Zur Pedogenese und Klassifikation von Marschböden des Unterweserraumes. I. Gesamtnährstoffe,Carbonatgehalt, Kationenbelag und Diatomeenflora als Indikatoren für Sedimentations-Bedingungen und Bodenentwicklung

Development and Classification of Marsh Soils from the Unterweser Region, West Germany. I. Total Nutrients, Carbonate Content, Exchangeable Cations and Diatom Flora as Indicators of the Role of Sedimentation Conditions in Soil Development This study was carried out to see how much sedimentation conditions determine the properties– in particular the Ca/Mg ratio – of marsh soils (fluvaquents of coastel areas). The following results show, that the marsh soils properties are not determined by different sedimentation conditions: – The vertic fluvaquents don't have a higher clay content than the mollic and aeric fluvaquents – The total (t) contents of P, Ca, Mg, K and Na varied because of different soil development – The Ca_t/Mg_t ratio in soils with CaCO₃ was higher than in soils without CaCO₃, and – related to the Ca_a/Mg_a ratio – it can also be used as a classification characteristic (a = exchangeable) – The Ca_a/Mg_a ratio varied greatly because of differences in exchangeable Ca content. Vertic fluvaquents sometimes, but not often, have a higher content of exchangeable Mg than the mollic and aeric fluvaquents. Comparing maps of the Weser area as it appeared at various times in the Holocene with the soil map, shows that the sedimentation pattern is invariably brackish-marine. This is further confirmed by the diotom flora of the soils tested. Thus the properties of marsh soils, long believed to be dependent on sedimentation conditions, are the product of different continuance and intensity of soil development.     

Zur Pedogenese und Klassifikation von Marschböden des Unterweserraumes. II. Die Bedeutung von Schwefelmetabolismus,Methanproduktion und Ca/Mg-Verhältnis für die Marschen-Klassifikation

Development and Classification of Marsh Soils from the Unterweser Region, West Germany. II. Importance of Sulfur Metabolism, Methane Production and Ca/Mg Ratio for Classifying Marsh Soils The importance of sulfur metabolism in each step of marsh soil development (Brümmer, 1968) is also confirmed for the marsh soils of the Unterweser region. Sulfur contents and sulfur fractions indicate that soil development has advanced further in brackish marshes than in marine and river marshes. The results give additional evidence that the various properties of marsh soils are only partly caused by sedimentation conditions. – The sedimentation areas (Müller, 1954) apply only to small regions. Thus, methane production predominates in the freshwater area, while sulfate reduction predominates in the marine area. Both processes occur at high rates in the brackish area. Classifying soils on the basis of the Ca/Mg ratio gives the same soil groups as Brümmers classification. Consequently, classifying the marsh soils of Niedersachsen on the basis of Ca/Mg ratio is a suitable method, if the idea that sedimentation conditions cause soil properties – especially the contents of exchangeable Ca and Mg – and the present designations of the soil groups are rejected.     

Rekonstruktion des Ausgangszustandes und Bilanzierung von Böden einer Moränenlandschaft

Reconstruction of the original composition and balancing of soils developed on glacial till In this paper a method for the reconstruction of the original composition of soils formed on heterogeneous glacial till is described. As an exampel the original contents of carbonates, iron and clay were calculated in two soils. The soils investigated are “Rostbraunerde” under forest and ?Braunerde”? under meadow. The “Braunerde” has been regularly irrigated with waste water for the last 70 years. The heterogenity of the fine earth of the parent material is caused by the successive deposition of materials with varying particle size distribution as well as in situ cryoclastic weathering of the different rock fragments. The reconstruction was calculated from the relation between the above mentioned weatherable components and less weatherable components in the pleistocenic sediments of Berlin. The sorting grade (So, Muller, 1962), median (Md) of the particle size distribution in the 2–600 γ fraction and the contents of coarse sand, Zr and Ti in the fraction 2-2000 pm were considered as unweatherable. The calculations were performed using multi regression analysis. The influence of the pedogenetic processes of decarbonatisation, acidification, clay formation and clay migration as well as the pedological changes resulting from the waste water irrigation were quantified through the comparison between the calculated original and the measured actual contents of the weatherable components.     

