• Authors:
    • Institute for the Study of Earth, Oceans and Space
  • Year: 2009
  • Summary: The DNDC model is a process-base model of carbon (C) and nitrogen (N) biogeochemistry in agricultural ecosystems. This document describes how to use the PC Windows versions of the DNDC model for predicting crop yield, C sequestration, nitrate leaching loss, and emissions of C and N gases in agroecosystems. Part I provides a brief description of the model structure with relevant scientific basis. Part II describes how to install the model. Part III and IV demonstrate how to conduct simulations with the site and regional versions of DNDC, respectively. Part V provides basic information for uncertainty analysis with DNDC. Part VI contains six case studies demonstrating the input procedures for simulating crop yield, soil C dynamics, nitrate leaching loss, and trace gas emissions. A list of relevant publications is included in Part VII. These publications provide more information about the scientific background and applications of DNDC far beyond this User's Guide. DNDC9.3 can run in two modes: site or regional. By selecting the mode, the users will open a corresponding interface to manage their input information for the modeled site or region.
  • Authors:
    • Jia, L.
    • Raun, W. R.
    • Schroder, J.
    • Zhang, H.
    • Chen, X.
    • Li, R.
    • Cui, Z.
    • Zhang, F.
    • Miao, Y.
    • Li, F.
  • Source: Soil Science Society of America Journal
  • Volume: 73
  • Issue: 5
  • Year: 2009
  • Summary: Optical sensor-based N management strategies are promising approaches to improve N-use efficiency (NUE) and reduce environmental pollution risk. The objective of this study was to evaluate an active optical sensor-based in-season N management strategy for winter wheat (Triticum aestivum L.) in the North China Plain (NCP). Initially, 10 field experiments were conducted at four villages in NCP in the 2004/05, 2005/06, and 2006/07 growing seasons to evaluate the in-season N requirement prediction developed by Oklahoma State University. Then the N application rates, winter wheat grain yield, NUE, economic returns, residual N content after harvest and apparent N loss were compared among three different management systems on a total of 16 farmer fields in 2005/2006 and 14 farmer fields in 2006/2007. The systems included a sensor-based system, a soil test-based approach crediting soil residual mineral N (N-min) to different depth at different growth stages, and common farmer practices. Averaged across site-years, the sensor-based, soil N-min-based N management strategies, and farmer practices produced similar grain yields but used 67, 88, and 372 kg N ha(-1), respectively. Nitrogen-use efficiencies were 61.3, 51.0, and 13.1% for the three methods of N recommendations, correspondingly. Their residual N content in the soil and apparent N loss were 115, 122, and 208 kg N ha(-1), and 4, 15, and 205 kg N ha(-1), respectively. The optical sensor-based N management strategy is relatively easy to use, has better potential to improve NUE and economic returns, and reduces residual soil N content and apparent N loss than other methods currently used in the NCP.
  • Authors:
    • Six, J.
    • Howitt, R. E.
    • Catalá-Luque, R.
    • Albarracin, M. V.
    • De Gryze, S.
  • Source: California Agriculture
  • Volume: 63
  • Issue: 2
  • Year: 2009
  • Summary: Agricultural management has a significant impact on the amount of greenhouse gases emitted by cropped fields. Alternative practices such as winter cover cropping and avoiding overfertilization can decrease the total amount of greenhouse gases that are produced. Policymakers are considering a structure in which parties (such as factories) who exceed their greenhouse-gas emissions cap can pay incentives to encourage farmers to adopt practices that curb greenhouse gases. Based on data from field studies and an ecosystem computer model, we assessed impacts on yields and the total potential for reducing greenhouse-gas emissions of certain alternative practices in California.
  • Authors:
    • Lorenz, N.
    • Eastridge, M. L.
    • Dick, R. P.
    • Barker, D. J.
    • Sulc, R. M.
    • Fae, G. S.
  • Source: Agronomy Journal
  • Volume: 101
  • Issue: 5
  • Year: 2009
  • Summary: The benefits of cover crops within crop rotations are well documented, but information is limited on using cover crops for forage within midwestern United States cropping systems, especially under no-tillage management. Our objective was to evaluate plant, animal, and soil responses when integrating winter cover crop forages into no-till corn (Zea mays L.) silage production. Three cover crop treatments were established no-till after corn silage in September 2006 and 2007 at Columbus, OH: annual ryegrass (Lolium multiflorum L.), a mixture of winter rye (Secale cereale L.) and oat (Avena sativa L.), and no cover crop. Total forage yield over autumn and spring seasons was 38 to 73% greater (P <= 0.05) for oat + winter rye than for annual ryegrass. Soil penetration resistance (SPR) in May 2007 was 7 to 15% greater (P <= 0.10) in the grazed cover crops than in the nongrazed no cover crop treatment; however, subsequent silage corn yield did not differ among treatments, averaging 10.4 Mg ha(-1) in August 2007. Compared with the no cover crop treatment, cover crops had three- to fivefold greater root yield, threefold greater soil microbial biomass (MB) in spring 2008, and 23% more particulate organic carbon (POC) concentrations in the 0- to 15-cm soil depth. integration of forage cover crops into no-till corn silage production in Ohio can provide supplemental forage for animal feed without detrimental effects on subsequent corn silage productivity, with the added benefit of increasing labile soil C.
