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ARS Home » Southeast Area » New Orleans, Louisiana » Southern Regional Research Center » Commodity Utilization Research » Research » Publications at this Location » Publication #308606
Title: Forms and lability of phosphorus in humic and fulvic acids

Author
item He, Zhongqi
item TAZISONG, IRENUS - Alabama A & M University
item SENWO, ZACHARY - Alabama A & M University

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 3/18/2015
Publication Date: 10/2/2015
Citation: He, Z., Tazisong, I.A., Senwo, Z.N. 2015. Forms and lability of phosphorus in humic and fulvic acids. In: He, H, Wu, F., editors. Labile Organic Matter - Chemical Composition, Functions, and Significance in Soil and the Environment. SSSA Special Publication 62. Madison, WI:Soil Science Society of America. p. 61-78.

Interpretive Summary: Humic matter is a mixture of amorphous, polydespersed substances with yellow to brown-black color. Humic substances are involved in many biological and ecological processes in soils and natural waters. Humic acid (HA) and fulvic acid (FA) are two major fractions of humic matter. HA is the humic fraction that is soluble in alkaline solution but precipitate on acidification of the alkaline extracts. FA is soluble in alkaline solution and remain soluble on acidification of the alkaline extracts. In this chapter, we review and discuss the forms and lability of humic-bound P based on our own and colleagues' research on various humic fractions obtained from the International Humic Substances Society and extracted from different agricultural soils. Analysis of these data reveals that the impact on lability of humic-bound P is in the order: sample origin > humic fraction type > management factors. Knowledge and insights derived from this chapter are helpful in promoting the research on the role of humic-bound P in P cycling and nutrition in agricultural ecosystems as well as in the environment.

Technical Abstract: Humic substances are involved in many biological and ecological processes in soils and natural waters. Characterization of phosphorus (P) associated with humic substances may shed light on the function of humic substances in P cycling and nutrition. In this chapter, we review and discuss the forms and lability of humic-bound P based on our own and colleagues' research on various humic fractions obtained from the International Humic Substances Society and extracted from different agricultural soils. Solution 31P NMR spectroscopy reveals that the majority of humic-bound P are present in the forms of orthophosphate, monoesters and diesters. Spiking with phytate confirms no phytate present in the examined humic fractions. The biotic and abiotic lability of humic bound P was evaluated by enzymatic hydrolysis and ultraviolet irradiation. The wet chemistry analysis shows that 10% to 63% of humic-bound P is labile. The impact on lability of humic-bound P is in the order: sample origin > humic fraction type > management factors. Application of the knowledge gained from the comprehensive characterization by solution NMR spectroscopy and wet chemistry analysis in future research may lead to improved understanding of the dynamics and mechanisms of transformations of humic-bound P from unavailable to bioavailable forms in soil and the environment.