Optical sensing of weed infestations at harvest

Authors: BARROSO, JUDIT - Oregon State University; McCallum, John; Long, Daniel

Submitted to: Sensors
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2017
Publication Date: 10/19/2017
Publication URL: https://handle.nal.usda.gov/10113/6477304
Citation: Barroso, J., Mccallum, J.D., Long, D.S. 2017. Optical sensing of weed infestations at harvest. Sensors. 17(10):2381. doi:10.3390/s17102381.
DOI: https://doi.org/10.3390/s17102381

Interpretive Summary: A combine harvester will pick up green weedy material in the harvested grain when the machine passes through patches of late maturing weeds such as Russian thistle. We tested the ability of an optical sensor, designed for on-the-go measurement of grain protein concentration, to detect the presence of this green matter in flowing grain and assess the potential usefulness of this information for mapping weeds at harvest. All seosnr readings were mappable with use of a GPS receiver. Green plant matter was detectable in the red waveband. Weed maps from the optical sensor showed an overall agreement of 76.3% with reference maps that were based on visual evaluations of three green weed species by experts. Information on weed distributions at harvest may be useful for controlling weeds post-harvest using variable rate technology for herbicide application.

Technical Abstract: Kochia (Kochia scoparia L.), Russian thistle (Salsola ssp.), and prickly lettuce (Lactuca serriola L.) are economically important weeds infesting dryland wheat (Triticum aestivum L.) production systems in the western United States. These weeds produce most of their seeds post-harvest. The objectives of this study were to determine the ability of an optical sensor, installed for on-the-go measurement of grain protein concentration, to detect the presence of green plant matter in flowing grain and assess the potential usefulness of this information for mapping weeds at harvest. Spectra of the grain stream were recorded continuously at a rate of 0.33 Hz during harvest of two spring wheat fields of 1.9 and 5.4 ha. All readings were georeferenced using a GPS receiver with 1 m positional accuracy. Chlorophyll of green plant matter was detectable in the red (670 nm) waveband. Maps of the chlorophyll signal from both fields showed an overall agreement of 76.3% with reference maps, one constructed prior to harvest and the other at harvest, based on visual evaluations of the three green weed species by experts. Information on weed distributions at harvest may be useful for controlling weeds post-harvest using variable rate technology for herbicide application.