Barley Tiller Response to Plant Density and Ethephon

Abstract

AbstractEthephon ([2‐chloroethyl] phosphonic acid), typically increases barley (Hordeum vulgare L.) spikes per square meter by increasing the frequency of late emerging green tillers, resulting in uneven crop maturity. This study was conducted to evaluate barley tiller grain yield and malting quality response to plant density and ethephon, with special reference to late‐emerging green tillers. Field studies were conducted at Powell, WY between 1987 and 1989 on a Garland clay loam (fine, mixed, mesic Typic Haplargid). Target plant densities of 150 and 300 plants m−2 were established. Ethephon was applied at the Zadoks growth stages (ZGS) of 13, 32, or 39, and one treatment was split‐applied at ZGS 32 and 39. Early emerging primary tillers (Tl, T2, and T3) and the main shoot contributed 86% of the total grain yield at high plant density vs. 73% at low plant density. In general, increasing plant density resulted in progressively greater differences for kernel plumpness and kernels per spike on the MS, Tl, T2, and T3. Ethephon applied at ZGS 39 reduced plant height 6 to 15 cm depending on year. Lodging was reduced by ethephon application, although the lodging level was low in every year of the study. Ethephon did not affect grain yield or protein content, but it often reduced volume mass and kernel plumpness compared to the untreated control. Regardless of ethephon treatment, kernels on late emerging tillers were of lower mass, volume mass, and plumpness than kernels on early emerging tillers. Ethephon applied at ZGS 39 increased the number of late emerging green tillers by 225 spikes m−2 compared with the control. These late emerging green tillers contributed 8% to the total grain yield but produced grain of substandard malting quality.