Soil Persistence of Herbicides for Corn, Sorghum, and Soybeans during the Year of Application

Abstract

Herbicides used in corn(Zea maysL.), sorghum [Sorghum bicolor(L.) Moench], and soybeans [Glycinemax (L.) Merr.] were applied in the spring and their persistence into late summer was determined during 1974 to 1976. Composite soil samples from the top 5 cm of field plots were taken each August and bioassayed in the greenhouse. Bioassay species used were winter wheat [Triticum aestivumL.) and soybeans for herbicides used in corn and sorghum, and winter wheat and white mustard(Brassica hirtaMoench) for herbicides used in soybeans. Soil persistence of triazine herbicides caused more injury to winter wheat, soybeans, and white mustard than any other class of herbicides tested. Atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] showed the most soil persistence of the five triazines evaluated. At normal field application rates, herbicides other than the triazines showed little injury to the bioassay plants. Soil persistence of herbicides was further reduced when combinations of reduced rates of each herbicide were utilized. Herbicides used for spring applications in corn showed more soil persistence in August than did the herbicides for sorghum, while herbicides for soybeans generally were least persistent. Postemergence herbicide applications resulted in more injury in bioassay species than preplant incorporated or preemergence applications. Persistence of some herbicides will restrict certain options to the grower such as changing crops in case of crop failure, fall planting of winter wheat, double cropping, or certain crop rotations.

Effects of Imazaquin Residues on Cotton (Gossypium hirsutum)

“…Eight cotton seeds were planted at a depth of 1.5 cm. At 5 days after emergence (DAE) 3 , the plants were thinned to 'Abbreviations: DAE, days after emergence. three uniform plants per pot.…”

“…Amount and frequency of rainfall affect herbicide longev ity (1,3). Imazaquin dissipation has been shown to be rapid under warm, moist soil conditions in laboratory studies (1,2).…”

Fall and Early Preplant Application Timing Effects on Persistence and Efficacy of Acetamide Herbicides1

“…The effect of fall and EPP application timing on efficacy and dissipation of flufenacet ϩ metribuzin and ME formulations of acetochlor has not been reported in the literature. A greenhouse bioassay is an effective procedure to determine bioavailability of herbicides in the soil solution (Bunting et al 2003;Burnside and Schultz 1978;Doub et al 1988;Zimdahl and Clark 1982). The objectives of this study were to evaluate the persistence and bioefficacy of three formulations of acetochlor (capsule suspension [CS], emulsifiable concentrate [EC], and ME), metolachlor, s-metolachlor, and flufenacet ϩ metribuzin when applied in fall and EPP application timings.…”

Early Preplant Application Timing Effects on Acetamide Efficacy in No-Till Corn (Zea mays)1

“…An effective procedure used to determine herbicide concentration is a greenhouse bioassay (Burnside and Schultz 1978;Doub et al 1988;Zimdahl and Clark 1982). The bioassay indicates the amount of bioavailable herbicide in the soil solution as shown by injury to a sensitive indicator species.…”