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Effects of Soil Properties on Plant‐Available Phosphorus Determined by the Isotopic Dilution Phosphorus‐32 Method
Author(s) -
Sen Tran T.,
Giroux M.,
Fardeau J. C.
Publication year - 1988
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1988.03615995005200050033x
Subject(s) - soil water , chemistry , oxalate , phosphorus , cation exchange capacity , adsorption , isotope dilution , dilution , environmental chemistry , inorganic chemistry , soil science , chromatography , geology , thermodynamics , mass spectrometry , physics , organic chemistry
A procedure using 32 P isotopic exchange kinetics was suggested to characterize the availability of soil P. The ratio of the radioactivity remaining in the solution over the total radioactivity ( r 1 / R ) was closely and inversely proportional to the maximum P‐fixation capacity (M) estimated by the Langmuir isotherm ( r = 0.82**, significant at the 0.01 probability level) and to the P‐buffering capacity (Mb) ( r = 0.71**). The 1/ r 1 / R ) ratio was also correlated with oxalate‐Al ( r = 0.69**) and oxalate‐Fe ( r = 0.35**). The kinetic parameter, n , described as the decrease of radioactivity remaining in the solution with time, was related to the soil pH ( r = −0.52**), the prevailing form of soil P (Mehlich ratio Q, r = −0.50**), the P‐fixation capacity ( r = 0.44**), and organic matter ( r = 0.44**). The isotopically exchangeable P ( E 1 value) was closely related to the plant P uptake on soils having low P‐adsorption capacity (Group III, r = 0.90**). However, E 1 value may overestimate the available P on high P‐fixing soils especially for acid Spodosols (Group I, r = 0.47**). The water soluble P ( M 1 ) or the labile P pool ( M 1 + M 2 ) showed a curvilinear (logarithmic) relationship with plant P uptake and the correlation coefficient was higher than that obtained from E 1 when grouping all soils together. The effect of soil properties on the relation between plant P uptake and E 1 , log M 1 , or log ( M 1 + M 2 ) was confirmed by the increase of the coefficient of determination ( R 2 ) of the multiple regression including soil parameters as second variable. An exponential relationship was observed between relative yield (%) and E 1 , M 1 , ( M 1 + M 2 ); the R 2 value was 50.4, 65.1, and 68.1%, respectively. The three classes of soil P fertility (poor, medium, rich) were established for E 1 , M 1 , and ( M 1 + M 2 ) according to the Cate and Nelson procedure.