Soil Persistence of Isopropalin and Oryzalin

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Abstract
The aerobic rate of disappearance of isopropalin (2,6-dinitro-N,N-dipropyl-cumidine) was slower than that of oryzalin (3,5-dinitro-N 4,N 4-dipropylsulfanilamide) in soil. The aerobic half-lives for isopropalin were 3.5 months and 13.3 months and for oryzalin 1.40 months and 4.35 months at 30 and 15 C respectively. A simple system was devised to create anaerobiosis in soil at 80% of field capacity. Both herbicides dissipated more rapidly under anaerobic conditions. The first order half-lives at 30 C in anaerobic soil were 0.17 months for isopropalin and 0.34 months for oryzalin. Neither first, second, nor half order kinetics were clearly superior in describing the degradation processes. Arrhenius activation energies suggested that the degradation processes were non-biological.