Die Aussagekraft von Gefäßversuchen im Vergleich zu Feldversuchen

The worth of pot experiments for use in comparison with field trials In pot experiments most growth factors are at an optimal level. As a result, plant yields often approach the maximum that is genetically possible. The application of pot experiment results to field conditions using pot surface area as a basis of conversion calculations is therefore questionable. In this paper, data of pot experiments are presented in which competition, as occurs as crop stands in the field, has been simulated by close placement of pots in a special revolving frame structure. Using this set-up, yields were obtained that corresponded to field grown crops provided that the total area within the frame was used in the conversion calculation and not the pot surface area. Using the area within the frame as a basis of conversion it was found that the amount of fertilizer applied, nutrient uptake, the number of ear bearing tillers and the thousand-grain weights were all similar to values obtained in field practice. The ground surface area is thus a suitable conversion factor for the comparison of pot and field experiments.     

Validierung eines 2-Regionen-Modells zur Simulation des Stofftransportes im Boden anhand von Laborsäulen- und Feldversuchen

Validation of a 2-domain-model for the simulation of solute transfer in soils by laboratory and field experiments The simulation of water and solute transfer in the unsaturated zone on the basis of the classical convective dispersive model gives dissatisfactory results in many cases. Especially in the zone of evapotranspiration the observed penetration depths of surface-applied chemicals often exceed calculated values. This has been attributed to preferential flow in domains with accelerated flow. The aim of the investigations presented here was to extend the conventional theory of solute transfer in order to enable improved model predictions without introducing too much complexity to the model which might reduce its applicability. The mobile-immobile-concept of Coats and Smith (1964) was chosen to extend the model FLOTRA (Wagner et al., 1992), which is based on the convective dispersive approach. The model parameters additionally needed by the model are the immobile water content θ_im and the solute transfer coefficient α. The applicability of the model was tested on the basis of several laboratory and field experiments. It is shown, that with the mobile-immobile-approach modeling results of water and solute transfer in the top soil layers, which are most important in view of soil and groundwater protection, were improved compared to the calculations with the classical convective dispersive model.     

Vergleichende Untersuchungen über das unterschiedliche Wachstum von Getreide im Feldbestand und in Gefäßen

Comparative investigations on the different growth of cereals in the field and in pots . Yields from pot trials, referred to soil surface area or soil volume, are generally higher than those obtained from field trials. The transposition of pot trial results to field conditions is thus debatable. Yields of summer wheat, obtained in the trials, described in this paper, were with the same fertiliser level about 47% higher in the pot trials than in the field. Additional nitrogen fertiliser even led to pot yields about 170% above the field yields. Phosphate fertiliser alone had no effect with the soils used. Nitrogen and phosphorus, on the other hand, particularly improved yields, so that pot yields in question were about 224% higher than those in the field. The phosphate content of the grain from pot and field trials only varied slightly, whilst in the straw it was greatly dependent on the yield and fertiliser applied. The lactate-soluble phosphate towards the end of the trials also largely corresponded to the uptake and fertiliser level. Ear number in the pot trials was higher than in the field trials by a factor of 2.5–3.1., depending on fertiliser application. The corn/straw ratio was approximately the same at 1:1.66 with the same fertiliser in both field and soil. With the higher fertiliser levels, usual in pot trials the ratio narrowed to 1:1.06. The comparatively higher pot yields are therefore in the first place the result of higher fertiliser applications. Competition for light and water, diminished in comparision to field plants, of pot plants plays a small role under normal weather conditions, on the other hand, but becomes active with much higher nutrient supplies.     

Einfluß von Müllkompost und Eisenverbindungen auf die Eisen-, Zink- und Manganaufnahme von Sonnenblumen und Mais im Gefäßversuch

Influence of compost and Fe-compunds on the uptake of Fe, Zn and Mn by sunflower and maize in pot experiments The influence of compost and different iron compounds on the uptake of Fe, Zn and Mn from calcareous soils was investigated in a pot experiment using sunflower and maize. Regardless of the iron compounds applied, the addition of compost resulted in an increase of the Zn content in both plant species. The compost treatment without Fe, resulted in a lower Fe content in sunflower and maize. This effect was partly or completely counteracted by the addition of Fe compounds. Very high Zn contents were observed in the Fe – EDTA treatments. The Zn content was further increased when compost was also added. In treatments in which compost was omitted none of the Fe compounds applied increased the Fe content of the plants.     

