Preparations with improved urease-inhibiting effect and urea-containing fertilizers containing the latter

A preparation comprising at least two different (thio)phosphoric triamides having structures of general formula (I)

• R1R2N—P(X)(NH2)2 (I)
• wherein
• X is oxygen or sulfur;
• R1 is a C1-C10-alkyl, C3-C10-cycloalkyl, C6-C10-aryl, or dialkylaminocarbonyl group;
• and
• R2 is hydrogen, or
• R1 and R2
• 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,
• wherein said at least two different (thio)phosphoric triamides differ in at least one of radicals R1 or R2 and
• wherein a first (thio)phosphoric triamide from among the at least two different (thio)phosphoric triamides accounts for an amount of from 20 to 40% by weight and a second (thio)phosphoric triamide from among the at least two different (thio)phosphoric triamides accounts for an amount of from 60 to 80% by weight, respectively, based on the total weight of all (thio)phosphoric triamides present.