Stickstoffernährung und Al-Toxizität bei Buchenjungpflanzen. I: Entwicklung von Buchenjungpflanzen in Abhängigkeit von der Form der Stickstoffernährung und dem Aluminiumgehalt der Nährlösung

Nitrogen nutrition and Al toxicity with young beech plants. I: Development of young beech plants in relation to the source of nitrogen and the Al content of the nutrient solution Young beech plants were grown in aerated nutrient solutions with different Al concentrations over a period of 14 weeks. Nitrogen was supplied in either NO₃- or NH₄-form. pH-changes of the solutions were either corrected to the initial pH of 4 after two days, or not corrected over a period of two weeks. Root growth of the beech seedlings was inhibited by Al. Reduction of root length and dry matter production was more severe if the plants were fed with ammonium nitrogen compared to nitrate nitrogen. Detrimental effect of Al on root growth was also influenced by the pH of the solution. NH₄-N-nutrition led to pH decrease and therefore to increased solubility and toxicity of aluminium. On the contrary, NO₃-N-nutrition weakened Al toxicity because of pH increase at the root surface and in the AFS. This led to an inactivation of Al in the form of insoluble hydroxy aluminium polymers. Compared to NO₃-N-nutrition NH₄-N promoted shoot growth. During 14 weeks no detrimental effect of Al on shoot growth was observed.     

pH-Änderungen in der Rhizosphäre von Mais- und Erdnußwurzeln

pH changes in the rhizosphere of peanut and maize roots pH changes in soil near growing peanuts and maize seedlings were measured using antimony microelectrodes. The roots of each plant actively altered pH, both at the root tip and root hair zone (maize) and immediately behind the root elongation zone (peanut). Along the root elongation zone and at distances greater than 10-15 cm from the root tip, pH moved towards the value in the soil outside of the rhizosphere. Peanut seedlings grown in unfertilized and NO₃-fertilized soil (initial pH 5.5) lowered soil pH by 1.5 and by 0.7 units, respectively; whereas maize seedlings caused pH increases of 1.0 and 1.5 units, respectively. In NH₄-fertilized soil, both seedlings caused soil pH to fall by 2-3 units. In an acid soil, pH changes occurred at distances of up to approximately 2.5 mm from root surfaces.     

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.     

Nährstoffauswaschung aus Weinbergsböden an der Mittelmosel

Leaching of plant nutrients from vineyard soils Leaching of plant nutrients particularly of nitrate from vineyard, arable, and forest soils of the Middle-Mosel have been investigated over a two-year period. Nitrate concentration in the leachate of vineyards amounted to an average of 326 mg NO₃/l and was about 10 to 20 times higher than the nitrate concentration in the leachate of arable and forest soils. According to the hydro-dynamic model assumptions on groundwater flow in the slates of the Rhenish Massif, the data obtained for the groundwater recharge (158-180 mm/year as gained in spring) and leaching of nitrate (144 kg N/ha/year) must be considered as minimum values. Hydrodynamic model assumptions suggest nitrate leaching rates of about 200 kg N/ha. Main reasons for the high leaching of nutrients are heavy fertilizer application and high mineralization rates in the vineyard soils favoured by relatively high soil temperatures and a high soil permeability.     

Der Einfluß des NO3 : NH4 -Verhältnisses in der Nährlösung auf Ertrag und Gehalte an organischen und anorganischen Ionen von Tomatenpflanzen

The influence of the relation between NO₃ and NH₄ in the nutrient solution on yield and organic and inorganic ion contents of tomato plants. . Tomato plants were grown in aerated media of oppositly varying supply of (NH₄)₂SO₄-and NaNO₃ with a constant N-quantity of 15 meq/1 or a quantity of NH₄-, NO₃ or (NO₃ + NH₄) increasing from 3 to 30 meq.N/1. Yield and ion content were determined. A maximum yield was achieved by a mixed N-supply i.e. 4 to 5 parts NO₃, 1 part NH₄-N and 7, 5 meq N/l. The “(C-A) value” was calculated by the content of the cationions “C” (=K⁺ + Na⁺ + Ca⁺⁺ + Mg⁺⁺ + NH₄⁺) and the inorganic anions “A” (= NO₃^? + Cl^? + H₂PO₄^? + SO₄^–). The “(C-A)” value is equivalent to the content of the organic anions. Furthermore we determined the citrate, malate, oxalate, and pektinate content. These make up 60–80% of the (C-A) value. The NO₃- and K content increase considerably, the Ca-, Mg-, Na-, Citrate, Malate and Oxalate content increase less pronounced, the Cl-, H₂PO₄- and SO₄- content decrease as the NO₃ content increases from 0–80%. If the medium contains 80–100% NO₃ - N, the NO₃ and K content remain almost constant, while the Ca-, Mg-, citrate, malate and oxalate content especially increase in this case. The K content decreases in the presence of a high (NH₄)₂SO₄ supply. Parallel to this the value (C-A) decreases greatly, so that it is less than the sum of the determined organic anions. In this case the content of organic anions obviously does not correlate with the (C-A) value. The yield correlates with the carboxylate contents. (C-A) values of 150–170 mval/100 gm. d. m. cause a lowering of the yield. The plants contain an almost equal amount of citrate, malate and oxalate. Depending on the N-concentration of the medium, the malate content will be a bit more than the amount of citrate in case of maximum yield. If there is a lack or toxicity in the medium the citrate content will be higher than the malate content. The yield per dry weight correlates positivly with the quotients of citrate and malate.     

