HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Salcedo, I. H. Articles by Sampaio, E. V. S. B. Search for Related Content PubMed Articles by Salcedo, I. H. Articles by Sampaio, E. V. S. B. Agricola Articles by Salcedo, I. H. Articles by Sampaio, E. V. S. B.

Reactivity of Phosphorus in Northeastern Brazilian Soils Assessed by Isotopic Dilution

Setor de Radioagronomia, Dep. de Energia Nuclear, Univ. Federal de Pernambuco, 50 730 Recife, PE, Brazil

* Corresponding author.

ABSTRACT

To diagnose fertilizer requirements in regions of high soil variability where P-fixing capacities can vary 100-fold, single-extraction P tests must be complemented by an evaluation of P sorption. The isotopic-dilution kinetics of ³²P was tested for its potential to measure available P and to predict the degree of soil-fertilizer P reactivity. Six soils from northeastern Brazil were fertilized with P, incubated (1, 42, and 84 d) and then seeded with pearl millet [Pennisetum glaucum (L.) R. Br.]. Soil samples were analyzed for water-soluble P (P_w), resin P, ³²P in solution 1 min after addition over ³² P added (R₁/R₀), rate of ³²P disappearance from solution between 1 and 100 min (n), reversible P (P_rev, determined by double isotopic dilution), mobile P (P_m = P_w + P_rev), and isotopically exchangeable P (E₁ and E-value [E] for 1-min and 24-h equilibrium periods, respectively). Use of R₁/R₀ successfully differentiated soils in terms of net fertilizer effects on P_w and P_m with time. We found that P_w and P_m were better predictors of plant P uptake than resin P, E₁, and E, since the latter quantities overestimated available P in a high-P-fixing Oxisol. Based on this and published data, we propose a critical value of R₁/R₀ (0.26) below which E values consistently overestimated labile P, while P_w correlated satisfactorily with available P. A modified technique overcomes limitations of measuring very low concentrations of P_w in such soils. To diagnose labile P and fertilizer responses in soils with R₁/R₀ > 0.26, we propose a simplified methodology that avoids the double isotopic dilution.

Received for publication November 18, 1988.

This article has been cited by other articles:

				E. Lombi, K. G. Scheckel, R. D. Armstrong, S. Forrester, J. N. Cutler, and D. Paterson Speciation and Distribution of Phosphorus in a Fertilized Soil: A Synchrotron-Based Investigation Soil Sci. Soc. Am. J., October 27, 2006; 70(6): 2038 - 2048. [Abstract] [Full Text] [PDF]

				E. Lombi, M. J. McLaughlin, C. Johnston, R. D. Armstrong, and R. E. Holloway Mobility and Lability of Phosphorus from Granular and Fluid Monoammonium Phosphate Differs in a Calcareous Soil Soil Sci. Soc. Am. J., March 1, 2004; 68(2): 682 - 689. [Abstract] [Full Text] [PDF]

				S. Sinaj, C. Stamm, G. S. Toor, L. M. Condron, T. Hendry, H. J. Di, K. C. Cameron, and E. Frossard Phosphorus Exchangeability and Leaching Losses from Two Grassland Soils J. Environ. Qual., January 1, 2002; 31(1): 319 - 330. [Abstract] [Full Text] [PDF]

				S. Sinaj, F. Machler, and E. Frossard Assessment of Isotopically Exchangeable Zinc in Polluted and Nonpolluted Soils Soil Sci. Soc. Am. J., November 1, 1999; 63(6): 1618 - 1625. [Abstract] [Full Text] [PDF]