Norwegian Journal of Agricultural Sciences : a laboratory soil incubation method to assess reactivity of liming materials for agriculture

Abstract

In order to establish a method for assessing reactrvity of liming materials for agriculture, a soil incubation method is introduced, in which a loamy soil which should be raised from pH 5.5 to 6.0 is adopted as a standard. The lime-soil interaction consists of two processes: dissolution of the liming material particles, and diffusion into the soil. Liquid chemical methods only estimate the dissolution rate over a short period, whereas the soil itself is the most precise medium for testing the agricultural liming materials, and for the slowly reacting silicates in particular, this would be an appropriate method. To refine this laboratory incubation method four extensive experiments were carried out in Norway, using loamy and peaty soils, adding several levels of carbonate liming materials of different particle size groups. Some of the experiments were run for at least 2.5 years, and correcting for the Scandinavian winter season 2.5 years in the laboratory should correspond to 5 years in the field. The characteristics of the two soil groups were very different, bul the relative differences between the liming materials remained principally the same, thereby presenting quite universal results. These investigations included limestones, Danish coral lime, dolomites and shell sand materials. The method was calibrated with Scandinavian field expcriments, which also supplemented the look-up tables with data on chalks. These look-up tables have enabled STIL (The National Agriculture lnspection Service) to forward annual documents on the ENV (Effective Neutralizing Value) of liming materials on the Norwegian market.