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Response of Soybeans to a Morphactin¹

Morphactins (a group of plant growth regulating chemicals) were observed to inhibit apical growth on soybeans [Glycine max (L.) Merr.] in North Carolina during 1971. One material, EMD-7301 (containing 12.5% of methyl-2- chloro-9-hydroxyfluorene-(9)-carboxylate) was evaluated under field conditions to determine the effects on plant height, lodging, seed weight, pods/plant, seed/pod, maturity, and grain yields.

Foliar applications of EMD-7301 at rates of 12.4, 24.7, 49.4, 98.8, 197.7, and 790.7 ml/ha at flower initiation failed to increase soybean yields over a 2-year period. A 10.5% yield increase occurred during the first year of study with the 49.4 ml/ha rate. Plant height was reduced by all application rates. Lodging was reduced by the 98.8 ml/ha rate. The highest rate of application (790.7 ml/ha) delayed maturity by 10.5 days, reduced the number of pods/plant by 54.5% and seed/pod by 19.4%, and had no effect on seed weights.

Key Words: Growth regulator • Grain yield • Components of yield • Methyl-2-chloro-9-hydroxyflourene-(9)-carboxylate

² Associate professor of crop science, N.C State U., Raleigh, NC 27607.

Received for publication June 17, 1974.