Der Einfluß von Mineralisationsvorgängen auf die Nährstoffdynamik von Böden: I. Mitt.: Die Umsetzung der organischen Substanz sowie Säurebildung

Abstract

In order to ascertain the changes in the availability of nutrients, induced by the biological activity of the soil, soil samples from the A-horizon of rendzina, brown earth, and staugley were supplied with dextrose, fructose, clover meal and straw meal, as well as with ammonium nitrate. After sterilization they were treated with different inoculations: a re-inoculation with the natural population or an inoculation with Penicillium nigricans . After 11 days of incubation, above all the transformations of the added organic matter, the formation of organic acids, and the resultant changes in the concentration of the hydrogen ions were examined. The carbon losses ranged, in general, between 20 and 30%, except with fructose addition, where the losses were less than 20%, and with brown earth and staugley in the dextrose variant with ammonium nitrate addition, where the losses are higher than 30%. In all the substrates that received additional carbon or nitrogen compounds, there occurred an enrichment of metabolic products, among others of organic acids. In rendzina the acid formation was only just slight after 11 days, while with straw meal addition the acid formation is completely lacking. Here the matter was decomposed up to the final products in most cases. In brown earth and staugley organic acids could be proved in all variants. This seems to indicate a certain tendency for maintaining the organic acids, but also for the presence of easily decomposable material even after 11 days. The resultant changes in the concentration of hydrogen ions are considerable in some cases. In rendzina the concentration of hydrogen ions decreased during the incubation, and with addition of clover meal it differed almost by one pH unit, compared with the initial value. In brown earth and staugley the concentration of hydrogen ions increased, except when clover meal was added. Both these soils had no chance for neutralizing the hydrogen ions, originating from microbial metabolic processes. The demonstrable increase of the pH value in all the soils with clover addition might have its origin in the ammonification of the organic N compounds abundantly present.