2010 Annual Report
Speed of development of enhanced atrazine degradation. Farmers depend on atrazine to provide residual weed control in corn but the continuous use of this herbicide can select for soil microorganisms that can rapidly degrade atrazine. However, it is not known how quickly the soil microorganisms adapt after atrazine application to degrade atrazine. Data from a field trial conducted by ARS and Colorado State University scientists showed that the rate of atrazine degradation increases within 7 days after application and reaches a maximum rate by 40 days after treatment. This ability to degrade atrazine is retained in the soil through the winter and into the following spring. This information is needed by growers who depend on atrazine to provide season long weed control.
Corn yield is linearly related to water Consumption. Farmers who irrigate crops but face inadequate water supplies need to know how best to allocate their water. Two years of field studies by ARS scientists at Fort Collins indicate that corn yield decreases linearly as water availability declines. The corn plant is able to efficiently utilize each increment of water to produce an additional increment of yield, up to it’s yield potential, as long as the water is applied when needed by the plant. In the Central Plains, this productivity is about 3 kg of corn grain per cubic meter of water consumed. This simple relationship allows a grower to predict the yield loss and costs of deficit irrigation and to estimate the value of applying additional irrigation water.
Modeling forage production under drought conditions. Ranchers need to adjust management when forage production is reduced by drought in order to maximize profit while preventing overgrazing. ARS scientist in Fort Collins, Colorado developed simple models of the relationship between production of mixed grass prairie and precipitation during the spring with data from ND and WY. The accuracy of prediction was improved with information about precipitation in the previous fall for WY. Ranchers experiencing spring drought in some locations will be able to easily predict the reduction of forage production using a spreadsheet that obtains precipitation data available on the internet.
Shaner, D.L., Wiles, L., Hansen, N. 2009. Behavior of Atrazine In Limited Irrigation Cropping Systems in Colorado: Prior Use Is Important. Journal of Environmental Quality. 38:1861-1869.
Bekir, B., Lindenmayer, B., Nissen, S., Westra, P., Shaner, D.L., Brunk, G. 2009. Absorption and Translocation of Aminocyclopyrachlor and Aminocyclopyrachlor Methyl Ester in Canada Thistle (Cirsium arvense). Weed Science. 58:96-102.
Gaines, T., Preston, C., Leach, J., Chisholm, S., Shaner, D.L., Nissen, S., Bukin, B., Patzoldt, W., Tranel, P., Webster, T.M., Vencill, W.K., Sammons, D., Wang, D., Westra, P. 2010. Weed Evolution To Herbicide Resistance. Proceedings of the National Academy of Sciences. Gene Amplification Confers Glyphosate Resistance in Amaranthuis palmerii. PNAS 1007:1029-1034.
Mckinnon, D., Shaner, D.L., Westra, P., Nisson, S. 2009. The Effects Of Surfactants, Mixing Time, Nozzle Types, Spray Volumes And Simulated Rain On 1-MCP Efficacy On Tomato (Lycopersicon Esculentum). Journal of the American Society for Horticultural Science. 44(6):1600-1603.
Shaner, D.L., Krutz, L.J., Henry, W.B., Hanson, B.D., Poteet, M.D., Rainbolt, C.R. 2010. Sugarcane Soils Exhibit Enhanced Atrazine Degradation And Cross Adaptation To Other Triazines. American Society of Sugar Cane Technologists. 30:1-11.