Rainout Studies

The rain-out shelters are utilized to control the amount of water a trial receives so that cultivars can be evaluated for drought tolerance. These structures are constructed using a greenhouse frame with removable sides to increase air movement. Drain tiles and a special draining system has been added to ensure that no moisture could move in from the surrounding area. Overhead sprinklers were placed for even distribution of water. This is very important for formation of the study, guaranteeing that all varieties are well established before starting the drought, and for monitoring and ensuring an even green up of the turf plots.

Digital Photography – using a digital camera eliminates the subjective rating and forces an objective rating of each individual plot. Photos are then analyzed using SigmaScan Pro with macros (special codes designed to tell the program what to analyze and how to present the data) created by Doug Karcher of the University of Arkansas. The program is able to discern and calculate the differences in each photo by separating varying shades of green and brown.

Our interest is not only in which varieties will dry-down at the slowest rate, but also which ones will recover and green-up the fastest.

Data has shown that the varieties cycled through the root study tables have an increased ability to handle drought. The results of the tall fescue study have been placed in charts and linked at the bottom of this page. These charts show improvement from Axiom to Axiom II (cultivar with a wide genetic base) and Wyatt to Wyatt II (cultivar with a narrow genetic base), after 2 cycles of selection for extended roots. This study was conducted over a period of 101 days without water. In each chart the length of the box indicates the confidence interval. With both varieties that were cycled through the root study tables, there was an increase in resistance to drought, and an increase in the ability to recover with the return of water. For example, 25% green cover would be reached by Axiom at 79 days while 25% green cover of Axiom II would be reached at 96 days. This results in a delay of irrigation by 17 days, while maintaining the same green cover. Data can be viewed by using the drop-down menu below. Included are examples of percent coverage and the difference between two tall fescue cultivars after 37 days of drought. Additional data may be accessed on the Root Study page by clicking here.

The rain-out shelter has been used to screen Kentucky Bluegrass and Texas-Kentucky Bluegrass Hybrids as well. The same varieties have been trialed in field studies and in the root study tables to determine which varieties have the most roots and drought resistance.

Data

Kentucky Bluegrass

Oregon – 2005 Trial

Charts

Kentucky Bluegrass

Oregon – 2005 Trial

Perennial Ryegrass

Oregon – 2002 Trial

Tall Fescue

Oregon – 2002 Trial

Other

Other Trials / Info