• Authors:
    • Donnarummo, M. G.
    • Castiglioni, P. P.
    • Bensen, R. J.
    • Anstrom, D. C.
    • Warner, D. C.
    • Wu, J.
    • Creelman, R. A.
    • Adams, T. R.
    • Repetti, P. P.
    • Nelson, D. E.
  • Source: PNAS: Proceedings of the National Academy of Sciences
  • Volume: 104
  • Issue: 42
  • Year: 2007
  • Summary: Commercially improved crop performance under drought conditions has been challenging because of the complexity of the trait and the multitude of factors that influence yield. Here we report the results of a functional genomics approach that identified a transcription factor from the nuclear factor Y (NF-Y) family, AtNF-YB1, which acts through a previously undescribed mechanism to confer improved performance in Arabidopsis under drought conditions.
  • Authors:
    • Paustian, K.
    • Williams, S.
    • Easter, M.
    • Breidt, F. J.
    • Ogle, S. M.
  • Source: Ecological Modelling
  • Volume: 205
  • Issue: 3-4
  • Year: 2007
  • Summary: Simulation modelling is used to estimate C sequestration associated with agricultural management for purposes of greenhouse gas mitigation. Models are not completely accurate or precise estimators of C pools, however, due to insufficient knowledge and imperfect conceptualizations about ecosystem processes, leading to uncertainty in the results. It can be difficult to quantify the uncertainty using traditional error propagation techniques, such as Monte Carlo Analyses, because of the structural complexity of simulation models. Empirically based methods provide an alternative to the error propagation techniques, and our objective was to apply this alternative approach. Specifically, we developed a linear mixed-effect model to quantify both bias and variance in modeled soil C stocks that were estimated using the Century ecosystem simulation model. The statistical analysis was based on measurements from 47 agricultural experiments. A significant relationship was found between model results and measurements although there were biases and imprecision in the modeled estimates. Century under-estimated soil C stocks for several management practices, including organic amendments, no-till adoption, and inclusion of hay or pasture in rotation with annual crops. Century also over-estimated the impact of N fertilization on soil C stocks. For lands set-aside from agricultural production, Century under-estimated soil C stocks on low carbon soils and over-estimated the stocks on high carbon soils. Using an empirically based approach allows for simulation model results to be adjusted for biases as well as quantify the variance associated with modeled estimates, according to the measured "reality" of management impacts from a network of experimental sites.
  • Authors:
    • Gal, A.
    • Hegymegi, P.
    • Smith, D. R.
    • Vyn, T. J.
    • Omonode, R.A.
  • Source: Soil & Tillage Research
  • Volume: 95
  • Issue: 1-2
  • Year: 2007
  • Summary: Although the Midwestern United States is one of the world's major agricultural production areas, few studies have assessed the effects of the region's predominant tillage and rotation practices on greenhouse gas emissions from the soil surface. Our objectives were to (a) assess short-term chisel (CP) and moldboard plow (MP) effects on soil CO2 and CH4 fluxes relative to no-till (NT) and, (b) determine how tillage and rotation interactions affect seasonal gas emissions in continuous corn and corn-soybean rotations on a poorly drained Chalmers silty clay loam (Typic Endoaquoll) in Indiana.
  • Authors:
    • Nicolardot, B.
    • Labreuche, J.
    • Grehan, E.
    • Merckx, R.
    • Oorts, K.
