Costs, Comparisons, and Effectiveness Using Chlorophyll Sensing Sprayers in a Chemical Fallow Operation

Project Overview

Project Type: Farmer/Rancher
Funds awarded in 2006: $6,950.00
Projected End Date: 12/31/2008
Region: Western
State: Oregon
Principal Investigator:


  • Agronomic: wheat


  • Crop Production: conservation tillage
  • Education and Training: demonstration, extension, farmer to farmer, on-farm/ranch research, participatory research
  • Farm Business Management: feasibility study, agricultural finance
  • Pest Management: precision herbicide use

    Proposal summary:

    Many of the 4.5 million acres of farmland in north-central Oregon and south-central Washington have reduced erosion and improved soil quality by adopting direct seeding of cereal crops. To continue this success in the region, which receives 8 to 12 inches of precipitation a year, producers need to find a way to cost effectively conduct a year of chemical fallow between crops. All too often, dealing with broadleaf weeds like kochia, marestail prickly lettuce and, especially, Russian thistle is prohibitively expensive. William Jepsen, who farms 3,500 acres 70 miles southwest of Pendleton, tackled the Russian thistle with a chlorophyll-sensing sprayer. Sensors a foot apart on a sprayer boom mounted on a four-wheeler put out beams of infrared and near-infrared light. When this light reflects the correct green color of Russian thistle, the valve opens and sprays the weed. Because the thistle grows in patches, the technology can cut herbicide use by 90%. Jepsen has built his own 40-foot-wide sprayer. He’ll use his grant to test the costs and effectiveness of the system, a novel use for chemical fallow.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.