Selecting soybean for adaptation to double cropping on the basis of full season plant height

Double-cropping soybean [Glycine max (L.) Merr.] shortens the growing season and reduces vegetative mass and seed yield. Soybean genotypes which produce greater vegetative mass may be better adapted to the double-crop system. This study was conducted to determine if tall soybean lines selected from full season plantings were better adapted to double-crop plantings than lines chosen from the same populations without regard to plant height. Four sets of soybean lines, with a tall and random height group in each set, were compared at Lexington, KY, in full season wide row and late planted narrow row (simulated double crop) cropping systems to determine the interaction between plant height and yield in the two different cropping systems. Soybean grown in the full season cropping system yielded an average of 32% more than when grown in the double-crop system. The height groups differed in yield in only one of the four sets. The cropping system x height group source of variation was not significant for yield in any set. Six of the eight lines ranked one or two for full season yield in each of the four sets were from the random height groups. Likewise, six of the eight lines ranked one or two for double-crop yield were also from the random height groups. Greater plant height did not consistently increase yield in the lower yielding double-crop environments. The selection of tall soybean lines did not provide improved adaptation to the double-crop cropping system.