Norflurazon soil carry-over studies historically have indicated a more rapid initial half life of from I to 9 months but normally from 30 to 60 days. The subsequent half life degradation is slower, usually on the order of from 6 to 12 months. There are direct correlations in carry-over with soil types, incorporation methods and the moisture/temperature factors. The practical aspect of this degradation pattern requires rotational crop restrictions. The active ingredient degrades to a des-methyl metabolite both in the soil and in plants. Soil degradation factors are photolysis, volatization and microbial degradation. Plant uptake also removes norflurazon from the soil.