Studies were initiated to develop a nutrient culture technique to select soybean [Glycine max (L.) Merr.] cultivars or breeding lines for tolerance to the herbicide metribuzin [4‐amino‐6‐tert‐butyl‐3‐(methylthio)‐as‐triazine‐5(4H) one]. Forty‐five soybean cultivars, representing determinate and indeterminate types commonly grown in the U.S., were screened in a modified Hoagland's nutrient culture containing 0.125 ppm metribuzin. Two cultivars, ‘CNS’ and ‘Wayne,’ and one breeding line, D66‐5566, were the most tolerant, showing only slight injury, whereas ‘Semmes’ and ‘Tracy’ were killed. Metribuzin caused severe injury to ‘Amsoy,’ ‘Chippewa 64,’ ‘Corsoy,’ ‘Clark 63,’ ‘Custer,’ ‘Delmar,’ ‘Arksoy,’ ‘Peking,’ ‘Dorman,’ and ‘Bragg.’ The remaining 30 cultivars were moderately injured. This technique will be useful in breeding programs to select for metribuzin tolerance.

The rate of emergence of near‐isogenic soybean [Glycine max (L.) Merr.] lines that differed in seed size was measured when germinated in Sharkey clay at moisture levels of 20, 22.5, 25, 27.5, and 30%. Weight per 100 seed of lines used was 9.5 g, 13.6 g, and 22.6 g. No emergence was observed at 20% moisture. The small and medium seed size gave more rapid emergence and greater root development than the large seed at each soil moisture level where germination occurred.

We measured the effect of several morphological characters upon seed yield in soybeans (Glycine max (L.) Merrill) by transferring each of the characters into a common background by a backcrossing program. Morphological characters studied were small seed, large seed, low number of seeds per pod, high number of seeds per pod, indeterminate growth, glabrousness, curly pubescence, dense pubescence, and narrow leaves. The effects of flower color and pubescence color were also studied. The only characters that influenced yield were indeterminate growth and glabrousness. We considered the lower yield for the indeterminate growth type to be the result of increased lodging and the lower yield of the glabrous line to be the result of early season injury by the potato leaf hopper (Empoasca fabae (Harris)).

‘Tracy′, ‘Tracy-M′, and ‘Centennial′, soybean [Glycine max(L.) Merr.] cultivars were evaluated under greenhouse and field conditions for their tolerance to metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5 (4H)-one]. The I50(50% injury) concentration of metribuzin, as determined in nutrient culture, for Tracy-M was more than three times the I50for Tracy, but was equivalent to the I50for Centennial. Data from greenhouse and field studies on Sharkey clay and Dundee silt loam soils indicated that Tracy-M was more tolerant to metribuzin than its parent selection, Tracy, but no more tolerant than Centennial when metribuzin was applied preplant soil incorporated or surface preemergence alone or in combination with several dinitroaniline herbicides.