Current technologies for recycling 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.
