Submitted to: European Conference on Precision Agriculture Proceedings
Publication Type: Abstract only
Publication Acceptance Date: 7/2/2003
Publication Date: 7/2/2003
Citation: GRAFF, C.D., KOSKINEN, W.C., ANDERSON, J., HALBACH, T.R., DOWDY, R.H. UNDERSTANDING THE SPATIAL VARIABILITY IN THE FIELD DISSIPATION OF ACETOCHLOR AND ISOXAFLUTOLE. EUROPEAN CONFERENCE ON PRECISION AGRICULTURE PROCEEDINGS. 2003. P. 39 Interpretive Summary:
Technical Abstract: Because soil properties such as organic carbon content (OC), percent clay, and pH can affect the field dissipation of certain herbicides, and they can significantly vary spatially across the landscape, it is possible that herbicide dissipation rates, and subsequent weed control, have spatial structure as well. Experiments at the Rosemount Experiment Station in Dakota County, MN were conducted to test whether precision management techniques can be used to study soil-herbicide interactions. The spatial variability of surface soil properties was characterized for a watershed cultivated in corn and displayed on a digital elevation model (DEM). Soil pH ranged from 5.5 to 7.5 and total organic carbon varied between 1.18 and 4.15. Textural fractions of % silt and % clay ranged from; 39 to 64% and 12 to 27%, respectively. Utilizing Arc/Info, terrain attributes such as slope, aspect, plan and profile curvature and flow accumulation were derived from the finely sampled DEM in order to determine if such attributes enhanced prediction of soil characteristics and/or herbicide residues. Acetochlor was applied 2.2 kg ha-1 for the 2000 and 2001 growing seasons. At selected times, soil samples were taken to a depth of 70 cm at numerous georeferenced locations having a range in soil properties representative of the site and analyzed for herbicide residues. Herbicide surface field dissipation rates (k) were calculated at each georeferenced location. The spatial distribution of k was modeled in Vesper and displayed with Surfer. Where significant correlation was found ( > 30%), regression kriging was performed. From this procedure, an interpolated map of k across the field could be obtained utilizing only existing soil property or terrain attribute data. A "boot strap" method was employed to validate the interpolated maps. Understanding how herbicide dissipation rates vary with soil characteristics could lead to reducing off-site transport via precision management, where soil properties and terrain attributes can be used to describe the distribution of the field dissipation rates.