Jh. Smelt et al., DEVELOPMENT AND DURATION OF ACCELERATED DEGRADATION OF NEMATICIDES INDIFFERENT SOILS, Soil biology & biochemistry, 28(12), 1996, pp. 1757-1765
The development of accelerated degradation of nematicides was studied
in incubation experiments with soils collected from trial plots at thr
ee long-term experimental fields. The plots had been treated annually
for periods of 3-10 years with aldicarb, oxamyl, ethoprophos, fenamiph
os or 1,3-dichloropropene (1,3-D). At one site (sandy soil: pH 7.3) hi
ghly accelerated degradation rates were measured for aldicarb, oxamyl
and ethoprophos in soil from plots treated three times. After 5 years
without further treatments, these high degradation rates were still pr
esent for aldicarb and oxamyl, but not for ethoprophos. At another sit
e (sandy soil; pH 5.6) little or no increase in the degradation rates
of aldicarb, oxamyl and ethoprophos was measured in soil from plots tr
eated 10 times. Three annual applications of fenamiphos to a loamy soi
l (pH 7.7), doubled the rate of loss of the total toxic residue compar
ed with the untreated soil. Fenamiphos and oxamyl did not show cross-e
nhancement when incubated in ethoprophos-adapted soils. After a lag-ti
me of 4-9 days degradation of 1,3-D was very rapid in all soils includ
ing controls which had been treated only once or twice well before the
sampling dates. Seven annual applications of 1,3-D resulted in only s
lightly shorter lag-times. An interval of 5 years without treatment re
sulted in only slightly longer lag-times. Simultaneous incubation of a
commercial dose of the fumigant methyl isothiocyanate inhibited the f
ast degradation of 1,3-D. (C) 1997 Elsevier Science Ltd.