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Phosphorus Relationships in Flooded Rice Soils with Low Extractable Phosphorus
Author(s) -
Shahandeh H.,
Hossner L. R.,
Turner F. T.
Publication year - 1994
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/sssaj1994.03615995005800040025x
Subject(s) - soil water , phosphorus , chemistry , oxalate , agronomy , desorption , soil test , environmental chemistry , oryza sativa , fertilizer , paddy field , adsorption , environmental science , soil science , inorganic chemistry , biology , organic chemistry , biochemistry , gene
Rice ( Oryza sativa L.) grain yields on some flooded soils are not increased by P fertilizer despite their low soil test P status determined on air‐dry soils by soil test methods such as Bray, Olsen, or Texas A&M. Conventional soil test methods apparently do not accurately assess the capacity of these soils to supply P to rice grown under flooded conditions. To test the possibility of an Fe‐P association, oxalate extractant (which would extract noncrystalline Fe and its associated P) was used to provide a more accurate measure of available P in flooded soil. Phosphorus response experiments were conducted on 10 rice soils under greenhouse and field conditions and related to the oxalate‐extractable Fe and P, P uptake, P adsorption, and P desorption under aerobic and anaerobic conditions. Oxalate‐extractable Fe significantly increased under anaerobic conditions in all soils including the soils that were nonresponsive to P and had low levels of extractable P using conventional extractants. Phosphorus adsorption and desorption data confirmed the importance of oxalate extractant in predicting P availability following anaerobiosis. The inability of Bray 1, Olsen, and Texas A&M soil test methods to accurately predict P availability in flooded rice soil appears to be due to their failure to extract the active reductant‐soluble P fraction. The measurement of P associated with poorly crystalline Fe by oxalate extractant is a useful soil test method for predicting the availability of P in flooded rice soils.