The estrogenic isoflavones of soybeans and their glycosides are products of the shikimate pathway, the target pathway of glyphosate. This study tested the hypothesis that nonphytotoxic levels of glyphosate and other herbicides known to affect phenolic compound biosynthesis might influence levels of these nutraceutical compounds in glyphosate-resistant soybeans. The effects of glyphosate and other herbicides were determined on estrogenic isoflavones and shikimate in glyphosate-resistant soybeans from identical experiments conducted on different cultivars in Mississippi and Missouri. Four commonly used herbicide treatments were compared to a hand-weeded control. The herbicide treatments were (1) glyphosate at 1260 g/ha at 3 weeks after planting (WAP), followed by glyphosate at 840 g/ha at 6 WAP; (2) sulfentrazone at 168 g/ha plus chlorimuron at 34 g/ha applied preemergence (PRE), followed by glyphosate at 1260 g/ha at 6 WAP; (3) sulfentrazone at 168 g/ha plus chlorimuron at 34 g/ha applied PRE, followed by glyphosate at 1260 g/ha at full bloom; and (4) sulfentrazone at 168 g/ha plus chlorimuron at 34 g/ha applied PRE, followed by acifluorfen at 280 g/ha plus bentazon at 560 g/ha plus clethodim at 140 g/ha at 6 WAP. Soybeans were harvested at maturity, and seeds were analyzed for daidzein, daidzin, genistein, genistin, glycitin, glycitein, shikimate, glyphosate, and the glyphosate degradation product, aminomethylphosphonic acid (AMPA). There were no remarkable effects of any treatment on the contents of any of the biosynthetic compounds in soybean seed from either test site, indicating that early and later season applications of glyphosate have no effects on phytoestrogen levels in glyphosate-resistant soybeans. Glyphosate and AMPA residues were higher in seeds from treatment 3 than from the other two treatments in which glyphosate was used earlier. Intermediate levels were found in treatments 1 and 2. Low levels of glyphosate and AMPA were found in treatment 4 and a hand-weeded control, apparently due to herbicide drift.

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Variability of peanut (Aruchis hypogaea L.) seedling spacing, and yeld were compared for a conventional and a vacuum-type planter in field studies conducted in 1991 and 1992. Vacuum-type planters have an improved seed metering system and are considered to be more precise. This added precision may serve to compensate for lower than normal seeding rates. Seeding rates evaluated decreased in a step-wise manner from the normal range of 123 to 101 kg/ha, to a minimum of 34 kg/ha. Spacing between individual seedlings was measured after emergence. The occurrence of tomato spotted wilt (TSWV) and southern stem rot were also determined. In 1991 and across aU seeding rates, variability in seedling spacing (i.e. standard deviation) was identical between the two planters. In 1992, at 3 of the five seeding rates (34,56, and 101 kg/ha) standard deviation was less with the vacuum planter. In both years yield and disease occurrencewas influencedonlyby seedingrate, and was independent of planter type. TSWV was inversely related to seeding rate, the opposite relationship occurred with southern stem rot. Maximum yield was achieved with a seeding rate of 101 kgha.