Phosphorus Forms and Mineralization Potentials of Alabama Upland Cotton Production Soils Amended with Poultry Litter

The essential role of phosphorus (P) in almost all biological processes has led to its extensive studies. Phosphorus in its inorganic form (Pi) is required for metabolic reactions and energy transfer. In contrast, organic P (Po) forms become bioavailable usually after hydrolysis to Pi. Organic P dephosphorylation in the soil environment is largely dependent on the stereochemical and stereoisomeric structures of the compounds in question. In addition, Po dephosphorylation also depends on the types and enzymes sources involved in such catalytic activities. This chapter focuses on P fractions and mineralization potentials of different P forms in poultry litter amended soils of northern Alabama cropped with cotton. Phosphorus forms characterized by solution 31P nuclear magnetic resonance (NMR) spectroscopy showed orthophosphate to be the dominant form, accounting for 63.6–76.1 % of the total P forms in these soils. A sequential fractionation was used to separate soil Pi and Po into several fractions. The fractionation revealed that soil Pi was mainly associated with Fe and Al oxides and was not readily bioavailable. Water-, Fe- and Al- associated Pi increased in soils treated with poultry litter compared with the control. The Ca-Al bound Po was the most abundant fraction with more than 40 % of the total Po but the Ca-Al bound Po values was lower for the control and no-tilled soils. Phosphatase enzymes were able to hydrolyze 7–62 % water, 17–53 % Ca-EDTA, 18–88 % Na-EDTA, 40–77 % H2SO4, and 50–75 % NaOH extractable Po. Information obtained from this study indicates that P dynamics and uptake in cotton soils amended with poultry litter is not well understood. More research is needed to better understand the impact of poultry litter application on P forms and mineralization potentials in cotton production soils.