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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #120639
Title: VALIDATION OF COTTON HADSS (HERBICIDE APPLICATION DECISION SUPPORT SYSTEM):YEAR 2.

Author
item Webster, Theodore
item CULPEPPER, A - UNIVERSITY OF GEORGIA
item HARDISON, G - GA COOPERATIVE EXTN SER

Submitted to: University of Georgia Research Report
Publication Type: Experiment Station
Publication Acceptance Date: 4/1/2000
Publication Date: 10/1/2000
Citation: Webster, T.M., Culpepper, A.S., Hardison, G.B. 2000. Validation of cotton HADSS (Herbicide Application Decision Support System): Year 2. 2000 University of Georgia Cotton Research and Extension Report. p.196-202.

Interpretive Summary: Chemical herbicides are a major production cost in commercial farm operations in the U.S. Both quality and quantity of crop yield are dependent on the numbers and kinds of weeds that compete with the crop for water and plant nutrients. Currently the best method to estimate crop yield loss involves quantifying weed densities. A computer program named Herbicide Application Decision Support System, HADSS for short, has been developed to assist growers in the decisions on herbicide use based on the kinds of weeds present, the number of weeds, and the efficacy of herbicides. Field studies were conducted in Georgia in 1999 (2 locations) and 2000 (4 locations) to compare net returns using the HADSS system versus expert recommendations for weed control. Counting weeds was found to be a laborious chore, and an alternative system of classifying weed densities as low, medium, high, or very high was developed. Results obtained using the alternate system were essentially the same as those obtained by counting weed densities and produced net returns comparable to those obtained using expert recommendations.

Technical Abstract: Software is currently being developed to help growers decide if weed problems require control, based on the biology of weed-crop interactions. The Herbicide Application Decision Support System or HADSS, is a powerful tool that is able to account for a multiple weed species complex when estimating yield loss. HADSS uses grower-supplied weed densities to estimate crop yield loss, and recommend a herbicide treatment, if needed. The estimated crop yield, crop selling price, basic growing conditions (crop and weed height, and moisture status), and herbicide efficacy are all accounted for when making a recommendation. The HADSS recommendations are ranked on the basis of net return to the grower. Through this study, we found that recommendations for HADSS were consistent with those of University of Georgia Cotton Weed Extension Specialists. Difference in net return of 15% or less between HADSS and the University experts occurred 83% %of the time. Upon closer inspection of the database, we found that herbicide efficacy ratings for bermudagrass and morningglory species were underestimated. The database will be changed to reflect these changes. Using the weed densities from our field studies, we were able to assign these values to different weed classes (low, medium, high, and very high). We concluded that estimates of weed density using weed classes will provide accurate estimates of weed yield loss and accurate weed control recommendations.