N-Wirkung von Rindergülle unter Zusatz von Dicyandiamid bzw. Stroh in Gefäß- und Lysimeterversuchen

Utilization of N in cattle slurry after addition of Dicyandiamide resp. straw in pot and lysimeter trials In a pot and lysimeter trial, leaching of nitrate of cattle slurry applied at different times (August, September, October, March) was tested with and without addition of DCD, and utilization of N by the following crop was determined. In a pot trial (sandy silt loam), the effect of additional straw manuring was also investigated. Pots were exposed to natural weather conditions from start of experiment (August) until sowing of rye grass (April). Application of straw as well as addition of DCD to slurry reduced leaching of N considerably. DCD addition with and without straw resulted in significantly higher N removals by rye grass. Unlike ammonium nitrogen “preserved” by DCD, slurry nitrogen biologically fixed by the rotting straw, however, was not yet available to the following rye grass crop (May to July). Slurry + straw + DCD generally led to higher amounts of residue N in the soil as a result of N balance. Also in the lysimeter trial, DCD reduced leaching of nitrate especially in vegetationless periods and thus improved the effect of cattle slurry applied in August resp. November (higher yields and N removals by silage maize).     

Halmverkürzung bei Hafer im Gefäßversuch durch CCC und Ancymidol

Growth reduction of oat in pot experiments by CCC and Ancymidol Pot experiments with oat to investigate the growth reducing effect of a mixture of CCC-Ancymidol in relation to time of application and N-fertilization led in the mean of 2 cultivars and 2 years to the following results: 1. Early application (age of plants: 50 days, stage K/L) of 20 mg CCC + 1,5 mg Ancymidol per pot resulted in a stem reduction of 21% at ripening, late application (age of plants: 64 days, stage L/M) of 18%. 2. The yield of kernels was not reduced by late application of growth regulators. The early application of growth regulators however decreased the kernel yield in some trials. 3. The two cultivars showed differences in stem reduction and kernel yield depending on time of application and level of N supply.     

Wachstum und Ernährung von Eberesche,Buche und Fichte im Gefäßversuch mit immissionsbelasteten Bodensubstraten aus dem Erzgebirge

Influence of simulated sulphur and nitrogen depositions on biomass and nutrient relationships of mountain ash, European beech and Norway spruce in a pot experiment with two soil substrates from the Ore Mountains Growth and nutrient relationships of mountain ash (Sorbus aucuparia), European beech (Fagus sylvatica) and Norway spruce (Picea abies) were investigated in a pot experiment with the two substrates rhyolithe (acidic) and basalt (alkaline). Additionally, depositions of sulphur (S) and nitrogen (N) as expected to occur in the Ore Mountains (Saxonia, Germany) in the future were simulated in order to test the species′ suitability for forest regeneration. After two years, aboveground biomass was significantly higher on basalt compared to rhyolithe for all species. The amount of S given (0 and 100 kg ha^—1 a^—1) and the dominant form of N applied (NH₄⁺:NO₃^— = 1:4 and 4:1; total amount of N given 80 kg ha^—1 a^—1) were of minor influence only. The contents of N and K in leaves or needles were higher on rhyolithe, whereas P, Ca, Mg and Mn contents were higher on basalt. Nutrient contents were only slightly affected by the amount of S supply and the NH₄⁺:NO₃^— ratio. In contrast to mountain ash, beech saplings exhibited considerable growth on rhyolite. It is therefore concluded that beech may be a suitable species for forest regeneration even on acidic soils suffering heavily from S and N immissions, whereas spruce will not tolerate high S loads. However, increasing N depositions by stimulating growth may cause deficiencies of Mg and K in both species.     

