Struvite as a P Fertilizer Source for Irrigated Vegetables on Calcareous Soils

Struvite derived from a proprietary fluidized bed reactor system that recovers ammonia and phosphate from nutrient rich fluids, including waste streams, is a pearl or granule based P fertilizer and marketed by Ostara as “Crystal Green (CG)”.  However, little is known on the efficacy of this product as a P fertilizer source on calcareous soils in the southwestern United States.  Field studies were conducted from 2010 through 2014 comparing this struvite P fertilizer source (CG) against, and in combination with, commonly used commercial P fertilizers (triple superphosphate (TSP) and mono-ammonium phosphate (MAP)).  Studies were conducted with lettuce (Lactuca sativa), watermelons (Citrullus lanatus), carrot (Daucus carota), potato (Solanum tuberosum), celery (Apium graveolens), and onions (Allium cepa).   For lettuce, CG produced higher yields than TSP in one experiment but lower yields than MAP in two experiments.  CG generally produced higher potato yields than MAP.  For most cropping systems, CG produced yields comparable to the conventional P sources.   Selected blends of CG and MAP show promise, especially for the longer season crops and crops grown into the warm season such as carrot and potato.