Hormesis of Glyphosate in Sugarcane.

Hormesis is defined as stimulating and beneficial effect of substances initially considered toxic in high doses, but at low doses does not have damage at plants. Glyphosate, the herbicide most widely used in agriculture, has been widely researched in studies of hormesis. The objective of this research was to evaluate the hormesis effect under low dose of glyphosate herbicide at morphological variables and the end yield of sugarcane. The experiments were carried out and evaluated during one-year of sugarcane cycle at plant crop in 2010 at APTA, Jaú, SP, Brazil. The variety used was the SP80-1842 and treatments were application and non-application of low dose of glyphosate. The application of the treatments was 70 days after planting and the low dose used was 1.8 g e a ha^-1 of glyphosate. In the first experiment was evaluated: tiller number, length of stems, number of internodes, internode length, diameter of stems, leaf area and dry mass of stems, leaves and shoots, at plots of three rows of three meters, in which was collected a meter for evaluations in 70, 105, 140, 175, 210, 245, 280 and 315 days after planting, in a randomized block with six replications. In the second experiment, of yield, were evaluated ton of cane per hectare (TCH) and ton pol per hectare (TPH). There were increases in all morphological variables with low doses application of glyphosate, except at internode length and diameter of stems. There was hormesis effect on crop yield, an increase of TCH and TPH of treated compared to non-treated with low dose of glyphosate. The increase in the morphological variables converged in an increase in yield; the application of low dose of glyphosate in sugarcane becomes a promising tool in their management.

Keywords: Saccharum spp., isopropylamine salt of glyphosate, low dose.