Premium
Forms and Lability of Phosphorus in Humic Acid Fractions of Hord Silt Loam Soil
Author(s) -
He Zhongqi,
Olk Daniel C.,
Cade-Menun Barbara J.
Publication year - 2011
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/sssaj2010.0355
Subject(s) - lability , chemistry , loam , humic acid , phytase , phosphorus , fertilizer , manure , environmental chemistry , soil water , agronomy , biochemistry , organic chemistry , biology , ecology
Phosphorus has long been known to be present in soil humic fractions, but little is known about specific P forms in humic fractions or their lability. We extracted the mobile humic acid (MHA) and recalcitrant calcium humate (CaHA) fractions from a Nebraska Hord silt loam soil (a fine‐silty, mixed, superactive, mesic Cumulic Haplustoll) under continuous corn ( Zea mays L.) receiving either inorganic fertilizer or animal manure. Solution 31 P nuclear magnetic resonance spectroscopy demonstrated that P in both MHA and CaHA was predominantly present in organic forms, mostly as orthophosphate monoesters. Spiking experiments indicated no phytate present in these humic fractions, but scyllo ‐inositol P was identified in all samples. Potato phosphatase hydrolyzed some humic‐bound P. Fungal phytase released more humic‐bound P, which may come from scyllo ‐inositol P. No additional P was released by including nuclease. Ultraviolet (UV) irradiation increased soluble inorganic P in MHA fractions, but total hydrolyzable P in MHA fractions did not increase, suggesting that the portion of P that was UV labile was also enzymatically hydrolyzable. In contrast, UV irradiation increased soluble inorganic P and total hydrolyzable P in CaHA fractions, which suggests that UV‐labile P in CaHA fractions did not overlap with enzymatically hydrolyzable P. Fertilization management did not significantly alter the lability of humic P in these humic fractions. This research has the potential to improve P management by increasing our knowledge of P lability for more efficient crop uptake.