Wirkung einer Abscisinsäure-Applikation auf die Cl−Translokation in Sojabohnen bei niedriger und hoher Besalzung des Nährmediums

Effect of abscisic acid in the root medium on Cl^? translocation in soybeans under low and high salt conditions With soybeans of the varieties ?Lee”? and ?Jackson”? the effect of abscisic acid (ABA) applied to the root medium in different concentrations (10^?4, 10^?5 and 10^?6M) on Cl^? translocation was investigated. Under low salt conditions (0,5 mM NaCl) ABA, depending on its concentration, strongly decreased Cl^? translocation to the shoot. At the highest ABA concentration, within 24 h the Cl^? content of the shoots was reduced to about 40 % of the control, the Cl^? accumulation within the roots was reduced about 25 %. However, the 10^?5 and the 10^?6M ABA treatment increased Cl^? accumulation in the roots but decreased Cl^? translocation to the shoot. Under high salt conditions (75 mM NaCI) ABA had no measureable effect on CI- translocation to the shoot. It was found that the genetic mechanism responsible for high CI- accumulation within the roots of ?Lee”? and high CI- translocation to the shoot of ?Jackson”? was not affected by ABA. ABA strongly inhibited transpiration. High ABA concentration in combination with low salt treatment decreased the transpiration rate up to 50 % of the control. ABA also inhibited transpiration under high salt conditions. This result is discussed considering the fact, that ABA added to the highly saline nutrient solution did not decrease the CI- translocation to the shoot. An investigation using ¹⁴C-ABA showed, the radioactive substance was taken up by the roots and translocated to the shoot independently from the salt treatment. The metabolism of the radioactive substance was different for roots and leaves. However, no difference could be observed by comparing the two soybeans varieties with or without salt treatment.     

Anwendung des Agrarökosystemmodells EPIC zur Prognose des Wasser- und Nährstoffhaushaltes von landwirtschaftlich genutzten Flächen auf Sandböden in Ost-Brandenburg

Predictions of water and nutrient dynamics from agricultural sites on sandy soils in East- Brandenburg The validity of the agroecosystem model EPIC was tested for two agricultural sites on sandy soils without groundwater located at the moraine landscape in East-Brandenburg. Measurements of soil moisture, soil nitrate, above ground plant biomass and yield from these two agricultural investigation sites were compared with the corresponding simulation results of the model. The calculations of the soil water balance show a good fit between simulated and observed soil moisture values. The comparison between simulated and measured above ground plant biomass presents an underestimation of biomass by the model at the beginning of crop growth in spring and an overestimation at the end of the vegetation period. EPIC shows also an overestimation of yield in this study. The observed and the simulated soil nitrate values show no fit. Probably one reason for this fact might be the kind of process modeling included in EPIC, which was designed for long term calculations up to 50 years. Another possible reason could be the over estimation of N-uptakes of plants in comparison with estimates of the N-demand of plants based on the simulated yields. However a clear reason for the insufficient calculations of soil nitrate status by the model could not be found in this study. Further analysis of mineralization, N-uptake of plants and N-Ieaching in EPIC must be done in future.     

Nährstoffgehalte von lössboden-toposequenzen in südniedersachsen und franken unter dem einfluss der bodenerosion

This paper deals with the effects of soil erosion on the horizontal and vertical distribution of nutrients in loess soil topo-sequences in southern Lower Saxony and Frankonia (W. Germany). Each topo-sequence consists of three parts: an upper plateau (or edge of a piedmont plain) with little soil erosion up to now, a slope which as a whole has been eroded very much, and a slope foot which is covered with colluvial sediments. Compared to the pure loess the soils contain more K, Na, and P, and less Ca. The distribution of the nutrients within the investigated topo-sequences is caracterized by high contents of potassium on the slopes, provided that the A₁-horizon is eroded, so that the B¹-horizon has come to the surface. Finally it is considered whether the erosion-made differentiation of nutrients has negative or positive consequences on the productiveness of the arable soils.     