Korrelationen von Enzymaktivitäten im Boden

Correlations of Enzyme-Activities in Soil Enzyme-activities often have been used as indicators of the biological state of soil. In this connection some questions may be posed: Which enzyme is the best indicator of biological activities in soil, what is the relationship of enzyme-activities to other ecological parameters and what is the interdependency between different enzymes? To answer these questions we measured activities of amylase, catalase, invertase, pectinase, urease, xylanase and cellulase at nine alpine and subalpine sites. Furthermore the CO₂-evolution, contens of nitrogen, carbon, organic matter, the soil density, total bacterial number and water capacity were determined. With these data correlation coefficients were calculated. The best relationships were found between cellulase-xylanase and amylase-invertase activities (Table 1). While catalase and pectinase are in the middle range, urease shows relatively low values. There are highly significant correlations between enzyme-activities and the content of nitrogen, carbon, organic matter, soil density or the CO₂-evolution (number of samples used for calculations was 68). Almost no correlations were found with total bacterial count (Table 2). For these calculations 34 samples of each parameter were used. To prove that the lower number of samples is not the reason for low correlation coefficients we computed data of 17 samples (Table 3). The water capacity is depending on soil density and content of organic matter and the correlations are in the same range (Comparison Table 1 and 3). This means that 17 samples of each parameter are enough for these calculations. Enzyme-activities proof therefore to be good indicators of the biological state of soil. It is inappropriate to characterise biological activities of soil by total bacterial counts only.     

Abbau und biozide Wirkung von Pflanzenschutz-und Schädlingsbekämpfungsmitteln im Boden am Beispiel von Kelevan

Degradation and biocide effect of chemical plant protecting agents and pesticides in soils by the example of the insecticide Kelevan By the example of the insecticide Kelevan it is proved that by means of a combined test plan degradation and biocide effect of chemical plant protecting agents and pesticides in soils can be tested simultaneously. For this test two different test soils as described in leaflet No. 36 of the Biologische Bundesanstalt (BBA), Braunschweig, are each divided in test samples of about 200 g dry matter. To answer the question whether besides the biotic an abiotic degradation of Kelevan and its primary subsequent products takes place in top soil, too, one part of the soil samples was sterilized by overheated steam. Afterwards these and the non-sterilized soil samples were treated with known amounts of Kelevan[cage-U-¹⁴C] and in accordance to leaflet No. 36 of the BBA stored in the dark at 22°U65% r. h. or under field conditions for different periods. To investigate the effect of Kelevan and its metabolites on microorganisms in top soil, further soil samples were treated with increasing amounts of Kelevan and also stored for different periods. At the end of storage periods on an average W,2 % of applicated radioactivities were recovered in the soil samples with Kelevan[cage-U-¹⁴C]. Whereas readioactivities of sterilized soil samples were nearly quantitatively extractable, increasing radioactivity amounts were held back under the same extraction conditions by the native soil samples, which were present as organic residue components of Kelevan(cagc-U-¹⁴C) and not as ¹⁴C-containing carbonate. During degradation, in both test soils as well under laboratory conditions as under field conditions, about one third of Kelevan[cage-U-¹⁴C] was transferred within 30 months via Kelevan acid[cage-U-¹⁴C] to Chlordecon[cage-U-¹⁴C] and about two thirds were transferred into various unknown ¹⁴C-labelled degradation products. The results of microbiological investigation prove that microorganisms were evidently neither selected nor decimated in both test soils by Kelevan and its degradation products.     

Einsatz der Taupunktmethode zur Charakterisierung von Matrix- und osmotischem Potential in einer Gefäßkultur mit unterschiedlichen Salzgehalten

Use of the dew point method to determine matrix- and osmotic soil water potentials in pot cultures under different salt stress Water consumption of festuca rubra was investigated under different salt stress as measured by the dew point method. Water content of the soil, total tension and water consumption was measured daily. At the end of the growing season the low salt stress plants had used nearly completely all water available and were under water stress. Plants under medium salt stress reduced transpiration in time and showed highest water content in the soil and in the plants after growing season. For the high salt stress plants the total water potential remained low due to the osmotic component. Dew point measurements were compared with other methods (Cl-concentration; electric conductivity). A close correlation was found in all cases, demonstrating the usefulness of the dew point method.     

