Effect of Planting Date on Yield and Other Characteristics of Soybeans 1

THE purpose of this investigation was to determine the response of soybean varieties differing in maturity when planted at several dates. Such information is important for making recommendations to growers and in the interpretation of experiments planted at different dates. Previous studies (2, 3, 5, 6, 8) indicate that generally early planting gave maximum seed yield. Feaster (3) and Osier and Cartter (6) report that early varieties should be planted later than late varieties for maximum yields, whereas Weiss et al. (8) found no significant differences for yield among planting dates of early varieties. Maturity of late varieties was affected less by late planting than that of genetically earlier varieties (3, 6, 8). Plant height was found to decrease with delay in planting (6, 8). Weiss et al. (8) report that date of planting had no effect on lodging whereas Osier and Cartter (6) found an increase in lodging with later plantings. Feaster (3) states that planting date had little influence on seed quality of late varieties but that seed quality was poorest from early plantings of early varieties. In general a delay in planting resulted in a decrease in oil content (2, 3, 4, 6, 7, 8) and an increase in protein content (2, 6, 7) and iodine number (2, 3, 6, 8). Weiss et al. (8) found that protein content was not affected by date of planting. Cartter and Hopper (1) report that the variance for oil and protein content and iodine number contributed by varieties was appreciably greater than that due to locations or years.