Prognose der mechanischen Belastbarkeit und der auflastabhängigen Änderung des Lufthaushaltes in Ackerböden anhand von Bodenkarten

Prediction of soil strength of arable soils and stress dependent changes in ecological properties based on soil maps Based on a database of at present 160 mechanical soil profile datasets, the site and horizon dependent mechanical soil strength expressed as precompression stress can be predicted by multiple regression analysis and used for documentation in maps at different scales. Stress dependent changes in air permeability or air capacity can be derived for the virgin compression stress range as well as the effect of stress propagation in soils or stress attenuation capacity and depth dependent changes of ecological properties. Thus, areas with defined mechanical sensitivity as a function of depth can be derived and recommendations for site adjusted farming techniques can be given. In addition it allows the agricultural machine industry to develop site adjusted machines to support the ideas of good farming practice, defined by the soil protection law of Germany.     

Zur Interpretation erhöhter Schluffgehalte in Böden des Bayerischen und des Oberpfälzer Waldes

On the interpretation of raised silt contents in soils of the Bavarian and Upper Palatinate Forest For the Bavarian and Upper Palatinate Forest (Bavaria), 41 representative pedons were examined for aeolian components using grain‐size analysis. Soils derived from loess (three pedons) are only available in the foreland of the Bavarian Forest near to the river Danube. Soils with aeolian fractions (one pedon) also exist in the adjacent part of the Bavarian Forest. No indication for loess components (37 pedons) were found in all other parts of this mountain range: these soils are missing a coarse‐silt maximum in their upper layer as should be expected for loess‐influenced soils. However, 17 of these pedons have a medium‐silt maximum in their upper layer interpreted as a result of intense physical weathering. Therefore, the widely occurrence of soils with aeolian components cannot be confirmed for this low‐mountain range of E Bavaria.     

Ermittlung des Redoxpotentials (Eh-Wert) von Böden und Grundwässern aus dem zeitlichen Verlauf der Elektrodendepolarisation

Calculation of redox potential in soil and groundwater from the curve of the electrode depolarization An inherent problem with redox potential measurements in soil and groundwater is the initial drift of potential readings. This is caused by electrode depolarization. The depolarization kinetics corresponds to a first-order process, mathematically described by an e-function. Based on the depolarization kinetics a method was developed to calculate redox potentials (E_h-values) from only short time (= 10 min) measured depolarization curves. Besides the E_h-value this procedure gives the depolarization constant λ. The method was tested and verified by a number of depolarization measurements in soils and groundwater.     

Die Rolle der mikrobiellen Biomasse und des mineralisch fixierten Ammoniums bei den Stickstoff-Transformationen in niedersächsischen Löß-Ackerböden unter Winter-Weizen. I. Poolgrößenveränderungen

Significance of microbial biomass and non-exchangeable ammonium with respect to the nitrogen transformations in loess soils of Niedersachsen during the growing season of winter wheat. I. Change of pool sizes Nitrogen transformations in loess soils have been examined by laboratory and field experiments. After straw application (· 8 t · ha^?1), N in microbial biomass (N_mic) increased by about 20 mg · kg^?1 soil (· 90 kg N · ha^?1 · 30 cm^?1) after 9 days of incubation (20 °C). Another laboratory experiment yielded an increase of about 400 mg of NH₄+-N · kg^?1 fixed by minerals within 1 h after addition of 1 M NH₄+-acetate. Defixation of the recently fixed NH₄+ after addition of 1 M KCl amounted to only 60 mg · kg^?1 within 50 days. In a field experiment with winter wheat 1991, an increase in N_mic of about 80 kg N · ha^?1 · 30 cm^?1 was observed from March to June. After July, growth of the microbes was limited by decreased soluble carbon concentrations in the rhizosphere. Different levels of mineral N-fertilizer (0, 177 and 213 kg N · ha^?1) did not affect significantly the microbial biomass. The same field experiment yielded a decrease of non-exchangeable ammonium on the “zero”-fertilized plot in spring by 200 kg N · ha^?1 · 30 cm^?1. The pool of fixed ammonium increased significantly after harvest. After conventional mineral N-fertilizer application (213 kg N · ha^?1). NH₄+-defixation was only about 120 kg N · ha^?1 · 30 cm^?1 until July.     

