Location: Soil and Water Management Research2010 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
Results of incubation experiments show that bioavailability of atrazine was similar for both organoclay formulations and free atrazine, however more atrazine was sorbed in soil when formulated as organoclay complexes. This suggests that atrazine applied as organoclay formulations can retard leaching and runoff, but is still bioavailable to degrading microorganisms and would be naturally attenuated by soil microorganisms. We have shown that a yeast, Candida xestobii, is able to grow using metolachlor as a sole carbon and energy source. This is the first reported pure isolated microbial culture capable of mineralizing metolachlor. These results suggest that it may eventually prove to be useful for metolachlor bioremediation efforts. Hundreds of soil samples have been extracted and analyzed to compare metolachlor dissipation and transport in soil from corn and soybean plots managed with conventional, conservation, strip or no tillage. Laboratory experiments have been initiated to determine the effect of different biochars on the sorption and leaching of different classes of herbicides. Obj 2 Progress: An experiment using rainfall simulators was conducted in SE Minnesota to determine the impact of winter cover crops on erosive losses of sediment and phosphorus. Data revealed that a rye cover crop is highly effective in reducing soil erosion on the fine-textured soils of SE MN. In another experiment in western Minnesota, we measured N and P in tile outflow from fields receiving large amounts of dairy manure, before and after the replacement of surface inlets with french drains. The french drains dramatically reduced sediment losses. The cooperator also changed fertilizer practices in the two test fields to allow us to document potential benefits from fertigation versus fall injection. We continued to monitor soil water quantity and quality below the root zone of a kura clover living mulch cropping system designed to reduce fertilizer input and to improve sustainability of biofuel. A large dairy operator has been interviewed and has provided inputs for the Integrated Farming System Model (IFSM). The model developer has modified IFSM to reflect operations on this farm, which is the largest one to be modeled to date. IFSM is being calibrated against field data collected from this farm. Obj. 3 Progress: Since the farmer decided to drain our undrained control field, we have moved our green house gas sampling equipment and are now comparing the drained field to an adjacent undrained native prairie. Over 375 soil cores were collected from corn plots with different fertilizer (banded inorganic fertilizer or no fertilizer) and drainage practices (conventional or controlled) for herbicide analyses, which represent the second field season of sample collection. Obj. 4 Progress: About 500 runoff water samples were analyzed for five pesticides completing the replicate field season of data evaluating new management strategies on fairway turf; five months of continuous runoff flow data and more than 500 snow-melt runoff samples were collected from fairway turf plots for analysis of fall fungicides from snow melt runoff.
1. Reduction in pesticide runoff from turf. Pesticides associated with the turfgrass industry have been detected in storm runoff and surface waters of urban watersheds; invoking concern of their potential environmental effects and a desire to reduce their transport to non-target locations. Quantities of chlorpyrifos, dicamba, dimethylamine salt of 2,4-dichlorophenoxyacetic acid (2,4-D), flutolanil, and mecoprop-p (MCPP) transported in runoff from bentgrass fairway turf managed with solid tine (ST) or hollow tine (HT) core cultivation were compared to determine which cultivation practice is more efficient at mitigating environmental risk. Plots receiving HT core cultivation showed a 10% and 55% reduction in runoff volume and a 15 to 57% reduction in pesticide transport with runoff at 63 d and 2 d following core cultivation. Estimated environmental concentrations of the pesticides in a surface water receiving runoff from turf managed with ST core cultivation exceeded the median lethal concentration (LC50) or median effective concentration (EC50) of nine aquatic organisms evaluated. Replacing ST core cultivation with HT core cultivation reduced surface water concentrations of the pesticides to levels below the LC50 and EC50 for most of these aquatic organisms; lessening risk associated with pesticides in runoff from the fairway turf. Results of the present research provide quantitative information that will allow for informed decisions on cultural practices that can maximize pesticide retention at the site of effects associated with the off-site transport of pesticides.
2. Metolachor degradation by a yeast and bacterium. Metolachlor is one of the most extensively used chloroacetamide herbicides. In this study, we examined soils with a history of metolachlor application for the presence of pure microbial cultures capable of degradation (catabolism) of this herbicide. We were able to isolate and characterize pure cultures of a yeast, Candida xestobii, and a bacterium, Bacillus simplex, that have the ability to catabolize metolachlor and use this herbicide as a sole source of carbon for growth. We also report that the yeast is able to rapidly degrade and mineralize other acetanilide herbicides, such as acetochlor and alachlor. These newly isolated organisms will allow us to obtain a better understanding of the biochemistry and genetics of acetanilide herbicides catabolism by microorganism, and will provide new tools for the bioremediation of environments impacted by these herbicides.
Papiernik, S.K., Koskinen, W.C., Yates, S.R. 2009. Solute Transport in Eroded and Rehabilitated Prairie Landforms. 1. Nonreactive Solute. Journal of Agricultural and Food Chemistry. 57:7427-7433.