Accuracy and cost effectiveness of GPS-assisted wild oat mapping in spring cereal crops

Abstract

Managing weed infestations in a spatially precise manner requires accurate and cost-effective weed identification techniques. The goal of our research was to quantify the accuracy of continuous weed presence–absence maps and assess how management based on those maps may affect producer net returns. Each continuous sampled map covered the entire field and contained vector polygons labeled as either wild oat presence or wild oat absence. The accuracy of the continuous wild oat maps at each sampling time was determined from georeferenced quadrats of wild oat densities. The accuracy of the continuous wild oat seedling maps ranged from 48.3 to 87.1% among the six site-years. The accuracy of the wild oat seedling maps improved by at least 8% when a 10-m buffer was included around areas mapped as wild oat presence. The accuracy of continuous wild oat panicle maps from the combine at harvest ranged from 65.8 to 90.9% among the six site-years. The variation in accuracy for the wild oat seedling maps among sites was greater than the accuracy of the panicle maps. Net returns ($ ha−1) for four site-years were calculated and compared for four possible weed management approaches on each field. A site-specific herbicide application to areas mapped as wild oat presence always generated higher net returns than a herbicide application over the entire field for four sites. A site-specific herbicide application to areas mapped as wild oat presence plus a surrounding 10-m buffer area only resulted in a higher net return in one of the 12 site-years compared with a site-specific herbicide application without the 10-m buffer. This site had the lowest (48.3%) wild oat seedling map accuracy, and uncontrolled wild oat had a high-yield effect. This research indicates that using a continuous weed sampling method based on presence or absence for site-specific herbicide application can be profitable over a herbicide application to the entire field, even with the associated technology cost and seedling map errors.

Assessment of a decision support system for chemical control of annual ryegrass (Lolium rigidum) in winter cereals

“…In that study, application of half doses of herbicides was the most profitable strategy in sites with yields above 5000 kg ha −1 , whereas no spraying could be the best option in sites with yields of below 3500 kg ha −1 . A similar conclusion has been reached in studies conducted in other semi‐arid areas (Van Wychen et al. , 2002), challenging the usefulness of high‐cost herbicides under low‐yield conditions.…”

Comparison of sampling methodologies for site‐specific management ofAvena sterilis

“…Scoring panicle density from a combine proved to be a reliable and relatively inexpensive method (9€ ha −1 ) to monitor A. sterilis abundance and to plan herbicide use. Prices charged commercially in Montana for continuous A. fatua mapping at harvest are very similar to our figures (Van Wychen et al. , 2002).…”

“…Because of the uncertainty associated with all these factors, the addition of buffer areas around the georeferenced weed patches has been used in various studies (Rew et al. , 1996; Van Wychen et al. , 2002).…”

Spatial and temporal dynamics of Sorghum halepense patches in maize crops

“…The results obtained in this study have several important implications for SSWM of S. halepense . Previous studies have shown that the economic feasibility of using SSWM systems is conditioned by the frequency of re‐mapping (Van Wychen et al. , 2002; Barroso et al.…”