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.     

Simulation des Anionen-Transports in ungestörten Bodensäulen unter stationären Fließbedingungen

Simulation of anion transport in undisturbed soil cores under steady-state flow conditions Miscible displacement experiments with undisturbed soil columns were carried out in the laboratory. Objective of the experiments was to collect information about the transport of Cl^? and NO₃^? through field soils. The experiments were carried out with a forest soil and an agricultural soil. The flow velocity of the chloride and the nitrate solution was either 1 cm/day or 0,3 cm/day. Of each soil there were 5 replicates. The effluent of each of the columns was analyzed and the collected data were used for model calculations. It was found that the breakthrough curves of Cl^? and NO₃^? were similar in shape. For the well-aggregated forest soil the apparent diffusion coefficient was much larger than for the agricultural soil. For both soils practically all of the chloride could be recovered in the effluent, but for nitrate considerable losses within the soil column were noted. It was also found that the chloride breakthrough could be described with a simple convection-dispersion equation. However a reduction of the total pore space, accounting for anion exclusion, was needed. Furthermore it was observed that for nitrate an additional sink term in the convection-dispersion equation was needed to account for the observed nitrate losses. It appears that the transport of nitrate and chloride through the soils that were studied can be described mathematically, provided the anion exclusion space and the rate of nitrate losses are known. The nature of the anion exclusion and the nitrate transformation needs further study.     

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.     

Die Bedeutung der Umsetzung von Weizenstroh im Hinblick auf den C- und N-Haushalt von Löß-Ackerböden

The significance of wheat straw decomposition with regard to the C- and N-cycle of a cultivated loess soil In 1984/85, a microplot experiment with ¹⁵N-enriched fertilizer was carried out on a field of the Calenberg loess area near Hannover (surface area of the plots: 1 ± 2 m; experimental soil: stagnigleyic cambisol from loess). On the one hand, the extent of immobilization as well as remobilization of native soil- and fertilizer-N associated with straw incorporation (± 8 t/ha) was quantified. On the other hand, the turnover as well as the alteration of C- and N-masses in the decomposing straw material was studied. About 70% of the initial dry organic matter of straw was mineralized within one year. An enrichment of fertilizer-N as well as native soil-N in the residues of up to 20 kg/ha was observed as compared to the initial N-mass. On a microplot cropped with winter-wheat, microbial N-immobilization of about 30–40 kg/ha (native soil-N and fertilizer-N) occured in the soil after straw incorporation. The immobilization extended to march 1985. Subsequent, associated with a C/N-ratio in the straw of 43, N-remineralization as well as -extramineralization was observed with 40 kg/ha at maximum in december 1985.     

Die Böden von Wallhecken in Schleswig-Holstein I. Klassifikation und Genese

Soils of Mound Hedges in Schleswig-Holstein I. Classification and Genesis In typical landscapes of Schleswig-Holstein soils of mound hedges were investigated (FAO (1989): Cumulic Anthrosol). New soils have been developed from the deposit of the mound hedge in less than 250 years. A classification with regard to the German classification of natural soils is suggested. The soil genesis from sandy deposits has reached the step of Dystric Regosols, groundwater has induced gleyic features. Soil genesis could be described chronologically, if time of deposition of these mound hedges is known. Some of the natural soils are conserved below the deposit. Pedogenesis in an area, changed by man, could be reconstructed. This is why systematic, scientific soil investigations of mound hedges may be very interesting.     

Bodenhydrologische Methoden zur Untersuchung ungestörter,skelettreicher Böden

Soil hydrological methods for investigations on undisturbed samples of skeleton-rich soils New methods are proposed, which allow the determination of moisture transmission properties of stony soils. A soil sampling technique is discussed whereby small monoliths are isolated from the surrounding soil and covered with polyester-soaked glassfiber sheets. With use of such irregularly shaped columns the soil moisture characteristic and the unsaturated hydraulic conductivity are determined by laboratory procedures. Starting with a saturated column, suction is applied and the resulting outflow is measured. At the same time the suction in the sample is registered and also the hydraulic gradient within the sample is determined. Also discussed is a procedure to install tensiometers in stony soils. The installation provides reliable data and the maintenance is easy. By building in a heating system in the tensiometers, these can be operated all year round.     

Die Bestimmung von selektiv freisetzbarem Kalium in Parabraunerde aus Löß und Pelosol aus Gipskeuper-Tonmergeln

The determination of preferentially releasable potassium in hapludalf from loess and chromudert from gipskeuper clay marl Octadecylammonium-chloride (ODA)-extractable potassium and interlayer potassium (K_ZW), exchanged after thermal dissociation of adsorbed NH₄, were determined on particle size fractions of soils from gipskeuper clay marl (typic chromudert) and loess sediments (shallow hapludalf). The extraction by ODA is a diffusion controlled K-exchange process. This is shown by the increase of K-release at small sample quantity and K-concentration in the extraction solution. The ODA-potassium supplies (= Biotit-K) of the two typic chromudert were significantly higher than that of the shallow hapludalf (34000 and 30000 kg/ha vs. 22000 kg/ha, to a depth of 55 cm). Biotit-K was highest in the 2-6μm-fraction for both soils. The smaller the particle size, the larger were the amounts of K_ZW In the clay fractions of all samples they reached between 70 and 80% of total K (K_t). XRD-data give evidence of different mineral genesis processes between the two types of sediments. This is supported by the K_ZW-values of the particle-size fractions. The selectively releaseable interlayer potassium is associated with wedge shaped layers of illite. It can be differentiated from the bulk interlayer potassium by its preferential extractability in the first 3 to 5 heating treatments. This potassium quantity is, on an average, 22% of total clay interlayer potassium.     

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.     

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.     