Nitrat‐Austräge auf intensiv und extensiv beweidetem Grünland,erfasst mittels Saugkerzen‐ und Nmin‐Beprobung II Variabilität der NO3‐ und NH4‐Werte und Aussagegenauigkeit der Messmethoden

Nitrate leaching from intensively and extensively grazed grassland measured with suction cup samplers and sampling of soil mineral‐N II Variability of NO₃ and NH₄ values and degree of accuracy of the measurement methods Data from a grazing experiment — comparison of mean values, see Anger et al. (2002) — were used to estimate within‐field variability to asses the accuracy of two frequently used methods of estimating NO₃ leaching on pastures: (1) the ceramic suction cup sampling (with 34 cups ha^—1 minimum, calculated climatic water balance, 4 leaching periods) and (2) using the soil mineral‐N method (vertical soil NO₃ and NH₄ content in 0—0.9 m (N_min) measured at the beginning and end of two winters on a minimum of 10 different areas of 50 m² each with a minimum of 7 different sample cores). These methods were used on two permanent pastures with high mean stocking density of cattle of 4.9 LU ha^—1 on 1.3 ha with N‐fertilization of 250 kg N ha^—1 (= intensive [I]) and 2.9 LU without N fertilization on a 2.2 ha pasture (= extensive [E]). The results show that NO₃ leaching on pastures was largely due to few selectively extremely high NO₃ amounts under a few excrement spots — mainly urine spots — which would not be sampled representatively with an acceptable effort in a conventional grazing experiment. In both grazing treatments, very large spatial variation occurred. This was greater between the different suction cups than between the compound mineral N samples of each area. Therefore, a marked skewness and kurtosis demonstrated a non‐normal distribution of samples from suction cups, while mineral N values did not show this effect consistently. Sampling selected mostly spots without noticeable influence of excrement, but a few samples with very high values identified evidently urine spots from summer or autumn grazing. The differences in mean coefficient of variation (CV) between the grazing treatments and estimation methods were mainly based on the stocking rate and the density of excrement spots. CV values were 131 % [I] / 242 % [E] for NO₃ leaching measured with suction cup samplers and of 71 % [I] / 116 % [E] for soil NO₃ values and 24 % [I] / 34 % [E] for soil NH₄ values in 0—0.9 m according N_min‐method. Results of the N_min method are obviously inaccurate even with a sampling intensity much greater than 70 cores ha^—1; and so making an estimation of NO₃ leaching by this method is unsatisfactory for pastures. Compared to this, the results of suction cup sampling are more convincing; but even with a tolerated deviation of ± 20 % from the empirically estimated average and with a 95 %‐confidence interval, the calculated mean minimum number of samples in our experiment should be increased to 146 and 265 suction cups ha^—1 for the intensively and extensively grazed treatments, respectively. This requirement would be prohibitive for many field experiments.     

Cu‐, Zn‐ und Cd‐Aneignungsvermögen von zwei Spinatgenotypen in Abhängigkeit von der P‐Versorgung und Wurzelexsudation

Cu, Zn, and Cd acquisition by two spinach cultivars depending on P nutrition and root exudation Within a spectrum of 11 spinach cultivars (cvs) differences in the Cu, Zn, and Cd contents of shoots had been noticed. The aim of this study was therefore to analyze in more detail the acquisition of Cu, Zn, and Cd by the most differing cultivars (Tabu and Monnopa) in dependence on P nutrition. The plants were grown in a low phosphorus Luvisol (pH 6.3; total contents Cu: 89, Zn: 297, Cd: 2.4 mg kg^—1) with two phosphorus levels in pots under natural conditions. For the determination of inflow, root length/shoot weight ratio and of the Cu, Zn, and Cd concentration in the soil solution (rhizosphere) plants were harvested 26 and 40 days after sowing. Root exudation of organic acids of the two cvs was measured 35 days after growing in quartz sand with different P supply. Both cultivars responded to P fertilizer by doubling their shoot weight. With increased P supply (0.68—0.77% P in shoot‐DM) both cultivars showed similar heavy metal contents in the shoot resulting from similar root length/shoot weight ratios (RSR) and net uptake rates of the three elements as well as the same element concentrations in the rhizosphere soil solution. Under P deficiency, however, cv. Tabu (0.52% P in shoot‐DM) showed in comparison with cv. Monnopa (0.48% P) higher Cu, Zn, and Cd contents of shoots although its RSR was smaller than that of cv. Monnopa. However, the inflow for Cu was higher and for Zn and Cd significantly higher compared with cv. Monnopa. This result of cv. Tabu corresponded with higher concentrations of Cu, Zn, and Cd of its rhizosphere soil solution, and its higher exudation rates of oxalate, citrate, and malate (3.9; 1.0; 0.7 nmol cm^—1 h^—1). The corresponding values for cv. Monnopa were: 1.7; 0.3; 0.4 nmol cm^—1 h^—1. The mobilization of Cu, Zn, and Cd by the excreted organic acids seems to be responsible for the higher Cu, Zn, and Cd inflow of cv. Tabu.     

