Dissipation of Glyphosate and Glufosinate Ammonium in Soil and Weed Control in Citrus Orchards

Glyphosate (GLY) and glufosinate-ammonium (GLUA) are broad-spectrum, non-selective, contact herbicides that are commonly used in fruit farms Achieving the separation and detection of glyphosate and glufosinate from soil samples by chromatography is a challenging task as they are ionic and highly water-soluble compounds. The aim of this study is conducted to determine the dissipation of GLY and GLUA applied at two dose levels in three-depth soils of orange orchards. The residues of GLY and GLUA were determined by the HPLC-UV detector. The residual detection limits of GLY and GLUA of the method were 0.03 and 0.05 ng/g in soil respectively. The obtained data indicated that GLY persistent in the soil is very short, only for 7 days, following applications of 1 to 2 kg/fed in the orange crop. GLUA dissipated in soil within 14 days of application, regardless of dose. The half-life (T/2) of GLY and GLUA were 1.68 and 1.42 days at 0 cm depth, respectively. There was no significant difference between the half-life of the two herbicides in soil at three depths. These results showed that GLY dissipation occurs rapidly in soil. However, GLUA was moderately persistent in soil. The two compounds tested showed a reduction of dry weight for four types of weeds after 14 days of recommended and double-rate application.