Schwermetall- und Nährelementgehalte von Pflanzen und Bodenproben schwermetallhaltiger Halden im Raum Bleiberg in Kärnten (Österreich) I. krautige Pflanzen

Heavy metal- and nutrient contents of plants and soil samples from metal liferous waste dumps in Bleiberg (Carinthia, Austria). I. herbaceous plants Lead and zinc concentration in the fine fraction (< 0,2 mm) of mine dump material were twice as high as in coarser fraction (2–0,2 mm) (table 1). Due to high metal levels in roots of several mine dump plants (table 3) interactions between plants and soil-microorganisms are assumed. Furthermore root originating exsudates (organic acids) are probably responsible for an increase in heavy metal availability in soil in spite of a general high pH of soil solution. The low mobility of lead within intact plants is caused by a selective affinity of this metal to cell wall pectines. On the other hand a physiological barrier (endodermis/pericycel) in primary roots of these plants is assumed, which partly prevents lead from upward transport into the shoots. Heavy metal compartmentation may be part of a tolerance mechanism diminishing a surplus of toxic metals within plant metabolism.     

Ökochemische Kennwerte des Bodens

Eco-chemical parameters of soils Parameters are described which allow the ecochemical characterization of the mineral substance, of the pool of mobilizable surface bound ions, and of the pool of dissolved ions. In the soil solution (dissolved ion pool) distinction is made between parameters quantifying nutrient and acid stress and indication parameters. Indication parameters, which are derived from the anion composition of the dissolved ion pool, allow the identification of the anion source. Anion sources may be located in the ecosystem itself (HCO₃^?, NO₃^?, organic anions), may be atmospheric deposition (SO₄^2?, NO₃^?, Cl^?) and may originate from fertilization.     

Mathematische Modellierung der Funktionen des Bodens im Stoffhaushalt von Ökosystemen

Mathematical modelling of the role of soil in ecosystem functioning The structure of ecosystems and the parameters necessary for their characterization are discussed under the aspect of matter balances. The main weight is layed on the regulatory role of transport processes and storage changes in soil. It is postulated that the quantitative ecological analysis of landscapes requires the application of computer models of the regulatory processes in soil as a method for minimizing the measuring expense. The basic equations describing transport processes and storage changes are discussed and their application for special problems of the balance of water and chemical elements is demonstrated.     

Bestimmung des Wasserentzuges aus dem Boden durch die Pflanzenwurzeln im Gelände als Funktion der Tiefe und der Zeit

Field determination of water withdrawal from soil by plant roots as a function of depth and time . The water flow through roots as a function of depth and time can be determined in homogeneously rooted, level soils with closed plant canopies, provided the total vertical water flow and the capillary water flow are known for the soil profile. Theory, measuring methods and some results on water withdrawal of wheat (fig. 2–4) and sugar-beet (fig. 5) roots on a loess grey-brown podsolic soil profile underlain by gravelly sand (fig. 1) are described. The time averaged rates (2–7 day periods) for water extraction by roots are up till about 12 × 10^?3 \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{{\rm cm}^3 {\rm water}}}{{{\rm cm}^3 {\rm soil} \cdot {\rm day}}} $\end{document} During the growth period variations of the depth of the effective root zone and of the extraction rate in distinct layers were found (fig. 6 + 7). A capillary rise from the subsoil into the effective root zone exists for some time (fig. 3); seepage water within the lower root zone causes a strong increase of extraction rates in these depths (fig. 4). The relative water extraction rate at the depths of 15 and 25 cm decreases with increasing soil water suction in the range between 150 and 10⁴ cm (fig. 8).     

Einfluß langjähriger Gülledüngung auf den Nährstoffhaushalt des Bodens. 1. Mitteilung: N-Akkumulation und N-Nachlieferungsvermögen

Influence of long-term slurry application on soil nutrients. 1. N accumulation and N mineralization potential The influence of longterm slurry applications on the total N content, N fractions and N mobilization potential of the soil was investigated. The following results were obtained:

• – Application of high amounts of slurry over a long period of time resulted in higher total N contents not only in the upper soil layers but also in the layer 60–90 cm.
• – In two sites the higher total N contents are mainly resulting from higher contents of hydrolyzable organic N compounds and in one site of higher contents of non hydrolyzable organic N compounds.
• – The influence of the slurry application on the content of non exchangeable NH₄⁺ is depending on the K saturation of the clay minerals.
• – In incubation experiments N mobilization of the soils supplied with slurry was higher as compared to soils supplied with mineral fertilizer.
• – A highly significant correlation is existing between N mobilization and the content of hydrolyzable organic N compounds and the N_org fraction, determined by means of EUF, respectively.
• – The N_min content of the soils supplied with slurry was higher during the whole growing season.