Abstract: The present invention primarily relates to the use of compositions comprising L-glufosinate and/or salts thereof in a glufosinate tolerant field crop in foliar application, wherein the compositions contain less than 5 mol.-% of D-glufosinate and/or salts thereof, based on the total amount of L-glufosinate and salts thereof, under certain environmental conditions to achieve an increase in the control of harmful plants and/or a reduction of phytotoxicity in the tolerant field crop. The present invention also relates to according methods of treating a tolerant field crop using the mentioned compositions.