Eine optimierte Methode zur Bestimmung der Proteaseaktivität in Sauren Waldböden

An optimized method for the determination of protease activity in acid forest soils A method for the determination of protease activity was tested for its applicability to acid forest soils (O-horizon and mineral soil). The influences of the following parameters on the protease activity and its determination were investigated: incubation time, substrate concentration. pH-value of the incubation solution, buffer solution, sample matrix and storage of soil samples. In consequence of the results an optimized method is proposed. The application of this modified method to two forest sites with contrasting N-transformation indicates, that also in acid forest soils the determination of protease activity allows significant differentiations.     

Eine verbesserte Methode zur Bestimmung der Anzahl von Endospermzellen in Weizenkörnern

An improved method for the determination of the number of endosperm cells in wheat grains A method is described, which allows a clear and quantitative determination of endosperm cells in wheat grains even during the late stages of grain filling. After treatment with pectinase the tissue of the endosperm disintegrates in single cells, in the same step the starch in the endosperm cells is dissolved. The nuclei of the endosperm cells are stained with hematoxylin, drawn by vacuum on to a millipore filter, and counted in the still recognizable cell structures under a microscope. This is advantageous for exact counting of all the endosperm cells.     

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 Stammbastanalyse als Methode zur Beurteilung des Ernährungszustands von Coniferen

Stem phloem analysis as diagnostic tool to evaluate the nutritional status of conifers During late fall 1975 needles and stem phloem were sampled from 4–10 trees each on 44 experimental plots, belonging to five trials with fertilizer and sewage sludge application in Scots pine and Norway spruce stands in southern Germany. Treating the nutrient contents of both tissues by means of variance, regression and discriminant analysis gave evidence, that stem phloem analysis can be used effectively to evaluate the supply of those stands with N,P and Ca. Phloem analysis has several advantages as compared with traditional foliar analysis: Technical sampling difficulties in older stands as well as the hazard of dilution effects are smaller and the seasonal variation of nutrient contents seems to be less pronounced. Preliminary phloem threshold levels for N and P deficiency with pine may lie around 0,46 and 0,07%, respectively. There is some indication, that spruce suffers from N deficiency if the nitrogen content of its phloem is below 0,42%.     

Eine Kombination der Thermogravimetrie mit der 15N-Tracertechnik zur Untersuchung von Huminsäurepräparaten

A combination of thermal analyses and ¹⁵N tracer technique for investigation of humic acids Differences in humic acids of two extreme variants of three long-term trials due to a three years intensive fertilization in a pot experiment are also to be found by means of thermogravimetry. Additionally the ¹⁵N contents of humic acids were investigated at certain temperatures according to the peaks given by thermogravimetric study. The ¹⁵N isotope is also incorporated in higher molecular compounds. The ¹⁵N content varies due to differences in humus content and composition of the soils used.     

Eine Infiltrationsmethode zur Messung der hydraulischen Leitfähigkeit im Felde

An infiltration method for measuring the saturated hydraulic conductivity under field conditions A new field method to measure the hydraulic conductivity under field conditions, developed by Reynolds and Elrick (1985), is presented and compared with a laboratory method using 100 cm³ cylinder cores.     

Eine Methode zur quantitativen Bestimmung von Pentachlorphenol in Umweltproben

A method for the quantitative determination of pentachlorophenol in environmental samples An analytical method is presented for the rapid extraction, purification and quantitative detection by gaschromatography of pentachlorophenol in environmental samples (plant, animal and soil samples). The detection sensivity of this method gets up to 5 ppb or 10 pg absolute.     

Die Stoffbilanzierung landwirtschaftlicher Böden - Eine Methode zur Früherkennung von Bodenveränderungen

Material balances of agricultural soil - A method for early recognition of soil alterations For agricultural soils of a lowland region in Switzerland the input and output of the elements nitrogen, phosphorus, copper, zinc, cadmium and lead were measured over two years. In spite of the fact that the emission standards are met there is a slow and steady increase of the P, Cu, Zn and Pb concentrations found in the plough layer. In accordance with the principle of prevention the metabolism of the soil should be controlled on a large scale in such a way that this concentration increase can be substantially reduced within decades. With the available analytical methods the observed concentration increases in the soil are clearly detectable only after decades. Regional annual material balancing of the relevant anthropogenic processes (farming, private households, industry and trade), however, allows early detection of small changes in concentration. Consequently, a soil protection strategy which obeys the principle of early prevention should be completed by regional material balances.     

