ARS | Publication request: Phosphorus recovered from swine wastewater as a fertilizer for cotton grown with conservation tillage

Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 14, 2011
Publication Date: May 10, 2012
Citation: Bauer, P.J., Szogi, A.A., Novak, J.M., Vanotti, M.B. 2012. Phosphorus recovered from swine wastewater as a fertilizer for cotton grown with conservation tillage. Journal of Cotton Science. 16:97-104.

Interpretive Summary: When phosphorus is precipitated from swine wastewater in an advance manure treatment process, it is recovered as calcium phosphate. We conducted this research to determine the usefulness of this material as a fertilizer for cotton grown with conservation tillage. Our field study included evaluating the recovered calcium phosphate at two particle sizes which are commonly used by the fertilizer industry. We found that plant available phosphorus in the soil was higher than a commercial fertilizer when the material was applied as small particles (between 0.5 to 1 mm). When applied as large particles (2 to 4 mm), the plant available phosphorus in the soil was similar to a commercial fertilizer. The recovered calcium phosphate has low water solubility so does not provide early season benefits to crops like more water soluble fertilizers. 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 suggest that this material can be used for conservation tillage crop production, especially if applied as small particles.

Technical Abstract: Current technologies for recycling phosphorus (P) from animal waste through precipitation result in non-conventional fertilizer products. The objective of this research was to evaluate the use of surface broadcasting recovered calcium phosphate as a P fertilizer source for cotton (Gossypium hirsutum L.) when grown after winter rye (Secale cereale L.) biomass crop using conservation tillage. Treatments in this two year field study were fertilizer material [no P fertilizer, recovered P with particle size of 0.5 – 1.0 mm, recovered P with particle size of 2.0 – 4.0 mm, and diammonium phosphate (DAP)]. Fertilizer application rate was 168 kg P2O5 ha-1. Plant available P (Mehlich 1) and soil water P in the surface 10 cm were measured monthly. Crop biomass and P uptake and cotton seed P were determined. The ranking among treatments both years for plant available soil P was recovered P in 0.5 – 1.0 mm particles > recovered P in 2.0 – 4.0 mm particles = DAP > control. For soil water P, DAP was consistently higher than the control, but the two particle sizes of recovered P were similar to the control. No differences occurred in rye growth or P uptake among the two recovered P treatments and the control either year. The DAP increased rye biomass and P uptake early in the season in the second year of the study, but not in the first. Treatments did not differ for cotton P uptake or yield. When used as a fertilizer, recovered calcium phosphate should be applied in small particles.