An composition comprising: (A) a mixture comprising at least one (thio)phosphoric acid triamide according to the general formula (I)

R.sup.1R.sup.2NP(X)(NH.sub.2).sub.2, wherein X is oxygen or sulfur; R.sup.1 is a C.sub.1 to C.sub.20 alkyl, C.sub.3 to C.sub.20 cycloalkyl, C.sub.6 to C.sub.20 aryl, or dialkylaminocarbonyl group; R.sup.2 is H, or R.sup.1 and R.sup.2 together with the nitrogen atom linking them define a 5- or 6-membered saturated or unsaturated heterocyclic radical, which optionally comprises 1 or 2 further heteroatoms selected from the group consisting of nitrogen, oxygen, and sulfur, and (C) at least one amine selected from the group consisting of (C1) a polymeric polyamine, and (C2) an amine containing not more than one amino group and at least three alkoxy- or hydroxy-substituted C.sub.2 to C.sub.12 alkyl groups R.sup.21, wherein at least one of the groups R.sup.21 is different to the other groups R.sup.21, and (C3) an amine containing not more than one amino group and at least two alkoxy- or hydroxy-substituted C.sub.2 to C.sub.12 alkyl groups R.sup.22, wherein at least one of the groups R.sup.22 bears the alkoxy or hydroxy substituent at a secondary or tertiary carbon atom and wherein at least one of the groups R.sup.22 is different to the other group(s) R.sup.22, and (C4) an amine containing at least one saturated or unsaturated C.sub.8 to C.sub.40 alkyl group R.sup.23, and (C5) a saturated or unsaturated heterocyclic amine which contains at least one oxygen atom as ring atom and which does not contain a further alkoxy group.