Program and Abstracts of the Annual Meeting of the Korean Agricultural Chemical Society - Rm3 - 11 - ; Behaviour of bentazon in the rice plant grown lysimeters throughout two growing seasons

When the herbicide ^(14)C-bentazon was applied to the 0.25㎡ lysimeters by the conventional method for the control of weeks of rice plants, 2.92%(lysimeter I)-17.08% (lysimeter II) of the originally applied radioactivities up to the 85th week after the application were percolated in total. The ^(14)C-radioactivities detected in straw, ear without rice grain. chaff, and hulled rice grain after harvest corresponded to 2.5∼3.2, 0.1, 0.05, and 0.03 ppm, respectively, in the first year, and 0.5∼0.6. 0.06∼0.08. 0.03. and 0.02 ppm, respectively, in the second year. in the two lysimeters. When ^(14)C-bentazon was incubated in soil at 15℃, 22℃, and 30℃, the amounts of ^(14)CO₂ evolved were 0.74%, 2.46% and 6.4%, respectively. of the originally applied radioactivity, suggesting that the degradation of bentazon in soil increased with soil temperature The number of microorganisms and the dehydrogenase activity of the lysimeter soil increased slightly after rice planting compared with pre-planting. ^(14)C-Radioactivities remaining in the 0∼40 cm soil depth were approximately 79.33% and 34.22% of the originally applied ones in lysimeter I and II at the end of the 2 years growing seasons, respectively. The activities of microorganisms in different soil layers were compared in terms of the amounts of ^(14)CO₂evolved. when soils of each layer were incubated at 30℃. Much higher amounts of ^(14)CO₂were evolved at the top 10㎝ soil layer, suggesting a higher microbial biomass in the surface area.