Fate of the Soil Residues of the Fungicide Flutolanil in a Microecosystem Planted with Rice Plants

The fate of soil residues of the fungicide flutolanil was elucidated in a microecosystem where rice plants were grown on two Korean soil types (A and B) containing fresh and 105-day-aged residues of [C]flutolanil. Amounts of evolved from soils A and B during aging period of 105 days were 10.9 and 23.8% of the originally applied C-radioactivities, respectively, indicating that aeration of the soil is more important than the organic matter content in the degradation of flutolanil, chemically and/or microbiologically, as evidenced by the soil texture. Amounts of evolved from soils A and B treated with fresh flutolanil residues in the presence of rice plants indicate that rhizosphere effect was greater than the soil texture in mineralization into , whereas, in the case of aged residues, soil texture was more effective in mineralization. Flutolanil residues in soil were tightly bound to soil organic matter and were not available to rice plants. After 42 days of rice growing, 77.0 and 72.1% of the C-radioactivity applied freshly remained in soils A and B, whereas 87.0 and 89.4% of 105-day-aged flutolanil residues remained, respectively. The nonextractable soil-bound residues of flutolanil were mainly incorporated into the humin fraction in soil A containing more organic matter (3.3%), and into the fulvic acid fraction in soil B containing less organic matter (1.3%). Degradation of flutolanil at 15 and 22 in German soils C and D was more chemical, while that at was more microbial, as indicated in soil D with a neutral pH of 7.2 and more organic matter favorable for microbial activity.