BARLEY TREATED WITH ETHEPHON .1. YIELD COMPONENTS AND NET GRAIN-YIELD

Ethephon [(2-chloroethyl)phosphonic acid] effectively reduces lodging in barley (Hordeum vulgare L.), but also may have positive or negative influences on grain yield and yield components even if lodging does not occur. The objective of this study was to investigate the effects of ethephon on yield and yield components of barley under western Canadian conditions. In 1987, 1988, and 1989 at Winnipeg MB, 'Argyle' conventional height and 'Samson' semidwarf barley were grown at 100 and 300 plants m-2 and treated with ethephon at Zadoks growth stage 35 or 45. At harvest, grain yield samples were taken by hand or by combine, and yield components were determined. When lodging occurred, Belgian lodging indices were determined. The two cultivars responded similarly to ethephon application. Hand-harvested grain yields were either unaffected or reduced by ethephon, but combine-harvested yield tended to be increased by ethephon in 1989 when lodging was severe in untreated plots. Reductions in hand-harvested grain yield of ethephon-treated plots were primarily due to reductions in kernels per spike, which occurred in all 3 yr for barley grown at both plant densities. Ethephon increased spikes per plant for barley grown at both 100 and 300 plants m-2 in 1987, which at the low plant density compensated for reductions in kernels per spike and kernel mass. Barley in ethephon-treated plots tended to be delayed in maturity compared with untreated plots. This was particularly true in 1987 and 1989, when late tiller emergence was promoted to the greatest extent by ethephon when moisture conditions were favorable. The potential for ethephon to cause yield reductions restricts the use of ethephon in western Canada to situations where the risk of severe lodging is high.