Kolorimetrische Bestimmung von Dicyandiamid in Böden

A colorimetric method for the determination of dicyandiamide in soils A colorimetric method derived from the diacetyl reaction for the determination of creatine has been developed for the determination of dicyandiamide in soil extracts. Dicyandiamide reacts with 1-naphtol and diacetyl forming a red colour complex with maximum absorption between 535 and 540 nm. The detection limit ranges between 0.1 and 0.3 mg dicyanidiamide-N/100 g soil. In soil extracts neither naturally occurring substances nor metabolites of dicyandiamide influenced this colour reaction. After addition of 1, 5, 10, 20 mg dicyandiamide-N to 100 g soil and immediate extraction by water an average recovery rate of 95% was found. The relative standard deviation amounted to ± 1.60%.     

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.     

Bestimmung von nichtaustauschbarem Ammonium in Böden mit einer Halbmikromethode

Determination of non exchangeable Ammonia in Soils by a semicro method A semi-micro version (sample weight 0,1 g) for the determination of nonexchangeable NH₄⁺ of soils, based on the method of Silva and Bremner (1966) is described. The results of the semi-micro version are compared with the original method. The regression-coefficient is r = 0,9906. Analysis time is reduced by a factor of 2, reagent needs approximately by a factor of 20. Exactness and reproducibility are satisfactory for routine measurements. Pampean soils from Argentina, analyzed with the semi-micro method contain between 50 and 90 ppm nonexchangeable NH₄⁺.     

Kurzfristige pH-Pufferung von Böden

Short-time pH buffering of soils Changes in pH of 60 soils after HCl addition were related to reaction time and soil characteristis. Between 80 and 100% of the added protons were taken up by the soils within a few seconds, resulting in the release of exchangeable Ca, Mg and Al in strongly acid soils. The decrease of proton activity between 0.25 and 30-70 h can be formally described as a diffusion process. pH buffering depended on soil pH and organic C content but not on clay content. Buffering decreased from pH 3.5 to about 6 and increased again up to pH 7. Increase of C_org increased buffering mainly from pH 6-7.     

Bestimmung der Lagerungsdichte in stark skeletthaltigen Böden

Determination of bulk density in stony soils A new method is represented which makes it possible to measure the bulk density easily even in the case of stony soils. First results demonstrate the reliability of this new method.     

Stickstoffdynamik von Böden mit Abwasserverrieselung

Nitrogen dynamic of soils with wastewater irrigation The nitrogen status of a Sandy Cambisol and a Loamy Luvisol of Berlin, which were flooded with wastewater over a period of 100 years were studied. The two-year examination of the water, redox and nitrogen dynamics showed great differences in nitrogen leaching and the intensity of nitrification and denitrification processes.     

Methodenvergleich zur pH-Bestimmung von Böden

Comparison of methods for determining of soil-pH Comparative studies are being described of pH-determinations in suspensions with m-KCl, 0.1 m-KCl, 0.01 m-CaCl₂ and water of soils derived from loess and sand. For a standard the pH-values in 0.01 m-CaCl₂-suspensions were chosen, considering, that such CaCl₂-solution reflects best conditions in natural soil solution. Mean differences of pH(H₂O)-, m-KCl- and 0.1 m-KCl-values as compared to pH(CaCl₂)-values were + 0.56, — 0.27 and — 0.02 for the soils derived from loess, and + 0.63, — 0.11 and + 0.18 for those from sand. Taking into account the pH-dependence of the difference pH(CaCl₂)-values were + 0.56 – 0.11, — 0.27 – 0.26 and — 0.02 – 0.21, for the soils derived from loess, and + 0.63 – 0.21, — 0.11 – 0.14 and + 0.18 – 0.10 for those from sand. Taking into account the pH-dependence of the difference of pH(H₂O)-values of sandy soils, and its dependence on the present electrolyte content with all soils, further the unequal differences of the pH(KCl)-values with soils from loess as compared to sand, and their particular large variability with soils from loess, it is being argued that the CaCl₂-method may only insufficiently be substitued by any one of these methods. pH-values obtained at a soil-to-liquid-ratio of 1:2.5 were only slightly different from those with a ratio of 1:1. A suspension effect could not be observed with the application of a glasselectrode.     

PH-Verteilung und Pufferung von Böden

PH-distribution and buffering of soils A frequency distribution of the pH values of 927 soils clearly reflects the three soil buffer ranges (carbonate, pH-dependent charge and aluminium release) by higher frequencies within these ranges and lower frequencies between them.     

Abbau von Monolinuron in verschiedenen Böden

Degradation of monolinuron in different soil types The degradation of ¹⁴C-methyl, -ureido- and -phenyl-labelled monolinuron was studied in laboratory experiments with different soil types. Mineralization of the ureido-group was followed by two methods. It was found, that the mineralization rate depends on the soil. For the herbicide monolinuron there was a definite degradation characteristic. The release of ¹⁴CO₂ from the methyl- and ureido-group was faster than from the phenylring. In soil extracts monolinuron was found together with one or two radioactive substances not yet identified. Soil respiration was unchanged after the application of monolinuron. In a sterile soil no degradation occurred.     