  • Source: Soil & Tillage Research
  • Volume: 95
  • Issue: 1-2
  • Year: 2007
  • Summary: The greenhouse gases CO2 and N2O emissions were quantified in a long-term experiment in northern France, in which no-till (NT) and conventional tillage (CT) had been differentiated during 32 years in plots under a maize-wheat rotation. Continuous CO2 and periodical N2O soil emission measurements were performed during two periods: under maize cultivation (April 2003-July 2003) and during the fallow period after wheat harvest (August 2003-March 2004). In order to document the dynamics and importance of these emissions, soil organic C and mineral N, residue decomposition, soil potential for CO2 emission and climatic data were measured. CO2 emissions were significantly larger in NT on 53% and in CT on 6% of the days. From April to July 2003 and from November 2003 to March 2004, the cumulated CO2 emissions did not differ significantly between CT and NT. However, the cumulated CO2 emissions from August to November 2003 were considerably larger for NT than for CT. Over the entire 331 days of measurement, CT and NT emitted 3160 +/- 269 and 4064 +/- 138 kg CO2-C ha(-1) respectively. The differences in CO2 emissions in the two tillage systems resulted from the soil climatic conditions and the amounts and location of crop residues and SOM. A large proportion of the CO2 emissions in NTover the entire measurement period was probably due to the decomposition of old weathered residues. NT tended to emit more N2O than CTover the entire measurement period. However differences were statistically significant in only half of the cases due to important variability. N2O emissions were generally less than 5 g N ha(-1) day(-1), except for a few dates where emission increased up to 21 g N ha(-1) day(-1). These N2O fluxes represented 0.80 +/- 0.15 and 1.32 +/- 0.52 kg N2O-N ba(-1) year(-1) for CT and NT, respectively. Depending on the periods, a large part of the N2O emissions occurred was probably induced by nitrification, since soil conditions were not favorable for denitrification. Finally, for the period of measurement after 32 years of tillage treatments, the NT system emitted more greenhouses gases (CO2 and N2O) to the atmosphere on an annual basis than the CT system. (C) 2006 Elsevier B.V. All rights reserved.
  • Authors:
    • Torbert, H. A.
    • Scopel, E.
    • Velazquez-Garcia, I.
    • Potter, K. N.
  • Source: Journal of Soil and Water Conservation
  • Volume: 62
  • Issue: 2
  • Year: 2007
  • Summary: While no-till management practices usually result in increased soil organic carbon (SOC) contents, the effect of residue removal with no-till is not well understood, especially in warmer climates. A multi-year study was conducted at six locations having a wide range of climatic conditions in central Mexico to determine the effect of varying rates of residue removal with no-till oil SOC. Mean annual temperatures ranged from 16 degrees C to 27 degrees C (61 degrees F to 81 degrees F). Mean annual rainfall ranged from 618 to 1099 min yr(-1) (24 to 43 in yr(-1)). Treatments consisted of annual moldboard plowing under residue and no-till with 100%, 66%, 33%, and no corn (Zea mays L.) residue retained oil the no-till surface. At five of the six locations, no-till with all surface residues removed maintained SOC levels above that of moldboard plowing which incorporated all residues. Retaining 100% of the crop residues with no-till always increased or maintained the SOC content. SOC increased in cooler climates, but as mean annual temperature increased, more retained crop residues were needed to increase the SOC. In tropical (mean annual temperature > 20 degrees C) conditions, 100% corn residue retention with no-till only maintained SOC levels. Mean annual temperature ad a greater impact oil SOC than did annual rainfall. It appears that, in warmer climates, residue in excess of that needed for erosion control may be used for animal fodder or energy production. At the higher temperatures, most of the residue will decompose if left oil the soil surface Without improving soil carbon contents.
  • Authors:
    • Mangum, R. W.
    • Coffman, C. B.
    • Teasdale, J. R.
  • Source: Agronomy Journal
  • Volume: 99
  • Issue: 5
  • Year: 2007
  • Summary: There have been few comparisons of the performance of no-tillage cropping systems vs. organic farming systems, particularly on erodible, droughty soils where reduced-tillage systems are recommended. In particular, there is skepticism whether organic farming can improve soils as well as conventional no-tillage systems because of the requirement for tillage associated with many organic farming operations. A 9-yr comparison of selected minimum-tillage strategies for grain production of corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and wheat (Triticum aestivum L.) was conducted on a sloping, droughty site in Beltsville, MD, from 1994 to 2002. Four systems were compared: (i) a standard mid-Atlantic no-tillage system (NT) with recommended herbicide and N inputs, (ii) a cover crop-based no-tillage system (CC) including hairy vetch (Vicia villosa Roth) before corn, and rye (Secale cereale L.) before soybean, with reduced herbicide and N inputs, (iii) a no-tillage crownvetch (Coronilla varia L.) living mulch system (CV) with recommended herbicide and N inputs, and (iv) a chisel-plow based organic system (OR) with cover crops and manure for nutrients and postplanting cultivation for weed control. After 9 yr, competition with corn by weeds in OR and by the crownvetch living mulch in CV was unacceptable, particularly in dry years. On average, corn yields were 28 and 12% lower in OR and CV, respectively, than in the standard NT, whereas corn yields in CC and NT were similar. Despite the use of tillage, soil combustible C and N concentrations were higher at all depth intervals to 30 cm in OR compared with that in all other systems. A uniformity trial was conducted from 2003 to 2005 with corn grown according to the NT system on all plots. Yield of corn grown on plots with a 9-yr history of OR and CV were 18 and 19% higher, respectively, than those with a history of NT whereas there was no difference between corn yield of plots with a history of NT and CC. Three tests of N availability (corn yield loss in subplots with no N applied in 2003-2005, presidedress soil nitrate test, and corn ear leaf N) all confirmed that there was more N available to corn in OR and CV than in NT. These results suggest that OR can provide greater long-term soil benefits than conventional NT, despite the use of tillage in OR. However, these benefits may not be realized because of difficulty controlling weeds in OR.
