PHYSIOLOGICAL STUDIES OF HIGHER YIELD IN NEW, EARLY-MATURING SOYBEAN CULTIVARS

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Abstract
The physiology of three soybean (Glycine max (L). Merrill) cultivars of Maturity Group 00 was studied to determine why the new cultivars Maple Arrow and McCall outyield the older cultivar Altona. Field trials were conducted at Elora, Ontario, in 1977 and 1978. The seed yields of the new cultivars averaged 12% higher than Altona over both years, although the three cultivars were within 3 days of the same maturity. The higher yields in the new cultivars appeared to be related to consistently longer bean-filling periods than in Altona, although a difference (P < 0.05) was detected only in 1978. Rates of bean filling in the new cultivars were no greater than in Altona, which also indicated that longer bean-filling periods contributed to higher yields in the new cultivars. Flowering dates for cultivars were not different. Similar maturity dates indicated that the new cultivars had shorter periods than Altona from maximum bean dry weight to final maturity. Other attributes differed little among cultivars in either year. Total dry matter accumulations were similar until bean filling began. Leaflet areas and dry weights, leaf area durations and harvest indices also did not differ. The results suggested that a long bean-filling period was a desirable trait in early-maturing soybeans.