Soil Phosphorus Dynamics in Response to Poultry Manure Amendment

Manure amendments are an excellent source of phosphorus (11) for crop production; however, animal manures differ in P availability. Poultry manure (PM) contains more stable mineral-associated P than many manures and may act as a longer-term P source when used in crop production. We used sequential fractionation and enzyme hydrolysis to evaluate the short-term effects of incorporating 0, 100, and 200 mg PM P kg(-1) of soil into two Maine soils. Results indicated that most PM P was present in the H2O- and HCl-soluble fractions (1936 and 5956 mg P kg(-1) manure, respectively), and that a large portion of stable organic P was present in the HCl fraction (3288 mg kg(-1)). Poultry manure application resulted in only a transient increase in H2O-P-i, implying rapid transfer to other fractions. A transformation of P-i from the NaHCO3 to the NaOH fraction was observed at Day 84 of the incubation with all treatments, indicating that soil properties influenced PM P dynamics. In the HCl fraction, some organic P became hydrolyzable and a portion was converted to other fractions. Comparing these data with those of a complementary study indicated that P from PM interacted differently with soil than did P from dairy manure. The observation of active interchange of P in different fractions during the incubation indicated that soil amendment with moderate levels of PM does not lead to accumulation of stable P forms and that the large HCl-P fraction (31.1% Of total P) unique to PM could act as a source of plant-available P in a short term (e.g., a growing season).