The relationship between the Na⁺, K⁺, Ca²⁺ and Mg²⁺ concentration in water extracts from composts made of anaerobic sewage sludge from the sugar industry and the electric conductivity of the extracts was investigated for the purposes of estimating the maturity of composts. The conductivity values proved to be correlated with the concentration of the cations. The determination coefficients were statistically significant (p = 0.05) for composts with an addition of structure-forming materials (straw, farmyard manure). This means that the measurement of conductivity can be used to estimate the degree of mineralisation of composted materials.

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