SOIL-TEMPERATURE AND WATER EFFECTS ON DISSIPATION OF COMMERCIAL AND STARCH ENCAPSULATED ATRAZINE FORMULATIONS

Experiments were conducted in controlled environment chambers to evalu ate the effects of temperature and soil water content on the time of d issipation of commercial (CF) and starch encapsulated (SE) atrazine fo rmulations to one-half the original concentration (T50), SE samples we re also analyzed for the amount of atrazine remaining within the starc h particles (percent encapsulation). The dissipation of CF atrazine wa s affected by changes in temperature and soil water content, SE atrazi ne dissipation was most influenced by changes in soil water content ra ther than temperature, Independent of soil water, there was no atrazin e dissipation from any formulation at 15 C, The T50 for CF atrazine at 20% soil water content was 53.4 and 29.9 d for 25 and 35 C, respectiv ely, At 20% soil water content, all SE treatments gave a T50 greater t han 60 d, The percent starch encapsulation at 20% soil water content w as greater than or equal to 55.8 and 30.4% for SE large and SE small, respectively, This high level of encapsulated atrazine accounts for th e reduced SE dissipation observed at 20% soil water content, At 40% so il water content, the dissipation of CF and SE small atrazine were not different for either 25 or 35 C, Compared to the CF, the SE large for mulation extended the T50 by 7.4 and 6.7 d at 25 and 35 C, respectivel y, At 40% soil water content, there was no encapsulated atrazine prese nt in SE formulations 60 DAT.