Vorstellung der SrCl2-Methode nach Bach zur Bestimmung der effektiven Kationenaustauschkapazität und Vergleich mit der NH4Cl-Methode

Presentation of the SrCl₂-method after Bach for the determination of the effective cation exchange capacity and comparison with the NH₄Cl-method The SrCl₂-method for the determination of the effective cation exchange capacity CEC_eff has been developed by Dr. H. Bach, a former geochemist of the “Geologisches Landesamt Schleswig-Holstein”. Exchangeable metallic cations in soils are displaced by a 0, 1 M SrCl₂-solution and analyzed from the percolate. Reexchange of strontium by a 0, 1 M MgCl₂-solution allows to determine the CEC_eff by analyzing for strontium in the second percolate. In comparison with the customary application of NH₄Cl, SrCl₂ shows the following advantages:

• 1 The nearly unbuffered SrCl₂-solution adopts instantly the pH of the soil.
• 2 In contrast to the weakly acid NH₄Cl-solution, no H₃O⁺-cations compete with the exchange cation. Furthermore, partial dissolution of clay minerals is prevented because of the near-neutral character of the SrCl₂-solution.
• 3 The SrCl₂-method can be applied on all types of soils including carbonate- and salt-bearing soils.
• 4 The amount of free (dissolved) cations can be approximated.

     

Zur Bestimmung der Kationenaustauschkapazität von Böden mittels Barium

Regarding the Determination of Cation Exchange Capacity of Soils with Barium Very often the cation exchange capacity (CEC) of soils is determined using Ba⁺⁺ as exchange cation. In soils with high contents of organic matter, Ba⁺⁺ cannot be desorbed completely by Mg⁺⁺ or H⁺ but by Ca⁺⁺. Soils containing vermiculite adsorb Ba⁺⁺ in non exchangeable form. The fixed Barium can only be determined by total digestion. Therefore in soils containing vermiculite the exchange with Ba⁺⁺ leads to an underestimation of the CEC.     

Vergleich zwischen Perkolation und Extraktion mit 1 M NH4Cl‐Lösung zur Bestimmung der effektiven Kationenaustauschkapazität (KAKeff) von Böden

Comparison between percolation and extraction with 1 M NH₄Cl solution to determine the effective cation exchange capacity (CEC_eff) of soils A simple method is proposed for the determination of the effective cation exchange capacity (CEC_eff). The soil is extracted with 1 M NH₄Cl‐solution, manually shaken for three times, and the exchangeable cations are determined by ICP‐OES and pH‐measurement. Comparison with corresponding results of the percolation method (n = 110 samples) shows good agreement in reproducibility, exchangeable cations (except Fe and Na), base saturation and CEC_eff.     

Die Bestimmung der Aggregatstabilität - ein Methodenvergleich

The determination of aggregate stability - a comparison of methods The mechanical load bearing capacity and strength of aggregates against external forces can be described and quantified by indirect test (wet sieving method) and direct tests (e.g. crushing test, direct shear test). With the mean of the crushing test and the direct shear test in the shear box it is possible to achieve definite stresses, with which the influence of pore water pressure on soil stability can be explained by the occurence of water menisci forces. It is also possible to proof the pore water pressure dependent increase of strain by the particle reorientation during the process of aggregation. By the method of wet sieving, however, the summarized effect of hydraulic and mechanical processes can be described qualitatively only. A definite relation to single processes is therefore not possible.     

Die analytische Bestimmung der Dehydrogenaseaktivität in Unterwasserböden

The analytical determination of dehydrogenase activity in underwater soils The determination of dehydrogenase activity in recent underwater soils is often troublesome, because of lack of homogeneity of the fresh samples. Mainly the occurrence of very low redox potentials in the lower horizons causes chemical reduction of triphenyl tetrazolium chloride (TTC), which gives misleadingly high dehydrogenase activities. This could be eliminated by a toluene treatment preceding the TTC incubation, by which bacterial dehydrogenase production is inhibited and chemical TTC reduction can be determined. Homogeneity is increased by intensive stirring immediately before weighing the aliquots.     

Die Bestimmung der Wasserspannungs- /Wasserleitfähigkeits-Beziehung von Bodenaggregaten

Determination of the unsaturated hydraulic conductivity of soil aggregates by use of microtensiometers The hydraulic properties of single aggregates were measured with the use of microtensiometers. They are small enough (tip diameter 1 mm, length 1–2 mm) that two of them can be installed inside an aggregate within a distance of 1–3 mm. The changes of water suction are measured with pressure transducers and recorded by a micro-computer. Results obtained for different aggregates show, that at the same water suction, the hydraulic conductivity of single aggregates is up to 2 orders of magnitude smaller than that of the bulk soil. The cross-over-suction value for aggregates can also be derived.     

Die Messung der Katalaseaktivität von Böden

The determination of Catalase Activity in Soils by Dr. Beck 1. The elaboration of a method for the determination of the activity of catalase in soils is described. The method envolves the gasvolumetric determination of oxygen released by decomposition of a H₂O₂-solution by soils, suspended in buffers in the presence and absence of the catalase inhibitor NaN₃. 2. The influences of the following factors on catalase activity were studied: Methods for the determination of developed oxygen, enzyme- and substrate concentration, inhibition of catalase by NaN₃, pH- and temperature-optima of catalase and the presence of plant residues in soils. 3. It was found, that there was only a little decrease in catalase activity when fresh or dried samples of soils were stored over a periode of 4 months under laboratory conditions. The catalase activity of different soils showed very good correspondence to the dehydrogenase activity of the soils and less correspondence to the amount of soil respiration and the amylase activity. No relation could be found to the number of microorganisms in soil.     

