Location: Application Technology Research Unit
Title: Plant canopy characteristics effect on spray deposition Authors
Submitted to: Aspects of Applied Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 24, 2013
Publication Date: January 8, 2014
Citation: Derksen, R.C., Ozkan, H.E., Paul, P., Zhu, H. 2014. Plant canopy characteristics effect on spray deposition. Aspects of Applied Biology. 122:227-235. Interpretive Summary: Effective application of fungicides requires precision placement of crop protection material in the area of plants most susceptible to infection. Few, if any, research based guidelines are available to provide recommendations on how to treat very different canopy types and target orientations. Label recommendations generally do not provide equipment recommendations for specific targets in the treatment area. The overall goal of this project was to evaluate the effect different spray parameters had on spray deposition in different parts of model, row-crop canopies. Trials over three years included as model targets, mature wheat canopies and mature, narrow-row soybean canopies. Application parameters evaluated in these studies included spray quality, spray discharge angle, air-assisted delivery, and spray volume. Spray deposition and coverage were used as measures of performance to compare treatments. Air-assisted delivery was more critical for deposition into a mature soybean canopy than the wheat canopy. Spray discharge angle significantly affected spray deposition, depending on location of the target. The 60 Degree spray discharge angle and Single-fan, Medium Quality nozzle was most effective for treating and protecting Wheat Heads against infection such as Head Scab but would not be effective for protecting lower areas of a mature soybean canopy against Asian Soybean Rust. A vertical spray discharge angle produced the highest deposition deep in a mature soybean canopy when making a non-air-assisted application. The Fine spray quality nozzle provides significantly better coverage throughout the Wheat canopy than Medium or Coarse quality nozzles. Coarse spray quality nozzles provided good spray deposition lower in the Wheat and Soybean canopies. Dual-fan nozzles were better at protecting wheat heads than single-fan nozzles with a vertical orientation. Results dual-fan nozzles varied in the more dense soybean canopy depending on the spray quality. These spray deposition and coverage results demonstrate to producers that different equipment settings could be used to improve crop protection on surfaces with different orientation and depth in the canopy.
Technical Abstract: While it is common for applicators to standardize their application parameters to minimize changes in settings during a season, this practice does not necessarily provide the best delivery when targeting different types of plant canopies and different zones within the canopy. The objective of this work was to identify application parameters for maximizing spray deposition and coverage on plant parts with vertical and horizontal orientations. Wheat field trials, conducted over three years, were designed to follow-up on previous soybean trials to evaluate the effect of spray quality, spray volume, and air assistance on the fate of sprays on vertical and horizontal portions of wheat plants. Over the range of application parameters evaluated, increasing the angle of the spray relative to vertical helped produce higher deposits on vertical plant sections in a wheat canopy. Vertical spray delivery was better at treating horizontal targets through a denser and deeper soybean canopy. Large droplet applications were more effective at getting spray material near the bottom of a narrow-row soybean canopy than onto the vertical heads or stems of wheat plants. Smaller droplet sizes were difficult to deliver down through a mature soybean canopy than medium or coarse spray quality sprays. These findings demonstrate that spray parameters should not be expected to perform similar in all canopy types and should be modified to the most effective delivery of the spray to the targeted treatment zones.