suitable to reduce the CO2 equivalent emitted after soil incorporation while vetch did not. For a thorough evaluation, net greenhouse gas emissions assessment should be extended to the entire N life cycle. Differences between calculated N2O emission factors and the default Tier 1 value of the Intergovernmental Panel on Climate Change (1%) confirmed the need for site- and fertilizer-specific estimations.
  • Authors:
    • Halvorson, A. D.
    • Archer, D. W.
  • Source: Soil Science Society of America Journal
  • Volume: 74
  • Issue: 2
  • Year: 2010
  • Summary: Recent soil and crop management technologies have potential for mitigating greenhouse gas emissions; however, these management strategies must be profitable if they are to be adopted by producers. The economic feasibility of reducing net greenhouse gas emissions in irrigated cropping systems was evaluated for 5 yr on a Fort Collins clay loam soil (a fine-loamy, mixed, superactive, mesic Aridic Haplustalf). Cropping systems included conventional tillage continuous corn (Zea mays L.) (CT-CC), no-till continuous corn (NT-CC), and no-till corn-bean (NT-CB) including 1 yr soybean [Glycine max (L.) Merr.] and 1 yr dry bean (Phaseolus vulgaris L.). The study included six N fertilization rates ranging from 0 to 246 kg ha-1. Results showed highest average net returns for NT-CB, exceeding net returns for NT-CC and CT-CC by US$182 and US$228 ha-1, respectively, at economically optimum N fertilizer rates. Net global warming potential (GWP) generally increased with increasing N fertilizer rate with the exception of NT-CC, where net GWP initially declined and then increased at higher N rates. Combining economic and net GWP measurements showed that producers have an economic incentive to switch from CT-CC to NT-CB, increasing annual average net returns by US$228 ha-1 while reducing annual net GWP by 929 kg CO2 equivalents ha-1. The greatest GWP reductions (1463 kg CO2 equivalents ha-1) could be achieved by switching from CT-CC to NT-CC while also increasing net returns, but the presence of a more profitable NT-CB alternative means NT-CC is unlikely to be chosen without additional economic incentives.
  • Authors:
    • Blanco-Canqui, H.
  • Source: Agronomy Journal
  • Volume: 102
  • Issue: 2
  • Year: 2010
  • Summary: Interest in producing cellulosic ethanol from renewable energy sources is growing. Potential energy crops include row crops such as corn (Zea mays L.), perennial warm-season grasses (WSGs), and short-rotation woody crops (SRWCs). However, impacts of growing dedicated energy crops as biofuel on soil and environment have not been well documented. This article reviews the (i) impacts of growing WSGs and SRWCs on soil properties, soil organic carbon (SOC) sequestration, and water quality, and (ii) performance of energy crops in marginal lands. Literature shows that excessive (>= 50%) crop residue removal adversely impacts sod and environmental quality as well as crop yields. Growing WSGs and SRWCs can be potential alternatives to crop residue removal as biofuel. Warm-season grasses and SRWCs can improve soil properties, reduce soil erosion, and sequester SOC. Crop residue removal reduces SOC concentration by 1 to 3 Mg ha(-1) yr(-1) in the top 10 cm, whereas growing WSGs and SRWCs increase SOC concentration while providing biofuel feedstocks. The WSGs can store SOC between 0 and 3 Mg C ha(-1) yr(-1) in the top 5 cm of soil, while the SRWCs can store between 0 and 1.6 Mg ha(-1) yr(-1) of SOC in the top 100 cm. The WSGs and SRWCs have more beneficial effects on soil and environment when grown in marginal lands than when grown in croplands or natural forests. Indeed, they can grow in nutrient-depleted, compacted, poorly drained, acid, and eroded soils. Development of sustainable systems of WSGs and SRWCs in marginal lands is a high priority.
  • Authors:
    • Urquiaga, S.
    • Alves, B. J. R.
    • Giacomini, S. J.
    • Aita, C.
    • Denardin, J. E.
    • Dos Santos, H. P.
    • Dieckow, J.
    • Mielniczuk, J.
    • Bayer, C.
    • Zanatta, J. A.
    • Conceição, P. C.
    • Jantalia, C. P.
    • Boddey, R. M.
  • Source: Global Change Biology
  • Volume: 16
  • Issue: 2
  • Year: 2010
  • Summary: Conservation agriculture can provide a low-cost competitive option to mitigate global warming with reduction or elimination of soil tillage and increase soil organic carbon (SOC). Most studies have evaluated the impact of zero till (ZT) only on surface soil layers (down to 30 cm), and few studies have been performed on the potential for C accumulation in deeper layers (0-100 cm) of tropical and subtropical soils. In order to determine whether the change from conventional tillage (CT) to ZT has induced a net gain in SOC, three long-term experiments (15-26 years) on free-draining Ferralsols in the subtropical region of South Brazil were sampled and the SOC stocks to 30 and 100 cm calculated on an equivalent soil mass basis. In rotations containing intercropped or cover-crop legumes, there were significant accumulations of SOC in ZT soils varying from 5 to 8 Mg ha-1 in comparison with CT management, equivalent to annual soil C accumulation rates of between 0.04 and 0.88 Mg ha-1. However, the potential for soil C accumulation was considerably increased (varying from 0.48 to 1.53 Mg ha-1 yr-1) when considering the soil profile down to 100 cm depth. On average the estimate of soil C accumulation to 100 cm depth was 59% greater than that for soil C accumulated to 30 cm. These findings suggest that increasing sampling depth from 30 cm (as presently recommended by the IPCC) to 100 cm, may increase substantially the estimates of potential CO2 mitigation induced by the change from CT to ZT on the free-draining Ferralsols of the tropics and subtropics. It was evident that that legumes which contributed a net input of biologically fixed N played an important role in promoting soil C accumulation in these soils under ZT, perhaps due to a slow-release of N from decaying surface residues/roots which favored maize root growth.
  • Authors:
    • Pepo, P.
  • Source: CEREAL RESEARCH COMMUNICATIONS
  • Volume: 59
  • Issue: Supplement
  • Year: 2010
  • Summary: The interactions of ecological conditions, genotypes and agrotechnical elements determine the yield quantity, quality and stability in cereal (wheat, maize) production. The applied input-level can modify the adaptive capacity of crop models to ecological conditions and resilience of agro-ecosystems. The effects of agrotechnical elements (crop rotation, fertilization, irrigation, crop protection, plant density) were studied in the long-term experiment on chernozem soil. Our scientific results proved that the high yields and good yield-stability were obtained in the input-intensive crop models, so these models had better adaptive capacity and resilience. Maize had lower ecological adaptive ability than winter wheat. The optimalization of agrotechnical elements reduces the harmful climatic effects so we can increase the resilience of cereals agro-ecosystems. The yields of wheat varied between 2 and 7 t ha -1 in extensive and 8 and 10 t ha -1 in intensive crop models and the yields of maize ranged between 2 and 11 t ha -1 and 10 and 15 t ha -1, respectively.