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United States Department of Agriculture

Agricultural Research Service

Research Project: Exotic and Emerging Plant Diseases of Horticultural Crops

Location: Horticultural Crops Research

Title: Effect of vegetative canopy architecture on vertical transport of massless particles

Authors
item Bailey, Brian -
item Stoll, Rob -
item Pardyjak, Eric -
item Mahaffee, Walter

Submitted to: Atmospheric Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 30, 2014
Publication Date: July 5, 2014
Citation: Bailey, B.N., Stoll, R., Pardyjak, E.R., Mahaffee, W.F. 2014. Effect of vegetative canopy architecture on vertical transport of massless particles. Atmospheric Environment. 95:480-489.

Interpretive Summary: This research developed and used a computer simulation to examine factors that influence particle dispersion in perennial agriculture canopies. We demonstrated that row spacing and canopy density are important factors in determining the extent of particle dispersion from a source within the plant canopy. The large space between crop rows common to perennial agriculture canopies cause particles to become trapped between rows and reduce spread across rows. These finding are important to understanding and predicting pathogen dispersion in perennial agricultural crops.

Technical Abstract: A series of large-eddy simulations were performed to examine the effect of canopy architecture on particle dispersion. A heterogeneous canopy geometry was simulated that consists of a set of infinitely repeating vegetation rows. Simulations in which row structure was approximately resolved were compared to 'equivalent' horizontally homogeneous canopies to explore how overall canopy density and horizontal heterogeneity influence the vertical transport of non-depositing massless fluid parcels. Results suggested that above the canopy top, canopy density and canopy heterogeneity had a minor effect on mean profiles of particle concentration. In denser canopies, where the penetration of canopy-top turbulence structures is inhibited, a substantial disconnect is created between the upper and lower canopy as particles tend to become trapped in the lower canopy. This was exemplified by increased particle concentrations within the denser canopies, particularly for releases in the lower canopy. Canopy heterogeneity increased structure penetration, particularly in cases of dense vegetation elements and large row spacing. This had the effect of decreasing canopy residence times and increasing vertical particle fluxes in the lower canopy by up to 100%, which was approximately double the increases seen in momentum fluxes due to heterogeneity. However, canopy heterogeneity also disrupted persistent vertical particle motions, which is likely responsible for the fact that heterogeneity increased the fraction of time spent by particles below the canopy top.

Last Modified: 7/28/2014
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