Summary
In order to study the influence of soil moisture on the availability of potassium a simulation model was used. The model is designed to describe the transport of a nutrient from the soil to plant roots and its distribution around a root. From a pot experiment, the measured K uptake of onion plants, grown in soil under different moisture levels, agreed satisfactorily with the calculated K uptake. The model is therefore regarded as a valid means of quantifying the dynamics of K in the soil around plant roots.
Calculations from a loess soil have shown that decreasing water content resulted in
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- a strong decrease of K transport from the soil to the root,
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- a faster decrease of the K concentration at the root surface and therefore
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- increasingly steep gradients of the K concentration around the root
With the root density found in this experiment the K concentration of the moist soil (θ∼ 0.4) decreased almost equally in the total soil volume whereas in the dry soil (θ ∼ 0.1) not much change occurred in the middle between two roots.
Therefore, the rate of K uptake per unit of root decreased much faster in the dry than in the moist soil. Calculations for sandy and loess soils, which have different water tension curves, have shown that the availability of K in the sandy soil is much more sensitive to changes in water tension than in the loess soil.
The simulation technique can thus be used to analyzed the influence of single factors on the availability of K and to estimate the extent of this influence.
Zusammenfassung
Um den Einfluss des Wassergehaltes des Bodens auf die Verfügbarkeit von Kalium zu untersuchen, wurde ein Rechenmodell angewendet, das den Transport eines Nährstoffs vom Boden zur Wurzel und dessen Verteilung in der Umgebung der Wurzel beschreiben soll. An einem Gefässversuch mit Zwiebelpflanzen bei unterschiedlicher Bodenfeuchte ergab die Rechnung eine befriedigende Übereinstimmung mit der gemessenen K-Aufnahme der Pflanzen. Daraus wird geschlossen dass das Modell realistisch genug ist, um auch die K-Dynamik im wurzelnahen Boden zu quantifizieren
Solche Rechnungen haben an einem Lössboden gezeigt, dass abnehmendem Wassergehalt
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- der K-Transport aus dem Boden zur Wurzel stark abnimmt,
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- dei K-Konzentration an der Wurzeloberfläche rascher sinkt, und daher
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- zunehmend steilere K-Konzentrations-Gradienten in Wurzelnähe enstehen.
Bei der gegebenen Wurzeldichte sinkt die K-Konzentration des feuchten Bodens im gesamten Volumen nahezu gleichmässig ab, während sie im trockenen Boden in der Mitte zwischen zwei Wurzeln nur wenig abnimmt. Die K-Aufnahmerate pro Einheit Wurzel sinkt daher in trockenem Boden viel rascher als in feuchtem Boden ab. Rechnungen an Sand- und Lössböden, die sich durch ihre Wasserspannungskurve deutlich unterscheiden, zeigen sinngemäss, dass ein Sandboden in seiner K-Verfügbarkeit auf Änderungen der Wasserspannung viel empfindlicher als ein Lössboden reagiert.
Die Modellrechnung ermöglicht es demnach, die Wirkung einzelner Faktoren der K-Verfügbarkeit zu erkennen und in ihrem Ausmass abzuschätzen.
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References
Adams F 1974 Soil Solution.In The Plant Root and its Environment. Ed. E W Carson. University Press of Virginia, Charlottesville.
Barber SA 1959 Relation of fertilizer placement to nutrient uptake and crop yield. II. Effects of row potassium, potassium soil-level, and precipitation.
Claassen N and Barber S A 1974 A method for characterizing the relation between nutrient concentration and flux into roots of intact plants. Plant Physiol. 54, 564–568.
Claassen N and Barber S A 1976 Simulation model for nutrient uptake from soil by a growing root system. Agron. J. 68, 961–964.
Claassen N, Syring K M and Jungk A 1986 Verification of a mathematical model by simulating potassium uptake from soil. Plant and Soil 95, 209–220.
Cushman J H 1979 An analytical solution to solute transport near root surfaces for low initial concentration. I. Equation development. Soil Sci. Am. J. 43, 1087–1090.
Hartge K H 1971 Die physikalische Untersuchung von Böden. Ferdinand Enke Verlag Stuttgart.
Kuchenbuch R and Jungk A 1982 A method for determining concentration profiles at the soil-root interface by thin slicing rhizospheric soil. Plant and Soil 68, 391–394.
Kuchenbuch R, Claassen N and Jungk A 1986 Potassium availability in relation to soil moisture. I. Effect of soil moisture on potassium diffusion, root growth and potassium uptake of onion plants. Plant and Soil 95, 221–231.
Newman E J 1966 A method of estimating the total root length in a sample. J. Appl. Ecol. 3, 139–145.
Nye P H and Marriott F H C 1960 A theoretical study of the distribution of substance around roots resulting from simultaneous diffusion and massflow. Plant and Soil 30, 459–472.
Paauw van der F 1958 Relations between the potash requirement of crops and meterological conditions. Plant and Soil 9, 254–268.
Passioura J B and Frere M H 1967 Numerical analysis of the convection and diffusion of solutes to roots. Austr. J. Soil Research 5, 149–159.
Rowell D L, Martin M W and Nye P H 1967 The measurement and mechanism of ion diffusion in soil. III. The effect of moisture content and soil solution concentration on the self-diffusion of ions in soils. J. Soil Sci. 18, 204–222.
Silberbush M and Barber S A 1983a Prediction of phosphorus and potassium uptake by soybeans with a mechanistic mathematical model Soil Sci. Soc. Am. J. 47, 262–265.
Silberbush M and Barber S A 1983b Sensitivity of simulated phosphorus uptake to parameters used by mechanistic-mathematical model. Plant and Soil 84, 93–100.
Vaidyanathan L V and Nye P H 1966 The measurement and mechanism of ion diffusion in soils. II. An exchange resin paper method for measurement of the diffusive flux. J. Soil Sci. 17, 175–183.
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Kuchenbuch, R., Claassen, N. & Jungk, A. Potassium availability in relation to soil moisture. Plant Soil 95, 233–243 (1986). https://doi.org/10.1007/BF02375075
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DOI: https://doi.org/10.1007/BF02375075