Die Bedeutung der K-Ca-Austauschisotherme für eine Beurteilung der K-Versorgung der Pflanzen bei Lößböden

K-Ca-exchange isothermes of soils from loess and the potassium supply of plants From 80 Ap-horizons of Luvisols and Phaeozems on loess from south of Hannover K-Ca-exchange isotherms and cation concentrations in saturation extracts were investigated. Though not K deficient these soils show a very wide range of available K. From the very high K-concentrations in the saturation extracts (up to 3 meq/1) of part of the soils it was concluded, that mass flow should be sufficient for plant needs of K. The only soil property varying the exchange isotherms seems to be the clay content (Fig. 4). In order to calculate available K from the exchange isotherms in the same way as available water from pF characteristics the isotherms were extended down to activity ratios, according to literature, marginal for plant uptake of K (Fig. 6). The estimated soil K content, sufficient for plant in loess soils, amounts to about half that considered marginal by the regional extension service. With the assumption that so called non exchangeable, but plant available K is essentially very slowly exchangeable, an experiment was performed at 80°C to accelerate the exchange and to establish a true equilibrium. The comparison between the new exchange curve and the 25°C curve (Fig. 8) seems to reveal additional 180–450 kg/ha · 30 cm bound with equal free energy of exchange as easily exchangeable K.     

Entwicklungen in der Ökologie der Bodenmikroorganismen—eine Übersicht

Developments in the ecology of soil microorganisms - a review In the ecology of soil microorganisms, much interest is focussed at present to the factors of soil microenvironment. The ability of solid particles to adsorb different microorganisms, their nutrients and metabolites is investigated. Furthermore, the macroecological factors, such as geographic locality, climate, soil temperature, moisture etc., which influence the distribution of different microorganisms in soils are considered. Microorganisms and their activity in soils of tropical and arctic regions are also investigated. Concerning the temperate zone, the extensive research of microbial ecology is continued, in order to maintain soil fertility and to solve different environmental problems.     

Der Einfluß der Expositionszeit auf die Höhe der Bodenatmung bei Anwendung der Lundegardhmethode

The influence of exposure time on the magnitude of soil respiration under employment of the Lundegardh-procedure To assess the role of carbon-rich soils under a potential climate change much more data are needed then currently available. These have to be collected also under conditions, where only limited technical and personal resources are available. Therefore the easy to be accomplished Lundegardh-procedure, which is accepted as a standard procedure for exposure times up to 24 hours (Anderson, 1982), was tested for its suitability to longer periods of exposure. For this purpose six Lundegardh-traps were installed on seven consecutive days (treatment B), and the means of the six repetitions added to a weekly value. In the immediate vicinity to the former, six Lundegardh-traps were installed for periods from one to seven days (treatment A) This was done during the warm season as well as in the winter. The comparison of the treatments A and B revealed a linear correlation, which allows to substitute cumulated daily values by values of traps, that have been installed for several days. However, the “chamber-effect”, an overestimation of respiration by the traps installed for more than 24 hours found by Tesarova and Gloser (1976) has to be considered. In the summer, the same degree of overestimation (16%) was found as reported by Tesarova and Gloser (1976). In the winter, far lower absolute values and therefore higher statistical importance of extremes led to an overestimation of 46%.     

Einfluß der Konzentration der Huminsäuren auf ihre Fragmentierung in Alkalilösungen

The influence of concentration of humic acids on their fragmentation in alkaline solutions The fragmentation of synthetic and other four natural humic acids with accending concentrations in sodium hydroxide solutions would be examined. It was found that the fragmentation decreases with increase of concentration of the humic acids. A critical concentration at 0,2% is needed for the begin of retard reactions and the micell formation. The fragmentation of humic acids with high fragmentation rate will be less influenced by change of the concentration than those whose fragmentation rate are low.     