  • Authors:
    • Wong, C. P.
    • Neely, C. L.
    • Schohr, T.
    • Oldfield, J. T.
    • Laca, E. A.
    • Kustin, C.
    • George, M. R.
    • Brown, J. R.
    • Alvarez, P.
    • Fynn, A. J.
  • Year: 2009
  • Authors:
    • Jordan, D.
    • Owen, M. D. K.
    • Wilson, R. G.
    • Young, B. G.
    • Weller, S. C.
    • Johnson, W. G.
    • Kruger, G. R.
    • Shaw, D. R.
    • Givens, W. A.
  • Source: Weed Technology
  • Volume: 23
  • Issue: 1
  • Year: 2009
  • Summary: A phone survey was administered to 1,195 growers in six states (Illinois, Indiana, Iowa, Mississippi, Nebraska, and North Carolina). The survey measured producers' crop history, perception of glyphosate-resistant (GR) weeds, past and present weed pressure, tillage practices, and herbicide use as affected by the adoption of GR crops. This article describes the changes in tillage practice reported in the survey. The adoption of a GR cropping system resulted in a large increase in the percentage of growers using no-till and reduced-till systems. Tillage intensity declined more in continuous GR cotton and GR soybean (45 and 23%, respectively) than in rotations that included GR corn or non-GR crops. Tillage intensity declined more in the states of Mississippi and North Carolina than in the other states, with 33% of the growers in these states shifting to more conservative tillage practices after the adoption of a GR crop. This was primarily due to the lower amount of conservation tillage adoption in these states before GR crop availability. Adoption rates of no-till and reduced-till systems increased as farm size decreased. Overall, producers in a crop rotation that included a GR crop shifted from a relatively more tillage-intense system to reduced-till or no-till systems after implementing a GR crop into their production system.
  • Authors:
    • Euliss, N. H. Jr.
    • Browne, B. A.
    • Tangen, B. A.
    • Gleason, R. A.
  • Source: Soil Biology and Biochemistry
  • Volume: 41
  • Issue: 12
  • Year: 2009
  • Summary: It has been well documented that restored wetlands in the Prairie Pothole Region of North America do store carbon. However, the net benefit of carbon sequestration in wetlands in terms of a reduction in global warming forcing has often been questioned because of potentially greater emissions of greenhouse gases (GHGs) such as nitrous oxide (N2O) and methane (CH4). We compared gas emissions (N2O, CH4, carbon dioxide [CO2]) and soil moisture and temperature from eight cropland and eight restored grassland wetlands in the Prairie Pothole Region from May to October, 2003, to better understand the atmospheric carbon mitigation potential of restored wetlands. Results show that carbon dioxide contributed the most (90%) to net-GHG flux, followed by CH4 (9%) and N2O (1%). Fluxes of N2O, CH4, CO2, and their combined global warming potential (CO2 equivalents) did not significantly differ between cropland and grassland wetlands. The seasonal pattern in flux was similar in cropland and grassland wetlands with peak emissions of N2O and CH4 occurring when soil water-filled pore space (WFPS) was 40-60% and >60%, respectively; negative CH4 fluxes were observed when WFPS approached 40%. Negative CH4 fluxes from grassland wetlands occurred earlier in the season and were more pronounced than those from cropland sites because WFPS declined more rapidly in grassland wetlands; this decline was likely due to higher infiltration and evapotranspiration rates associated with grasslands. Our results suggest that restoring cropland wetlands does not result in greater emissions of N2O and CH4, and therefore would not offset potential soil carbon sequestration. These findings, however, are limited to a small sample of seasonal wetlands with relatively short hydroperiods. A more comprehensive assessment of the GHG mitigation potential of restored wetlands should include a diversity of wetland types and land-use practices and consider the impact of variable climatic cycles that affect wetland hydrology.
  • Authors:
    • Wyse, D. L.
    • Buckley, D. H.
    • DeHaan, L. R.
    • Crews, T. E.
    • Mai, J. G.
    • Mangan, M. E.
    • Young, L.
    • Broussard, W.
    • DuPont, S. T.
    • Culman, S. W.
    • Glover, J. D.
    • Reynolds, H. L.
    • Turner, R. E.
