Tonmineral- und K-Ca-Austauscheigenschaften von Oberböden des Nährstoffpotentialversuches Hallertau

Clay mineralogy and K-Ca-exchange properties of surface soils from the nutrient potential trial Hallertau (Bavaria) In soils of four locations of the Hallertau nutrient potential trial, with a soil texture consisting of sand, silty sand, silty loam and sandy clayey loam, clay mineral properties were measured with the standardized glycerol expansion method and with n-alkylammonium (Rn_c-NH₃⁺-clay). The expandable minerals of the sandy soils consist exclusively of smectites s.s., (s.s. = sensu stricto) with 0.42 to 0.28 charge equivalents per formula unit (p.f.u.). The expandable minerals of the loams are an assemblage of smectites s.s. and vermiculites. The total layer charge of the smectites s.s. extend from 0.54 to 0.28 charge eq. p.f.u. The fine clay fractions (< 0.1 μm) do not contain vermiculites. The layer charge density of vermiculites with homogeneous charge in the coarse fractions varies between 0.60 and 0.95 charge eq. p.f.u. The immediate K-Ca-exchange was extended with the values of the continued K exchange versus Ca at low K intensity. The Q/I isotherms of sandy soils have a more pronounced curvature than the isotherms of the loams; in all cases, however, the exchange curves have a continuous form. This phenomen is discussed in terms of the clay mineralogy of the soils. After 8 years without K fertilizing, samples gave values between 168 and 497 kg smectite-K/ha for the surface soils. The constant rates of K-desorption vary between 12.8 and 28.7 kg K/ha (surface soil). The rates are better differentiated between unfertilized and fertilized soils for the loams than for the sandy soils. The constant rates of K release were found to be controlled at an AR-level between 1.6 · 10^?4 M^1/2 (unfertilized sandy soil) and 5.2 · 10^?4 M^1/2 (fertilized sandy clayey loam soil).     

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.     

Stickstoffernährung und Al-Toxizität bei Buchenjungpflanzen. II: Mineralstoffgehalte junger Buchen in Abhängigkeit von der Form der Stickstoffernährung und dem Al-Gehalt der Nährlösung

Nitrogen nutrition and Al toxicity with young beech plants. II: Mineral contents 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 4,0 after two days, or not corrected over a period of two weeks. The cation contents of the roots and shoots were greater if the nitrogen was supplied in NO₃-form. Increasing Al concentrations in the nutrient solutions led to an increase in Al contents and a decrease in Ca- and Mg-contents in roots and shoots.     

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.     

Der Einfluß unterschiedlicher Kalium- und Nitraternährung auf pH-Änderungen in der Rhizosphäre

The Influence of potassium and nitrate nutrition on pH changes in the rhizosphere Seedlings of winter wheat, barley, sunflower, peanut and field bean were grown in soils differing in K and nitrate content. pH changes of the rhizosphere soil were measured periodically with antimony electrodes. In soils relatively poor in K the lowest pH values were measured at the root surface of the dicots (maximum pH decrease from 5 to 4.2), while soil pH increases from 5 to 5.4 in contact with roots of the monocots. Increasing K addition caused decreasing pH near peanut and field bean roots. In soils fertilized with K, monocot roots also decreased soil pH. In a K-rich soil the roots of the dicots decreased pH even after addition of 6.6 mg NO₃-N/100 g soil, while the roots of the monocots did not change pH. The pH changes are explained by an imbalance between anion and cation uptake, causing release of protons or hydroxyl ions. The reason for the differences in behaviour between monocots and dicots may be due to the differing cation-exchange capacity of the plant roots, causing a higher cation uptake by dicots and therefore greater proton release.     

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.     

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

Heavy metal- and nutrient contents of plants and soil samples from metalliferous waste dumps in Bleiberg (Carinthia, Austria). II. Woody plants Needles, stem- and root-samples from coniferous trees (Norway spruce and Scots pine), taken from a waste dump habitat and an offmine-site in Bleiberg (Carinthia) were analysed on their macronutrient-and heavy metal-contents. No significant age dependent differences in N-and P-content of the two species were observed. The highest potassium levels occured in the youngest needle age group. The needles of the trees from the mining dump site show increasing Ca- and Fe- concentrations with increasing needle age. The Mn-contents of needles collected in offmine-sites were higher than those from the waste dump. The Mg-levels in the needles from both sites are remarkably low, a symptom of undersupplement. High Pb- and Zn-concentrations were determined in older needles of waste-dump-trees. Because of rather high Pb- and Zn-levels in the roots of the trees from this site a physiological transport barrier is assumed, which partly inhibits the upward lead transport; on the other hand lead is partly deposited in stem-wood of the two species. The heavy metal contents of roots from mining dump site are interpreted as an effect of high metal stress in the fine fraction of soil material.     

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.