Umsatz von 15N markiertem Nitratstickstoff im Boden in Abhängigkeit von Strohdüngung und Bodenfeuchte

Turnover of ¹⁵N labelled nitrate nitrogen in soil as related to straw application and soil moisture In incubation experiments the effect of straw application on the turnover of ¹⁵N labelled nitrate has been studied at two soil moisture levels (brown podzolic soil). High ¹⁵N losses were found at the high soil moisture level. These losses are supposed to originate from denitrification. At both soil moisture levels straw application reduced significantly the ¹⁵N losses. Straw application resulted in a remarkable decrease of the ¹⁵NO₃ content in the soil and promoted the incorporation of ¹⁵N into the organic soil fraction. The incorporation of ¹⁵N into α-amino N and particularly into the rest hydrolyzable-N fraction was favoured by straw, while the incorporation into the amide-N fraction was hampered. Exhaustive cropping (Lolium multiflorum and Sinapis alba) on the soil incubated before with ¹⁵N, showed that the ¹⁵N incorporated into the organic fraction was poorly available. Thus straw application resulted in significant yield depression. It is assumed that the fraction of the rest hydrolyzable N is hardly available to plants.     

Dicyandiamidabbau im Boden in Abhängigkeit von der Temperatur

Effect of temperature on the breakdown of dicyandiamide in the soil The breakdown of dicyandiamide in a soil (sandy silty loam, pH 6.2, 0.13 % N) was investigated in relation to temperature. 1. The rate of conversion of dicyandiamide (DCD) (20 mg DCD-N/100 g soil) to guanylurea increased with rising temperature (10°–90°C). After 20 days, 14–100 % of the added DCD was metabolized. Small amounts of DCD (0.67 resp. 1.34 mg DCD-N/100 g soil) were broken down completely within 20–80 days at 8°–20°C. 2. Guanylurea was transformed to guanidine and then to ammonium. Increasing temperature in the region of 10° and 30°C accelerated the transformation. At higher temperatures (up to 70°C) an accumulation of guanidine occurred.     

Stickstoffbilanz von 15N-Harnstoff bzw. 15N-Ammonsulfatsalpeter mit Dicyandiamid in Gefäßversuchen zu Grünhafer und Sommerweizen

Recovery of Nitrogen of ¹⁵N-urea and ¹⁵N-ammonium sulfa-nitrate with addition of dicyandiamide in pot trials with green oats and spring wheat In pot trials with green oats and spring wheat, the effect of ¹⁵N-urea (UR) and ¹⁵N-ammonium sulfa-nitrate (ASN) with addition of the unlabelled nitrification inhibitor dicyandiamide (DCD) was investigated on the basis of equal amounts of N by fully taking into account the DCD-N, with respect to yield, N-removal, distribution of ¹⁵N in plants and soil (sandy loam, pH 6.5) as well as the fate of DCD.

• 1 In Neubauer experiments with green oats, 62–69% of fertilizer-N were found in the shoots, 21–31% in the roots and 4–9% in the soil. In Mitscherlich trials with spring wheat, 85–88% of fertilizer-N were found in grain and straw, 7–10% in the roots and 3–4% in the soil. ¹⁵N-recovery, in all cases was between 98-100%, thus exhibiting pratically no loss in course of the experiment.
• 2 Yields of green oats (shoots), resp. spring wheat (grain and straw) were about 4-11 % lower in pots with DCD; on the contrary, N-contents and removal were somewhat higher compared to control without DCD.
• 3 With conditions given by these pot trials (strong root penetration, favourable temperature, repeated supply during early growth, slow soil-specific decomposition), water-soluble DCD was taken up partly by the plants and appeared mainly in leaves resp. straw. In grains of spring wheat, DCD-contents were, however, very low (maximum 3 ppm DCD-N); in roots it could not be detected. In comparison, analysis of crop-material in field trials showed no DCD in grains and only very few ppm DCD in straw.
• 4 In pots with DCD, the residual-N in the soil was higher, probably because of the prolonged time of reaction between ammonium and the organic matter of the soil.

     

Die Wirkung von Branntkalk auf den Wasserhaushalt eines vulkanischen Aschenbodens aus Südchile (Trumao) im Gefäßversuch

Effect of burnt lime on water regime of a soil formed on volcanic ashes in Southern Chile (Trumao) A dystrandept of the south of Chile was mixed with 5% in weight CaO. The variation in water balance of limed and unlimed samples of this soil was studied. The liming provokes a disminution in the evaporation. The surface of the limed soil drys very rapidly, in relation to its unlimed equivalent, in such a way that it serves as a transpiration barrier. The decrease in the water loss favourably influenced growth of lettuce plants.