• Authors:
    • Ogle, S.
    • Del Grosso, S.
    • Delgado, J.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 86
  • Issue: 3
  • Year: 2010
  • Summary: It is difficult to quantify nitrogen (N) losses from agricultural systems; however, we can use 15N isotopic techniques to conduct site-specific studies to increase our knowledge about N management and fate. Our manuscript analyzes two reviews of selected 15N isotopic studies conducted to monitor N fate. The mechanistic foci of these studies include crop residue exchange and N fate in farming systems. Analysis of the data presented in these studies supports the claim that the average N losses are greater from inorganic N fertilizer inputs than organic crop residue N inputs. Additionally we conducted unique DAYCENT simulations of the effects of crop residue on nitrous oxide (N2O-N) emissions and nitrate (NO3-N) leaching. The simulation evaluations support the crop residue 15N exchange studies and show lower leaching and N2O-N emissions from crop residue sources when compared to N fertilizer. The 15N data suggest that the N in the crop residue pool must be recycled, and that this is a slower and more protected pool when compared to the readily available fertilizer. The results suggest that the Intergovernmental Panel on Climate Change (IPCC) methodology should be reevaluated to determine whether the direct and indirect N2O-N emission coefficients need to be lowered to reflect fewer N2O-N emissions from high C/N crop residue N inputs. The data suggest that accounting for nutrient cycling has implications for public policy associated with the United Nations Framework Convention on Climate Change (UNFCCC) and mitigation of N2O-N emissions from agricultural soils. Additional crop residue exchange studies, field N2O-N and NO3-N leaching and support model evaluations are needed across different worldwide agroecosystems.
  • Authors:
    • Greenhouse Gas Working Group
  • Year: 2010
  • Summary: Approximately 6% of all greenhouse gas (GHG) emissions originating in the United States (U.S.) come from agricultural activities.1 These gases are in the form of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). However, by employing proper management techniques, agricultural lands can both sequester carbon and reduce CO2, CH4, and N2O emissions, thereby reducing their GHG footprint. Cap-and-trade climate change legislation, currently under discussion in the legislative and executive branches, may have broad and long-term implications for the agricultural sector. In order to determine the role of agriculture in GHG emissions and capture, a full life cycle accounting of GHG sources and sinks is needed. The American Society of Agronomy (ASA), Crop Science Society of America (CSSA), and Soil Science Society of America (SSSA) have examined the evidence for GHG emissions and sequestration typical of agricultural systems in six U.S. regions (Figure 1): • Northeast • Southeast • Corn Belt • Northern Great Plains • Pacific • Southern Great Plains This report summarizes current knowledge of GHG emissions and capture as influenced by cropping system, tillage management, and nutrient source. Additionally, topics requiring further research have been identified.
  • 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:
    • 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:
    • 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:
    • McKenzie, R. H.
    • Bremer, E.
    • Olson, B. M.
    • Bennett, D. R.
  • Source: Canadian Journal of Soil Science
  • Volume: 90
  • Issue: 2
  • Year: 2010
  • Summary: The risk of P leaching increases on land that receives manure at rates sufficient to meet crop N requirements, but calcareous subsoils may minimize P loss due to P adsorption. An 8-yr field experiment was conducted to determine the effects of different rates of manure on the accumulation and leaching of soil P in a coarse-textured (CT) soil and a medium-textured (MT) soil under typical irrigation management in southern Alberta. Treatments included a non-manured control and four rates of cattle ( Bos taurus) manure (20, 40, 60, and 120 Mg ha -1 yr -1, wet-weight basis). In manured treatments, P addition ranged from about 80 to 450 kg P ha -1 yr -1, while P removal by annual cereal silage crops ranged from 15 to 22 kg P ha -1 yr -1. High soil test P (STP) concentrations occurred to a depth of 0.6 m at the CT site and 0.3 m at the MT site. Increase in STP concentration to 0.6 m was equivalent to 43% of net P input, and increase in total soil P was equivalent to 78% of net P input. Non-recovery of net P input suggests that P loss by leaching occurred at these sites and that leaching was more prevalent at the CT site. These calcareous soils have considerable potential to hold surplus P, but may still allow P leaching.
  • Authors:
    • Larney, F. J.
    • McKenzie, R. H.
    • Olson, B. M.
    • Bremer, E.
