Average soybean (Glycine max (L.) Merr.) yields have increased considerably due to changes in cultivars and cultural practices. To evaluate the genetic improvement, yields, lodging, and plant height of 21 cultivars were determined in 3 years. Most of these cultivars were involved in essentially two cycles of recurrent selection. Yield increases were 26 and 16% for the first and second cycles of selection, respectively, while lodging decreased 21 and 20%. Plant height increased slightly.

Soybean [Glycine max L. (Merr.)] introductions PI 171451, PI 227687, and PI 229358; commercial cultivars ‘Amsoy 71’ and ‘Beeson’; and F3 and F4 generations of four resistant‐susceptible crosses were field tested for resistance to leaf feeding by second‐instar cabbage looper larvae (Trichoplusia ni Hubner). The three plant introductions were highly significantly more resistant than the two commercial cultivars. The parental range in feeding scores was recovered in the F4 generation even though the number of progenies was small. Heritabilities were estimated by correlation of F3 with F4 feeding scores and ranged from 6 to 44%. The possible linkage of maturity genes with genes for resistance to cabbage looper feeding in the plant introductions (maturity adapted to the Southern U.S.) did not appear to be a factor in transferring resistance to cultivars adapted in more northern latitudes.

Dates of emergence, flowering, beginning pod fill, termination of flowering, and physiological maturity were recorded for two soybean [Glycine max (L.) Merr.] cultivars from each of the maturity groups I to V. The cultivars were planted on five dates at three Missouri locations in 1971, 1972, and 1973, and at weekly intervals at Columbia, Mo., in 1972 and 1973. Daily maximum and minimum temperatures were used to calculate five thermal unit methods with no base temperature subtracted, four methods with a base temperature subtracted, and two methods using quadratic formulas.Thermal units with a base temperature subtracted, including the “growing degree day method” used by the corn industry, and thermal units using quadratic formulas were the best for predicting flowering. The number of thermal units was not better than calendar days for predicting post‐flowering development. Prediction of flowering was more accurate for early cultivars than for late cultivars, suggesting that another factor (probably day‐length) also influenced flowering and had its greatest effect on the later maturing cultivars.