Effect of Nitrogenous Materials on the Uptake of Triazine Herbicides

Abstract

An application of potassium nitrate or urea to the soil of detopped potted tomato plants [Lycopersicon esculentum Mill.] increased the rate of exudation from the stumps of the plants from 100 to over 300% and increased the concentration of 2-chloro-4-ethylamino-6-isopropylamino-s-triazine [atrazine] in this augmented exudate from 9 to 40%. Atrazine applied to the soil at 2:00 PM was detected in the stump exudate within 10 min and with an application of 3500 μg per pot it was approaching its maximum concentration by the end of 3 hr. The build-up in the concentration of atrazine in the exudate occurred at a faster rate in plants treated with potassium nitrate than in water control plants. Increasing the soil temperature from 10 to 30 C increased the rate of exudation and at each temperature an application of potassium nitrate or of urea increased the concentration of atrazine in the augmented exudate. In addition to atrazine, 2-chloro-4,6-bis(isopropylamino)-s-triazine [propazine], 2-methoxy-4,6-bis(isopropylamino)-s-triazine [prometone], and 2-methoxy-4-ethylamino-6-isopropylamino-s-triazine [atratone] were applied at 1750 and 3500 μg/pot. The concentration of these triazines in the exudate increased directly with their solubility in water. An application of urea increased the concentration of all four triazines in the exudate.