K. Mengel's research while affiliated with Justus-Liebig-Universität Gießen and other places

Publications (226)

Article
Fresh water is a limited resource and its efficient use in agriculture represents a great challenge. The objective of the investigation was, to test a new subsoil irrigation technique for obtaining high grain yields and water use efficiency in comparison with furrow irrigation still used in Middle East. Clay pipes of the subsoil irrigation had a pa...
Article
Mengel, K. and Geurtzen, G. 1988. Relationship between iron chlorosis and alkalinity in Zea mays. - Physiol. Plant. 72: 460–465. Maize (Zea mays L. cv. Anjou 21) grown in nutrient solution with Fe-EDTA and with nitrate as the sole nitrogen source showed typical Fe-chlorosis symptoms after a growth period of 14–21 days. Alkalinity in roots, stems an...
Article
Changes of EUF-extractable nitrogen (N) (nitrate, ammonium, organic N) in 20 arable bare soils, subsequently planted with ryegrass (Lolium multiflorum L.) and cutting three times were investigated in pot experiments. All 20 soils responded qualitatively in the same way. During the period of bare soil, there was a significant increase of EUF-extract...
Article
Until now not much about Fe concentrations in soil solutions is known because of difficulties to extract the soil solution and to determine the low Fe concentration in them. Therefore a technique was elaborated by which a mixture of 1:1 soil–quartz sand sample with a soil moisture of 80% of maximum water holding capacity was spread in a Buchner fun...
Article
From all plant nutrients N fertilizer rates deserve highest attention as too high rates may result in nitrate leaching, volatilisation of N2O (greenhouse gas) and affect the farmers’ profit. Too low rates will also depress the profit. The problem is accentuated by the fact that crops not only feed from soil inorganic but also from organic soil N. M...
Article
The activities of starch synthesizing enzymes were investigated in wheat grains (Triticum aestivum L. cv. Kolibri) throughout the grain development period. Starch phosphorylase (E.C. 2.4.1.1.) activity was especially high during the early period of grain development, while starch synthase I (ADP glucose α-glucan 4-α-glucosyl-transferase, E.C. 2.4.1...
Article
Full-text available
Young spruce trees [Picea abies (L.) Karst.) exposed to acidic fog (pH 3) showed a disintegration of the epicuticular waxes of the current year's needles as compared with trees treated with a fog of pH 5. The fog treatment was followed by a period in which the trees received different water supply. Under water stress conditions, trees that had been...
Article
Transport of glucose 1-phosphate (G1P) and highly purified triose phosphate into storage tissue amyloplasts was studied. Isolated amyloplasts from potato (Solanum tuberosum L., dihaploid stock, HH 258) were transport-functional and metabolically active in starch synthesis. Fourty percent of the amyloplasts were intact and there was only a small deg...
Article
Shading of maize plants (Zea mays L. cv. Blizzard) reduced net H+ extrusion by roots and increased K+ release, whereas there was no significant effect on anion efflux in deionized water. With lower light intensity the concentrations of carbohydrates in the roots decreased, but ATP levels and energy charge remained unchanged. Also, shading raised th...
Article
The relationship between the apoplastic pH in young sunflower roots (Helianthus annuus L.) and the plasmalemma ferric chelate reductase (FC-R; EC 1.16.1.7) activity in roots was investigated. The hypothesis was tested that a high apoplastic pH depresses FC-R activity, thereby restricting the uptake of Fe2+ into the cytosol. Until recently, little h...
Article
The photoproduction of eta-mesic 3He has been investigated using the TAPS calorimeter at the Mainz Microtron accelerator facility MAMI. The total inclusive cross section for the reaction gamma3He-->etaX has been measured for photon energies from threshold to 820 MeV. The total and angular differential coherent eta cross sections have been extracted...
Article
It is generally accepted that soil microorganisms play an important role in producing siderophores which enhance the availability of soil Fe to higher plants. There is not much direct experimental evidence to support this supposition, however, because it is difficult to grow plants under sterile conditions over long periods. The object of this inve...
