Schätzung der Denitrifikation in landwirtschaftlich genutzten Böden. II. Ergebnisse und Bewertung

Estimating denitrification in agriculturally used soils: II. Results and evaluation This is the second of two papers describing a denitrification model. Whereas in the first paper the model approach was described, the second paper deals with results obtained with the model. To evaluate the model's performance, 14 profiles in the catchment area of a water-work were studied in detail. For each site the potential and the actual annual denitrification rates were estimated. It was found that the least favorable conditions for denitrification occurred in the sandy soils of the study area. Consequently, estimated denitrification rates were lowest (< 10 kg N ha^?1 a^?1) in these soils. Estimated denitrification rates were highest (50 kg N ha^?1 a^?1) in peal and river plain soils, with either a high amount of organic matter and/or a high groundwater table. In silty loess soils, denitrification losses were estimated to be 20 to 35 kg N ha^?1 a^?1. With use of the anion concentrations in the surface layer of the groundwater, a plausibility study was conducted to evaluate the estimated denitrification losses. Its results show that the values obtained are realistic. However, a true calibration of the model is still necessary.     

Quantitative Mineralbestimmung in der Schlufffraktion von Böden auf der Grundlage der chemischen Analyse und unter Anwendung der Karl-Fischer-Titration. II. Ergebnisse bei Böden aus Geschiebedecksand,Geschiebemergel und Löß

Quantitative estimation of the mineralogical composition from silt-fractions of soils on the basis of the chemical analysis and by application of the Karl-Fischer-titration. II. Results obtained with soils from glacial sand, boulder marl and loess The contents of micas and feldspars were quantified in the silt-fractions from horizons of a podsolic brown earth developed on glacial sand and of lessives on loess as well as on boulder marl by using a method that has been described in detail in part I. Three components each of micas and of feldspars, namely muscovite (Ms), phlogopite (Phl), annite (Ann), orthoclase (Or), albite (Ab) and anorthite (An) were determined. The silt fractions of the three investigated soils are similar in their mineralogical composition. Feldspars are composed of equally high amounts of Or and Ab. Micas are dominated by the Ms-component. Apparently the mica content of the silt fractions is reduced during soil development, whereas no significant changes can be found for feldspars. The loss of micas is responsible for the decreasing potassium content of the silt fractions.     

Ammoniakemissionen aus alternden Pflanzen und bei der Zersetzung von Ernterückständen

Ammonia emissions from senescing plants and during decomposition of crop residues NH₃ emissions from plant stands, measured under simulated environmental conditions with the wind tunnel method, ranged between 0.8 and 1.4% of the N content of the shoot, equivalent to 1.1 to 2.9 kg NH₃-N ha^?1. The highest emissions were observed in faba beans whereas the emissions in winter wheat, spring rape and white mustard were lower. The total NH₃ emissions were not affected by removing a part of the ears (sink reduction), but emissions occurred earlier, as did the plant senescence. This suggests that the NH₃ emissions are closely related to senescence. NH₃ emissions from decomposing crop residues ranged from 0.9 to 3.7% of the N content. The emissions from sugar beet leaves and potato shoots with high water content reached from 8.6 up to 12.6 kg N ha^?1, whereas the emissions from field bean straw with high dry matter and N content were relatively low. (3.1 kg N ha^?1, or 0.9% of the N content). The NH₃ emissions from sugar beet leaves were reduced by 81% by ploughing and 63% by mulching.     

Mobilität und Pflanzenverfügbarkeit von Phosphor aus organischen und anorganischen Formen in der Rhizosphäre von Lolium perenne

Mobility and availability of phosphorus from organic and inorganic forms in the rhizosphere of Lolium perenne 1.) In pots (sandwich-technique according to Helal and Sauerbeck), where the soil (A_p-horizon of an Alfisol-Udalf from loess) was separated into a root chamber and an outer chamber (up to 10 mm away from the root chamber), the phosphorus (P) availability of super-P, rock-P (Hyper-P) and organic P [myo-inositol-2-mono-P di(cyclohexylammonium) salt] was studied. P was applied at a rate of 50 mg P kg^?1 soil only in the outer chamber. This P fertilization resulted in significant increase of CAL- and water-extractable P in the treatment with organic P and super-P compared to the P₀ treatment. During 6 cuts of Lolium perenne organic P showed the same effect on the P-uptake of plants as super-P. Compared to the treatment without P, rock-P had no effect on the P-uptake. The higher P-uptake of Lolium perenne both in the super-P- and organic P-treatment was reflected at the end of the experiment only by the CAL-P content differences between root chamber and outer chamber. The highest activity of acid phosphatase, measured in air dried soil was found in the root chamber of the organic P treatment The content of EUF extractable organic P was significantly higher in the root chamber of the treatments with super-P and organic P than in the P₀- and rock-P-treatment. 2.) The P elution was studied with 2 soils (A_p-horizon of an Alfisol-Udalf from loess pH: 6.4; A_h-horizon of a basaltic brown soil pH: 5.4) under lab conditions in columns. In the super-P-and organic P-treatment leached P was mainly inorganic. In the soil with low pH value (5.4), P was leached in the treatment with super-P or organic P in a higher amount of organic P than in the soil with pH 6.4. The results of this experiment do not show in which form the applied organic P was moved to the roots or displaced in the soil.     

