That comprises a first member I, which comprises a first receptacle 1 for a precise slurry or liquid manure sample with volume V1, a second member II, which comprises a second receptacle 2 for a precise water sample with volume V2, in order to prepare a dilution of the sample to be analyzed, characterized in that said members and receptacles are configured in such a way that they are susceptible to being coupled to one another in order to obtain said dilution, the volume ratio V1/V2 being determined such that the concentration of ammonium nitrogen (NH4 +-N) in liquid manure may be directly obtained from the electrical conductivity. The invention also relates to the process and the kit which use said device. Advantageously, all the parts of the device are susceptible to being integrated in a detachable manner to form a single piece.
