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Manure and Mineral Fertilizer Effects on Seasonal Dynamics of Bioactive Soil Phosphorus Fractions
Author(s) -
Schwartz R. C.,
Dao T. H.,
Bell J. M.
Publication year - 2011
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj2011.0165
Subject(s) - phosphorus , chemistry , sorghum , manure , agronomy , loam , fertilizer , zoology , phosphate , soil water , environmental chemistry , environmental science , biology , soil science , organic chemistry
Seasonal fluctuations in bioavailable soil P can influence soil test results and associated assessment of off‐site transport risk. Our objective was to evaluate changes in soil P speciation and availability with time following applications of grain fed cattle ( Bos taurus ) manure or monoammonium phosphate (MAP). Beef cattle manure or MAP was applied at a targeted rate of 200 kg P ha −1 on a Pullman clay loam (fine, mixed, superactive, thermic Torrertic Paleustolls) in 2005 and 2006 and planted to grain sorghum [ Sorghum bicolor (L.) Moench]. Soil samples (0–0.15 m) were collected before and throughout the growing season and analyzed for Mehlich‐3 phosphorus (Me3P), 1:10 water‐extractable phosphorus (WEP10), water extractable cations, pH, and fractions of bioactive soil phosphorus (TBIOP), which comprised 1:100 water extractable P, ethylenediamine‐N,N,N′,N′‐tetraacetate (EDTA)‐exchangeable inorganic phosphorus (EEPi) and the EDTA‐exchangeable phosphohydrolase‐labile phosphorus (EPHP). Levels of soil Me3P, WEP10, and all fractions of TBIOP in MAP‐amended plots fluctuated significantly ( p < 0.05) during both seasons. Except for Me3P, manure amended plots also exhibited significant ( p < 0.05) seasonal variations in soil extractable P and a delayed release of P that extended well into the growing season. In contrast, fluctuations in extractable soil P in unamended plots were not significant except EPHP. In water extracts, a significant ( p < 0.05) dependence of solution P on pH and Ca suggested that precipitation‐dissolution reactions contributed to observed seasonal fluctuations in P. Fluctuations in total bioactive soil P were two to four times greater than aboveground biomass P highlighting the importance of accounting for seasonal dynamics in assessing offsite P transport risks.