Die Phosphatmobilität im Hochmoorboden in Abhängigkeit von der Düngung

Phosphate mobility in relation to fertilizing effects in raised-bog peat The phosphate solubility of raised-bog peat soils is very different from the phosphate solubility of mineral soils. Compared to mineral soils the losses of phosphates by leaching are 10 to 20 times higher. This mobility of phosphates is destined by the quantity, kind and time of fertilizing, land use (grassland or arable land) and fertilizing technique. Field and lysimeter trials with raised-bog peat soils show: 1. Water soluble phosphates are quickly translocated and leached. 2. Water insoluble phosphates are quickly solved and leached in raised-bog peat soils. The mobility of the phosphates decreases with increasing pH-value of the top soil and topdressing. At a pH-value of 4,O nearly 80% of Thomasphosphat and nearly 70% of Hyperphos phosphates are leached in lysimeter trials; at pH-value of 4 3 only 17 % of Thomasphosphat and 15 % of Hyperphos phosphates are leached. 3. To minimize leaching losses phosphate fertilizingin spring is recommended to reduce the phosphate leaching. 4. The phosphate leaching in grassland is twice or thrice less than in arable land.     

Die Standortsbewertung der biologischen Aktivität von Böden über Ermittlung der Bodenatmung und der zellulolytischen Aktivitatät im Feld

Intersite estimation of biological activity of soils by determination respiration and cellulolytical activity in the field A temperature differentiated scale of estimation is presented, which is derived from long-term investigations of respiration and cellulolytic activity. This is suitable for intersite comparison of different soil-ecosystems. Investigations in spring are representative and could be done during mapping the soil-ecosystems. It exists a strong correlation to the quality of the humus body and to the available nutrients.     

Die Erodibilität ausgewählter Böden der bayerischen Schichtstufenlandschaft

Erodibility of Selected Soils in the Bavarian Scarpland A laboratory rainfall simulator was used to determine the erodibility (K-factor of the USLE) of 6 soils. 3 of the soils were developed from mesozoic sediments (an Ochrept and an Udipsamment from sandstones, an Udorthent from shale), an Udalf and an Udorthent of loessial origin, and an Udorthent, that was developed from a silty-loamy cover. The measured K-values of the loessial soils agreed well with the calculated. But the calculated K-factors for the 3 Jurassic soils underestimated their erodibility. The erodibility of the silty-loamy soil was overestimated. It could be shown that the measured erodibilities agreed better with field data than the calculated.     

Die räumliche Variabilität von Schwermetall-Konzentrationen in Niederschlägen und Sickerwasser von Waldstandorten des Sollings

Local variability in the heavy metal concentrations of precipitation and seepage water from forest sites in the Solling Concentrations of Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb in precipitation and seepage water have been measured continuously with local replicates during a 6-months period at a beech and a spruce forest site. Variation coefficients of the avarage concentrations were, in most cases, well below 30 %, being mainly caused by local differences. Comparison of means showed a significant increase of heavy metal concentration in the canopy drip of beech (Mn, Fe, Pb) and spruce (Cr, Mn, Fe, Ni, Zn, Pb) compared to bulk precipitation measured in the open field. Concentration of Mn, Co, Ni, Zn and Cd in the seepage water is significantly higher under spruce compared to beech. These results point at higher filter efficiency of the spruce canopy, compared with beech, for air pollutants, but a smaller retention capacity of the soil under spruce for heavy metals.     

Die Veränderung der Phosphatintensität der Bodenlösung eines Pelosol-Pseudogleys nach Grünlandumbruch

Long-term change in phosphate intensity in a clay soil after turning grassland into arable land In a 7years field experiment on a poorly drained clay (Pelosol-Pseudogley) after turning permanent grassland into arable land, the phosphate concentration in the soil solution (P_l) decreased and P retention (P_s) increased even if as much as 265 kg P ha^?1 was added in excess of plant uptake. Neither loss in organic matter nor disaggregation of the well aggregated grassland soil by soil management seemed to be responsible for this decrease in P_l. Instead, a slight increase in pH within the 7 years and, to a lesser extent, a concomitant increase in exchangeable Ca are assumed to have caused the decrease in P_l. Laboratory experiments in which pH, exchangeable Ca and ionic strength were varied support the field results. A multiple correlation between P_l and pH plus exchangeable Ca explained 89% of the variation of P_l whereas pH and Ca alone explained only 76 and 42%, respectively. Solubility data placed the solutions around the hydroxyapatite (HA) isotherm even when P-fertilizer were added in excess of plant uptake. It seems unlikely, therefore that HA governs P_l in this soil. Instead, the results are in favour of surface P adsorption to determine P_l. The effect of exchangeable Ca and ionic strength is then explained by their effects on the thickness of the electric double layer which in turn influences P adsorption.