Growth and Yield of Winter Wheat as Influenced by Chlormequat Chloride and Ethephon

Lodging can be a constraint in wheat (Triticum aestivum L.) production, therefore interest exists for use of plant growth regulators (PGRs) such as Chlormequat chloride or CCC (2-Chloroethyl-N, N, N-trimethylammonium chloride) and ethephon [(2-Chloroethyl) phosphonic acid] for lodging control. Field experiments were conducted in New York in 1985 and 1986 on a Honeoye silt loam (fine-loamy, mixed mesic Glossoboric Hapludalfs) to examine the influence of CCC (1.37 kg ha⁻¹ a.i. at Zadoks Growth Stage (GS) 31) and ethephon (0.40 kg ha⁻¹ a.i. at GS 39) on vegetative and reproductive growth of two winter wheat cultivars, Geneva and Houser. Leaf, stem, and spike phytomass were determined at 10-d intervals from GS 25 to 95, and kernel number and weight were determined on 15 main-culm spikes at 3 to 4-d intervals during the grain-filling period. The CCC application reduced culm and total phytomass by 9% at GS 45, whereas ethephon reduced spike and total phytomass by 10 and 8% at GS 55 and GS 75, respectively. Neither PGR had an effect on total or component phytomass at harvest. In 1985, a year when no lodging occurred, ethephon and CCC yielded the same compared with the yield of the check (6.12, 6.60, and 6.39 Mg ha⁻¹, respectively). In 1986, a year of considerable lodging, ethephon reduced lodging compared with that of CCC and the check, which was reflected in a higher kernel growth rate (1.00, 0.84, and 0.81 mg kernel⁻¹ day⁻¹), kernel weight (43.4, 39.8, and 38.9 mg), and grain yield 5.73, 4.71, and 5.30 Mg ha⁻¹, respectively) in the more lodging-susceptible cultivar, Houser. The data indicate that, under the environmental conditions of this study, CCC does not benefit wheat and that ethephon should be utilized only under severe lodging conditions. Contribution from the Dep. of Agronomy, Cornell Univ. Research supported in part through Hatch Project, 125-6422, USDA.