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The Longer‐Term Phytoavailability of Biosolids‐Phosphorus
Author(s) -
Miller Matt,
O'Connor George A.
Publication year - 2009
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/agronj2008.0197x
Subject(s) - biosolids , phosphorus , nutrient , environmental science , fertilizer , environmental chemistry , agronomy , zoology , chemistry , environmental engineering , biology , organic chemistry
Phosphorus based nutrient management could limit biosolids application to rates based on crop fertilizer P recommendations (P‐based rates). Determinations of biosolids P phytoavailability relative to inorganic P fertilizers are necessary when P‐based rates are mandated. Previous shorter‐term (≤4 mo) studies successfully distinguished P phytoavailability differences among biosolids, but the longer‐term (>4 mo) phytoavailability of biosolids‐P is incompletely characterized. Furthermore, no a priori tool exists to distinguish biosolids relative P phytoavailability differences. A 16‐mo greenhouse study was conducted to characterize the longer‐term phytoavailability of biosolids‐P and to identify a useful measure of biosolids‐P phytoavailability. Seven biosolids and triple super phosphate (TSP) were used as P sources and applied to an Immokalee soil (sandy siliceous, hyperthermic Arenic Alaquod) at three P application rates: 56 (P‐based rate), 112, and 224 kg ha −1 (N‐based rate). Bahiagrass ( Paspalum notatum Flugge) was grown continuously in soil columns and harvested every 4 to 8 wk to characterize P uptake. The longer‐term relative P phytoavailability of less soluble‐P biosolids was ∼50 to 80% that of TSP, but more soluble‐P biosolids were as phytoavailable as TSP. Estimates of biosolids relative P phytoavailability were well correlated with biosolids phosphorus saturation index (PSI; the molar ratio of oxalate‐extractable P to oxalate‐extractable iron and aluminum) values, suggesting that biosolids PSI values could be used to distinguish P phytoavailability differences among biosolids. Biosolids application rates should increase to account for the reduced relative P phytoavailability of less soluble‐P biosolids, but no application rate adjustment is warranted more soluble‐P biosolids.