Einfluß langjähriger Gülledüngung auf den Nährstoffhaushalt des Bodens. 2. Mitteilung: Bindung und Löslichkeitskriterien der Bodenphosphate

Influence of long-term slurry application on soil nutrients. 2. Fractions and solubility criteria of soil phosphorus Fractions and solubility criteria of soil phosphorus accumulated by long-term slurry application were investigated. The following results were obtained:

• – Slurry application mainly resulted in higher concents of inorganic phosphorus, especially Fe-Al-P, even in deeper soil layers.
• – The accumulation of inorganic phosphorus resulted in an increase of phosphorus availability in all conventional extraction methods used, as well as in higher phosphorus concentration of the soil solution.
• – In the upper soil layers of luvisols and in the deeper soil layers of diluvial sandy soils organic phosphorus was enriched, but did not significantly influence phosphorus intensity and delivery.
• – Compared to soils supplied with mineral fertilizers there are no particularities in phosphorus dynamics, from which differences in the interpretation of “available” phosphorus values with respect to phosphorus recommendation scales could be concluded.

     

Die Rolle der mikrobiellen Biomasse und des mineralisch fixierten Ammoniums bei den Stickstoff-Transformationen in niedersächsischen Löß-Ackerböden unter Winter-Weizen. II. Umsetzung von 15N-markiertem Stickstoff

Significance of microbial biomass and mineral fixed ammonium with respect to the nitrogen transformations in loess soils of Niedersachsen during the growing season of winter wheat. II. ¹⁵N-turnover Field experiments 1988/89 on a fallow plot of the southern Niedersachsen loess area with straw application (δ 10 t · ha^?1, homogeneously incorporated by hand) yielded an increase in microbial biomass-N (N_mic) by 60 kg N · ha^?1 · 30 cm^?1 until March 1989 and further 40 kg N · ha^?1, till May which was almost completely remobilized until harvest. For a cropped plot (with winter wheat and 10 t · ha^?1 straw incorporation), N immobilization was of similar magnitude. Up to 18% of the applied ¹⁵N-fertilizer (185 kgN · ha^?1) were microbially immobilized. In contrast to 1988/89, no significant mass change of N_mic occurred in 1991 due to straw application (δ 10t · ha^?1). Variations in the amount of N_mic were nearly independent on the treatment (crop, with 140 kg fertilizer-N · ha^?1 or without N-fertilizer, respectively; fallow plot without fertilizer-N) within a range of 225-400 kg N · ha^?1 · 30 cm^?1. Directly after N-application (each 70 kg N · ha^?1 in March and in May), up to 100% of the fertilizer-N were assimilated by the microbes. Subsequently, remobilization of the immobilized nitrogen occurred within 2 (in March) or 6 weeks (in May), respectively. Simultaneously, organic soil-N was mineralized after each N-application and minerally fixed for us biggest part. Between March and June, the fixed NH₄+ decreased by about 112 kg · ha^?1 · 30 cm^?1.     

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.     

Einfluss eisenhaltiger Klärschlämme auf Kenngrößen der P‐Verfügbarkeit in Ackerböden

