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Title: Site-Specific Weed Management in Growers' Fields: Predictions from Hand-drawn Maps

Author
item WILES, LORI
item BOBBIT, R - GEOSPATIAL EXPERT
item WESTRA, P - COLORADO STATE UNIVERSITY

Submitted to: CRC Press
Publication Type: Book / Chapter
Publication Acceptance Date: 8/31/2006
Publication Date: 2/20/2007
Citation: Wiles, L., Bobbit, R., Westra, P. 2007. Site-Specific Weed Management in Growers' Fields: Predictions from Hand-drawn Maps. Chapter 5. In F. Pierce and D. Clay, eds. Applications of GIS for Agriculture, Volume I,CRC Press

Interpretive Summary: Growers may be able to protect water quality by controlling weeds with 30-80% less herbicide with site-specific weed management (SSWM). SSWM is varying weed management within a field to match the variation in the number and species of weeds among and between weed patches in a field. However, SSWM requires expensive technology, so growers will not adopt SSWM until they are confident that the benefits will justify the cost. The benefits depend on the size, shape, arrangement and weed populations of patches, and how management can be varied. We developed WEEDSITE software so growers can investigate benefits of postemergence SSWM in irrigated corn specifically for their weed populations and implementation of SSWM. Four strategies of SSWM are evaluated from the user's hand drawn field and weed maps. We think WeedSite can be useful tool for growers, agricultural consultants and students to learn about possible benefits of SSWM because evaluations are both consistent with what is known about the variation in the benefits of SSWM and relevant to current management practices. The software is free.

Technical Abstract: Herbicide may be reduced 30 to 80% without impacting crop yield with site-specific weed management (SSWM), a strategy of varying weed management within a field to match the variation in the weed population. However, growers will not adopt SSWM until they are confident that the benefits will justify the cost. Predicting the outcomes of SSWM is difficult because benefits vary with weed populations and how management can be varied. WEEDSITE software was developed so growers could investigate benefits of postemergence SSWM in irrigated corn specifically for their weed populations and implementation of SSWM. Georeferenced weed maps and GIS software are not needed. Four strategies of SSWM can be evaluated based on hand drawn weed maps. The program has three components: a GIS module for drawing weed maps, creating sprayer grids, and displaying maps of outcomes of SSWM; a model to simulate biological and economic outcomes of weed management; and algorithms that identify the optimal SSWM from the predicted outcomes. Net gain from SSWM, area of the field not treated, herbicide use, yield loss from weed competition, and weeds left in the field are calculated. Evaluations are consistent with what is known about the benefits of SSWM.