Abstract
Mobilization of soil P as the result of plant-induced changes of soil pH in the vicinity of plant roots was studied. Seedlings of ryegrass were grown in small containers separating roots from soil by a 30-μm meshed nylon screen which root hairs could penetrate but not roots. Two soils were used, a luvisol containing P mainly bound to calcium and an oxisol containing P mainly bound (adsorbed) to iron and aluminum. Plant-induced changes of soil pH were brought about by application of ammonium-or nitrate-nitrogen. After plants had grown for 10 d the soil was sliced in thin layers parallel to the root mat which had developed on the screen, and both soil pH and residual P determined. Mobilization of P was assessed by P-depletion profiles of the rhizosphere soil.
Soil pH at the root surface decreased by up to 1.6 units as the result of ammonium N nutrition and it increased by up to 0.6 units as the result of nitrate N nutrition. These changes extended to a distance between 1 and 4 mm from the root surface depending on the type of soil and the source and level of nitrogen applied. In the luvisol, compared to zero-N treatment, P mobilization increased with the NH4-induced decrease in pH, whereas the NO3-induced pH increase had no effect. In contrast, in the oxisol a similar pH decrease caused by NH4 nutrition had no effect, whereas the pH increase caused by NO3 increased markedly the mobilization of soil P. It is concluded that in the luvisol calcium phosphates were dissolved by acidification, whereas in the oxisol adsorbed phosphate was mobilized by ligand exchange.
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References
Adams F 1974 Soil solution. In The Plant Root and Its Environment, Ed. E WCarson. pp 441–482. University Press of Virginia, Charlottesville, VA.
Bekele T, Cino B J, Ehlert P A J, van derMaas A and vanDiest A 1983 An evaluation of plant-borne factors promoting the solubilization of alkaline rock phosphates. Plant and Soil 75, 361–378.
Blair G J, Mamaril C P and Miller M H 1971 Influence of nitrogen source on phosphorus uptake by corn from soils differing in pH. Agron. J. 63, 235–238.
Earl K D, Syers J K and McLaughlin J R 1979 Origin of the effects of citrate, tartrate and acetate on phosphate sorption by soils and synthetic gels. Soil Sci. Soc. Am. J. 43, 674–678.
Hedley M J, Nye P H and White R E 1982a Plant-induced change in the rhizosphere of rape seedlings. (Brassica napus, var. Emerald). Plant-induced change in the rhizosphere of rape (Brassica napus, var. Emerald). II. Origin of pH change. New Phytol 91, 31–44.
Hedley J M, White R E and Nye P H 1982b Plant-induced change in the rhizosphere of rape (Brassica napus, var. Emerald). III. Changes in L value, soil phosphate fractions and phosphatase activity. New Phytol. 91, 45–56.
Hoffland E, Findenegg G R and Nelemans J A 1989 Solubilization of rock phosphate by rape. II. Local root exudation of organic acids as a response to P-starvation. Plant and Soil 113, 161–165.
Jungk A 1967 Einfluss von Ammonium- und nitratstickstof auf das Kationen-Anionen-Gleichgewicht in Pflanzen und seine Beziehung zum Ertrag. Landw. Forsch., 21. Soheft, 50–63.
Kirkby E A and Mengel K 1967 Ionic balance in different tissues of the tomato plant in relation to nitrate, urea and ammonium nutrition. Plant Physiol. 42, 6–14.
Kitson R E and Mellon M G 1944 Colorimetric determination of phosphorus as molybdovanadophosphoric acid. Ind. Eng. Chem. Anal. Ed. 16, 379–383.
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.
Kurmies B 1972 Zur Fraktionierung der Bodenphosphate. Die Phosphorsäure 29, 118–151.
Lindsay W L and Moreno E C 1960 Phosphate phase equilibria in soils. Proc. Soil Sci. Soc. Am. 24, 177–182.
Marschner H and Römheld V 1983 In vivo measurements of root induced pH change at the soil-root interface: Effect of plant species and nitrogen source. Z. Pflanzenphysiol. 111, 241–251.
Murphy J and Riley J P 1962 A modified single solution method for determination of phosphate in natural waters. Anal. Chim. Acta 27, 31–36.
Nagarajah S, Posner A M and Quirk J P 1968 Desorption of phosphate from kaolinite by citrate and bicarbonate. Soil Sci. Soc. Am. Proc. 32, 507–510.
Nye P H 1981 Change in pH across the rhizosphere induced by roots. Plant and Soil 61, 7–26.
Nye P H 1984 pH change and phosphate solubilization near roots. An example of coupled diffusion processes. ASA Special Publication No. 49, 89–100.
Parfitt R L 1978 Anion adsorption by soils and soil materials. Adv. Agron. 30, 1–50.
Pirschle K 1931 Nitrat und Ammoniumsalze als Stickstofquellen für höhere Pflanzen bei konstanter Wasserstoffionen-konzentration III. Planta 14, 583–676.
Riley D and Barber S A 1971 Effect of ammonium and nitrate fertilization on phosphorus uptake as related to root induced pH change at the soil-root interface. Soil Sci. Soc. Am. Proc. 35, 301–306.
Scheffer F, Ulrich B and Benzler J H 1960 Bestimmung von Phosphorsäure und Kieselsäure als Molybdänblau. Landw. Forsch. 13, 191–201.
Welp G, Herms U and Brümmer G 1983 Einfluss von Bodenreaktion, Redoxbedingungen und organischer Substanz auf die Phosphatgehalte der Bodenlösung. Z. Pflanzenernaehr. Bodenkd. 146, 38–52.
Youssef R A and Chino M 1988 Development of a new rhizobox system to study the nutrient status in the rhizosphere. Soil Sci. Plant Nutr. 34, 461–467.
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Gahoonia, T.S., Claassen, N. & Jungk, A. Mobilization of phosphate in different soils by ryegrass supplied with ammonium or nitrate. Plant Soil 140, 241–248 (1992). https://doi.org/10.1007/BF00010600
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DOI: https://doi.org/10.1007/BF00010600