    • Ferris, H.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 137
  • Issue: 1-2
  • Year: 2009
  • Summary: Perennial vegetation can provide multiple ecosystem services essential for sustainable production more effectively than production systems based on annual crops. However, the ability of annually harvested, unfertilized perennial systems to sustain long-term yields while also maintaining ecosystem services has not been widely studied. Here we compare the impacts of harvested perennial grass and annual crop fields on ecosystem functioning in KS, USA. Despite the lack of mineral fertilizer applications, the aboveground harvests of perennial fields yielded similar levels of N compared to those of conventional high-input wheat (Triticum aestivum) fields and at only 8% of the in-field energy costs. Their 75-yr cumulative N yield per ha was approximately 23% greater than that from the region's wheat fields. In terms of aboveground food webs, perennial fields harboured greater numbers and/or diversity of insect pollinators, herbivores and detritivores. Belowground, perennial grass fields maintained 43 Mg ha-1 more soil carbon and 4 Mg ha-1 more soil nitrogen than annual crop fields in the surface 1 m. Soil food webs in perennial fields, as indicated by nematode communities, exhibited greater food web complexity and stability than did those in annual crop fields. In surrounding watersheds, increased annual cropland was correlated with higher riverine nitrate-nitrogen levels. Given their benefits, harvested perennial grasslands provide valuable ecological benchmarks for agricultural sustainability.
  • Authors:
    • Al-Kaisi, M. M.
    • Guzman, J. G.
  • Source: Journal of Environmental Quality
  • Volume: 39
  • Issue: 1
  • Year: 2009
  • Summary: In addition to their aesthetic and environmental qualities, reconstructed prairies can act as C sinks and potentially offset rising atmospheric CO2 concentration. The objective Of this Study was to quantify C budget components of newly established prairies on previously cultivated land. Net ecosystem production (NEP) was estimated using a C budgeting approach that assessed SOC content, soil surface CO2-C emission, and above- and belowground plant biomass. Study was conducted in southern Iowa, in 2005 to 2007. Results show that differences between sites for potential total C input were primarily due to root biomass contributions, which ranged from 0.8 to 5.4 Mg C ha(-1). Average potential aboveground biomass C input was 2.7 Mg C ha(-1) in 2006 and 5.5 Mg C ha(-1) in 2007. Total soil CO2-C emissions from heterotrophic respiration increased as prairie age increased from 2.9 to 4.0 Mg C ha(-1) and 3.1 to 4.7 Mg C ha(-1) in 2006 and 2007, respectively. Determination of NEP showed that the 1998 and 2003 reconstructed prairie sites had the greatest potential for soil C sequestration at 4.1 and 4.4 Mg C ha(-1). Increases in SOC content were only observed in the youngest established prairie site (2003) and the no-till site in 2003 at 2.1 and 2.6 Mg C ha(-1) yr(-1), respectively. Declines of SOC sequestration rates occurred when potential C equilibrium was reached (R-h = NPP) within 10 yr since prairie establishment.
  • Authors:
    • Folley, J. A.
    • Kucharik, C. J.
    • Cahill, K. N.
  • Source: Ecological Applications
  • Volume: 19
  • Issue: 8
  • Year: 2009
  • Summary: We investigated carbon cycling and ecosystem characteristics among two prairie restoration treatments established in 1987 and adjacent cropland, all part of the Conservation Reserve Program in southwestern Wisconsin, USA. We hypothesized that different plant functional groups (cool-season C3 vs. warm-season C4 grasses) between the two prairie restoration treatments would lead to differences in soil and vegetation characteristics and amount of sequestered carbon, compared to the crop system. We found significant (P < 0.05) differences between the two prairie restoration treatments in soil CO2 respiration and above- and belowground productivity, but no significant differences in long-term (~16-year) carbon sequestration. We used a biometric approach aggregating short-term observations of above- and belowground productivity and CO2 respiration to estimate total net primary production (NPP) and net ecosystem production (NEP) using varied methods suggested in the literature. Net ecosystem production is important because it represents the ecosystem carbon sequestration, which is of interest to land managers and policymakers seeking or regulating credits for ecosystem carbon storage. Such a biometric approach would be attractive because it might offer the ability to rapidly assess the carbon source/sink status of an ecosystem. We concluded that large uncertainties in (1) estimating aboveground NPP, (2) determining belowground NPP, and (3) partitioning soil respiration into microbial and plant components strongly affect the magnitude, and even the sign, of NEP estimates made from aggregating its components. A comparison of these estimates across treatments could not distinguish differences in NEP, nor the absolute sign of the overall carbon balance. Longer-term quantification of carbon stocks in the soil, periodically linked to measurements of individual processes, may offer a more reliable measure of the carbon balance in grassland systems, suitable for assigning credits.