Der Einfluß von Mineralisationsvorgängen auf die Nährstoffdynamik von Böden: II. Mitt.: Veränderung der Nährstoffbindungsformen und Löslichkeits-verhältnisse von Kalium und Phosphor

Abstract

After 11 days of incubation under the conditions described in the first information, i.e., addition of organic matter in the form of dextrose, fructose, clover dust, and straw dust; re-in-oculation of the soils with their natural population or with Penicillium nigricans , with addition of nitrogen (ammonium nitrate) or without such addition, the following changes occurred in the availability of nutrients. The content of water-soluble calcium increased in the examined soil types rendzina, brown earth, and staugley by about the double amount. It depends, however, also on the carbon sources applied, since the nutrient release is especially high with dextrose and fructose addition, respectively. The same applies to the addition of ammonium nitrate. The correlation co-efficients show with brown earth and staugley a significant negative correlation between the p H values, ascertained after incubation, and the content of water-soluble calcium from: brown earth r = -0,66, staugley r = -0,59, rendzina r = ±0. The reason for this may probably be found in the shifting of the carbonate: bicarbonate ration in both the first-mentioned soil types. The content of water-soluble potassium increased by desorption processes, above all in staugley, a soil type with a higher part of anorganic colloids. With rendzina and brown earth and in the control as well, immobilizations are indicated by the addition of dextrose and fructose, respectively. Contrary to this, addition of straw, but above all of clover resulted in essential increases; the same applies to the addition of nitrogen. Again the correlation coefficients show a significant relation between p H value and water soluble potassium: brown earth r = 0.71, staugley r = 0.62, rendzina r = 0.40. The content of lictate-soluble potassium increased with staugley during incubation again, but also rendzina showed an essential increase beyond the initial value. The addition of nitrogen improves the solubility. With both the soil types poorer in humus, a relation between the p H value after incubation and the lactate-soluble content of potassium is found: brown earth r = 0.81, staugley r = 0.71. The detected content of exchangeable potassium differs only slightly from that of the lactate-soluble, except in rendzina. This soil type shows distinctly that it possesses greater reserves of potassium in more difficultly available forms that were easier accessible to the ammonium acetate solution than to the calcium lactate. The exchangeable potassium as well as the non-exchangeable potassium are, however, exceptions excluded (dextrose and fructose addition), forms of K-linkage which by relatively short-timed changes of the biological activity can be less influenced. The content of lactate-soluble phosphate is subject to small increases only; a certain part of the dissolved phosphate, however, was evidently immobilized, especially by addition of nitrogen and by inoculation. With calcium, aluminuim, and iron phosphates, re-arrangements into other forms of linkage take place during incubation. In rendzina and brown soil the content of calcium phosphate increases at the expence of aluminium and iron phosphates. For the increase of calcium phosphate above all the addition of dextrose and clover is responsible. The highest degree of convertion during incubation takes place with aluminium phosphates. Evidently a greater part of them is also immobilized. The iron phosphates are distinctly altered in their content only in brown earth.