Premium
Phosphorus in Hawaiian Kikuyugrass Pastures and Potential Phosphorus Release to Water
Author(s) -
Mathews B. W.,
Carpenter J. R.,
Sollenberger L. E.,
Tsang S.
Publication year - 2005
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2004.0393
Subject(s) - oxisol , phosphorus , pasture , chemistry , ultisol , oxalate , inceptisol , ammonium oxalate , environmental chemistry , saturation (graph theory) , agronomy , zoology , soil water , environmental science , biology , soil science , inorganic chemistry , mathematics , organic chemistry , combinatorics
Pasture systems in Hawaii are based primarily on kikuyugrass ( Pennisetum clandestinum Hochst. ex Chiov.). Relationships among kikuyugrass P concentration, animal P requirements, and various soil P determinations are needed to help identify source areas for implementing pasture management strategies to limit P loss via overland flow. A total of 51 rotationally stocked kikuyugrass pastures (>20 yr old) with contrasting soil chemical properties were sampled. A satisfactory predictive relationship between modified‐Truog (MT)‐extractable phosphorus (P MT ) and dissolved (<0.45‐μm pore diameter), molybdate‐reactive phosphorus (DRP) desorbed from soil in a water extract (DRP WE ) was found when 0‐ to 4‐cm‐depth data for the soil orders with medium to high DRP WE (two Mollisols and an Inceptisol) were pooled separately from those with low DRP WE (five Andisols, three Ultisols, and an Oxisol). The oxalate phosphorus saturation index (PSI ox ) procedure was the best predictor of DRP WE across soil orders when oxalate‐extractable molybdate‐reactive phosphorus (RP ox ) was used to calculate PSI ox (PSI ox RP) rather than when total oxalate‐extractable phosphorus (TP ox ) was used (PSI ox TP). There was little DRP WE until PSI ox RP exceeded 6% or PSI ox TP exceeded 8%. A more empirical dilute‐acid phosphorus saturation index (PSI MT ) was also calculated using P MT and MT‐extractable iron (Fe MT ) and aluminum (Al MT ). The PSI MT procedure showed some utility in predicting DRP WE , was positively related to the PSI ox procedures, and can be more readily performed in agronomic soil testing laboratories than PSI ox The present research suggests that while Hawaiian kikuyugrass pastures tend to be sufficient to high in forage P, potential soil P release to water only appeared to be a possible environmental concern for the Mollisol and Inceptisol sites.