TILLERING AND YIELD RESPONSES TO ETHEPHON IN 3 BARLEY CULTIVARS

Ethephon (2-chloroethylphosphonic acid) is applied to cereal crops to control lodging. Tillering and yield may also be affected, although the response depends on the species, cultivar, and rate and time of application. A field study was conducted during 1988 and 1989 at Lacombe, AB, to assess ethephon effects on tillering and yield in irrigated spring barley (Hordeum vulgare L.). Ethephon was applied at 0.3 and 0.6 kg ha-1 at Zadoks growth stage 43 to 'Klages,' 'Leduc,' and 'Bonanza' barley. There was no lodging in either year. Ethephon reduced plant height in both years. Tillers were separated into three groups at harvest: (i) early fertile, if they had been formed early in the season and produced mature grain, (ii) early sterile, if formed early and produced no grain, or (iii) late, if produced post treatment. In 1988, all cultivars produced significant late tiller number and biomass m-2 increases (6- to 8-fold and 9- to 16-fold, respectively, at 0.6 kg ha-1) in response to ethephon (Klages > Leduc > Bonanza). In Klages, early fertile tiller number m-2 was reduced at 0.3 kg ha-1 ethephon, while the number of early sterile tillers m-2 increased by a factor of 2.5 with each increase in ethephon rate. Yield and harvest index were reduced by ethephon treatment in all the cultivars. Grain mass was unaffected by treatment; however, grains spike-1 decreased significantly (by 26-36% at 0.6 kg ha-1) with increasing rate. In 1989, a significant increase in number and biomass of late tillers m-2 was observed in two cultivars (Klages > Bonanza) in response to ethephon. Averaged across cultivars, the number of early sterile tillers m-2 increased twofold with each increase in ethephon rate. There was no effect of ethephon on yield in 1989, although the harvest index of Klages was reduced due to the increased late tiller biomass. Ethephon induces tillering in barley when applied at Zadoks 43, although the degree of tillering is dependent upon cultivar and environmental conditions.