EFFECT OF FORMULATION AND TILLAGE PRACTICE ON VOLATILIZATION OF ATRAZINE AND ALACHLOR

Conservation tillage practices are being implemented by many farmers t o conserve water and soil resources. These practices may modify the so il surface in ways that differentially effect dissipation of pesticide when compared to conventionally tilled fields. We measured volatiliza tion of atrazine 2-chloro-4-ethylamino-6-isopropylamino-s-triazine] an d alachlor [2-chloro-2'-6'-diethyl-n-(methoxymethyl) acetanilide] appl ied as either an experimental starch-encapsulated formulation or as a commercial formulation, containing atrazine as a wettable powder and m icroencapsulated alachlor, to adjacent no-till and conventionally till ed corn fields in Maryland. Both formulations were applied at the same rate; 1.7 kg ha(-1) for atrazine and 2.8 kg ha(-1) for alachlor. Afte r 35 d, cumulative volatilization of alachlor from conventionally till ed fields was 14% of that applied for both formulations. Cumulative vo latilization of alachlor was less from no-till fields with 9% of the c ommercial formulation and 4% of the starch-encapsulated formulation be ing lost. After 35 d, cumulative volatilization of the commercial form ulation of atrazine from the conventionally tilled field was 9% of tha t applied compared with 4% of that applied to the no-till field. Starc h encapsulation reduced volatilization losses of atrazine to <2% of th at applied for both tillage practices. Starch encapsulation appears to be a viable formulation modification for reducing volatilization loss es of herbicides, especially from no-till fields.