Pflanzenverfügbarkeit der Phosphatvorräte ackerbaulich genutzter Böden. -Langfristige Feldversuche zur Nutzbarkeit des Bodenphosphors und zur Bewertung der Bodenuntersuchung -

Availability of Phosphate Reserves in Arable Soils - Long Term Field Experiments for Assessing Soil P Reserves and Critical Soil Test Values - The objective of this work is to quantify the plant availability of soil P reserves accumulated by former fertilizer applications, the possibility of utilizing them by arable field crops and to determine critical soil test values. For this purpose several long term field experiments with large plots without replicates were initiated in 1977 on luvisols from loess (pH 6.8 – 7.4) in Lower Saxony with a sugar beet - winter wheat - winter barley/winter wheat crop rotation. Annual P applications were 0, 45, 90, 135 and 180 kg P₂O₅/ha as triple phosphate. Application of other fertilizers and plot management were according to farmer's practice. Despite of high yield levels phosphate response of plants was only 2 % at its maximum in the average of all crops in 15 years. This was confirmed by small plot experiments with four replicates placed into the large plots after 9 years, when soil P levels had been differentiated under the influence of plant P removal and P application. Herewith in agreement, shoot P concentration was found within the range generally regarded sufficient. It is therefore concluded that plant P demand has been fully satisfied by soil P reserves. Soil P test values, monitored by the P(H₂O) method of Sissingh, decreased markedly in 15 years, when no P was applied, they remained approximately constant when P application was equal to P removal and they increased when P addition was higher than P removal. Plants on a site with 4 mg P(H₂O)/L initially had severe P deficiency. Maximum yield was obtained when the soil P level was raised to 11 mg P(H₂O)/L. It is concluded that P reserves, which are often high in German arable soils, can be utilized by field crops and thus be lowered to about 10 mg P(H₂O)/L by reducing or omitting P dressings. For practical purposes it is suggested to restrict P application, if necessary at all, to the sugar beet crop in the rotation because they often respond more than small grain.     

Automatische Registrierung der Feuchtdichte und der Wassergehaltsänderung eines Bodens durch Messung der Absorption von Gammastrahlen (Geländemessung)

Determination of the moisture density and the water content variation of a soil by measuring the absorption of gamma rays A method is described with which above all the density and its changing (water content) can be measured automatically. A collimated gamma ray (137-Cs) is measured according to the absorption principle. Two tubes are inserted into the soil as parallel as possible about 50 cm apart. In the one tube a gamma ray source, in the other one a detector simultaneously moves step by step in a homogeneous manner up and down. The density and the changing of the water content is calculated from the measured counting rate. The measuring time for each step is variable, but usually about 5–10 minutes are chosen. The difference in depth between the stations can also be varied. The accuracy of the instrument in field use amounts to:

• 1 Water content changing: ± 0.0015 g/cm³
• 2 Soil density: ± 0.003 g/cm³

The solution power is such that horizontal layers of about 10 mm thickness can be distinguished in respect to the water content changing.     

Eine Split-root-Technik zur Untersuchung der Nährstoffverfügbarkeit in Abhängigkeit vom Wassergehalt im Boden

A Split-Root Technique for the Investigation of the Relationship between Nutrient Availability and Soil Water content . Nutrient availability in soils depends among other factors on soil water content. In order to investigate the quantitative relationship between availability and soil water content a special technique was developed. This split-root technique has to fulfil several conditions. 1. This technique must be able to allow to differentiate between the direct influence of water supply on plant growth and the influence of soil water content on nutrient availability and the effect of the latter on plant growth. 2. It must grant a sufficient supply of water oxygen and all nutrients to the plant with the exception of that nutrient the availability of which is to be examined. 3. A predetermined water content or water tension should be maintained as constant as possible during the experiment. These requirements are best met with by means a split-root technique. The experiments were carried out in such a way that the plants were grown in a container consisting of three compartments of which the centre one contained quartz sand whereas the two outer compartments were filled with soil (fig.1). Each plant had half of its root system growing in the sand and half of it in the soil. The quartz sand was supplied with a nutrient solution containing all nutrients except the one the availability of which is to be examined. The water content of the soil was regulated by means of ceramic filter candles which were linked to a water reservoir. This water reservoir was kept under negative pressure according to the required water tension in the soil. The water tension in the soil was monitored by 2–4 tensiometers in each of the soil compartmens (tab.1). Water tension up to pF 2.7 could be established and maintained in the soil. There was little variation of water tension during an experiment (3 weeks) and the moisture distribution in the soil was uniform. In order to obtain good reproducibilities the experiments were carried out in growth chamber.     

