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Availability of Residual Phosphorus from Long‐Time Rock Phosphate and Superphosphate Applications to Groseclose Silt Loam
Author(s) -
Moschler W. W.,
Krebs R. D.,
Obenshain S. S.
Publication year - 1957
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/sssaj1957.03615995002100030011x
Subject(s) - phosphorite , loam , phosphorus , phosphate , fertilizer , silt , apatite , chemistry , agronomy , phosphate fertilizer , environmental chemistry , mineralogy , environmental science , geology , soil water , soil science , paleontology , organic chemistry , biology
The availability of residual phosphorus from long‐time superphosphate applications to Groseclose silt loam exceeded that of rock phosphate. Based on A values, residual phosphorus from superphosphate was approximately four times as available as that from rock phosphate. Data on total, Truog, and NaHCO 3 ‐soluble phosphorus showed that: (1) more of the superphosphate had reacted with the soil than had rock phosphate; (2) more of the phosphorus applied as superphosphate had accumulated in the silt and clay factions of the soil and, based on solubility in NaHCO 3 , was relatively available; and (3) more of the phosphorus applied as rock phosphate had accumulated in the sand fraction of the soil and was relatively unavailable, as judged by solubility in NaHCO 3 . Apparently, some of the rock phosphate had not reacted with the soil and was still in its original molecular combination. X‐ray analysis revealed the presence of apatite or a mineral similar to apatite in the sand fraction of soil that had received rock phosphate. The mineral, which gave pronounced reflections at the same values obtained from rock phosphate fertilizer, was not found in soil receiving superphosphate. Approximately three‐quarters of the phosphorus applied over a 40‐year period from either source was present in the soil as residual phosphorus. This quantity nearly doubled the total phosphorus content of the soil. Crop yields on plots receiving the two fertilizers have been equal except for the first few years when superphosphate produced higher yields.