Leaching and degradation of 4-aminopyridine-14C in several soil systems

Leaching and degradation of 4-aminopyridine (a frightening agent for protecting grain crops from blackbirds) was studied in seven soils. Carbon-14-labeled 4-aminopyridine was strongly adsorbed onto soil colloids, with the degree of adsorption related to pH. Application of seven in. of simulated rainfall over 20 days to surface-treated alkaline soils leached 0.02% to 0.18% of the¹⁴C; radioactivity was detected in the runoff from only one of the four acidic soils. Degradation of 4-aminopyridine-¹⁴C to¹⁴CO₂ was negligible in soils incubated up to two months under anaerobic conditions. Under aerobic incubation, there was a one-week lag before extensive breakdown began. Degradation rates increased with increasing temperature and soil moisture during incubation, but soil composition had a greater influence. After three months at 30°C and 50% moisture, evolution of¹⁴CO₂ ranged from 0.4% for a highly acidic loam (pH 4.1) to more than 50% for a lighter-textured, alkaline, loamy sand (pH 7.8); the half-life of 4-aminopyridine in soils under these test conditions ranged from 3 to more than 22 months. A theoretical scheme is presented for the degradation of 4-aminopyridine in soils.