Effect of paraquat on the nitrogen-fixing activity of white clover

Abstract
The effect of paraquat at rates equivalent to 0, 70 and 280 g a.i.[active ingredient]/ha, on the N-fixing activity of white clover (Trifolium repens L. ''Grasslands Huia'') was studied. Plants were grown in nutrient culture, and the N-fixing activity was determined using the acetylene reduction method. Paraquat caused a marked decrease in the N-fixing activity, both on a per plant and a unit weight basis. The change was detectable 24 h after spraying, and no recovery was detected by day 16.