Dissipation of Glyphosate and Glufosinate Ammonium in Soil and Weed Control in Citrus orchards, under Egyptian Conditions

: Glyphosate (GLY) and glufosinate ammonium (GLUA) are broad spectrum, non-selective, contact herbicides which are commonly used in fruit farms. Achieving the separation and detection of glyphosate and glufosinate from soil samples by chromatograph are 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 HPLC-UV detector. The residual detection limit 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 soil is very short, only for 7 days, following applications of 1 to 2 kg/fed in 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 in 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