Soil Moisture and Effectiveness of Preemergence Herbicides

Abstract
The relation between soil moisture and the effectiveness of preemergence herbicides for control of giant foxtail (Setaria faberii Herrm.) was studied under greenhouse conditions using surface soil from Drummer silty clay loam with 25, 31, and 37% moisture. Herbicides used were 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine), ethyl N,N-dipropylthiocarbamate (EPTC), 3-amino-2,5-dichlorobenzoic acid (amiben), α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin), 2-chloro-N-isopropylacetanilide (propachlor), and 2-chloro-N-(methoxymethyl)-2',6'-diethyl-acetanilide (hereinafter referred to as CP 50144). The effectiveness of atrazine and EPTC was increased when soil moisture was raised from 25 to 31%, but no further increase was obtained at 37% moisture. Response to amiben increased linearly and response to trifluralin decreased linearly with increasing moisture. Increasing moisture within this range had little effect on propachlor or CP 50144.