PERSISTENCE AND BEHAVIOUR OF PYRAZOSULFURON-ETHYL IN TRANSPLANTED RICE ECOSYSTEM
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Date
2009-07-10
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK, BENGALURU
Abstract
Sorption studies were conducted with pyrazosulfuron-ethyl using
the batch equilibrium technique and HPLC analysis. Four different
paddy growing soils of Kathalagere, Mandya, Mudigere and Mangalore
soil. The sorption isotherm (n) values were 0.104, 0.101, 0.085 and
0.165 of Kathalagere, Mandya, Mudigere and Mangalore soils
respectively. Freundlich constants ‘K’, ‘Koc’ and ‘Kc’ values were range
from 5.45 to 9.52, 1099.46 to 1436.12 and 32.24 to 49.07 in different
soils and described in the order of Kathalagere > Mandya > Mudigere >
Mangalore, which is also in the order of decreasing organic matter
content in the soils. The coefficient of determination showed an
improvement 96 per cent using quadratic functions, the cumulative
desorption of five days was ranged from ranged from 22.3 to 41.1 mg kg-
1 in Kathalagere soil, 25.6 to 49.4 mg kg-1 in Mandya soils, 37.1 to 51.9
mg kg-1 in Mudigere soil and 39.9 to 55.7 mg kg-1 in Mangalore soil. To
study persistence and residues of pyrazosulfuron-ethyl in soil and
ground water in transplanted rice ecosystem. Pyrazosulfuron-ethyl was
applied at 25 g a.i. ha-1 and 50 g a.i. ha-1 with and without addition of
FYM on flooded rice. The study revealed that the residue of
pyrazosulfuron-ethyl in soils ranged from 0.0103 and 0.0199 mg kg-1
respectively (T2 & T4) on 2nd day of application. And with out FYM the
residues were 0.0116 and 0.0229 mg kg-1 respectively (T1 & T3). The
degradation of the initial residue with the time taken in both the
treatments were up to 35 days. The half-life of pyrazosulfuron-ethyl
ranged from 17.7, 16.6, 21.8 and 19.3 days for T1, T2, T3 and T4
respectively. After two weeks the residues were detected in ground water
collected from both the piezometers which were applied with
recommended and double the recommended dose of pyrazosulfuronethyl.
A maximum of 0.0154 mg kg-1 on 21st day and minimum of 0.0023
mg kg-1 pyrazosulfuron-ethyl residues on 35th day were detected in
underground water.
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