Morphologie und Alter von Böden der Südlichen Frankenalb und der nichtkarbonatische Mineralbestand der Kalksteine

Morphology and age of soils in the ‘Südliche Frankenalb’ and the noncarbonate mineral composition of the limestones Soils in the ‘Südliche Frankenalb’ are described according to their local particle size and color characteristics, and their typical situation in the landscape. ‘Solifluction’ (mixing of limestone fragments with terra fusca solum) and sedimentation of aeolian material were the important processes which complicate the reconstruction of soil formation. The quantities of carbonate-free residues of limestones vary in a wide range between 0.7 and 25.4%. With this property, a grain size- and a mineralogical property, the limestone samples are separated by discriminant analysis in three groups. In contrast, the clay mineral composition of all the limestone residues is very homogeneous. In the fine clay fraction (< 0.2 μm) and coarse clay fraction (2-0.2 μm) illite and illite/smectite mixed layer minerals are the predominant minerals with proportions of 90% and 80–85%, respectively. The time necessary for soil formation is calculated to be 1.6 (20 cm depth, IIT-horizon) and 2.7 million years (36 cm depth, IIT + Bv₂-horizon), respectively. This calculation is based on a Malm Delta limestone (0.7% residue). The carbonate output is calculated from CaCO₃ solution rates in the CO₂-H₂O system and actual leaching rates derived from local climate data. The period of soil formation from other limestones was not as long.     

Die Ermittlung der Porengrößenverteilung aus der Körnung,dem Gehalt an organischer Substanz und der Lagerungsdichte

The estimation of pore size distribution from texture, organic matter content and bulk density Using regression analysis the dependence of the pore size distribution of soils on the compactness and percentage of organic matter, clay and silt was studied on 450 soil horizons. From the results nomograms for determination of the pore size distribution were constructed. The average deviation between pore size distribution as read from the nomograms compared and determined in the laboratory is ～ ± 3 Vol.-%.     

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.     

Gefügeänderung bei Andosolen Südchiles als Folge der Nutzung seit der Rodung

Changes in soil structure as caused by land use after clearing virgin forest Three groups of volcanic ash soils from southern Chile were investigated to evaluate the change of porosity, penetrometer resistance and packing characteristics of virgin forest soils due to different forms of land use during a variable length of time. The different forms of land use were pasture, arable land and reforestation with Pinus radiata. Afforestation tended to loosen the soil and to increase soil strength, whereas pasture use or a pasture-arable land rotation showed severe compressions. Compressions, as noticed in the ash soils under study, appeared to be more pronounced than is generally observed in mineral soils.     

Wirkung der Kaliumdüngung auf die Kaliumverfügbarkeit in der Rhizosphäre von Raps

Influence of potassium supply on the availability of potassium in the rhizosphere of rape (Brassica napus) Potassium depletion of the soil in the proximity of roots was studied in order to obtain quantitative information on the availability of potassium. For this purpose rape seedlings were grown in pots which separate roots from soil by a fine meshed screen; root hairs penetrated the screen. The soil adjacent to the screen was sliced by microtome into layers about 0.1 mm thick which were separately analysed for k. Plant roots strongly depleted the soil in their proximity; further distant ranges remained unchanged. A loess derived loam, brought to different levels of exchangeable K by precropping or K application, was equally depleted to 150 μmoles/100g soil at the root surface. Therefore, the quantity of K released from this source increased with initial K level. In addition, the distance of the depletion zone extended with K level from 4,6 to 6.3 mm from the surface of the root cylinder. Hence, the volume of soil contributing K to the root increased from 0.7 to 1.2 cm³ per cm root length. The combination of these two parameters, i.e. the quantity of exchangeable soil K released per unit of root length increased by a factor of 20 whereas exchangeable soil K was raised by a factor of 4.5 only. K uptake of the plants after 4 days was in agreement with the depletion of exchangeable soil K in the high K treatment only. The other treatments had obviously taken up considerable percentages of nonexchangeable K. This fraction was released from the soil ranging less than 1.5 mm from the root. The distance of the K depletion zone was also extended by application of NaCl and MgCl². Because of cation exchange, K concentration of the soil solution was increased, K buffer power decreased and, therefore, K diffusion was enhanced. It is concluded that plants in the field do not uniformly deplete the total rooted soil volume. Whereas roots in their proximity strongly deplete the soil including parts of nonexchangeable K they do not even use exchangeable K in a slightly greater distance. The quantity of K available per unit of root length is, therefore, determined by both - the degree of soil K depletion at the root surface and -the distance of the depletion zone, i.e. the volume of soil that contributes K to the root. Either factor was markedly affected by the level of soil K and thus by K application.     

