An amino acid based biostimulant program could reduce glyphosate phytotoxicity on turf-type tall fescue

The herbicide glyphosate, an aromatic amino acid synthesis inhibitor, is effective against annual bluegrass (Poa annua L) but it is not selective, therefore its use in turfgrass is very limited. However, an amino acid based biostimulant treatment over the turfgrass stand could minimize the glyphosate phytotoxicity while controlling annual bluegrass emerging seedlings. Laboratory and field experiments were conducted to investigate if an amino acid based biostimulant program, before and after a glyphosate application for annual bluegrass control, could prevent or reduce the herbicide phytotoxicity on (Schreb.) Dumort]. A mature turf was treated with the biostimulant at 20, 40, 60 or 80 L ha-1 in a preventive strategy; or in a curative strategy at 20 L ha-1 after a 0.28 kg ai ha-1(0.22 kg ae ha-1) glyphosate application, that was also sprayed over P annua seedlings that had NDVI, chlorophyll content, and dry clipping weight were determined. In both types of experiments, preventive applications of the biostimulant at high glyphosate application, while lower biostimulant application doses and a curative strategy were ineffective. Annual bluegrass control was erratic as it was totally affected by glyphosate only in the second field experiment.