Die Oberflächenladung der Ton-Humusfraktion aus Schwarzerden als Funktion von pH und Ca-Konzentration

Surface charge of clay-humus fractions from Chernozems as a function of pH and Ca-concentration The charge characteristics of clay-humus fractions from A-horizons of several Chernozems as a function of Ca concentration and pH of the soil solution was investigated. The surface charge was measured by titration with charge compensating polyelectrolytes; the endpoint was at zero potential. A logarithmic dependence of the surface charge [mol_c/kg] on the Ca concentration of the soil solution in the range ? 2 mmol/L was observed. The influence of pH on the surface charge was almost linear over a wide range of pH-values, the change in pH-dependent charges being most pronounced for the horizons with low Ca saturation on the exchange sites. It was also found that the competition between protons and Ca ions for the exchange sites leads to a distinct decrease of the influence of Ca concentration on the surface charge in acid environment. The reason for slaking of the soil surface and of the displacement of clay-humus particles in Chernozems could be attributed to an increase in surface charge with decreasing Ca concentrations after leaching of lime. According to the present findings the drop in mobility of the clay-humus fractions during acidification could be explained by a charge compensating effect of protons and aluminium ions.     

Schätzung der nutzbaren Feldkapazität und Luftkapazität von anthropogenen Bodenhorizonten aus einfach zu bestimmenden Kennwerten

Estimating soil water and air capacity from physical properties in anthropogenic substrate horizons Up to now there is no appropriate method available to estimate soil water and air capacity in anthropogenic substrate horizons. The “Bodenkundliche Kartieranleitung” (German soil classification key) was developed for natural soils and can be applied to anthropogenic soils only with limited validity. For developing an estimation system, a data base of 197 anthropogenic substrate horizons was established, consisting of soil characterizations gained from own investigations and from literature. By using multiple linear regression analysis, estimating models were developed to calculate soil water and air capacity derived from values of soil bulk density, texture, amount of skeleton and content of organic matter. Though every regression model proved to be highly significant, some gained coefficients of determination less than 50%. Absolute mean standard errors of estimate vary between 3.4 and 9.1 Vol%.     

Mikroskalige Variabilität der Bodenlösungschemie - Ergebnisse eines Laborversuchs zum Vergleich von Standard- und Mikro-Saugkerzen

Microscalic variability of soil solution chemistry - results of a laboratory experiment comparing standard - with micro suction cups In a laboratory experiment with an undisturbed soil column, the chemistry of soil solution collected by a standard suction cup (Ø 2 cm) was compared with that of 20 micro suction cups (Ø I mm) installed in the same soil depth. The standard cup showed comparable concentrations of inorganic anions with the soil column leachate, because preferably the main water paths of the soil column were sampled. In contrast, about 30 % of the micro suction cups sample soil compartments that have a different solution chemistry. In these cases the differences between standard and micro suction cups decrease in the order nitrate, chloride, sulfate. Standard suction cups seem to be the right sampling device for the investigation of element fluxes through soil. To get information about plant availability of ions they are inadequate, due to their dimension. Here micro suction cups are more appropriate, because their dimension is comparable to plant roots.     

Schwefel-Eintrag aus der Atmosphäre in Schleswig-Holstein

Atmospherical sulfur deposition in Schleswig-Holstein In order to quantify the atmospherical sulfur deposition and to investigate factors for the depositions variability during 1983 precipitation samples from five meteorological stations in Schleswig-Holstein were collected. Using the bulk-sample method dry and wet deposition were recorded together. In the year of the investigation sulfur-deposition was 20 kg/ha S in List on Sylt, 19 in Schleswig, 11 in Kiel, 14 in Lübeck and 17 in Quickborn near Hamburg. There was no correlation between sulfur concentration and pH value of the samples. In contrast sulfur-concentration showed a close relation to amount of weekly precipitations. On many soils sulfur is only added by atmospherical deposition, which is sometimes not sufficient to meet the requirements of agricultural crops in Schleswig-Holstein. Having a negative sulfur balance in soils an increase of sulfur deficiency is expected in the future.     

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.     

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).