Untersuchungen zur Gibberellin- und Cytokininaktivität in verschiedenen Entwicklungsstadien der Karottenwurzel

Investigations on gibberellin and cytokinin activity in carrot roots at various developmental stages In various developmental stages of carrot plants (Daucus carota L.) different ratios of cytokinin and gibberellin activities were observed in the storage root. In the mature carrot root cytokinin activity dominates gibberellin activity. In the storage root of the carrot two gibberellin-like, one gibberellin-antagonistic and four cytokinin-like components were found. One of the gibberellin-like components exists also in bound form.     

Veränderungen der Blattspreiten und des Chlorophyllgehaltes der Fahnenblätter von Winterweizen durch Wachstumsregulatoren

Changes of leaf-blades and chlorophyll content of flag leaves from winter wheat due to growth regulator application In pot experiments with winter wheat at two N-levels the effect of CCC and Ancymidol on the morphology, the chlorophyll content and the slope of the chorophyll degradation after anthesis were studied. The area of the blades and the number of flag leaves per pot were increased by the higher N-supply and by the growth regulators as well, resulting in a larger leaf area of flag leaf-blades per pot. In all cases the mixture of CCC + Ancymidol at the higher N-level reached the maximum values. The late intermediate harvesting showed distinct differences in the chlorophyll concentration of the flag leaf-blades and the total amount of chlorophyll of all flag leaf-blades per pot, whereby a delay of senescence in the growth regulator trials compared with the control could be proved.     

Eine Einrichtung zur Beregnung von Bodensäulen

A device for the irrigation of soil columns An irrigation device was designed for maintaining a constant water flow in soil columns over a long period of time. The apparatus consists of three construction elements: A balance for the dosage of the water, a sprinkler to distribute the water on the soil surface and an electronic time control to adjust different time steps. The wide range of possible rain intensities is shown. The mean variation of the water pulses and their distribution over the surface are discussed. The apparatus exhibits good results in long duration experiments.     

Testung und Vergleich verschiedener Methoden zur Beurteilung des N-Ernährungszustandes von Winterweizenbeständen

Test and comparison of different nitrogen status indicators of winter wheat crops Six methods of N diagnosis were tested and compared regarding practicability and accuracy of predicted fertilizer requirements in three years of winter wheat experiments at Bernburg Chernozem site. Plant analysis for total N in shoot dry matter as well as the quick tests for nitrate in the stem (with diphenylamino sulphuric acid and with indicator strips, respectively) partly indicated considerable N demand and gave recommendations for fertilizer doses, which were not transformed into grain yield during the dry weather conditions of the experimental years. Besides, the comparison of both quick tests showed unsatisfactory agreement. Values from the test with indicator strips were less accurate. The reflectance (at 550 nm wave length) of detached youngest leaves was correlated with N content in the shoot dry matter. Visual evaluation of leaves, using colour charts, did not give the expected results. In field measurements of crop reflectance the near infrared waveband and the calculated “Ratio Vegetation Index” showed to be particularly sensitive.     

EDV-gestütztes Meß- und Auswerteverfahren zur Bestimmung der ungesättigten Wasserleitfähigkeit nach der Verdunstungsmethode

A Computer-aided Measuring and Evaluation Method for the Determination of the Hydraulic Conductivity in the Unsaturated State according to the Evaporation Method Multiple methods for the determination of the unsaturated flow depend on the water content or the soil-moisture tension have been published by so far. Their major drawback is the large consumption of time for the measuring and/or for the evaluation. The here presented combination of devices for the application of the evaporation method including its software permit a faster determination of parameters and a presentation in an analytic mode.