Influence of iron content in sewage sludges on parameters of phosphate availability in arable soils The use of iron salts for the P elimination in sewage plants is widely used. But it is not clear whether the P availability in arable soils is negatively influenced by iron compounds or not. The aim of the investigations was, therefore, to study the influence of two sewage sludges with a high and a low Fe content respectively on P sorption and phosphate concentration (P_i) in the soil solution after application of CaHPO₄ or sewage sludge to 5 loamy and 4 sandy soils (pot experiments and 1 silty loam (field experiment)). Soils were analyzed 1, 6, and 13 months after P application. Sludge Gö contained 12 kg P and 65 kg Fe (t DM)^—1 (P : Fe = 1 : 5.4) and sludge Sh 25 kg P and 39 kg Fe (t DM)^—1 (P : Fe = 1 : 1.5). The basic P application was 60 kg P ha^—1 (= 30 mg P (kg soil)^—1 in the pot experiment, as sludge or as CaHPO₄). P uptake by maize was determined in a separate pot experiment with a loamy soil and the same P application rate. The P sorption capacity remained similar in all soils after application of sludge Sh (P : Fe = 1:1.5) compared with soils without sludge, however, after application of sludge Gö the P sorption increased by 16% (0—59%). After application of sludge Sh the mean P_i concentration increased in loamy soils by 34% and in sandy soils by 15%. On the other hand the P_i concentration decreased after applying sludge Gö by 13% and 36% as compared to the controls of the respective soils. In the field experiment the P_i concentration of plots with a high P level (50 mg lactate soluble P (kg soil)^—1) was also significantly decreased after application of 10 t sludge Gö (126 kg P ha^—1) in comparison with triple phosphate. One month after the application of increasing amounts of sludge Gö (5, 10, 15 t DM ha^—1) both the concentration of oxalate‐soluble Fe in the soil and the P sorption were increased. The elevated relationship between these two parameters was highly significant (r² = 0.6 — 0.97). Plant uptake of P was less after application of sludge Gö than after application of sludge Sh and much less than P uptake from CaHPO₄. Sewage sludges with a P : Fe ratio of 1 : 5 should not be recommended for agricultural use, as the P availability is significantly reduced. Iron salts should not be used for conditioning of sludges.     

Nitrat‐Austräge auf intensiv und extensiv beweidetem Grünland,erfasst mittels Saugkerzen‐ und Nmin‐Beprobung I Einfluss der Beweidungsintensität

Nitrate leaching from intensively and extensively grazed grassland measured with suction cup samplers and sampling of soil mineral‐N I Influence of pasture management Leaching of nitrate (NO₃^—) from two differently managed cattle pastures was determined over four winters between 1993 and 1997 using ceramic suction cup samplers (with min. 34 cups ha^—1); additionally, vertical soil mineral‐N content in 0—0.9 m (N_min) was measured at the beginning and end of two winters (with min. 70 different sample cores ha^—1). The experimental site in the highlands north‐east of Cologne, Germany, is characterized by high annual precipitation (av. 1,362 mm between 1993 and 1996). An intensive continuous grazing management (1.3 ha, fertilized with 250 kg N ha^—1 yr^—1, average stocking density 4.9 LU ha^—1, = [I]) was tested against an extensive continuous grazing system (2.2 ha, av. 2.9 LU ha^—1; no N‐fertilizer but an estimated proportion of Trifolium repens up to 15 % of total dry matter in the final year, = [E]). The results can be summarized as follows: (1) Mean leaching losses of NO₃‐N, estimated from suction cup sampling and balance of drainage volume, were 85 kg NO₃‐N ha^—1 [I] and 15 kg NO₃‐N ha^—1 [E] during three wet winters with drainage volumes between 399 and 890 mm; in a dry winter with 105 mm calculated percolation, nitrate leaching decreased by a factor of 5 for both grazing treatments. (2) Although the amount of mineral N in soil (N_min) sampled in late autumn showed differences between intensive and extensive grazing, the N_min method permits no certain indication of the risk of NO₃ leaching. For example, during the winter period 1994/95 a reduction of mineral N in the soil (0—0.9 m) in both grazing treatments was found (—33 [I] / —8 [E] kg NO₃‐N ha^—1 and —26 [I] / —21 [E] kg NH₄‐N ha^—1) whereas during the winter 1996/97 an increase in almost all mean mineral N values occurred (+10 [I] / +2 [E] kg NO₃‐N ha^—1 and +10 [I] / —10 [E] kg NH₄‐N ha^—1). (3) In spite of the differences between both methods, the experiment shows that NO₃‐N leaching under extensive grazing could be reduced almost to levels close to those under mown grassland.     

