Behaviour of the soil residues of the herbicide quinclorac in the micro-ecosystem (pot)

Rice plants were grown for 42 days in the specially made micro-ecosystem(pot) containing two different soils treated with fresh and 60-day-aged residues of []quinclorac, respectively, to elucidate the behaviour of the herbicide quinclorac residues in the soils. Amounts of evolved from two soils treated with different residues with and without vegetation were all less than 2.2% of the total , indicating that there was little microbial degradation of quinclorac in soil. -Radioactivity absorbed and translocated into rice plants from soil A and B containing fresh quinclorac residues was 8.4 and 24.2%, respectively, of the originally applied , while 5.5 and 17.7%, in aged residue soils. These results indicate that larger amounts of were absorbed by rice plants from soil B with less organic matter and clay than soil A, and the uptake of []quinclorac and its degradation products decreased with aging in soil. After 42 days of rice growing, 84.5 and 61.8% of the applied freshly to soil A and B, respectively, remained in soil, whereas, in the case of aged soils, 86.3 and 67.7% of the applied did. Meanwhile, without vegetation, more than 98.3% of the applied, in both fresh and aged residues, remained in soil, suggesting that quinclorac was relatively persistent chemically and microbiologically. Most of the non-extractable soil-bound residues of []quinclorac were incorporated into the organic matter and largely distributed in the fulvic acid portion.