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Soil Phosphorus Availability as Measured by Displaced Soil Solutions, Calcium‐Chloride Extracts, Dilute‐Acid Extracts, and Labile Phosphorus
Author(s) -
Soltanpour P. N.,
Adams Fred,
Bennett A. C.
Publication year - 1974
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/sssaj1974.03615995003800020010x
Subject(s) - loam , chemistry , phosphorus , sorghum , chloride , calcium , soil water , zoology , agronomy , soil science , geology , biology , organic chemistry
Five rates of Ca(OH) 2 and four rates of Ca(H 2 PO 4 ) 2 · H 2 O were added in all combinations to samples of a P‐deficient, low pH, sandy loam soil. The treated soil was subjected to several wetting‐drying‐pulverizing cycles to facilitate equilibration. Soil solutions were subsequently displaced from subsamples and analyzed; other subsamples were extracted for P with 0.01 M CaCl 2 and dilute acide (0.025 N H 2 SO 4 + 0.05 N HCl); “labile P” was determined on subsamples from each treatment; a sorghum‐sudangrass hybrid ( Sorghum bicolor X S. sudanese ) was grown in the greenhouse to measure P availability. Maximum yield of test plants was obtained at about 22 µm of P in the displaced soil solution, 12 µm of P in the CaCl 2 extract, 80 ppm P on soil‐weight basis in dilute‐acid extract, and 50 ppm of “labile P” on soil‐weight basis. The P uptake was highly correlated with the logarithm of P concentration in soil solution ( r 2 = 0.93) and CaCl 2 extract ( r 2 = 0.93), logarithm of “labile P” ( r 2 = 0.86) and concentration of P in dilute acid extract ( r 2 = 0.87). All indexes were nearly equal as indicators of P availability.