Influence of various fertilization on the mineralogical composition of clay fractions in long‐term field experiments

Abstract

AbstractSoil samples from several long‐term experiments in the German Democratic Republic (GDR) were taken from plots with and without K‐supply. The fine, medium and coarse clay fractions were isolated using ultrasonic dispersion and sedimentation techniques and then investigated by x‐ray. Comparisons between the mineralogical compositions found and the results of x‐ray analyses of clay fractions from untreated Ah‐horizons of the same sites point to accelerated mineral transformations in unfertilized plots. Reductions in the illite contents are proved using the x‐ray diffraction diagrams. In connection with the question of the transformational products of this accelerated illite weathering, a new possibility for evaluation by curve‐fitting Lp‐corrected x‐ray diffraction diagrams was tested on one example. The degradation of the illites is partly accompanied with drastic reductions in the amounts of Ca‐lactate soluble and adsorbed K. Organic fertilization with 10 to 15 tons of farmyard manure per hectare per year prevented these negative mineralogical changes.