2011 Annual Report
1a.Objectives (from AD-416)
Enhance carbon sequestration for improved soil quality and erosion control; Quantify the form and release of major nutrients as affected by soil redox potential; and Determine the impacts of conservation tillage on fate of pesticide in soil.
1b.Approach (from AD-416)
Quantify dissolved organic carbon in runoff samples from subwatersheds in the St. Joseph River; Identify enzymes as soil quality indicators; Monitor effects of changing soil redox potential on nutrient form and release; and Quantify the fate of atrazine, metolachlor and glyphosate under varying temperature and crop residue; Quantify the competition between glyphosate and phosphorus and glyphosate and potassium for possible nutrient decline due to glyphosate usage.
Since 2004, ARS scientists have monitored trace gas emissions and carbon sequestration at two experimental sites: Agronomy Center for Research and Extension, west of West Lafayette, IN, a Mollisol (prairie derived) soil; and Throckmorton Purdue Ag Center, south of Lafayette, IN, an Alfisol (forest derived) soil. Both sites include corn-soybean rotations (five treatments) and grass management plots. Research over the last five years has focused on understanding how current management systems impact carbon (C) sequestration and reduce greenhouse gas emissions. Going forward, we are focusing on innovative systems that might lead to increased C sequestration and reduced greenhouse gas emissions.
Over the last five years we sampled 16 experimental watersheds to answer the question of how implemented conservation practices impact soil quality and C sequestration. Sites included: South Fork (IA), Walnut Creek (IA), Leon River (TX), Little River (GA), Ft. Cobb (OK), Cedar Creek (IN), Beasley Lake (MS), Choptank (MD), Durham (NH), Cheney Lake (KS), Upper Big Walnut Creek (OH), Upper Snake River (ID), Mark Twain River (MO), Topashaw Creek Canal (MS), Goodwin Creek (MS), and Jobos Bay (PR). This number far exceeded the original four proposed watersheds. As a result, analyses progressed slower than anticipated, however soil analyses for 10 of the watersheds have been completed. One paper is in press and two other papers are being prepared.
Dissolved Organic Carbon (DOC) in a number of subwatersheds in the St, Joseph River Watershed was monitored from 2003-2007. This work is in tandem with the National Soil Erosion Research Laboratory’s Conservation Effects Assessment Project (CEAP) water quality project. Data are being analyzed for publication. Since we are currently analyzing the data, conclusions have not yet been made, however preliminary examination of the data shows that the greatest flushes occur in late spring and early summer, as plant root systems are growing rapidly, indicating that a good portion of the DOC is likely derived from plant growth.
Scientists are continuing to monitor changes in soil quality characteristics, carbon sequestration and productivity in a field experiment designed to determine impacts of corn residue removal on the soil. We are also following changes in soil biochemistry (soil enzyme activity) over time. Results should contribute to the development of best management practices for biofuel feedstock crops.
A set of experiments is underway in the field and in the laboratory to study the impact of redox potential on nutrient cycling as related to the frequent periods of soil saturation followed by drainage. Up until now, little attention has been paid to the impact of this cycling system.
A constant temperature room was constructed to conduct the redox experiments and collect data on nutrient form and release. Those experiments have been completed using the redox instrumentation developed earlier at the National Soil Erosion Research Laboratory, but modified for this study. A greenhouse study is underway.
Herbicides affect nutrient cycling. Farmers have observed symptoms of nutrient deficiency in crops where the herbicide glyphosate has been used for several years in a row. ARS scientists at West Lafayette, IN found that one reason for this is that long term exposure to glyphosate affects soil enzyme activities pivotal in nutrient cycling. These findings will impact weed management decision making with soil quality and crop yield in mind.
Soil factors contributing to poor canopy growth. Soil and crop management practices on agricultural fields may cause changes in soil quality which in return affects the sustainability of the land for future crop production. ARS scientists from West Lafayette, IN and Ames, IA observed many cases of underdeveloped corn canopy in parts of the field while the rest of the field had normal corn growth. We thought that crop growth would be related to soil quality and we wanted to identify which soil quality parameters were related to the poor corn growth. We collected soil samples from both healthy and poor growth areas and analyzed for their physical, chemical and biological properties. It was difficult to find significant differences in these soil properties between normal and poor canopy areas due to changing soil types and textures. We used a soil quality model (Soil Management Assessment Framework or SMAF) that accommodates changes in soil types and textures, and assigns different scores for different measured soil property values and produces an overall soil quality index. From our results, we could not find a single cause for the poor corn growth across all the fields, but if we looked at individual fields, we found low soil organic matter, poor nutrient cycling, low extractable phosphorus, high bulk density, and low water-filled pore space were factors causing the low soil quality scores at poor corn growth areas. Using the soil quality model and its scoring system, consultants and land managers can identify causes for poor crop yield and develop management schemes to improve poor performing areas of the fields.
Greenhouse gas emissions (GHG). GHG are presumed to induce anthropogenic global warming, and agriculture has been identified as a contributor to these gas accumulations in the atmosphere. ARS scientists at West Lafayette, IN conducted research to assess the influence of cropping systems management on nitrous oxide, methane and carbon dioxide emissions from an Alfisol (forest derived soils) in the eastern Cornbelt. Corn/soybean rotation plots were established, as were plots in native grasses or Sorghum/Sudan grass. Greenhouse gas fluxes were monitored throughout the growing season from 2004 through 2007. Fluxes of nitrous oxide and carbon dioxide were significantly correlated with soil temperature. Nitrous oxide emissions were greatest from corn plots, intermediate for soybean plots and lowest from native grass plots. Annual trends in methane emissions indicated that these soils typically absorbed atmospheric methane. Carbon dioxide emissions were only assessed for corn plots, with no significant differences observed for the different management scenarios tested. This is one of few studies to provide estimates of GHG emissions from Eastern Cornbelt Alfisols. This impacts our ability to assess and predict crop and soil management impacts on climate change through the inclusion of the results in GHG emission models and lead to the development of best management practices.
Omonode, R.A., Vyn, T.J., Smith, D.R., Gal, A. 2011. Nitrous oxide emissions in corn following three decades of tillage and rotation treatments. Soil Science Society of America Journal. 75:152-163.
Wilhelm, W.W., Hess, J.R., Karlen, D.L., Johnson, J.M., Muth, D.J., Baker, J.M., Gollany, H.T., Novak, J.M., Stott, D.E., Varvel, G.E. 2010. Balancing limiting factors and economic drivers for sustainable midwestern U.S. agricultural residue feedstock supplies. Industrial Biotechnology. 6(5):271-287.
Smith, D.R., Hernandez Ramirez, G., Armstrong, S.D., Bucholtz, D.L., Stott, D.E. 2011. Fertilizer and tillage management impacts on non-carbon-dioxide greenhouse gas emissions. Soil Science Society of America Journal. 75(3):1070-1082.