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

Submitted to: National Agricultural Aviation Association Meeting
Publication Type: Proceedings
Publication Acceptance Date: December 9, 2009
Publication Date: December 9, 2009
Citation: Zhang, H., Lan, Y., Lacey, R., Hoffmann, W.C., Martin, D.E., Fritz, B.K., Lopez, J. 2009. Ground-based spectral reflectance measurements for efficacy evaluation of aerially applied glyphosate treatments. National Agricultural Aviation Association Meeting. Paper No. AA09-004.

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 herbicide applications during some growth stages without significant impact on yield. The objective of this study was to use ground-based spetral reflectance to characterize efficacy of glyphosate applied by conventional and novel aerial spray nozzles. A computerized crop monitoring system was developed that combined data from a global positioning system with other instruments that measured crop height, canopy structure, biomass, and crop physiological indicators. The integrated crop monitoring system simultaneously accepted inputs from all of these instruments as the tractor-mounted instruments moved through the field. This research showed that reflectance data obtained from either an aerial or ground-based platform can be used to compare efficacy of aerial herbicide application using different nozzle technologies. For this study, aerial herbicide applications performed within labeled recommendations were efficacious, regardless of the nozzle technology employed.

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 in 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 areas 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.