The present invention relates to a composition comprising a) an anionic compound having wetting and dispersing properties selected from the group of a1) an alkyl naphthalene sulfonate, a2) a naphthalene sulfonate-formaldehyde condensate that may optionally be alkyl substituted and mixtures thereof, and b) a nitrogen-containing surfactant selected from the group consisting of alkylamine alkoxylates, alkylamidoamine alkoxylates, alkanolamides and their alkoxylates, alkylamidopropylamines, betaines, amino acids, or any mixtures thereof, wherein < the weight ratio between a) and b) is between 99.99 : 0.01 and 40 : 60 while > the molar amount of anionic sulfonate and, if any are present, carboxylate groups in the composition is in excess of the molar amount of nitrogen-containing groups. These compositions exhibit synergistic wetting properties as compared to the surface-active components taken alone. Further, the compositions also exhibit an increased rainfastness. The compositions can be used as a wetting agent and/or as an agent for increasing rainfastness in cleaning or agrocultural formulations. The invention also relates to an agrocultural formulation per se.La présente invention concerne une composition comprenant a) un composé anionique présentant des propriétés de mouillage et de dispersion choisi parmi le groupe constitué de a1) un alkyle naphtalène sulfonate, a2) un condensat naphtalène sulfonate-formaldéhyde pouvant éventuellement être substitué en alkyle, et leurs mélanges, et b) un tensioactif contenant de lazote choisi parmi le groupe consistant en les alkoxylates dalkylamine, les alkoxylates dalkylamidoamine, les alkanolamides et leurs alkoxylates, les alkylamidopropylamines, les bétaïnes, les acides aminés, ou des mélanges quelconques de ces composés, le rapport massique entre a) et b) étant compris entre 99,99 : 0,01 et 40 : 60, alors que la quantité molaire de sulfonate anionique et, sils sont présents, des groupes carboxylates dans la composition excè
