2009 Annual Report
1a.Objectives (from AD-416)
Quantify the impact of agricultural practices and environmental changes on surface/atmosphere exchange of greenhouse gases (GHG) in order to develop farming systems that reduce global warming potential (GWP) and promote soil C sequestration; Develop farming systems that permit the removal of biomass for energy production while protecting soil resources; Identify and overcome agronomic impediments to the adoption of farming practices, such as reduced tillage, cover crops, and companion crops, that are developed to reduce GWP and permit stover harvest.
1b.Approach (from AD-416)
We will participate in a multi-location effort to identify farming practices that will help slow the increase in atmospheric concentrations of the greenhouse gases CO2, N2O, and CCH4. Our approach will include continuous, field-scale measurement of the surface/atmosphere exchange of all three gases in three adjacent fields under different management. Parallel plot-scale studies will be conducted with chamber-based gas exchange measurements to permit testing of a broader variety of tillage, nitrogen (N) fertility, and rotation strategies. In the second principal area of inquiry, we, again in cooperation with other ARS locations, will examine the soil sustainability of harvesting corn stover for ethanol production. Our goal is to test the hypothesis that cover or companion crops can fill the role of the removed stover in supplying carbon (C) compounds to maintain soil organic matter. We will explore the use of forage digestibility analyses to characterize the quality and quantity of C compounds contained in corn stover and in cereal rye, kura clover, and selected other cover crops. The third component of this project will focus on identifying and correcting practical, agronomic impediments to adoption of the practices mentioned above. In the upper Midwest, the major hindrance to wider use of cover crops, companion crops, and reduced tillage has been the perception that they will reduce the yield of the subsequent crop, due to such factors as cold, compacted spring seed bed conditions and adverse effects on N availability. We will test and refine theories describing near-surface heat and water flow and develop sensors to more easily measure soil bulk density. We will also conduct plot-scale studies of the effects of reduced tillage and cover crops on N losses by leaching and gaseous emissions. The results of this research will facilitate the development of better reduced tillage and cover crop systems for northern soils.
A field study was initiated examining the effects of alternative versus conventional fertilizer management on N2O emissions and nitrate leaching in a coarse-textured soil under both dryland and irrigation management for corn production. A mobile, on-site trace gas analysis laboratory and automated gas flux sampling system was deployed at this site in Becker, MN. A field study examining the combined effects of tillage and fertilizer management in a silt loam soil was continued for a second year in Rosemount, MN. Modeling and error analyses to evaluate chamber methods for measuring soil-to-atmosphere greenhouse gas emissions were expanded to include stochastic analysis of random errors in sampling and analytical techniques and a simplified method for quantifying theoretical errors. A chamber-based method for measuring soil emissions of ammonia was developed (in initial stages). A three-year field evaluation of cropping system and fertilizer management influences on soil emissions of nitrous oxide and carbon dioxide was completed, which showed that N2O emissions following anhydrous ammonia application in corn were twice as high as emissions following urea application.
Laboratory incubations assessing the initial impacts of fast-pyrolysis sawdust biochar additions on net greenhouse gas production and herbicide sorption and dissipation were conducted. The laboratory incubations indicated, at least for the Minnesota soil evaluated, that the addition of biochar suppressed microbial production of CO2 and N2O, and oxidation of CH4. These results are important due to the growing interest in using soil applied biochar as a means of carbon sequestration. In addition to the laboratory incubations, field plots have been established examining 4 different biochar amendments to assess impacts at the field plot scale. The second year of measurements examining the impacts of pyrostourublin fungicide applications on the soil system has been conducted. Collaboration with the Foundation for Arable Research in Lincoln, New Zealand was initiated which is focusing on the impact of strobilurin fungicides on the soil microbial community. Laboratory incubations have been initiated examining the impacts of strobilurin fungicides on the degradation of corn residue with and without fungicide applications.
An investigation of the impacts of corn stover removal on soil properties was initiated under the auspices of a Sun Grant awarded to several ARS locations participating in the multi-location REAP project. Experiments were set up at 3 locations, in cooperation with colleagues from the University of Minnesota. At each site, plots were laid out for two levels of stover removal, plus a no-removal control and two types of tillage. The corn was harvested with a prototype combine that can simultaneously harvest grain and stover. Soil samples were collected immediately after harvest, and the harvested stover was sampled as well to permit full carbon accounting and to track nutrient flows in the system. This experiment will be repeated for at least two more years, with additional measurements planned to examine the impact of stover removal on trace gas emissions.
Biochar amendments increase herbicide sorption and decrease N2O production. ARS scientists in St. Paul, Minnesota in cooperation with ARS scientists from 5 other locations (Ames, IA; Kimberly, ID; Big Spring, TX; Florence, SC; Prosser, WA) have initiated research as part of the new ARS multi-location Biochar and Pyrolysis Initiative. The initial research assessed the impacts of biochar amendments on trace gas and herbicide sorption /dissipation in a Minnesota soil through laboratory incubations. The use of pyrolysis to generate biochar has promise as a carbon sequestration tool to convert easily degradable biomass into a stable form of carbon (biochar). These initial laboratory incubations indicate a reduction in CO2 respiration, CH4 oxidation as well as a reduction in the nitrous oxide (N2O) production potential of the soil as well as increased sorption of herbicides following biochar amendments. This research has lead to an invited oral presentation at the North American Biochar conference (Aug 9-12, 2009) as well as an accepted manuscript in Chemosphere. This research is directly linked to the Cross-Location Project: Greenhouse gas reduction through agricultural carbon enhancement network (GRACEnet).
