Nitrogen availability and glyphosate hormesis on white oat

Abstract

Background:  The effect of low rates of glyphosate has been widely studied in several crops. Low nitrogen stress reduces carbohydrate synthesis and we hypothesize that hormesis from glyphosate occurs at low nitrogen availability.

Objective:   To evaluate the effects of glyphosate hormesis at different levels of nitrogen on the growth and yield of white oat.

Methods:   A two-factor factorial (2x7) was conducted in field testing at nitrogen levels (50 and 90 kg ha^-1) and low rates of glyphosate rates (0 - 180 g a.e. ha^-1). The glyphosate was applied at the second node already formed. The growth and yield were evaluated.

Results:  Plant height was not affected by the nitrogen levels. A low rate of glyphosate induced a plant height increase up of around 10%, but the stimulus was no maintained over in the time. Glyphosate hormesis had a greater effect on dry weight under low nitrogen than under high nitrogen conditions. The glyphosate provided a 43% increase in dry weight at a low nitrogen level when applied at rates consistent with a 4.1% field rate. Glyphosate hormesis increased the yield by approximately 30%, and the yield was higher yield under low nitrogen conditions.

Conclusions:  The plant height stimulus from low doses of glyphosate was not sustained over time. Glyphosate hormesis stimulus persisted and culminated in an increase in dry weight and grain yield. The hormesis effect on dry weight and yield is more pronounced under lower nitrogen availability.

Keywords:  Avena sativa ; low rate; herbicide; growth stimulus; yield