Bestimmung von Mikronährstoffen und Schwermetallen in Böden mit dem Verfahren der Elektro‐Ultrafiltration (EUF) durch Zugabe von DTPA

With the electro–ultrafiltration (EUF) technique, the plant availability of several plant nutrients in soils can be characterized. The basic principle of EUF is that an electric field is induced using platinum electrodes. Ions in the soil suspension move either to the cathode or to the anode and are filtrated through ultra‐membrane filters. In the standard EUF procedure, two extractions steps are used: 30 min at 20°C and 5 min at 80°C. However, the determination of micronutrients and heavy metals with the standard EUF procedure is not possible, because the solubility of these elements in water is low and most of the watersoluble elements are precipitated when passing the platinum electrodes. The addition of DTPA, a well known complexing agent, during a third EUF fraction (5 min at 80°C) enables extraction of micronutrients and heavy metals. Highest concentrations in the 33 soils of the study were found for iron, followed by zinc, manganese, lead, copper, and nickel. Lower concentrations were obtained for cobalt, chromium, cadmium, and molybdenum. For two soils, the EUF/DTPA procedure was compared to CaCl₂/DTPA and EDTA soil extraction methods, showing that higher or comparable amounts were found with CaCl₂/DTPA and much higher amounts with the EDTA method. These results reveal that the EUF/DTPA technique in principle can be used for the determination of plant‐available micronutrients and heavy metals. However, in a next step the relationship between EUF/DTPA‐extractable elements and their availability for plants needs to be quantified.     

Vernachlässigte Phosphor‐ und Kaliumdüngung im ökologischen Landbau senkt die biologische Stickstofffixierung bei Rotklee und den Kornertrag bei nachfolgendem Hafer

Neglected P and K fertilization in organic farming reduces N₂ fixation and grain yield in a red clover‐oat rotation N₂ fixation is the most important N source in organic farming. An insufficient P, K, and S supply to legumes may reduce their N₂ fixation capacity. Consequently, the total yield of plant production may also be reduced. This problem was studied in a pot experiment with red clover followed by oat. Soil was taken from a field where organic farming had been practiced for more than 30 years without applying any mineral fertilizers or buying additional fodder. The soil (luvisol from loess) was characterized by: pH (CaCl₂) 5.4; lactate‐soluble (CAL) P 5 mg kg^–1 and K 110 mg kg^–1. 6 kg dry soil were mixed with 400 mg P applied as (i) triplesuperphosphate (TSP), (ii) rock phosphate (RP) or (iii) compost from organic household residues (BAK). An additional treatment (iv) with TSP received 1000 mg K as K₂SO₄ (TSP+K) and an additional treatment with RP (v) received only 200 mg P (RP/2). A control treatment received no fertilizer. P application significantly improved the P nutritional status of the plants (P content) and increased the N amount in the shoots of red clover (with 400 mg P per pot by 64 % to 139 % as compared to the control) and the dry matter (DM) yield by 60 % to 130 %. No significant differences between TSP and RP were found. The application of BAK resulted in a significantly higher N yield than the application of RP and TSP. The treatment TSP+K resulted in the highest DM yield (230 %), removal of P was 343 %, of K 228 %, and of N 239 % as compared to the control plants. This indicates a synergistic effect of P, K, and S on N₂ fixation, which was also found with BAK. Oat grown after red clover increased its grain yield by 132 % (200 mg P as RP) to 165 % (400 mg P treatments). This was mainly due to a higher P uptake (up to 172 %) and a higher N uptake (up to 172 %) as compared to the control.     

Schätzung der mikrobiellen Biomasse von Böden aus anthropogenen und natürlichen Substraten — ein Beitrag zur Standortbewertung

Field estimation of the microbial biomass of soils derived from natural and anthropogenic parent materials Whereas the estimation and evaluation of physical and chemical soil properties is possible with the use of widely accepted methods, there is still no procedure with respect to microbiological parameters. Therefore, our objective was to develop a field procedure for estimating the integral parameter ”︁microbial biomass”. For this purpose, microbial biomass data (C_mic in dry matter) of soils developed in natural parent materials from 116 sites in Germany and abroad were analyzed. Additionally, C_mic in 33 German soils developed in anthropogenic parent materials was determined. In the soils under consideration, C_mic varied between 100 and 4000 kg ha^—1 in the upper 30 cm. For soils of natural substrates statistical relations between C_mic and the humus and clay content as well as pH were derived. From these parameters which are combined as the diagnostic characteristics of humus a simple procedure for estimating C_mic of arable soils was developed. For soils developed in anthropogenic parent materials, however, an estimation procedure was developed that uses the nature of the parent material and the degree of soil development. To evaluate the estimated amount of C_mic, a frame consisting of 6 classes is proposed: < 200 kg ha^—1 (= very low), 200—400 kg ha^—1 (= low), 400—800 kg ha^—1 (= moderate), 800—1600 kg ha^—1 (= medium), 1600—3200 kg ha^—1 (= high), and > 3200 kg ha^—1 (= very high).