Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/11/2007
Publication Date: 9/10/2007
Citation: Bauer, P.J., Szogi, A.A., Vanotti, M.B. 2007. Agronomic effectiveness of calcium phosphate recovered from liquid swine manure. Agronomy Journal. 99:1352-1356.
Interpretive Summary: In a new swine manure treatment process, phosphorus is recovered from the liquid portion of the manure as calcium phosphate. We conducted this research to determine the usefulness of this material as a fertilizer for growing plants. Our greenhouse study included evaluating the recovered calcium phosphate at two particle sizes which are commonly used by the fertilizer industry. We found that the material can be used as a readily available phosphorus source when applied as small particles (between 0.5 to 1 mm). When applied as large particles (2 to 4 mm), the recovered calcium phosphate appears suitable as a slow release fertilizer. These results will be used by swine growers adopting this new manure treatment technology. The results appear also to be of significance for the fertilizer industry because they demonstrate that this material is useful as a phosphorus source.
Technical Abstract: A new manure treatment technology developed as an alternative to anaerobic lagoons on swine (Sus scrofa domesticus) farms includes solid-liquid separation and subsequent recovery of soluble phosphorus (P) as calcium phosphate from the wastewater. The objective was to determine the agronomic effectiveness of this calcium phosphate material. A greenhouse study was conducted with annual ryegrass (Lolium multiflorum). Three fertilizer materials were evaluated: the recovered P in two particle sizes (0.5 to 1.0 mm and 2.0 to 4.0 mm), and commercial triple superphosphate (TSP). Fertilizer rates were 0, 22, 44, 88, and 176 mg P/kg soil. Three harvests of the ryegrass were made at two-week intervals. Total P uptake increased linearly with application rate for all three fertilizer materials. At the highest application rate, total P uptake was 37.8 mg/pot for TSP, 26.2 mg/pot for the recovered P with small particle size, and 9.0 mg/pot for the recovered P with large particle size. Chemical analysis of the recovered P material revealed that over 99% of the P2O5 in the recovered calcium phosphate was plant available P, mostly as citrate-soluble. Mehlich-3 extractable soil P at the end of the experiment indicated that little of the large particle size of recovered P material dissolved and became available during this short 10-week study. The recovered P from swine wastewater can be useful as a readily available P source or as a slow release fertilizer depending on granule size.