  • Authors:
    • Worth, D.
    • Desjardins, R. L.
    • Dyer, J. A.
    • VergĂ©, X. P. C.
  • Source: Agricultural Systems
  • Volume: 94
  • Issue: 3
  • Year: 2007
  • Summary: In order to demonstrate the impact of an increase in production efficiency on greenhouse gas (GHG) emissions, it is important to estimate the combined methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) emissions per unit of production. In this study, we calculated the GHG emissions from the Canadian dairy industry in 2001 as a fraction of the milk production and per dairy animal. Five regions were defined according to the importance of the dairy industry. N2O and CO2 emissions are directly linked with areas allocated to the dairy crop complex which includes only the crop areas used to feed dairy cattle. The dairy crop complex was scaled down from sector-wide crop areas using the ratios of dairy diet to national crop production of each crop type. Both fertilizer application and on-farm energy consumption were similarly scaled down from sector-wide estimates to the dairy crop complex in each region. The Intergovernmental Panel on Climate Change (IPCC) methodology, adapted for Canadian conditions, was used to calculate CH4 and N2O emissions. Most of the CO2 emission estimates were derived from a Fossil Fuel for Farm Fieldwork Energy and Emissions model except for the energy used to manufacture fertilizers. Methane was estimated to be the main source of GHG, totalling 5.75 Tg CO2 eq with around 80% coming from enteric fermentation and 20% coming from manure management. Nitrous oxide emissions were equal to 3.17 Tg CO2 eq and carbon dioxide emissions were equal to 1.45 Tg. The GHG emissions per animal were 4.55 Mg CO2 eq. On an intensity basis, average GHG emissions were 1.0 kg CO2 eq/kg milk. Methane emissions per kg of milk were estimated at 19.3 l CH4/kg milk which is in agreement with Canadian field measurements.
  • Authors:
    • Adee, E. A.
    • Nafziger ,E. D.
    • Hoeft, R. G.
    • Lal, R.
    • Jagadamma, S.
  • Source: Soil & Tillage Research
  • Volume: 95
  • Issue: 1-2
  • Year: 2007
  • Summary: Agricultural soils can be a major sink for atmospheric carbon (C) with adoption of recommended management practices (RMPs). Our objectives were to evaluate the effects of nitrogen (N) fertilization and cropping systems on soil organic carbon (SOC) and total N (TN) concentrations and pools. Replicated soil samples were collected in May 2004 to 90 cm depth from a 23-year-old experiment at the Northwestern Illinois Agricultural Research and Demonstration Center, Monmouth, IL. The SOC and TN concentrations and pools, soil bulk density (rho(b)) and soil C:N ratio were measured for five N rates [0 (N-0), 70 (N-1), 140 (N-2), 210 (N-3) and 280 (N-4) kg N ha(-1)] and two cropping systems [continuous corn (Zea mays L.) (CC), and corn-soybean (Glycine max (L.) Merr.) rotation (CS)]. Long-term N fertilization and cropping systems significantly influenced SOC concentrations and pools to 30 cm depth. The SOC pool in 0-30 cm depth ranged from 68.4 Mg ha(-1) for N-0 to 75.8 Mg ha(-1) for N-4. Across all N treatments, the SOC pool in 0-30 cm depth for CC was 4.7 Mg ha(-1) greater than for CS. Similarly, TN concentrations and pools were also significantly affected by N rates. The TN pool for 0-30 cm depth ranged from 5.36 Mg ha(-1) for N-0 to 6.14 Mg ha(-1) for N-4. In relation to cropping systems, the TN pool for 0-20 cm depth for CC was 0.4 Mg ha(-1) greater than for CS. The increase in SOC and TN pools with higher N rates is attributed to the increased amount of biomass production in CC and CS systems. Increasing N rates significantly decreased rho(b) for 0-30 cm and decreased the soil C:N ratio for 0-10 cm soil depth. However, none of the measured soil properties were significantly correlated with N rates and cropping systems below 30 cm, soil depth. We conclude that in the context of developing productive and environmentally sustainable agricultural systems on a site and soil specific basis, the results from this study is helpful to strengthening the database of management effects on SOC storage in the Mollisols of Midwestem U.S. (c) 2007 Elsevier B.V. All rights reserved.
