Chemical disinfestation and metabolic integrity of soil

Abstract

Field disinfestation in autumn with normal or increased dosages of 1,3-dichloropropene, metham-sodium or chloroform, and in spring with ethoprophos, did not, or hardly, affect the degradationin situ of some herbicides applied in spring. However, during laboratory incubation of samples from the disinfested plots, sometimes decreased herbicide degradation rates or increased lag phases were found. The top few centimetres of the field soil, on which the herbicides were sprayed, apparently largely escaped fumigation. Accordingly, effects of fumigation on herbicide degradation, organic matter and N metabolism were stronger in samples from the 10–20 cm layer than in samples from 0–10 cm. In the laboratory fumigation of soil samples with CHCl3 was much more drastic in inhibiting herbicide degradation, N mineralisation and nitrification; inoculation with 10% fresh soil, however, greatly accelerated the recovery of these processes. Therefore, in practice prolonged or drastic effects of chemical soil disinfestation on metabolic integrity of the soil are not to be expected.