Interactions of Light, Temperature and Moisture on Terbutryn Toxicity

Abstract

Toxicity of soil-applied 2-( tert -butylamino)-4-(ethylamino)-6-(methylthio)- s -triazine (terbutryn) to cucumbers ( Cucumis sativus L. ‘Gemni’) and oats ( Avena sativus L. ‘Nodaway’) was increased 2.2 times when the light intensity was raised from 11,000 to 22,000 lumens/m 2 and 1.5 times when the moisture level was raised from low (25 to 50% field capacity) to high (75 to 100% field capacity). When the temperature was raised from the low level (19 C day, 14 C night) to the high level (29 C day, 24 C night) toxicity of terbutryn to oats was increased 1.6 times and toxicity to cucumber was increased 1.3 times. Analysis of interactions of the three variables on toxicity of terbutryn showed that environmental conditions favoring rapid growth resulted in an increase in phytotoxicity.