Winter rye can provide additional biomass production in corn/soybean systems. There is a critical need for development of farming systems that can satisfy the demand for biomass energy while maintaining food production and environmental protection. Winter cover crops in corn/soybean systems are one option, but the potential regional productivity of such systems is unknown. We developed a model to estimate this, using known properties of winter rye and existing weather data from locations across the region, and found that there is potential to produce 1-8 metric tons per hectare of additional biomass, with the lowest potential in the more northern states. However, the model also indicates that the additional water use of the cover crop will affect the primary cash crop in some years and locations, so supplemental irrigation may be necessary to realize this potential. This information can provide guidance for the development of sensible biofuel policies and can also help farmers in assessing the costs and benefits of winter cover crops.
Urea fertilizer decreased N2O emissions compared to anhydrous ammonia in continuous corn and corn/soybean cropping systems in Minnesota. Corn and soybean production together account for nearly half of all land used for crops in the U.S. and comprise approximately 8% of total area of the lower 48 states. Anhydrous ammonia and urea are the two most commonly used nitrogen fertilizers in the U.S. Use of these fertilizers can lead to soil-to-atmosphere emissions of nitrous oxide (N2O) gas. N2O is 300 times more potent as a greenhouse gas than carbon dioxide on a pound-for-pound basis. Therefore, measuring soil emissions of N2O associated with production of corn and soybean and using anhydrous ammonia and urea is essential to developing accurate greenhouse gas inventories for agriculture. The objective of this study was to compare N2O emissions in plots managed for more than 15 years under continuous corn cropping versus corn-soybean rotation in fields in southeastern Minnesota. Over three growing seasons, N2O emissions from continuous corn were nearly identical to emissions from the corn-phase of the corn-soybean rotation when either anhydrous ammonia or urea fertilizer was used. However, in both systems, N2O emissions with anhydrous ammonia were twice the emissions with urea. Emissions from the soybean phase of the rotation were lower than the corn-phase. The management-specific estimates of N2O emissions obtained in this study will assist both scientists and policy makers in improving their estimates of greenhouse gas emissions from agriculture, and in developing improved management practices for mitigating these emissions.
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La Scala, N., Lopes, A., Spokas, K.A., Archer, D.W., Reicosky, D.C. 2009. Short-Term Temporal Changes of Bare Soil CO2 Fluxes Described by First-Order Decay Models. European Journal of Soil Science. 60(2):258-264.
Rice, P.J., Horgan, B.P. 2009. Fungicide and Nutrient Transport with Runoff from Creeping Bentgrass Turf. International Turfgrass Society Research Journal. 11(1):61-76.
Spokas, K.A., Forcella, F. 2009. Software Tools for Weed Seed Germination Modeling. Weed Science. 57(2):216-227.
Venterea, R.T., Spokas, K.A., Baker, J.M. 2009. Accuracy and Precision Analysis of Chamber-Based Nitrous Oxide Gas Flux Estimates. Soil Science Society of America Journal. 73(4):1087-1093.
Venterea, R.T., Baker, J.M. 2008. Effects of soil physical nonuniformity on chamber-based gas flux estimates. Soil Science Society of America Journal. 72:1410-1417.
Schutte, B.J., Regnier, E.E., Harrison, S.K., Schmoll, J.T., Spokas, K.A., Forcella, F. 2008. A hydrothermal seedling emergence model for giant ragweed (Ambrosia trifida). Weed Science. 56:555-560.
La Scala, N., Lopes, A., Spokas, K.A., Archer, D.W., Reicosky, D.C. 2009. First-Order Decay Models to Describe Soil C-CO2 Loss After Rotary Tillage. Scientia Agricola. 66(5):650-657.
Gu, C., Maggi, F., Venterea, R.T., Riley, W.J., Hornberger, G.M., Xu, T., Spycher, N., Steefel, C., Miller, N.L., Oldenburg, C.M. 2009. Aqeuous and Gaseous Nitrogen Losses Induced by Fertilizer Application. Journal of Geophysical Research-Biogeosciences. 114:GO1006. [doi:10.1029/2008JG00788].
Clark, C.M., Hobbie, S., Venterea, R.T., Tilman, D. 2009. Long-lasting effects on nitrogen cycling 12 years after treatments cease despite minimal long-term nitrogen retention. Global Change Biology. 15(7):1755-1766.
Burger, M., Venterea, R.T. 2008. Nitrogen Immobilization and Mineralization Kinetics of Cattle, Hog and Turkey Manure Applied to Soil. Soil Science Society of America Journal. 72(6):1570-1579.
Lee, X., Griffis, T.J., Baker, J.M., Billmark, K., Kim, K.H., Welp, L.R. 2009. Canopy-scale kinetic fractionation of atmospheric carbon dioxide and water vapour isotopes. Global Biogeochemical Cycles. 23(1):GB1002. [doi:10.1029/2008GB003331].