ARS | Publication request: Ground-based spectral reflectance measurements for evaluating the efficacy of aerially-applied glyphosate treatments

Submitted to: Biosystems Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 9, 2010
Publication Date: August 24, 2010
Citation: Zhang, H., Lan, Y., Lacey, R., Hoffmann, W.C., Martin, D.E., Fritz, B.K., Lopez, J. 2010. Ground-based spectral reflectance measurements for evaluating the efficacy of aerially-applied glyphosate treatments. Biosystems Engineering. 107:10-15.

Interpretive Summary: Glyphosate, a nonselective contact herbicide, is used extensively for weed control in agricultural production systems. Use of glyphosate has increased dramatically due to the introduction of transgenic crop varieties that tolerate over-the-top or directed applications during some growth states without significant impact on yield. The objective of this study was to characterize efficacy of glyphosate applied with conventional and novel aerial spray nozzles using real-time crop assessments as the measure of efficacy. A computerized crop monitoring system was developed that combined data from a global positioning system with other instruments that simultaneously measured crop height, canopy structure, biomass, and spectral reflectance data, which is an indicator of crop health. Aerial herbicide applications performed within labeled recommendations were efficacious, regardless of the nozzle technology employed. The results show that ground-based spectral reflectance data can be used to rapidly assess glyphosate efficacy and will aid researchers and growers in assessment of herbicides treatments to field crops.

Technical Abstract: Aerial application of herbicides is a common tool in agricultural field management. The objective of this study was to evaluate the efficacy of glyphosate herbicide applied aerially with both conventional and emerging aerial nozzle technologies. A Texas A&M University Plantation weed field was set up on a randomized complete block design with three replicates. Four aerial spray technologies treatments: electrostatically-charged nozzles powered off, electrostatically charged nozzles powered on, conventional flat-fan hydraulic nozzle and rotary atomizers were tested. Spectral reflectance measurements were acquired with a ground-based sensing system for all treatment plots to evaluate glyphosate efficacy and performance of aerial spray technologies. Three field measurements were carried out at 1, 8, and 17 days after treatment (DAT). Statistical analyses indicated that glyphosate applied with different methods killed the weeds effectively compared to untreated area at 17 DAT. Electrostatically-charged nozzles powered on, conventional flat fan nozzles and rotary atomizers had better performance than the electrostatically charged nozzles powered off. The results provide applicators with guidance for aerial application equipment setups that can result in herbicide savings and optimized applications in other crop.