Profit-maximizing seeding rates and replanting thresholds for soybean: Maturity group interactions in the Mid-South

Abstract

Considerable interest in adopting earlier-maturing soybean [ Glycine max (L.) Merr.] cultivars exists among producers in the Mid-Southern United States, as the potential for irrigation water savings and improved labor and equipment scheduling are attractive. Previous reports suggested that maturity group (MG) selection should depend primarily upon yield and not irrigation requirements, as irrigation savings generally did not offset lower yield of earlier MG. This research, however, did not account for differences in seeding rate recommendations. This report considered results from a conventional soybean (MG 00 to MG VI) population density trial (seeded at 10–100 seeds m −2) conducted at Fayetteville, AR for 3 years. The analysis revealed that planting soybean at the economically optimal seeding rate can lead to substantially different investment in seed (an average of $97 ha −1 for MG 00 vs. $27 ha −1 for MG VI). The results also indicated that later-maturing soybean exhibited greater flexibility in environments with plant establishment uncertainty, as the yield response to plant population density was less pronounced and investment in seed was lower compared to earlier-maturing cultivars. Later-maturing varieties did exhibit larger changes in optimal seeding rates over time than earlier-maturing varieties, however. Based on our results, a producer would be advised to examine yield potential of different MG soybean and to consider planting a range of cultivars within MG II–VI. Finally, while the numeric results of this research were location and cost specific, the analyses provided guiding principles for other regions with similar characteristics for crop establishment and replanting thresholds.