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.
Highlights
White oats (Avena sativa L.) is a multi-purpose cereal integrated as a human food, due to its content of quality protein and soluble fibers
For plant height at 23 and 38 days after application (DAA), and weight of a thousand grains (WTG) an effect was only verified for the glyphosate rate (Table 1)
Stimulatory effects of low rates of glyphosate on the height of height of white oat were observed, where plant height increased by 18 g a.e. ha-1 of glyphosate at 23 AD, while at 38 DAA the increase occurred up to 7.2 g a.e. ha-1 (Figure 2)
Summary
White oats (Avena sativa L.) is a multi-purpose cereal integrated as a human food, due to its content of quality protein and soluble fibers It is used in animal nutrition, being used for hay, silage, feed composition and forage (Malavolta and Moraes, 2007). Objective: To evaluate the effects of glyphosate hormesis at different levels of nitrogen on the growth and yield of white oat. 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 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
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