Location: Soil and Water Management Research2012 Annual Report
1a. Objectives (from AD-416):
1. Integrate knowledge of retention, transformation, and transport of agrochemicals, including newer pesticides and veterinary pharmaceuticals, in soil and water, to facilitate selection and validation of management practices at the field to landscape scale that minimize potential offsite transport to surface and ground waters. 2. Identify practices that protect water quality and conserve soil resources in emerging farming systems of the North Central U.S. 3. Quantify the impact of agricultural drainage management systems on net greenhouse gas emissions and pesticide leaching losses. 4. Quantify the environmental impact of Best Management Practices on water quality in turf systems.
1b. Approach (from AD-416):
Results from research on factors affecting possible offsite transport of agrochemicals (nutrients, pesticides, and veterinary chemicals) to surface and ground waters, conducted on multiple scales (laboratory, field plots, and mini-watersheds) in an interdisciplinary manner, will be used to develop management practices that are relevant to protecting surface and ground waters in the North Central United States. Research will be conducted in interconnected experiments on basic processes affecting agrochemicals, spatial and temporal variation of processes, and impacts of management practices on environmental fate of agrochemicals. For instance, basic research on fate of pesticides and veterinary pharmaceuticals will be conducted in the laboratory on soils from selected field plots and watersheds to obtain basic information on processes. This information will be used in turn to help explain results of management practice effects on fate of agrochemical in fields and small watersheds. Management practices to be studied include: new cropping systems associated with large dairy operations; farming systems providing carbon sources for ethanol production; agricultural drainage management systems; and turf management systems. We will obtain information on the spatial and temporal variability of the processes and an assessment of the impact of altering the agronomic management practices on off-site transport of pesticides and fertilizers from non-agricultural, i.e. turf, and agricultural systems. Information obtained will include: an assessment of the predictive ability of transport models to simulate runoff and estimate chemical loading to surface and ground waters; identification of management practices that protect water quality and conserve soil resources in emerging farming systems in North Central U.S; and redefined agricultural systems models that can predict the impact of management of agricultural drainage systems on net greenhouse gas emissions in tile drained fields under the different climate and soil conditions of the Midwest corn belt.
3. Progress Report:
Obj. 1 Progress: Collected river water samples and sediments from four sub-watersheds, with varying land uses, to evaluate profiles of pesticides and veterinary pharmaceuticals. This data will be used to delineate contaminant sources and lead to the development of mitigation strategies. Collaborative efforts were also established with the University of Hawaii due to joint interest in the fate of pesticides in biochar amended soils. Incubations have also been conducted for the impact of biochar on the sorption of aminocyclopyrachlor (i.e., ImprelisTM). Laboratory incubations are also being continued on the impact of strobilurin fungicides on soybean residue mineralization as well as the impact of tillage management on soil quality and microbial corn stover mineralization. Obj. 2 Progress: We monitored drainage flow and water quality for the third year in a large-field scale (65 ha) comparison of dairy slurry application methods – injection versus center pivot irrigation. There was no spring snow melt runoff because of a dry and warm winter. Sensors to measure drainage tile effluent conductivity were installed in order to study the fraction of drainage that derives from rock inlets (French drains) and that which derives from shallow water table baseflow. The first cropping year was begun in a new research project on companion cropping and its potential impact on water quality in irrigated corn/soybean systems. Four blocks of randomized treatments were established under a center pivot irrigator and soybeans were planted. Eight plots were instrumented with soil moisture sensors and soil samples are being taken biweekly. A device for extracting intact soil cores was obtained from DuPont and a machine shop was hired to make necessary modifications. Upon completion, this will be used to install lysimeters in each plot. Obj. 3 Progress: A sequence of biochars has been acquired for conducting the laboratory studies. The ARS Lab in New Orleans, LA made a suite of biochars from lignin, almond shells, and hardwood materials at 4 different temperatures (350, 500, 650, and 800°C) and the ARS lab in Florence, SC created a series of biochars from different mixtures of feedstocks (switchgrass, pine, and swine solids). Lab incubations have been established examining the impact of these biochars on nitrification/denitrification rates in soils as well as sorption impacts of pesticides and model humic substances. Obj. 4. Sample analysis and data analysis of runoff samples from turf managed with hollow tine core cultivation versus hollow tine core cultivation with verticutting was completed. Experimental turf plots were stripped of the existing turf and reseeded with either traditional creeping bentgrass or low input fine fescue. Once established, the new turf will be used in experiments to evaluate the hypothesis that replacing traditional turfgrass with low input turfgrass, utilizing biochar amended soil, and selection of new maintenance practices that enhance water management will reduce the off-site transport of contaminants (excess nutrients, pesticides) with runoff.