Die N-Mineralisierung von Böden im Laborbrutversuch

N mineralization in soils under laboratory incubation conditions The potential rate of release of nitrogen by the organic matter in agriculturally used soils was determined under laboratory conditions by means of incubation. Mineralization of the more resistant soil organic matter proceeded linearly with time during an incubation period of 2–3 weeks, when field-moist and air-dried samples were used and at the beginning of the incubation experiment sufficient water was added to bring them to saturation. Mineralization was taking an exponential course in soils with additions of easily decomposable organic matter or in soils with a higher proportion of organic residues from crops. For the 14 investigated arable and grassland soils great variations in the average daily rate of mineralization were found ranging from 5–60 μg N_min/10 g DM. The data correlated very well with the biomass (r = 0.96) and the cell-free protease activity (r = 0.98) of the soils. Different measures of soil management (preceding crops, application of sewage sludge, addition of heavy metals) had a more or less pronounced influence on the rate of mineralization. The optimum temperature was 50°C for N mineralization and 26°C for nitrification. Contrary to nitrification, the soil reaction had only little influence on mineralization and proved also independent of the N_min content of soils. The results indicate that ammonification of organic N compounds may largely proceed via the microbial biomass.     

Eignung von 0,1 M BaCl2-Lösung zur Bestimmung der Kationenaustauscheigenschaften kalkhaltiger Böden

Determination of the CEC of carbonate soils with unbuffered 0.1 M BaCl₂ Soils containing carbonates and precipitated calcium carbonate, respectively, were percolated with unbuffered 0.1 M BaCl₂ followed by 0.1 M MgCl₂ and anorganic acids of the same concentration. The measured concentration of bases (including Ba⁺⁺) in the percolates indicates, that precipitation of Ba⁺⁺ or exchange with Ca⁺⁺/Mg⁺⁺ on carbonate surfaces occurs during percolation, which leads to an overestimation of exchangeable bases. From the total amount of Ba⁺⁺ bounded in such a way the less part is dissolved/exchanged by MgCl₂ solution in the following leaching step. So the CEC of carbonate soils seems to be generally overestimated too, by the method applied in a not exactly measurable degree.     

Die Verwendung von Antimon-Elektroden zur pH-Messung in Böden

The application of antimony electrodes for soil pH measurements Glass electrodes are unsuitable for long-term, micro-volume pH measurements in soils because of their form, size and drying of the glass membrane. Sb-electrodes are suited for pH measurements in soils whose oxygen saturation does not vary excessively. pH values determined with Sb electrodes decrease with increasing water tension or decreasing moisture. Colour changes of pH indicators confirm this trend.     

Unterscheidbarkeit von Humusfraktionen in Böden bei unterschiedlicher Bewirtschaftung

Differences in the properties of soil organic matter as a result of differing soil managements The organic matter of 62 soil samples from 20 farms was analyzed by the following methods: total organic C, “light” C (density < 2 g/ml) and C content and Q 4/6 of extracts obtained with NaF and NaOH solutions under different conditions. The soil samples were obtained from 10 pairs of adjacent plots; in each pair one of the plots was under “conventional”, the other under “bio-dynamic” management. The results obtained by the different laboratory methods evidenced more or less clearly the different managements. C extracted by shaking the soil with 0,5 % NaOH was most significant in that respect. The results as a whole are coherent in showing that in the soils under bio-dynamic treatment of higher content of the more easily decomposable fractions of the organic matter as compared with the soils under conventional treatment can be detected by rather simple means.     

Die Adsorption von HCB und DDD in Böden

The Adsorption of HCB and DDD by soils A method for studying the adsorption of substances with low water solubility by soils has been set up. The method has been verified by two chemicals (HCB, DDD) and a number of different soils. The results have shown a significant correlation between the distribution ratio and the content of organic carbon.     

Extraktion von Schwermetallen aus Böden mit Ionenaustauscherharz

Extraction of Heavy Metals from Soils by Ion Exchangers The aim of this investigation was to optimize an extraction method for the analysis of available heavy metals (Cd, Cu, Pb, Zn) in soils. LEWATIT was used as an ion exchanger (IEX) which absorbs heavy metals specificly. A special extraction vessel with two chambers was developed to recover the IEX from the soil solution. Nitric acid was used for the desorption of heavy metals from the ion exchanger. The described method measures water soluble and exchangeable ions as well as acid soluble heavy metals. The amount of acid soluble heavy metals can be regulated by conditioning the IEX with K⁺. Using an IEX conditioned with 30% K⁺, the maximum change of pH in the soil solution was 2 units. This is the same range of acidity changes occuring in the rhizosphere of plants by nutrient uptake. The extract contains no organic compounds. Thus the co-determination of stabil organic complexes is excluded. Accordingly, this method is also feasible for the investigation of forest soils with humic layers.