No abstract

There is an argent need to find safer, environmentally friendlier as well as efficient alternatives. Effect of some fumigants on activities of dehydrogenase (DHase), peroxidase (POD), and polyphenol oxidase (PPO) in soil was carried out. Three types of fumigants were tested: true-fumigants; dimethyl disulfide (DMDS), fumigant generators, phosphine (PH3), 1,4-Dichlorobenzene (1,4-D), and formaldehyde (CH2O), and bio-fumigants an essential oil of garlic, jojoba, citrus, and argan. Mini-atmosphere method was used for fumigant generators and soil drench method was used for true-and bio-fumigants. The results revealed that DMDS at concentration of 2000 and 20 mg/kg inhibited soil enzymes within the first four days, then reach the level of the enzymatic activity of a control soil sample. Almost the same trend of the effect of phosphine was obtained from either aluminum phosphide (AlP) or zinc phosphide (Zn3P2). Phosphine at 5 mg/L caused an increase in the DHase, POD and PPO activities while, at 150 mg/L, it caused inhibition approximately of 25%. Various essential oils proved to be harmless or very low effect for the soil enzymes. For the effect of all fumigants, the maximum enhancement percentage in the DHase was 37.5% while the maximum inhibition was 25%. Also, the maximum induction was 30% while the maximum reduction in POD activity was 42%. In addition, 48% and 40% were the maximum of stimulation and reduction, respectively in the PPO. Therefore, the activities of DHase, POD, and PPO found to be sensitive to fumigants and proved to be a good indicator of the degree of soil contamination with tested fumigants.