Chapter
Fertilizers in the broadest sense are products that improve the levels of available plant nutrients and/or the chemical and physical properties of soil, thereby directly or indirectly enhancing plant growth, yield, and quality. Fertilizers are classified in terms of their chemical compounds. Straight fertilizers generally contain only one primary n...
Article
The measurement of the magnetic moment of the δ+ resonance using the reaction γp → π0γ′p was presented. A deviation of radiated photon, from a soft bremsstrahlung cross section at higher energies, was observed. The determination of electromagnetic structure of the δ by measuring a γ transition within the resonance was also elaborated.
Article
Full-text available
Differential cross sections of the reactions (gamma,pi(0)pi(0)) and (gamma,pi(0)pi(+/-)) have been measured for several nuclei (1H,12C, and (nat)Pb) at an incident-photon energy of E(gamma)=400-460 MeV at the tagged-photon facility at MAMI-B using the TAPS spectrometer. A significant nuclear-mass dependence of the pipi invariant-mass distribution i...
Article
Full-text available
The reaction gammap-->pi(0)gamma'p has been measured with the TAPS calorimeter at the Mainz Microtron accelerator facility MAMI for energies between sqrt[s]=1221-1331 MeV. The cross section's differential in angle and energy have been determined for the photon gamma' in three bins of the excitation energy. This reaction channel provides access to t...
Article
The hypothesis of this investigation is that a substantial proportion of nitrogen (N) released by roots of entire plants into the soil are amino acids which are transported from upper plant parts to roots via phloem and from the phloem released into the root apoplast. From here amino acids may diffuse directly into the outer medium (soil or nutrien...
Chapter
The objective of the investigation was to study the relationship between EUF (Electro-ultrafiltration) extractable N, EUF extractable carbon and interlayer NH4+ on net N mineralization and N uptake of ryegrass (Lolium multiflorum cv. Aubade) cultivated in Mitscherlich pots on 20 different arable soils. Grass of the first harvest (first cut) exclusi...
Article
Morphology and organisation of leaf tissue is such that it accomodates the uptake of gaseous plant nutrients, whilst that of roots the uptake of water-soluble solutes. These water soluble plant nutrients are mainly supplied with fertilizers. Only in exceptional cases where nutrients are strongly fixed by soils or where aerial nutrient requirement o...
Article
The main objective of the present work was to clarify the causal relationship between leaf apoplastic pH increase and Fe chlorosis under alkaline growth conditions. It has been shown that nitrate supply in contrast to ammonium supply induced a pH increase in the apoplast of young green leaves of Helianthus annuus which was followed within 12 hours...
Chapter
The normal range of Mo concentration in agricultural soils is 0.8 – 3.3 mg/kg (Kubota 1977). Values can vary widely, however, depending on soil parent material. Soils derived from granitic rocks, shells, slates or argillaceous schists are often high in Mo whereas highly weathered acid soils tend to be deficient (Gupta 1997a). (1997) divide Mo into...
Chapter
Life is intimately associated with water, and particularly with water in its liquid phase. Water is the form in which the H atom, an essential element of all organic molecules, is absorbed and then assimilated in the course of photosynthesis (page 147). About 500 g of water is absorbed by roots to produce 1g organic material and thus may be conside...
Chapter
In the previous chapters all elements which have been considered, with the possible exception of Na, are essential plant nutrients. Without any one of these essential elements the plant would be unable to complete its life cycle. All these elements too play a part in plant metabolism although their essential roles are in some cases still incomplete...
Chapter
The average K+ content of the earth’s crust is in the order of about 23 g/kg. By far the greatest part of this K+ is bound in primary minerals and in the secondary clay minerals which largely make up the clay fraction of the soil of particle size less than 2 µm.
Chapter
Nitrogen is one of the most widely distributed elements in nature. It is present in the atmosphere, the lithosphere, and the hydrosphere. As can be seen from Table 7.1 the atmosphere is the main reservoir for N (Delwiche 1983).
