Pre-Emergence Weed Control in Soybeans

Abstract

NE of the major problems in present-day soybean production is weed control. The increased interest in profitable soybean production in recent years has stimulated a demand for a satisfactory and economical means of chemical control to supplement cultural practices. The gradual shift from solid planting to row planting has practically eliminated the problem of weeds between rows, but it has not solved the critical problem of weed growth in the row. Weed infestations, in the row, which survived cultivation were found to reduce soybean yields approximately 10 percent (9). Weeds not only compete with the soybeans for nutrients, moisture, and light, but also interfere with harvesting operations and may lower the quality of the soybean seed. Soybeans are excellent weed competitors after they become well established and when environmental conditions are favorable for rapid growth. However, their competitive efficiency is at a minimum from the time of planting to the time the soybean plants form a dense vegetative cover. An economical and reliable means of chemical control of weeds, particularly during this critical 4 to 6 week period, would be desirable for supplementing present means of cultural control. Because of the sensitivity of the soybean plant to present day herbicides, it appears that preemergence chemical treatments would be more promising than postemergence treatments. In order to receive wide acceptance under Delaware conditions, the herbicide must be satisfactory for use on the light textured soils which are predominant in the soybean producing areas of the state. Among the most troublesome weeds are pigweed (Amaranthus retroflexus), lamb's quarters (Chenopodium album), ragweed (Ambrosia artemisiifolia), morning glory (Ipomea spp.) and crabgrass (Digitaria spp.). This paper is a summary of the performance of various herbicides evaluated as pre-emergence treatments on soybeans during the three-year period, 1954 to 1956 inclusive.