  • Authors:
    • Voroney, P.
    • Kay, B.
    • Warland, J.
    • von Bertoldi, P.
    • Parkin, G.
    • Wagner-Riddle, C.
    • Jayasundara, S.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 79
  • Issue: 2
  • Year: 2007
  • Summary: Best management practices are recommended for improving fertilizer and soil N uptake efficiency and reducing N losses to the environment. Few year- round studies quantifying the combined effect of several management practices on environmental N losses have been carried out. This study was designed to assess crop productivity, N uptake from fertilizer and soil sources, and N losses, and to relate these variables to the fate of fertilizer 15N in a corn ( Zea mays L.)- soybean ( Glycine max L.)- winter wheat ( Triticum aestivum L.) rotation managed under Best Management ( BM) compared with conventional practices ( CONV). The study was conducted from May 2000 to October 2004 at Elora, Ontario, Canada. Cumulative NO3 leaching loss was reduced by 51% from 133 kg N ha(-1) in CONV to 68 kg N ha(-1) in BM. About 70% of leaching loss occurred in corn years with fertilizer N directly contributing 11 - 16% to leaching in CONV and < 4% in BM. High soil derived N leaching loss in CONV, which occurred mostly ( about 80%) during November to April was attributable to 45 - 69% higher residual soil derived mineral N left at harvest, and on-going N mineralization during the over-winter period. Fertilizer N uptake efficiency ( FNUE) was higher in BM ( 61% of applied) than in CONV ( 35% of applied) over corn and wheat years. Unaccounted gaseous losses of fertilizer N were reduced from 27% of applied in CONV to 8% of applied in BM. Yields were similar between BM and CONV ( for corn: 2000 and 2003, wheat: 2002, soybean: 2004) or higher in BM ( soybean: 2001). Results indicated that the use of judicious N rates in synchrony with plant N demand combined with other BMP ( no- tillage, legume cover crops) improved FNUE by corn and wheat, while reducing both fertilizer and soil N losses without sacrificing yields.
  • Authors:
    • Boast, C. W.
    • Ellsworth, T. R.
    • Mulvaney, R. L.
    • Khan, S. A.
  • Source: Journal of Environmental Quality
  • Volume: 36
  • Issue: 6
  • Year: 2007
  • Summary: Intensive use of N fertilizers in modern agriculture is motivated by the economic value of high grain yields and is generally perceived to sequester soil organic C by increasing the input of crop residues. This perception is at odds with a century of soil organic C data reported herein for Morrow Plots, the world's oldest experimental site under continuous corn (Zea mays L.). After 40 to 50 yr of synthetic fertilization that exceeded grain N removal by 60 to 190%, a net decline occurred in soil C despite increasingly massive residue C incorporation, the decline being more extensive for a corn-soybean (Glycine max L. Merr.) or corn-oats (Avena sativa L.)-hay rotation than for continuous corn and of greater intensity for the profile (0-46 cm) than the surface soil. These findings implicate fertilizer N in promoting the decomposition of crop residues and soil organic matter and are consistent with data from numerous cropping experiments involving synthetic N fertilization in the USA Corn Belt and elsewhere, although not with the interpretation usually provided. These are important implications for soil C sequestration because the yield-based input of fertilizer N has commonly exceeded grain N removal for corn production on fertile soils since the 1960s. To mitigate the ongoing consequences of soil deterioration, atmospheric CO2 enrichment, and NO3- pollution of ground and surface waters, N fertilization should be managed by site-specific assessment of soil N availability. Current fertilizer N managment practices, if combined with corn stover removal for bioenergy production; exacerbate soil C loss.