Chapter
The mean Ca concentration of the earth’s crust amounts to about 36.4 g/kg. It is thus higher than that of most other plant nutrients (see Table 11.1). Calcium in the soil occurs in various primary minerals. These include the Ca bearing Al-silicates such as feldspars and amphiboles, Ca phosphates, and Ca carbonates. The latter are particularly impor...
Chapter
It is now over 50 years ago since Hoagland and co-workers reported their fundamental findings on ion uptake by plants (Hoagland 1948). In experimenting with fresh water alga Nitella and the sea water alga Valonia they found that the ion concentrations in the vacuoles of these two algae did not correspond to the concentrations in the respective alga...
Chapter
Manganese occurs in various primary rocks and particularly in ferromagnesian materials. The Mn released from these rocks by weathering forms a number of secondary minerals the most prominent being pyrolusite (MnIVO2) and manganite [MnIIIO (OH)]. Manganese and Fe oxides often occur together in nodules and iron-pans. Total Mn levels may differ consid...
Chapter
During the growing period roots act as a sink collecting available nutrients to be utilized in the synthesis of organic plant constituents. After the termination of growth and the start of decay, the process is reversed and nutrients are released into the soil from the breakdown of plant debris. Not all nutrients taken up by plants over the growth...
Chapter
The total B concentration in soils is in the range of 20 – 200 mg/kg dry weight, most of which is inaccessible to plants. The available, hot water soluble fraction in soils adequately supplied with B ranges from 0.5 – 2.0 mg B/L (Sillanpaä 1982). Boron containing soil minerals include tourmaline (30–40 mg B/kg) which is very insoluble and the very...
Chapter
The objective of the investigation was to study the relationship between EUF (Electro Ultra Filtration) extractable N, EUF extractable carbon and interlayer NH4+ on net N mineralization and N uptake of ryegrass (Lolium multiflorum cv. ‘Aubade’) cultivated in Mitscherlich pots on 20 different arable soils. Grass of the first harvest (first cut) excl...
Chapter
An outstanding feature of life is the capability of living cells to take up substances from the environment and use these materials for the synthesis of their own cellular components or as an energy source. The supply and absorption of chemical compounds needed for growth and metabolism may be defined as nutrition and the chemical compounds require...
Chapter
Iron makes up about 5% by weight of the earth’s crust and is invariably present in all soils (see Table 11.1). The greatest part of soil Fe usually occurs in the crystal lattices of numerous minerals. The primary minerals in which Fe is present include the ferromagnesian silicates such as olivine, augite, hornblende and biotite. In biotite and illi...
Chapter
A principal step of Fe supply of entire plants is FeIII reduction in the root apoplast which controls the uptake of Fe2+ into the cytoplasm. We developed a new dye, ferrozine diboronic acid, which was coupled to the root cell wall and thus -to our knowledge for the first time- we could measure FeIII reduction directly in the root apoplast. It was s...
Chapter
The average Zn concentration in uncontaminated soils is in the range of 17 to 160 µg Zn/g soil (Reed and Martens 1996). Most of it is present in the lattice structure of primary and secondary minerals (Huang 1989). The radius of Zn2+ is very similar to that of Fe2+ and Mg2+. To some extent therefore Zn2+ may substitute for these ions by isomorphous...
Book
This is the 5th edition of a well-established book Principles of Plant Nutrition which was first published in 1978. The same format is maintained as in previous editions with the primary aim of the authors to consider major processes in soils and plants that are of relevance to plant nutrition.This new edition gives an up-to-date account of the sci...
Chapter
Sulphur occurs in the soil both in inorganic and organic forms but in most soils organically bound S provides the major S reservoir. In most instances in soils of humid and semi humid areas the range of total S is from 100 to 1000 mg S/kg, a range that is similar to that of total P (Syers et al. 1987). Organic S concentration generally decreases wi...
