Effect of Soil and Climate on Herbicide Dissipation

The persistence of five herbicides in six soils across Nebraska can be ranked from greatest to least as follows: 5-bromo-3-isopropyl-6-methyluracil (isocil) at 5 and 25 1b/A, 2-chloro-4,6-bis-(isopropylamino)- s -triazine (propazine) at 3 and 9 1b/A, 2-chloro-4-ethylamino-6-isopropylamino- s -triazine (atrazine) at 3 and 9 1b/A, trichlorobenzyl chloride (hereinafter referred to as TCBC) at 7 and 49 1b/A, and 3-(3,4-dichlorophenyl)-1-methoxyl-1-methylurea (linuron) at 3 and 9 1b/A. Soil texture differences (sandy loam, very fine sandy loam, silt loam, and silty clay loam) had a greater influence on herbicide residue carryover than did climatic differences across Nebraska during 1962 to 1968. Soil carryover of herbicide residues was greater in coarse rather than fine-textured soils and in the drier regions of western than in eastern Nebraska. Leaching of herbicides into the soil profile was an avenue of herbicide dissipation.