High and low volume sprayer technologies in sorghum stubble. Applicationefficiencyandenvironmentalrisks

Keywords: droplet density, hollow cone, water sensitive cards


The use of low application rates in systemic herbicides spraying is a usual practice in Argentina. Field trials were carried out with a self propelled boom sprayer in sorghum stubble with the aim of evaluatin the efficiency and environmental risks of glyphosate® application alternatives. Two spraying techniques were compared: High application rate (AV) with TT 11002 Teejet® nozzles and 70 l ha-1, and Low application rate (BV) with AD5 AC13 Albuz® hollow cone nozzles and 30 l ha- 1. Droplets density (DD), coverage (C), and Volume Median Diameter (VMD) were quantified by water sensitive cards and image processing software CIR 1,5® at three locations: between row crops (EL), near row crop (EI)  and above sorghum cover residue (ES). Efficiency was calculated from droplets stains and corrected by chromatography determination of solution recovery on Petri dishes. Both techniques exceeded the recommended droplet density for herbicides, but AV was significantly higher. Coverage was 13.77% and 11.06% for AV in ES and EI, while in BV it only reached values of 3.46% and 2.36%, with significant differences between treatments. In EL there were no differences. Solution recovery rate was 51.56% in AV and 21% in BV over ES.  BV had low efficiency values in DD, C and TR. Weeds control near sorghum row crop may be compromised by the low amount of glyphosate that reaches this location and increase environmental risk contamination.