Chapter
Phosphorus in soils occurs almost exclusively in the form of orthophosphate with total P concntrations usually in the range of 500–800 mg/kg dry soil. Quite a substantial amount of this P is associated with organic matter and in mineral soils the proportion of organic P lies between 20 and 80% of the total P.
Chapter
The Mg concentation of most soils generally lies in the range of between 0.5 g/kg for sandy soils and 5 g/kg for clay soils. Higher levels are found in clay soils because Mg is present in relatively easily weatherable ferromagnesian minerals, such as biotite, serpentine, hornblende and olivine with average Mg concentrations of 130, 250, 150, and 24...
Chapter
There is no clear division between elements which are toxic to plants and those which have a beneficial or even essential effect. The effect of any element on the plant depends not only on its chemical properties but also on its concentration and the presence and concentrations of other elements. The physiological age and species of the plant cornc...
Chapter
Higher plants have specialized organs characterized by specific metabolic processes. For growth and crop production one may distinguish between organs in which primary organic molecules are produced and organs in which organic matter is stored or consumed. In Crop Physiology the former are called physiological sources and the latter physiological s...
Chapter
Copper occurs in the soil almost exclusively in divalent form. The largest fraction of Cu is usually present in the crystal lattices of primary and secondary minerals. In addition a high proportion of Cu is bound by the soil organic matter. The Cu ion is adorbed to inorganic and organic negatively charged groups and is dissolved in the soil solutio...
Chapter
Soil is a heterogeneous material consisting of three major components: a solid phase, a liquid phase and a gaseous phase. All three phases specifically influence the supply of nutrients to plant roots. The solid phase is the main nutrient reservoir. The inorganic particles of this phase contain cationic nutrients such as K, Na, Ca, Mg, Fe, Mn, Zn,...
Chapter
It is hypothesised that a substantial proportion of nitrogen released by roots of entire plants into the soil are amino acids which are transported from shoot to root via phloem and from the phloem released into the root apoplast. From here amino acids may diffuse directly into the outer solution (soil or nutrient solution). Alternatively, amino ac...
Article
The suitability of three 15N application methods (15NH3 fumigation, split-root technique, 15N pre-cultivation) for the estimation of N net rhizodeposition (NRD) of wheat plants into soil has been tested and compared under similar conditions and at the same developmental stage. The results were as follows: 1. The use of the 13N tracer technique allo...
Article
Full-text available
The release of nitrogen by roots of intact spring wheat plants into the soil and other losses, mainly of volatile N, have been investigated in two subsequent years from tillering until maturation, by use of a new technique for plant labelling with 15N. Plants were at first labelled by growing them in a 15N nutrient solution until tillering and then...
Article
It is hypothesized that the release of interlayer K+ from phyllosilicates is initiated by a very low K+ concentration in ambient soil solutions and near mineral surfaces. Under natural conditions, one of the factors resulting in this low K+ concentration is K+ uptake by plant roots. If this is true then K+ trapped by a ion exchanger should also ind...
Article
 Maize (Zea mays L.) and sunflower (Helianthus annuus L.) grown on a calcareous soil showed poor growth and/or were chlorotic in spite of abundant Fe in the roots. It has been hypothesized that microbial siderophores chelate Fe (III) in the soil, and that in this form Fe is transported towards the root apoplast. On the calcareous soil, total and ap...
Article
It has been hypothesized that under NO(3)(-) nutrition a high apoplastic pH in leaves depresses Fe(3+) reductase activity and thus the subsequent Fe(2+) transport across the plasmalemma, inducing Fe chlorosis. The apoplastic pH in young green leaves of sunflower (Helianthus annuus L.) was measured by fluorescence ratio after xylem sap infiltration....
Article
A fluorimetric ratio technique was elaborated to measure apoplastic pH in the outer root cortex of maize (Zea mays L.) grown hydroponically. A newly synthesized fluorescent probe, fluorescein boronic acid (pKa = 5.48), which covalently binds to the cell wall of the outer cell layers, was used. Under conditions of saturating ion concentrations the a...
