Effect of formulation on the movement of atrazine, alachlor, and metribuzin in a coarse-textured soil

Atrazine, alachlor and metribuzin are three widely used herbicides which have been detected in groundwater. Increased concerns over pesticide use have stimulated interest in developing formulations that reduce environmental risks such as groundwater contamination. The effect of controlled release formulations and acrylic polymer additives on herbicide movement in a Plainfield sand was evaluated in field and soil column experiments. Controlled release formulations included starch-based encapsulations of the three herbicides and a commercially available microencapsulation.Field and column studies indicated that starch encapsulations were not effective in reducing alachlor movement compared to the conventional emulsifiable concentrate formulation. However, the alachlor microencapsulation resulted in greater surface concentrations and reduced leaching of the herbicide compared to emulsifiable concentrate and starch-based controlled release formulations. Compared to the dry flowable formulation, starch encapsulation did not affect metribuzin distribution in the field but slightly reduced leaching in columns.In soil columns, acrylic polymer additives reduced atrazine leaching from 9-21% compared to the atrazine without the additives when 7.6 cm of water were applied. With increased water volume and time, the effectiveness of several polymer treatments diminished. Starch encapsulation was more effective than any polymer additive in retarding atrazine movement. Nearly all of the recovered starch encapsulated atrazine was retained in the surface 5 cm of the column compared to less than 18% of the dry flowable formulation. While the starch encapsulated atrazine evaluated was effective in reducing atrazine leaching, the formulation has resulted in reduced bioavailability and weed control in field trials.Oat bioassays conducted in the greenhouse indicated that smaller starch encapsulated granules increased atrazine bioavailability and provided activity equivalent to the unencapsulated atrazine formulation. The smaller granules were also effective in reducing atrazine leaching. This study indicates that finer starch granules should result in adequate atrazine bioavailability for weed control in addition to reduced leaching.U of I OnlyETDs are only available to UIUC Users without author permissio