1. Combining increased landscape water storage with supplemental irrigation to reduce sediment, nitrogen, and phosphorous losses. Due to ever-increasing population and the need to improve global nutrition, agricultural production must continue to increase. At the same time, it is necessary to improve the environmental footprint of agriculture, particularly losses of sediment, nitrogen, and phosphorus. ARS researchers at St. Paul, MN showed that these goals can be simultaneously addressed within the U.S. Corn Belt by combining increased landscape water storage with supplemental irrigation. This will reduce flooding and associated nutrient losses while stabilizing yields and permitting the adoption of alternative cropping practices, like cover crops and living mulches, which provide environmental benefits but increase the risk of soil moisture depletion. Annual precipitation and stream flow have increased substantially over the past 50 years, so there is water available to supply supplemental irrigation if it can be stored during periods of excess. Restoration of wetlands and construction of ponds could provide that storage, which would provide wildlife habitat, serve as a buffer to reduce downstream losses of sediment and nutrients, and result in additional crop biomass for forages or renewable fuels. Producers would benefit from this additional productivity and also from the reduced financial risk associated with irrigation-stabilized yields, while the broader public would enjoy the environmental benefits.
2. Landscapes effects on herbicide fate. In eroded lands, soil properties that influence herbicide fate are highly variable at different locations in the landscape. Understanding the variation in herbicide sorption and dissipation is essential to characterize weed control efficacy and the potential for chemical run-off. ARS researchers at Brookings, SD and St. Paul, MN evaluated the sorption and/or dissipation of 4 herbicides in surface soils from an eroded prairie. Soil organic carbon in the eroded upper slope was about half that in the depositional lower slope. Soil retention of saflufenacil, aminocyclopyrachlor, and picloram was on average 3-5 times higher in the lower slope than in the upper slope. For these herbicides, retention was dependent on the amount of soil organic carbon. However, metolachlor showed the same retention in soils from these landscape positions, despite the large difference in soil properties. Dissipation proceeded at approximately the same rate in both soils. Results emphasize the need for compound- and soil-specific information if regulatory agencies and producers are to accurately predict pesticide fate in soil.
3. Selected biochars can sequester atmospheric carbon dioxide. A potential abatement strategy to increasing atmospheric levels of carbon dioxide (CO2) is to sequester atmospheric CO2 into a more stable form through the use of pyrolysis. Biomass feed stocks are used to generate a more stable carbon form (biochar) that is returned to the soil sequestering atmospheric carbon into a slower cycling pool, resulting in alterations in plant growth/yield and microbial soil processes. However, the mechanisms behind the “biochar effect” have not been fully elucidated. In the present work, ARS researchers at St. Paul, MN have developed an analytical method for the evaluation of sorbed polycyclic aromatic hydrocarbons (PAH), specifically applicable to the analyses of biochar and biochar + soil combinations. We have optimized the solvent used and extraction time with the analysis being conducted by GC-MS. These findings could provide additional insight and direction in the evaluation of biochar prior to the soil application. These results are significant to farmers and policy makers and will assist scientists and engineers in developing improved biochars based on properties to minimize greenhouse gas implications and improve soil carbon management.
4. Fall/Winter manure application. Land application of animal manures is challenging in northern latitudes because cool, wet spring time conditions typically prohibit manure spreading prior to planting. Thus, producers often spread manure during the period starting just after fall harvest and at times continuing throughout the winter. ARS researchers at St. Paul, MN evaluated the amount of nitrogen (N) and phosphorus (P) lost through runoff and leaching when dairy manure was applied at soil temperatures characteristic of early fall (60°F), late fall (40°F), and winter (30°F). Manure was applied to soil cores at three different times from October through December (2009) and the cores were subjected to rainfall simulations (November – December, 2009) and natural precipitation events (January – March, 2010). The amount of nitrate-N remaining in the soil at the conclusion of the test was greatest for the winter application treatment. Over winter losses of P were impacted by soil temperature and freeze/thaw condition, with the winter treatment having twice the total P loss compared to the early fall treatment. These findings will help dairy operators reduce the environmental impact of manure application.
Krueger, E., Ochsner, T., Baker, J.M., Porter, P.M., Reicosky, D.C. 2012. Rye-corn silage double-cropping reduces corn yield but improves environmental impacts. Agronomy Journal. 104(4):888-896.