WASTEWATER CHEMISTRY AND FRACTIONATION OF BIOACTIVE PHOSPHORUS IN DAIRY MANURE

Authors: Dao, Thanh; LUGO-OSPINA, ANCIZAR - USDA, ARS, ANRI, AMBL; Reeves Iii, James; ZHANG, H - OK STATE UNIVERSITY

Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/2/2005
Publication Date: 3/31/2006
Citation: Dao, T.H., Lugo-Ospina, A., Reeves Iii, J.B., Zhang, H. 2006. Wastewater chemistry and fractionation of bioactive phosphorus in dairy manure. Communications in Soil Science and Plant Analysis. 37:907-924.

Interpretive Summary: As phosphorus is excreted in manure as inorganic and organic forms, confined animal feeding operations waste management also means that the operator has to be conscious of manure handling and collection, and manure storage practices. Storage conditions may be optimized to minimize the conversion of insoluble phosphorus to soluble bioavailable forms to reduce the risk of transport and dispersion of manure phosphorus prior to or during land application. Accurate information about manure phosphorus is also needed because of the high variability of phosphorus content over time and space. Bioactive forms are also important from an environmental perspective because they are biologically reactive. Accurate knowledge of manure composition, rates, and timing of land application can be optimized to prevent nutrient buildup and to reduce bioactive P loss from fields containing excessive levels of manure nutrients. The study was conducted to develop an enzymatic fractionation method for bioactive forms that are present in 107 samples of dairy manure collected across the northeastern US. The results showed that the entire sample set had a larger P fraction that was readily hydrolyzable by added phytases in manure of dairy cattle. The use of an enzymatic system shows that the source P forms are biologically active or susceptible to biodegradation. The approach may increase the practicality of widespread measurements of nutrient availability in animal manure and help livestock producers more efficiently manage their manure resources and comply with their nutrient management plans in threatened watersheds near major surface water bodies and fragile estuary ecosystems.

Technical Abstract: Accurate information about bioactive organic forms of phosphorus (P) in animal manure is important for the application of appropriate post-excretion treatment of manure because organic P forms are considered bioavailable upon hydrolysis. The study was conducted to (1) develop a fractionation method for bioactive forms that are present as water-soluble and complexed inorganic and organic P in 107 samples of dairy manure collected across the NE US, and (2) determine the relationships between these P forms and other manure chemical characteristics. Detailed knowledge of P chemistry and transformation processes may contribute to the development of multi-modal manure treatment approaches. Water-extractable P (WEP) varied considerably between sampling locations, ranging from 4 to 1355 mg L-1, and was weakly correlated to total P (TP) content of the manures. Water-extractable P and anion-exchange P (AEP) were more closely related (r2 = 0.478) and suggested that, as simple as the measurement of WEP is, manure WEP may be a quick indicator of bioactivity and impact of dairy manures on aquatic environment. More notably, the results showed that the entire sample set had a larger P fraction that was readily hydrolyzable by exogenous phytases. The phytase- hydrolyzable P (PHP) assay corroborated the presence of phytic acid (IP6) and other myo-inositol phosphomonoesters in manure of dairy cattle. The conditions of the fractionation of PHP in dairy manure are mild and tend to preserve the chemical integrity of bioactive P forms. The simplicity of the PHP fractionation procedure may increase the practicality of widespread measurements of composition and P bioavailability in animal manure.