110
N. Sethunathan et al.
inhibiting microbially mediated reactions of both nitro group reduction and hydrolysis (Sudhakar-Barik and Sethunathan, 1979). The persistence of parathion
was not altered in the simultaneous presence of even 100 ppm of either HCH
or 2,4-D.
The impact of pesticide combinations, vis-a-vis single applications, on
microbial activities involved in pesticide degradation and biochemical transformations of importance to soil fertility merits more intensive study, particularly
because the environment is subjected to pressure from more than one pesticide.
From the standpoint of economical and efficient use of pesticides, especially in
tropical agriculture, use of appropriate combinations could provide a potential
means of increasing the persistence of readily biodegradable and short-lived
pesticides, as clearly demonstrated with benomyl-parathion interaction. However, caution is warranted in such controlled persistence studies, since increased
persistence of generally short-lived but highly toxic pesticides, such as several
organophosphorous insecticides, under the impact of combinations may generate
new problems of environmental pollution.
4.5. CONCLUSION
There is concern over environmental safety with recent increases in the
number and quantity of synthetic pesticides, particularly the persistent chlorinated
hydrocarbons, being introduced into tropical areas of intensive agriculture. There
are considerable gaps in our knowledge of pesticide behavior and transport under
more realistic field conditions in the tropics. Despite increasing use of inorganic
fertilizers, little is known on the interaction between fertilizers and pesticides
in the soil environment. Pesticide loss via volatilization, photodecomposition,
and microbial degradation may be considerable under tropical conditions, but
field measurements of the relative proportions of the pesticides lost due to these
forces are not available. The extent of chemically catalyzed reactions in the
environment merits more intensive study in the light of recent demonstration of
the involvement of hydrogen sulfide in the transformation of parathion and
mercury. Microbial degradation is by far the most powerful means of detoxifying
many pesticides in the environment. But seeding the polluted environments with
microorganisms capable of degrading pesticides is of questionable value owing
to the inherent problems in the establishment of introduced microorganisms and
possibly other side effects. Alternatively, selective stimulation of indigenous soil
microflora with pesticide-degrading capabilities by suitable cultural practices,
for example, flooding and organic matter amendment, provides a more effective
and practical means of decontaminating pesticide-polluted environments.
N. Sethunathan et al.
inhibiting microbially mediated reactions of both nitro group reduction and hydrolysis (Sudhakar-Barik and Sethunathan, 1979). The persistence of parathion
was not altered in the simultaneous presence of even 100 ppm of either HCH
or 2,4-D.
The impact of pesticide combinations, vis-a-vis single applications, on
microbial activities involved in pesticide degradation and biochemical transformations of importance to soil fertility merits more intensive study, particularly
because the environment is subjected to pressure from more than one pesticide.
From the standpoint of economical and efficient use of pesticides, especially in
tropical agriculture, use of appropriate combinations could provide a potential
means of increasing the persistence of readily biodegradable and short-lived
pesticides, as clearly demonstrated with benomyl-parathion interaction. However, caution is warranted in such controlled persistence studies, since increased
persistence of generally short-lived but highly toxic pesticides, such as several
organophosphorous insecticides, under the impact of combinations may generate
new problems of environmental pollution.
4.5. CONCLUSION
There is concern over environmental safety with recent increases in the
number and quantity of synthetic pesticides, particularly the persistent chlorinated
hydrocarbons, being introduced into tropical areas of intensive agriculture. There
are considerable gaps in our knowledge of pesticide behavior and transport under
more realistic field conditions in the tropics. Despite increasing use of inorganic
fertilizers, little is known on the interaction between fertilizers and pesticides
in the soil environment. Pesticide loss via volatilization, photodecomposition,
and microbial degradation may be considerable under tropical conditions, but
field measurements of the relative proportions of the pesticides lost due to these
forces are not available. The extent of chemically catalyzed reactions in the
environment merits more intensive study in the light of recent demonstration of
the involvement of hydrogen sulfide in the transformation of parathion and
mercury. Microbial degradation is by far the most powerful means of detoxifying
many pesticides in the environment. But seeding the polluted environments with
microorganisms capable of degrading pesticides is of questionable value owing
to the inherent problems in the establishment of introduced microorganisms and
possibly other side effects. Alternatively, selective stimulation of indigenous soil
microflora with pesticide-degrading capabilities by suitable cultural practices,
for example, flooding and organic matter amendment, provides a more effective
and practical means of decontaminating pesticide-polluted environments.