U.S. flagAn official website of the United States government
                    Here's how you know **Official websites use .gov**
                            
                            A **.gov** website belongs to an official government organization in the United States.
 **Secure .gov websites use HTTPS**
                            
                            A **lock** (                            
                              A locked padlock                                                      
                            
                            ) or **https://** means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.


Menu Agricultural Research Service
						
                    U.S. DEPARTMENT OF AGRICULTURE
 close



Research
                Research Home
                            National Programs
                            Research Projects
                            Scientific Manuscripts
                            International Engagement
                            Scientific Software/Models
                            Databases and Datasets
                            Office of Scientific Quality Review
            Media
                News & Features
                            Multimedia
                            Briefing Room
                            Down on the Farm
                            Press Room
                            Science in Your Shopping Cart
                            Scientific Discoveries
                            Tellus
                            Under the Microscope
            About ARS
                About ARS Home
                            Staff Directory
                            Labs and Research Centers (Map)
                            Headquarter Offices
                            Organizational Chart
                            Employee Services (REE Employees Only)
                            Office of Outreach, Diversity, and Equal Opportunity
            Work With Us
                Work With Us Home
                            ARS Vacancies at USAJOBS
                            Careers at ARS Information
                            Scientific Collaborations
                            Extramural Agreements
                            1890 Faculty Research Sabbatical ProgramSearch small
                    Search
            
            ARS Home
                                About ARS
                                Contact Us




ARS Home Research Publications at this Location





- ARS National Programs
- Search for a scientific manuscript
- Search for a research project
- ARS Software
- Programs and Projects
- Collaborations
- Subjects of Investigation
- Publications

Title:   Author  item
                                            Malone, Robert

                                                         - *Rob*item
                                            Shipitalo, Martinitem
                                            DOUGLASS, L - UNIV. OF MARYLANDitem
                                            Owens, Lloyditem
                                            Nelsen, Terryitem
                                            WARNER, R - UNIV. OF KENTUCKYitem
                                            BYERS, M - KENTUCKY STATE UNIVERSITY
  Submitted to: Transactions of the ASAE
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 2/15/2000
                                    Publication  Date: N/A
                                    Citation: N/AInterpretive Summary: Soil cores are often used to assess herbicide movement through soil or to assess contaminant transport models.  When macropores (root channels, worm holes, cracks, etc.) are present, the suitability of soil cores for these purposes is questionable because vertical water movement is through only a small portion of the total porosity.  Our objectives were to determine if  soil samples are adequate to 1) assess vertical herbicide movement and 2) assess a contaminant transport model in a soil subject to macropore flow. The results indicate that soil samples can be a poor indicator of subsurface herbicide movement and a poor method to assess contaminant transport models.  These findings will help researchers design experiments whose objective it is to: 1) assess vertical pesticide movement or 2) assess the predictive ability of contaminant transport models.  This research indicates that, in soils subject to macropore flow, it may be  unwise to rely solely on soil cores to indicate vertical pesticide movemen or to assess the vertical predictive ability of contaminant transport models.
                                Technical Abstract: When macropores are present, the suitability of soil cores to assess herbicide movement through soil or as the sole means to evaluate contaminant transport models is questionable.  Therefore, our objectives were to determine if soil samples are adequate for these purposes.  To accomplish this, atrazine and alachlor were surface-applied to 30 by 30 by  30 cm blocks of undisturbed, no-till silt loam soil at three moisture levels (dry, intermediate, wet) then subjected to a 0.5-h, 30 mm simulated rain.  Percolate was collected in about 10 mL increments from the base of the blocks using a 64-cell grid lysimeter.  After percolation ceased, the soil was sampled by slicing the blocks into eight, 3.75 cm-thick, horizontal slabs.  The contaminant transport model GLEAMS was used to predict herbicide concentration in the percolate after calibration of herbicide concentration in the bottommost soil section and percolate  volume.  Herbicide concentrations in percolate were significantly greater than background and higher in the dry soil blocks than in the wet soil.  In contrast, a negative correlation was observed between herbicide concentration in the percolate and that in the bottommost soil layer. Moreover, herbicide concentration in most subsurface soil samples were not significantly greater than background.  Although calibration of GLEAMS resulted in accurate prediction of percolate volumes and bottom layer soil herbicide concentrations, herbicide concentrations in percolate were under-predicted in most instances.  Our results indicate that soil samples can be a poor indicator of subsurface herbicide movement and inadequate as the sole means to assess contaminant transport models in soils subject to macropore flow.


Return to top


Connect with ARS Sign up


ARS Home
                            USDA.gov
                            Plain Writing
                            Policies & Links
                            Civil Rights Statements
                            FOIA
                            Accessibility Statement
                            Privacy Policy
                            Non-Discrimination Statement
                            Quality of Information
                            USA.gov
                            WhiteHouse.gov