Article
The objective of the investigation was to identify the most important organic N-containing fractions extracted from soils by electroultrafiltration (EUF) or a CaCl2 solution, respectively, and their importance for nitrogen mineralization. The investigation comprised 19 agricultural and one forest top soil. Net N mineralization was tested in Mitsche...
Chapter
Nitrogen release from intact wheat roots (Triticum aestivumn L.) into the soil was investigated at different growth stages and under two temperature regimens and flooding conditions. The influence of vanadate was also studied. Since methods used until now for such studies have their shortcomings we developed therefore a new technique: Spring wheat...
Chapter
The inactivation of Fe under alkaline conditions as found in soil solutions of calcareous soils was investigated in the root apoplast of Helianthus annuus and Zea mays by two experimental treatments: i) calcareous soils and ii) NO3− (with and without bicarbonate). The concentrations of Fe in the roots were determined and Fe deficiency symptoms were...
Article
The objective of this investigation was to examine whether the silt in loess-derived soils represents a major K+ source for plants. The experiment was carried out with 14 arable loess-derived soils (Alfisols) from which, in one series, the clay was removed and in which, in another series, complete soils were used. In this work, the latter are denot...
Article
Most of the nitrogen (N) in agricultural soils is organically bound, while the N uptake by plants and also the N losses from the soil-plant system into the environment are as inorganic N. The electro-ultrafiltration (EUF) method and the extraction by a CaCl2 solution extract an organic N fraction (Norg) that is thought to provide information about...
Article
Comparative physiological studies on iron (Fe) chlorosis of Vicia faba L. and Helianthus annuus L. were carried out. High internal Fe contents in Vicia cotyledons (16–37 μg) were completely used for plant growth and Fe chlorosis was not inducible by the application of nitrate (with or without bicarbonate). In Helianthus, low quantities of Fe in the...
Article
The performance of PbWO<sub>4</sub> as a fast and compact scintillator material for calorimetry at energies well below 1 GeV has been investigated using a collimated beam of monoenergetic photons with an energy between 50 and 790 MeV provided by the tagged photon facility of MAMI at Mainz. In continuation of previous experiments with electrons, a l...
Article
Starch is an important agricultural product deposited in vegetative and reproductive storage organs (sinks) of various crop species. Starch yield may in some cases be limited by photosynthesis, i.e. source-limited. This is particularly true for starch synthesized in potato tubers. Here, the physiological sink is characterized by a symplastic phloem...
Article
Acid mist (pH 3) precipitation led to a degradation of the epicuticular waxes of the youngest needles. Under the influence of frost drought in spring those affected trees resulted in a detrimental decline in needle water potential and turgor potential. The results indicate that a damaged, poor cuticle loweres the water retention capability and incr...
Chapter
Spring wheat plants were labelled in 15N nutrient solution and then transplanted in pots filled with soil. The 15N release was analysed six days after transplantation (tillering), ear emergence, beginning of grain filling and full naturity. At these stages the 15N was analysed in the plant and in the soil. Release rates of labelled N were low in th...
Conference Paper
The performance of PbWO<sub>4</sub> as a fast and compact scintillator material for calorimetry at energies well below 1 GeV has been investigated using a collimated beam of monoenergetic photons with an energy between 50 and 790 MeV provided by the tagged photon facility of MAMI at Mainz. In continuation of previous experiments with electrons, a l...
Article
Global known phosphate deposits are a finite resource which will run out in about four centuries at the present consumption rate. Since about 90% of the phosphate mined is used for fertilizer, soil and fertilizer phosphate should be efficiently used. Various agronomic measures are discussed relevant for saving phosphate and avoiding losses. Phospha...
Article
Full-text available
PbWO<sub>4</sub> has been selected as the most appropriate scintillator material for future calorimeter projects at LHC to detect high energy photons in the multiple GeV range. In spite of the low yield of scintillation light, the applicability of the scintillator to detect photons and particles at energies well below 1 GeV has been studied using m...
