Metolachlor variations

In contrast to measuring 0C or values, the measurement of pesticide degradation half-lives (t. / ) in soils is a much more difficult and time-consuming task. Hence, the spatial variations in t. trs could not be assessed in as much detail as we did with OC and K. . Metolachlor and aldicarb TTR half-lives were measured in a selected number of soil samples collected from the Georgia field site. Soil samples were selected to represent the three major soil series present at the site (Clarendon, Ardilla, and Tifton) and the four major morphologic soil horizons (0-20, 25-46, 48-63, and 94-107 cm) within the crop root zone. Soil samples collected from 4 depths at 10 sites were used to characterize aldicarb TTR degradation rates. Metolachlor half-lives were measured in soils taken from four depths at one site for each soil series and also in samples collected at two depths (0-20 cm and 94-107 cm) at 6 sites. 

The data for observed variations in metolachlor t-are presented in Table I. Of the three sampling sites witnin the Clarendon series, the shortest distance between two sites (G-13 to K-15) was about 60 m, while the sites K-15 and H-9 were the farthest, located about 100 m from each other. Of the five sampling locations, the greatest separation distance was about 200 m between J-4 (Tifton) and J-18 (Ardilla). Metolachlor t values measured... 

FIGURE 6. Spatial variations in OC and K, values for three pesticides (aldicarb, metolachlor, and diuron) at the Georgia site. 

Table I. Variations in Metolachlor Degradation Half-Lives (days) Measured in Soils from the Georgia Site...

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