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Chlormequat and Ethephon Timing and Grain Production of Spring Barley

Dep. of Plant Science, P.O. Box 4000, Macdonald Campus of McGill University, 21,111 Lakeshore Road, Ste. Anne de Bellevue, QC. Canada H9X 1CO

^* Corresponding author.

Several plant growth regulators increase the number of spike-bearing tillers and have potential as lodging control agents for spring barley (Hordeum vulgare L.). The objective of this study was to evaluate the effects of chlormequat (2-chloroethyl trimethylammonium chloride, CCC) and ethephon (2-chloroethyl phosphonic acid) timing on yield components, grain yield, and agronomic traits. A 4-yr field study using the cultivars, ‘Leger’ and ‘Cadette’, was conducted on Bearbrook clay soil (fine, mixed nonacid, mesic Humaquept) at McGill University, in Quebec, Canada, from 1987 to 1990. Treatments consisted of application of CCC (1.2 kg ai. ha^–1) and ethephon (0.48 kg ai. ha^–1) at Zadoks growth stages (ZGS) 13,30, and 39. Yield components were measured on a plot and a spike basis with separation of spikes into main culms and tiller culms. Early application of CCC at ZGS 13 enhanced grain number per spike, hut not grain yield due to compensations among yield components. At ZGS 30, ethephon application increased tiller-derived spikes per square meter up to 265% compared to the unsprayed control, while treatment with CCC increased Leger grain yield by more than 10% in two of the 4 yr of this study. This yield increase was attributable to a slight increase in the number of grains per spike^–1. Ethephon applied at ZGS 39 reduced plant height and lodging, but decreased yield by up to 27% because of reductions in the number of grains per spike, the main culm spike number, and/or weight per grain. These results indicate that in regions with a short crop-growing season, where lodging is uncommon, early application of CCC or ethephon is not justified for grain production, and that caution must be taken when applying ethephon to spring barley at the currently recommended rate and stage for lodging control.

Received for publication March 11, 1991.