Location: Soil and Water Management Research2012 Annual Report
1a. Objectives (from AD-416):
1. Develop and test systems for sustainable co-production of food and fuel, as a contributor to the ARS Renewable Energy Assessment Project (REAP). 2. Develop guidelines for the optimization of soil fertility and C sequestration using organic and biochar amendments, for field and specialty crops. 3. Enable reduced N2O emissions from fertilized cropping systems through improved understanding of controlling mechanisms, as a contributor to the ARS Greenhouse Gas Reduction through Agricultural Carbon Enhancement network (GRACEnet).
1b. Approach (from AD-416):
Field experiments will be conducted at three locations, each using 3 treatments: zero, intermediate, and full stover removal. We will measure soil organic carbon (SOC) changes and gas exchange. Research will also be conducted at the UMN’s Rosemount Research and Outreach Center (ROC) and on private farm fields in MN. Research at Rosemount will take place in two 20 ha fields with similar soil types, one managed as a conventional corn-soybean rotation; the other in a corn-soybean rotation, but with winter rye cover crop seeded by helicopter in late summer. Latent and sensible heat flux and net ecosystem exchange of CO2 will be measured by eddy covariance. Yield and ancillary soil, physiological and micrometeorological variables will also be measured for 4-years. Soil sampling for SOC analysis will be conducted biennially. Data will be used to test a model of rye production and water use (RyeGro). Field research will also be conducted at Rosemount MN and Arlington WI, supplemented by greenhouse research in St. Paul. Four treatments will be evaluated using a completely randomized design with 3 replications: (i) control, (ii) biochar, (iii) biochar plus manure, and (iv) manure. Biochar will be applied at 20,000 lb ac-1. Three other biochar treatments, derived from macadamia nut, wood pellet, and lump hardwood charcoal, will also be evaluated. Biochar production temperatures will be varied according to constant heating time and thermal time equivalency tests. Experiments will be conducted to examine impact of post-processing of biochar by thermally or chemically activation. All biochars will be analyzed for elemental composition, surface area, thermal stability, and CEC. Incubations will assess the impacts of biochar amendments on GHG production. For the greenhouse studies, 5 different specialty crops will be investigated with respect to biochar impacts on germination, growth, and uptake of volatile chemicals. Lab incubation experiments will be conducted to evaluate the inhibition of ammonium and nitrite oxidation rate due to the presence of free ammonia and free nitrous acid. Three different soils used for corn production in MN, IA, and eastern Canada will be examined. The methods will be adapted from procedures used to quantify nitrification inhibition kinetics in wastewater. Parameters obtained in the lab experiments will be incorporated into previously developed nitrification and N2O emissions models that account for both steps of nitrification, N2O production pathways, microbial N2O reduction, and gaseous diffusion. Plot experiments will be conducted over two consecutive growing seasons at the UMN ROC in Rosemount, MN in long-term research plots split into subplot treatments. Each main plot will first be randomly sub-divided by N rate so that each subplot will receive the same total N rate during the growing season, with N rate levels of 0, 7.5, 15, 20 and 25 g N m-2. Each N rate treatment will then be randomly sub-divided into two timing treatment sub-subplots consisting of (a) a single pre-plant urea application, or (b) two split post-plant urea applications. Soil-to-atmosphere N2O fluxes will be measured using chamber methods.