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.     

Bilanzierung der Tonbildung und -verlagerung sowie der Tonmineralumwandlung in Löß-Parabraunerden

Balances of alteration and migration of clay fractions and clay minerals in Gray Brown Podzolic Soils from Loess Balances of alteration and migration of clay fractions, clay minerals, K, Mg and Fe bound in clay silicates were calculated for Gray Brown Podzolic Soils (Parabraunerden) derived from Young Pleistocene Loess below arable and forest land in the district south of Würzburg. The extent of clay formation lies between 63 and 98 kg/m², of which 60–80 % belong to the fraction <0.1 μm. The clay migration varies between 35 and 51 kg/m², the fractions < 0.2 μm (especially the fraction <0.1 μm) predominating, the coarse clay being involved only to a smaller extent. During Holocene soil formation 121 kg illite, 16 kg vermiculite and 11 kg kaolinite per m² are formed in the clay fraction (< 2 pm). The loss of smectite amounts to 68 kg/m². The biggest alterations of the clay mineral quantities occur in the fraction <0.1 pm; they indicate a smectite-illite transformation. Illite, at 23 kg/m², accounts for half of the clay migration, followed by smectite and vermiculite each at 9 kg/m² and kaolinite at 5 kg/m². When comparing the migrated with the present amounts no preference of certain clay minerals during clay migration can be determined. In the clay fractions the gained Fe (3.07?4.32 kg/m²) and K (2.75?3.84 kg/m²) predominate over Mg (0.57?1.15 kg/m²). The three elements accumulate to the greatest extent in the fine clay fraction. The element migration parallels the gain. The balances of the elements are discussed in connection with pedogenic illite formation as well as biotite and vermiculite disintegration.     

Einfluß der Strohdüngung auf den Verlauf der N-Mineralisation eines Löß-Parabraunerde-Ap-Horizontes im Säulen-Brutversuch

The influence of straw manure on the course of N-mineralization of a luvisol-A_p-horizon in incubation experiments with soil columns In 1983 and 1984, different treated soil columns were incubated at 35°C to investigate N-mineralization and -immobilization of a luvisol-Ap-horizon (length of the column: 30 cm; diameter: 8 cm). Treatments were as follows: ?undisturbed”?, ?disturbed”? and ?disturbed + straw”? (quantity of straw: =8 t/ha/30 cm; particle size: 10 cm). (soil characteristics: 17,5% clay, 76,5% silit, 6% sand). In 1983 up to 65 kg/ha/30 cm of inorganic nitrogen were assimilated microbially as the result of straw (C/N of straw: 132:1) compared to ?undisturbed”? and ?disturbed”?. After 65 days of incubation immobilization was reserved. The soil water content amounted 65% of the water holding capacity. In 1984 incubation under same conditions, but a C/N of straw of about 80:1, yielded an immobilization of about 55 kg/ha/30 cm compared to ?undisturbed”?. Comparing the straw treatment to ?disturbed”? a maximal immobilization of 45 kg/ha/30 cm was registrated. In the treatments with field capacity up to 55 kg/ha/30 cm were determined as difference between ?straw incorporated”? and ?disturbed”?. A reverse of immobilization resulted after ca. 65 days at both water levels. Concerning the untreated monoliths netto-mineralization was highly reduced particularly in the lower part of the Ap-horizon.