Chapter
A fluorescein boronic acid conjugate has been used as a pH-sensitive dye in the root apoplast and because of its likely links to boric acid-binding sites. The marker (Glüsenkamp et al.; German Patent Application) is non-toxic to cell growth up to concentrations of 100 μM and stains almost exclusively the apoplastic space of sunflower and maize root...
Article
During cultivation of legumes soil is acidified due to proton release from roots. As a consequence of proton release, plants accumulate organic anions which may, if returned and decomposed in the soil, neutralize the soil acids. Until now the detailed processes responsible for the change in soil pH after incorporation of plant material have not bee...
Article
The short-term effect of NaNO3 or (NH4)2SO4 application on CH4 oxidation was measured under laboratory conditions with sieved soils collected from the top layer (0–12 cm) of a loamy and a sandy soil. The soils were incubated in sealed flasks and the CH4 and CO2 concentrations in headspace were measured periodically. On each gas sampling date the so...
Article
Organic matter incorporated into soils may influence soil pH. Until now the detailed processes responsible for a change in soil pH after the incorporation of organic matter were not completely understood. We studied the effects of organic anions, glycine as a representative of amino acids, and glucose as a representative of carbohydrates on soil pH...
Article
Major known fractions of soil nitrogen are amino nitrogen (proteins, peptides), polymers of amino sugars, and NH4 + fixed in interlayers of 2:1 minerals. Only a small percentage of the total soil organic N is easily mineralizable and contributes to the pool of mineral soil N. Predominant sources of mineralization are amino-N and polymers of amino s...
Chapter
Ein pH-Anstieg des Bodens kurz nach der Düngung mit Pflanzenmaterial wurde wiederholt festgestellt (HUE und AMIEN 1989, KRETSCHMAR et al. 1991, BESSHO und BELL 1992, BAREKZAI und MENGEL 1993). Die Erklärungen für den pH-Anstieg sind aber bisher nicht einstimmig. Eine davon lautet, daß die Kationen wie Ca2+, Mg2+ und K+ des Pflanzenmaterials die sau...
Article
Nitrogen fixation, growth and yield in faba bean (Vicia faba L.) are all adversely affected by water shortage. The objective of this investigation was to examine the effects of water stress on symbiotic nitrogen fixation and plant nitrogen status and to compare yield formation in four different cultivars. Water stress was applied at different times...
Article
Full-text available
Drought stress was induced in symbiotically N2-fixing alfalfa (Medicago sativa L. cv. Franken neu) by adding PEG 6000 to the nutrient solution, thus decreasing the water potential to −0.5 MPa. Relative water content and leaf water potential were significantly reduced after a 3- and 5-day stress period. This resulted in inhibited dry weight producti...
Article
Intact potato storage cells (Solanum tuberosum L., dihaploid stock, HH 258) were fed for 10.5 days with [1-13C] labelled glucose and fructose (both 1.5% w/v) during the course of amyloplast development. Tissue samples were sequentially harvested at various stages during starch synthesis. The randomization of the 13C label between carbon atoms 1 and...
Article
We investigated the question of whether exchangeable K+ is a reliable factor for K+ availability to plants on representative arable soils (Aridisols) rich in K+-bearing minerals. Five soils with different textures were collected from different locations in Pakistan and used for pot experiments. The soils were separated into sand, silt, and clay fra...
Article
The article describes factors and processes which lead to Fe chlorosis (lime chlorosis) in plants grown on calcareous soils. Such soils may contain high HCO3 - concentrations in their soil solution, they are characterized by a high pH, and they rather tend to accumulate nitrate than ammonium because due to the high pH level ammonium nitrogen is rap...
Article
A hypothesis has been presented and tested that bicarbonate (HCO3) and nitrate (NO3) are the most important anions inducing iron (Fe) chlorosis because these anions increase the pH of leaf apoplast which in turn depresses ferric‐iron [Fe(III]) reduction, and hence, the uptake of Fe into the symplasm. Experiments with young sunflower (Helianthus ann...
