Decomposition of 11 dinitroaniline herbicides was determined following 7 days exposure to unfiltered solar radiation in July and compared with that in the dark. Radiolabeled herbicides were applied at 1 kg/ha to dry soil thin layer plates. Decomposition of all dinitroanilines was higher when exposed to sunlight than if held in the dark under otherwise similar conditions. Thermal decomposition was noted for all dinitroanilines except profluralin [N-(cyclopropylmethyl)-α,α,α-trifluoro-2,6-dinitro-N-propyl-p-toluidine] and dinitramine (N
4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine). Photodecomposition for each herbicide was: 7.8% AC 92390 [N-(1-ethylpropyl)-2,6-dinitro-3,4-dinitro-3,4-xylidine], 8.2% isopropalin (2,6-dinitro-N,N-dipropylcumidine), 9.0% butralin [4-(1,1-dimethylethyl)-N-(1-methylpropyl)-2,6-dinitrobenzenamine], 9.9% pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine], 17.1% benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine), 18.4% trifluralin (α,α,α-trifluoro-2,6-dinitro-N-N-dipropyl-p-toluidine), 26.6% oryzalin (3,5-dinitro-N
4-dipropylsulfanilamide), 30.4% fluchoralin [N-(2-chloroethyl)-2,6-dinitro-N-propyl-4-(trifluoromethyl)aniline], 40.6% nitralin [4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline], 47.6% profluralin, and 72.3% dinitramine.