3. Progress Report:
Obj 1: We have completed three years of data collection at two sites measuring changes in soil carbon and measuring N2O and CO2 emission from plots with differing levels of stover removal. The results will be reported at a Sun Grant conference in October and submitted for publication within the next 6 months. A calibrated/validated winter cover crop model was used to develop regression relationships that, with GIS mapping capabilities, enabled an estimate of aboveground biomass yield of a winter rye cover crop, intended for cellulosic biofuel, after/before corn/soybeans across the US Corn-Soybean Belt. We are in the fourth year of a collaborative experiment with Univ. of WI, to measure productivity and environmental impact of kura clover living mulch forage cropping systems. An experiment has been initiated under a center pivot at Rosemount where we had previously established a new kura clover crop. Treatments were imposed in spring 2012. Obj 2: Charred and uncharred wood pellets were applied to triplicate field plots in Rosemount, MN. Initial data collection has occurred for the pre- and post-application soil chemistries and weekly greenhouse gas (GHG) flux monitoring is ongoing. The ARS Lab in New Orleans, LA created a sequence of biochars using lignin, almond shells, and hardwood at 4 temperatures (350, 500, 650, and 800 oC). Lab incubations were established examining impact of these biochars on GHG production. Greenhouse bench studies were established to examine the impact of a variety of biochar x soil x crop combinations on crop growth. New on-farm collaborators have been identified and the first year of data from these studies are being compiled. Obj 3: A series of lab incubation experiments were conducted to determine the potential for accumulation of nitrite as an intermediate product of nitrification and corresponding N2O production rates under a range of fertilizer addition rates using anhydrous ammonia, urea, and urea amended with chemical inhibitors in 2 different soils from corn production fields. An existing computer code describing soil N2O production and emissions was modified to allow for any arbitrary mathematical formulation to describe both steps of nitrification kinetic in soil as influenced by toxicity of free ammonia and/or nitrous acid. A new collaboration was established with the Univ. of New Hampshire Institute for the Study of Earth, Oceans, and Space who will modify an existing N2O emissions (DNDC) model to account for nitrite accumulation during nitrification with comparison to our lab data. A replicated plot field experiment was established in Rosemount, MN to examine effects of fertilizer addition rate (6 levels) and timing (single vs. three split applications) on N2O emissions. This experiment was expanded in scope to compare both corn grown in a monoculture to corn in a corn/soybean rotation using external funds obtained from the Minnesota Corn Growers Association.
1. Unraveling the effects of reduced tillage on soil N2O emissions. Because of its high global warming potential, changes in soil nitrous oxide (N2O) emissions could substantially alter the total greenhouse gas (GHG) budget of cropping systems. No till (NT) and reduced till (RT) are increasingly being employed for a variety of reasons, including the potential to increase soil carbon storage and decrease soil CO2 emissions as well as conserve water and reduce erosion, but the effects of NT and RT on N2O emissions have not been consistent among studies performed to date. A global meta-analysis of 239 direct comparisons between Conventional Till (CT) and NT/RT was performed by an ARS research scientist in St. Paul, Minnesota and scientists from the University of California-Davis and Northern Arizona University. The analysis concluded that the vertical placement of N fertilizer was important in determining whether NT/RT increased or decreased N2O emissions compared with CT. In studies where N fertilizer was initially placed 5 cm or deeper in the soil, N2O emissions tended to be lower with NT/RT by about 25% compared with CT, especially in humid climates. In contrast, when N fertilizers were placed closer to the biologically-active soil surface, N2O emissions tended to be greater or not different with NT/RT. These results will be helpful in optimizing tillage and fertilizer management practices to reduce N2O and total GHG emissions.
2. Developed first estimates of cellulosic biofuel potential of winter rye double-cropping in the U.S. Corn-Soybean Belt. Increasing U.S. cropland area dedicated to biofuel crops over the past decade has raised concern over fuel versus food competition. One approach to reduce the concern is to raise cellulosic biomass crops during the fall-through-spring period between major summer crops. This research estimated potential biomass production from fall-planted winter rye that could potentially be harvested for cellulosic biofuel prior to spring planting in corn-soybean and continuous corn cropping systems in the U.S. Corn-Soybean Belt. Using a simulation modeling approach, we estimated the average biomass yield for 30 locations within the study region to be 1.9 ton/ac of dry matter. Total potential annual biomass production for the entire land base was projected to range from 120 to 170 million tons equivalent to 1.9 to 2.5 quadrillion British Thermal Units (BTU) of energy content. These results provide researchers and policymakers with quantitative estimates of double-crop biofuel production that can be compared to other U.S. biofuel options.
Spokas, K.A., Novak, J.M., Stewart, C.E., Cantrell, K.B., Uchimiya, S.M., Dusaire, M.G., Ro, K.S. 2011. Qualitative analysis of volatile organic compounds on biochar. Chemosphere. 85(5):869-882.