Chapter
In various experiments carried out under controlled conditions in the greenhouse, we have shown that acid mist (pH 2.7-3.0) application affected the cuticle of spruce trees and led to a decomposition and melting of epicuticular waxes. Trees with such an affected cuticle had the same transpiration rate as control trees if abundant soil water was ava...
Article
Ensete (Ensete ventricosum W. Cheesm.) is a root crop which stores starch in the root and in the lower part of the stem. It is grown in the southwest of Ethiopia and due to its drought resistance, it is of outstanding importance for the supply of food to the local population. Until now virtually nothing is known about the response of Ensete to fert...
Article
The cultivation of symbiotic legumes and the consequent small uptake of nitrate by the host plant depresses soil pH and impairs subsequent legume growth. The rate of soil pH decline depends on the soil H⁺ buffer power, climatic conditions, soil permeability, and on the kind of legume cropping. It is shown for some leguminous crop species from the t...
Article
The re-uptake of sugars driven by the proton gradient was studied in sugar net-release and net-uptake experiments using roots of intact maize (Zea mays cv. Blizzard) and field bean (Vicia faba L. cv. Alfred) plants. The net release of sugars into the root medium (0.1 mM CaSO4) was stimulated by: the protonophore CCCP (10 µM); the sulfhydryl reagent...
Chapter
Full-text available
The re-uptake of sugars driven by the proton gradient was studied in sugar net-release and net-uptake experiments using roots of intact maize (Zea mays cv. Blizzard) and field bean (Vicia faba L. cv. Alfred) plants. The net release of sugars into the root medium (0.1 mM CaSO4) was stimulated by: the protonophore CCCP (10 ~tM); the sulfhydryl reagen...
Article
The effect of different long-term soil-cultivation systems (ploughing, two types of cultivator, notillage) on organic N, extracted with the electroultrafiltration (EUF) technique, was studied in two arable soils, a Luvic Phaeozem derived from loess and a Eutric Cambisol. A modified EUF extraction procedure (the 80°C fraction extended from 5 to 90 m...
Article
Pot experiments carried out with rye grass focused on two major aims: (1) to examine the importance of extractable organic soil N for net N mineralization and N uptake of plants and (2) to study decomposition and mineralization of organic matter incorporated into the soils, as related to extractable organic soil N fractions. Soil extraction was car...
Article
The objective was to test whether the K+ release rate of nonexchangeable K+ can be measured with a modified electro-ultrafiltration technique. The cumulative K+ extraction curves obtained with an extraction at 400 V and 80°C were described by the first-order equation, the parabolic diffusion equation, the power function, and the Elovich equation, w...
Article
The experiments were focused on the question whether the plasmalemma ATPase activity (proton pump) has an influence on the efflux of major inorganic ion species. Efflux from roots of intact Trifolium pratense, Hordeum vulgare, Glycine max, and Zea mays was examined into a solution containing 100 μM CaCl2 and 500 μM NH4⁺ as sulfate in the control so...
Article
Net release and net uptake of sugars by roots of intact maize (Zea mays cv. Blizzard) and field bean (Vicia faba L. cv. Alfred) were studied at micromolar external sugar concentrations that are relevant to the rhizosphere. Besides various sugars not further characterized there was net release of glucose, fructose, sucrose, arabinose, ribose, and ga...
Article
The hypothesis that the microbial decomposition of organic matter low in organic nitrogen leads to an increase in soil pH was tested and confirmed in a pot experiment with two different soils into which mature cherry leaves were incorporated. Einfluß des mikrobiologischen Abbaus reifer Blätter auf den pH-Wert des Bodens Die Hypothese, daß der mikro...
Chapter
Crop production has a positive energy balance which even can be improved by an adequate fertilizer application. World phosphate reserves are limited and therefore fertilizer phosphate should be used with high efficiency. In intensive animal farms phosphate rates may exceed by far the demand of the crop and therefore result in a heavy waste of phosp...