Cesium- und Strontiumaustauscheigenschaften von Marschböden

Cesium and Strontium Exchange Properties of Marsh Soils The cesium and strontium exchange properties of some typical marsh soils of the estuary and lower river Weser region were described. Soil samples were taken according to the existing soil maps 1:25000 of Lower Saxony e.g. a “sea marsh soil”. a “brackish marsh soil”, and a “river marsh soil”. The exchange properties were determined by Cs/Ca and Sr/Ca exchange curves (Q/I relations) as generally used in soil potassium research. In addition to the Q/I relations the following investigations were carried out: - Cs and Sr desorption experiments (one time equilibration with Ca⁺⁺ solutions) - Cs and Sr reexchange experiments (eight times equilibration with water, Ca⁺⁺, Ba⁺⁺, and K⁺ solutions) - the naturally-occuring Cs and Sr contents of the soils including amounts caused by imissions or fallout, respectively - clay mineral composition and swelling of layer silicates due to saturation with Ca⁺⁺, Sr⁺⁺, Cs⁺, and K⁺ ions. Q/I relations as well as desorption and reexchange experiments indicated strong cesium and low strontium fixation by the soils investigated. This was considered the reason for the stronger transfer of Sr from soil to plants as compared with Cs. Furthermore, the reexchange experiment revealed nearly complete reversibility of the Sr sorption reactions by equilibration with the divalent cations Ca⁺⁺ and Ba⁺⁺ and some Sr fixation after treatment with K⁺ solutions. However, cesium was much better reexchanged by K⁺ than by Ca⁺⁺ and Ba⁺⁺ ions. This led to the conclusion that Cs fixed in interlayer positions of clay minerals could be remobilized by potassium and ammonium fertilization. The naturally-occuring Cs contents of the soils were found to be below the detection limit of the analytical methods used. The contents of naturally-occuring exchangeable Sr, however, was in agreement with the amounts of “labile Sr” as derived from the Sr/Ca exchange curves. Concerning the cesium exchange properties a clear distinction between “sea and river marsh soils” on the one hand and “brackish marsh soils” on the other hand was established due to differences in clay mineral composition and swelling state of 1:2 layer silicates. The different cesium exchange properties of the two soil groups could also be verified by more or less pronounced hysteresis effects of sorption (Q/I relation) and desorption curves.     

Die Chromosomenzahlen von Thymian und Bohnenkraut

Ohne Zusammenfassung     

Die Komplexierung von Cu,Pb und Cd durch heißwasserlösliche Huminstoffe II. Die Stabilität der gebildeten Komplexe

Complexation of Cu, Pb, and Cd by hot water soluble humic substances II. The stability of the complexes Soxhlet extracts of terrestrial and underwater soils were used to determine polarographically the stability of heavy metal complexes. Stability constants were calculated using the law of mass action. They were independent of concentration at levels higher than 2 mg Cd or 5 mg Pb/g humic substance, respectively. For Cu, constants increased below 8 mg Cu/g. At pH values in the polarographic medium between 4 and 8, the stability of the Pb complexes increased markedly with increasing pH. In most cases this was also valid for the copper complexes, cadmium complexes were either not influenced by pH or stability maximum was obtained at about pH 5. Drying of the samples before extraction did not alter significantly complex stabilities. Complex stabilities increased with increasing degree of humification for oligotrophic, underwater soils and nutrient poor, low moor peat, but reduced horizons of eutrophic gyttjas exhibited lower stability values.     

Die Sorption von Phosphat an carbonatreichen Unterwasserböden

The sorption of phosphate by underwater soils rich in carbonate The phosphate sorption isotherms for carbonate rich under water soils (Unterwasserboden) can frequently be linearized by a modified Freundlich-isotherm when one assumes that, because of previously sorbed phosphate, the concentration of the equilibrium soil solution, P_1,0 is greater than 0. However, in many cases, the character of the phosphate sorption can be adequately determined with only one phosphate addition (P_s,500). Both methods show that for dried samples from under water soils, the samples from reduced horizons have a higher P sorption than for the associated oxidized horizons. This can be explained by the presence of very sorption active ferrihydrite which has precipitated from previously biologically reduced material.     

Die Persistenz von Chlorcholinchlorid in Weizenpflanzen während der generativen Wachstumsphase und in lagernden Weizenkörnern

The persistance of chlorocholine chloride in wheat plants during the reproductive stage and in the kernels during storage In pot experiments with spring wheat the metabolization of the growth regulator chlorocholine chloride (CCC) has been studied during the reproductive stage. Also the persistance of ¹⁴C labelled CCC in wheat kernels has been examined during a period of one year. The following results were obtained:

• 1 The mobility of CCC in the plant was very low. Even when CCC was applied at a late stage (beginning of ear emergence), 98 to 99% of the applied ¹⁴C activity remained in the shoots and only 1 to 2% were translocated towards the ears. Also when CCC was twice applied the CCC content in the ears amounted only to 1 to 2 ppm.
• 2 Chlorocholine chloride was very stable in the plants and only a small percentage was converted to choline. Thus by far the main proportion of the applied ¹⁴C activity was recovered in the form of CCC and only 2 to 5% were found in the choline fraction. ¹⁴C activity in the other chemical fractions of the plant material was extremely low or zero.
• 3 In the choline fraction of the kernels the ¹⁴C activity amounted to 12% of the total ¹⁴C activity and thus was twice as high as in the straw. This relatively high 14C label in the choline fraction could be related to metabolic processes typical for grain growth. It is also possible that choline synthesized in the leaves is more easily translocated towards the kernels than chlorocholine chloride.
• 4 The mature kernels stored at room temperature did not show any metabolization of CCC during a period of one year. Neither the total ¹⁴C activity nor the content of CCC were altered significantly during this time.