  • Source: Canadian Journal of Soil Science
  • Volume: 90
  • Issue: 4
  • Year: 2010
  • Summary: Land application of livestock manure has caused concern about excess nutrients in soil and the potential risk to water quality. Application of manure based on crop-nutrient requirements is considered a beneficial management practice. A field study was conducted to assess the feasibility and impact of crop-based N and P application rates of cattle ( Bos taurus) manure and compost for crop productivity and accumulation of extractable soil N and P. The 6-yr (2002-2007), small-plot field study included 10 amendments: control (CONT), annual synthetic fertilizer N (F-N), annual synthetic fertilizer P (F-P), annual synthetic fertilizer N plus P (F-NP), annual N-based manure (M-N), annual P-based manure (M-P), three times the P-based manure once per 3 yr (M-3P), annual N-based compost (C-N), annual P-based compost (C-P), and three times the P-based compost once per 3 yr (C-3P). Amendments were arranged in randomized complete block design with five replicates and applied based on annual soil testing and nutrient recommendations. The test crops were triticale (* Triticosecale rimpaui Wittm.) and barley ( Hordeum vulgare L.) silage managed under irrigation. Dry matter yields for CONT and F-P were significantly smaller than for the other treatments. There were generally no significant differences among the six organic and F-NP amendments. Apparent N recovery (ANR) was greatest for F-NP (45%) and F-N (41%), followed by the P-based organic amendments (26-34%), M-N (15%), and smallest for C-N (10%). Apparent P recovery (APR) was greatest for F-NP (30%) and smallest for M-N (6%) and C-N (4%). The APR for the P-based organic amendments ranged from 14 to 22%. Application of the amendments did not result in the accumulation of excess nitrate N in the soil profile. The M-N and C-N amendments applied for 6 yr increased extractable P in the 0- to 0.15-m soil layer from 12 mg kg -1 to 121 and 156 mg kg -1, respectively. Crop productivity and soil nutrient responses indicated that assumptions made for P and N availability in manure and compost were reasonably accurate. Based on the results, P-based application of manure or compost can achieve optimum crop yield and prevent nutrient build-up in soil. Under the conditions of this study, the amount of land required to accommodate P-based application would be five to seven times more for manure and eight to ten times more for compost compared with N-based application.
  • Authors:
    • Pepo, P.
  • Source: 45th Croatian & 5th International Symposium on Agriculture
  • Year: 2010
  • Summary: In non-irrigated treatment the maximum yields of winter wheat were 5590 kg ha -1 in biculture (maize-wheat) and 7279 kg ha-1 in triculture (peas-wheat-maize) in 2007 year characterized by water-deficit stress. In 2008 (optimum rain amount and distribution) the maximum yields were 7065 kg ha -1 (biculture) and 8112 kg ha -1 (triculture) in non irrigated conditions. The fertilization surpluses of wheat were 2853-3698 kg ha -1 (non-irrigated) and 3164-5505 kg ha -1 (irrigated) in a dry cropyear (2007) and 884-4050 kg ha -1 (non-irrigated) and 524-3990 kg ha -1 (irrigated) in an optimum cropyear (2008). The optimum fertilizer doses varied N150-200+PK in biculture and N50-150+PK in triculture depending on cropyear and irrigation. The optimalization of agrotechnical elements provides 7,8-8,5 t ha -1 yields in dry cropyear and 7,1-8,1 t ha -1 yields of wheat in good cropyear, respectively. Our scientific results proved that in water stress cropyear (2007) the maximum yields of maize were 4316 kg ha -1 (monoculture), 7706 kg ha -1 (biculture), 7998 kg ha -1 (triculture) in non irrigated circumstances and 8586 kg ha -1, 10 970 kg ha -1, 10 679 kg ha -1 in irrigated treatment, respectively. In dry cropyear (2007) the yield-surpluses of irrigation were 4270 kg ha -1 (mono), 3264 kg ha -1 (bi), 2681 kg ha -1 (tri), respectively. In optimum water supply cropyear (2008) the maximum yields of maize were 13 729-13 787 (mono), 14 137-14 152 kg ha -1 (bi), 13 987-14 180 kg ha -1 (tri) so there was no crop-rotation effect. We obtained 8,6-11,0 t ha -1 maximum yields of maize in water stress cropyear and 13,7-14,2 t ha -1 in optimum cropyear on chernozem soil with using appropriate agrotechnical elements.
  • Authors:
    • Siebert, S.
    • Portmann, F. T.
    • Doll, P.
  • Source: Global Biogeochemical Cycles
  • Volume: 24
  • Issue: 1
  • Year: 2010
  • Summary: To support global-scale assessments that are sensitive to agricultural land use, we developed the global data set of monthly irrigated and rainfed crop areas around the year 2000 (MIRCA2000). With a spatial resolution of 5 arc min (about 9.2 km at the equator), MIRCA2000 provides both irrigated and rainfed crop areas of 26 crop classes for each month of the year. The data set covers all major food crops as well as cotton. Other crops are grouped into categories (perennial, annual, and fodder grasses). It represents multicropping systems and maximizes consistency with census-based national and subnational statistics. According to MIRCA2000, 25% of the global harvested areas are irrigated, with a cropping intensity (including fallow land) of 1.12, as compared to 0.84 for the sum of rainfed and irrigated harvested crops. For the dominant crops (rice (1.7 million km 2 harvested area), wheat (2.1 million km 2), and maize (1.5 million km 2)), roughly 60%, 30%, and 20% of the harvested areas are irrigated, respectively, and half of the citrus, sugar cane, and cotton areas. While wheat and maize are the crops with the largest rainfed harvested areas (1.5 million km 2 and 1.2 million km 2, respectively), rice is clearly the crop with the largest irrigated harvested area (1.0 million km 2), followed by wheat (0.7 million km 2) and maize (0.3 million km 2). Using MIRCA2000, 33% of global crop production and 44% of total cereal production were determined to come from irrigated agriculture.
  • Authors:
    • Ju, X. T.
    • Qiu, S. J.
  • Source: Better Crops with Plant Food
  • Volume: 94
  • Issue: 4
  • Year: 2010
  • Summary: In the north China plain, the amount of N fertilizer and irrigation application in greenhouse vegetable systems is about three to five times that in conventional cereal systems. Over a decade of shifting from the conventional cereal systems to greenhouse vegetables, the capacity for nutrient cycling within these greenhouse systems has fallen. Additionally, the content of inorganic C in the soil profile under greenhouse systems has shown a dramatic decline.