• Authors:
    • Mauder, M.
    • MacPherson, J. I.
    • Srinivasan, R.
    • Grant, B.
    • Worth, D.
    • Smith, W. N.
    • Pattey, E.
    • Desjardins, R. L.
  • Source: Agricultural and Forest Meteorology
  • Volume: 150
  • Issue: 6
  • Year: 2010
  • Summary: Nitrous oxide (N2O) emissions are a large proportion of the agriculture sector's contribution to the greenhouse gas inventory of most developed countries. The spatial and temporal variability of N2O emissions from agricultural soils has long been considered the main factor limiting our ability to estimate N2O emissions, particularly the emissions associated with the spring snowmelt period. Tower and aircraft-based flux measurement systems and a process-based model were used to quantify N2O emissions for four years (2000, 2001, 2003 and 2004) in an agricultural area of eastern Canada, near Ottawa, where a corn-soybean crop rotation dominates. A tower-based system, which relies on the flux gradient technique, provided diurnal N2O emissions at a field scale. An aircraft-based system, which relies on the relaxed eddy accumulation technique, provided N2O emissions for two similar agricultural regions and the denitrification and decomposition (DNDC) model was used to estimate daily N2O emissions at a regional scale. In most cases, aircraft-based N2O emissions measurements were comparable for the two agricultural regions. Corresponding tower-based measurements which were collected over a field in the Ottawa area showed similar emission patterns to the aircraft-based measurements but in some cases the tower-based emissions were larger, as expected. This is because the footprint of aircraft-based measurements always incorporated a significant amount of crops such as soybean and other types of vegetation which do not receive additional nitrogen fertilization as well as waterlogged areas that do not emit N2O. While in three of the four years, the tower-based measurements were made over a tile drained field where nitrogen fertilizer had been applied the previous year. The N2O emissions patterns after planting were also similar for both aircraft and tower-based systems, but again they were slightly larger for the tower-based system. Aircraft-based N2O flux measurements are also compared to the N2O emissions obtained using the most recent version of the process-based model DNDC. Tests showed that DNDC gave comparable N2O emissions estimates for the measurement period as a whole, but was not always able to correctly predict the timing of peak emissions.
  • Authors:
    • ERS,USDA
  • Volume: 2012
  • Year: 2010
  • Authors:
    • Batlle-Bayer, L.
    • Batjes, N. H.
    • Bindraban, P. S.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 137
  • Issue: 1-2
  • Year: 2010
  • Summary: This paper reviews current knowledge on changes in carbon stocks upon land use conversion in the Brazilian Cerrado. First, we briefly characterize the savanna ecosystem and summarize the main published data on C stocks under natural conditions. The effects of increased land use pressure in the Cerrado and current uncertainties of estimations of changes in land cover and land use are reviewed next. Thereafter, we focus on soil organic carbon (SOC) dynamics due to changes in land use, particularly conversion to pastures and soybean-based cropping systems, and effects of management practices such as soil fertilization, crop rotations and tillage practices. Most studies considered here suggest that more intensive agriculture, which include no-till practices and the implementation of best or recommended management practices (RMP), reduces SOC losses after land use conversion from conventional tillage-based, monocropping systems; however, these studies focussed on the first 0.3 m of soil, or less, and seldom considered full carbon accounting. To better estimate possible global warming mitigation with agriculture in the Cerrado more comprehensive studies are needed that analyse fluxes of the biogenic greenhouse gases (GHG; CO 2, N 2O and CH 4) to determine the net global warming potential (GWP). Follow up studies should include the application of an integrated modelling system, comprised of a Geographic Information System (GIS) linked to dynamic modelling tools, to analyse SOC dynamics and make projections for possible changes in net C flows in the Cerrado region upon defined changes in soil use and management.
  • Authors:
    • Alluvione, F.
    • Del Grosso, S. J.
    • Halvorson, A. D.
  • Source: Soil Science Society of America Journal
  • Volume: 74
  • Issue: 2
  • Year: 2010
  • Summary: Nitrogen fertilization is essential for optimizing crop yields; however, it increases N2O emissions. The study objective was to compare N2O emissions resulting from application of commercially available enhanced-efficiency N fertilizers with emissions from conventional dry granular urea in irrigated cropping systems. Nitrous oxide emissions were monitored from corn (Zea mays L.) based rotations receiving fertilizer rates of 246 kg N ha-1 when in corn, 56 kg N ha-1 when in dry bean (Phaseolus vulgaris L.), and 157 kg N ha-1 when in barley (Hordeum vulgare L. ssp. vulgare). Cropping systems included conventional-till continuous corn (CT-CC), no-till continuous corn (NT-CC), no-till corn-dry bean (NT-CDb), and no-till corn-barley (NT-CB). In the NT-CC and CT-CC systems, a controlled-release, polymer-coated urea (ESN) and dry granular urea were compared. In the NT-CDb and NT-CB rotations, a stabilized urea source (SuperU) was compared with urea. Nitrous oxide fluxes were measured during two growing seasons using static, vented chambers and a gas chromatograph analyzer. Cumulative growing season N2O emissions from urea and ESN application were not different under CT-CC, but ESN reduced N2O emissions 49% compared with urea under NT-CC. Compared with urea, SuperU reduced N2O emissions by 27% in dry bean and 54% in corn in the NT-CDb rotation and by 19% in barley and 51% in corn in the NT-CB rotation. This work shows that the use of no-till and enhanced-efficiency N fertilizers can potentially reduce N2O emissions from irrigated systems.
  • 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:
    • 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:
    • 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:
    • 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:
    • 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:
    • Wang, L.
    • Chen, Z.
    • Chen, X.
    • Wan, Y.
    • Yang, W.
    • Gong, W.
    • Yan, Y.
  • Source: PLANT PRODUCTION SCIENCE
  • Volume: 13
  • Issue: 4
  • Year: 2010
  • Summary: The relay strip intercropping system of wheat-corn-soybean is widely used in southwest China. However, it is hard to obtain a stable production of soybean with this system, since soybean plants grow under shading by corn; the stems are thinner and susceptible to lodging. We examined the effects of seed treatment with uniconazole powder (0, 2, 4 and 8 mg kg -1 seed) on the growth of soybean seedlings under relay strip intercropping, some morphological characteristics and yield. The seedling height, first internode length, cotyledonary node height and leaf area per plant were decreased, while the stem diameter, root dry weight, shoot dry weight, root volume, leaf greenness and root to shoot dry weight ratio were increased by uniconazole treatment. The root vigor and root active absorption area were also increased significantly by uniconazole treatment. Moreover, 2 and 4 mg kg -1 uniconazole powder treatment increased shoot dry weight, number of pods per plant, number of seeds per pod and seed yield significantly. Thus, the results suggested that seed treatment with uniconazole powder at a suitable concentration can improve soybean seedling growth, resist the lodging and also increase the seed yield under shading by corn in relay strip intercropping system.