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Growth, Yield, and Yield Components of Maize as Influenced by Ethephon

Dep. of Agronomy, Cornell Univ., Ithaca, NY 14853
15 Avenue 9-66 Zone 13 Guatemala City, Guatemala, Central America., formerly Dep. of Agronomy, Cornell Univ.

^* Corresponding author.

Considerable interest exists for use of plant growth regulators to control lodging in maize (Zea mays L.), thereby reducing yield losses. Field experiments were established in New York during the 1985 and 1986 growing seasons on a Honeoye silt loam (fine-loamy, mixed, mesic Giossoboric Hapludalt) to evaluate a lodging-susceptible and lodging-tolerant hybrid (‘Cornell 281’ and ‘Pioneer 3901’, respectively) under recommended (64 000 plants ha^–1) and high plant densities (76 000 plants ha^–1) in the absence and presence of ethephon [(2-chloroethyi) phosphonic acid], which was applied at the 15th to 16th leaf stage at 0.42 kg ha^–1 a.i. Measurements of dry phytomass and leaf area were taken at 10-d intervals and leaf area index (LAI), net assimilation rate (NAR), and crop growth rate (CGR) were calculated. In the dry 1985 season, ethephon had no effect on phytomass, NAR, and CGR, whereas in the wet 1986 season, ethephon reduced all three growth parameters. Plant density and hybrid did not influence the growth response to ethephon in this study. Although ethephon reduced lodging by 64%, it had no effect on grain yield. An interaction, however, was observed between ethephon and hybrids. Ethephon increased grain yield of Cornel1281 (7.78 to 8.24 Mg ha^–1), and decreased grain yield of Pioneer 3901 (9.63 to 8.56 Mg ha^–1). Ethephon also increased kernel weight of Cornell 281 (263 to 266 mg), and decreased kernel weight of Pioneer 3901 (282 to 264 mg), which probably caused the grain yield interaction. Ethephon, however, significantly decreased kernels per ear (494 to 474) in both hybrids. The data suggest that ethephon can enhance the yield of maize when lodging is a problem, but may decrease grain yield in the absence of lodging because of its potential deleterious effect on kernel number and growth.

Key Words: Phytomass • Leaf area index • Net assimilation rate • Corp growth rate • Stalk lodging • Zea mays L.

Received for publication June 5, 1987.