Comparing Manure Derived Struvite with Pure Struvite and Commercial Fertilizer for Growing Canola in a Growth Chamber.

Abstract

Concerns of phosphorus (P) contribution to eutrophication of water bodies is now resulting in stricter regulations of P use and release to the environment. As well, it is a limited natural resource on the plant and P scarcity is now seen as a possibility. These factors hav increased pressure to remove P from waste streams (e.g., municipal wastewater and hog manure) and reuse it. Hence the P precipitate struvite (MgNH₄PO₄ 6 H₂O) is a compound that will likely increase in importance over the next few years as an agricultural fertilizer.  Struvite recovery processes produce struvite of different levels of purity, often correlated to the expense of the process. The central question of this research is if struvite derived from hog manure (with its impurities) is comparable to pure struvite, and how these compare to commercial P fertilizer for agronomic uses. Five rates of application for each P source were used for growing canola in a low P alkaline soil over 56 days. Dry biomass yield and plant P uptake showed that pure struvite and manure struvite gave similar results, but that commercial fertilizer produced significantly greater biomass at each of the five rates of application. P uptake was very similar between amendments except at the highest rates where commercial fertilizer had greater P uptake. These results indicate additional expense in struvite reactor design for increased struvite purity is not needed from an agronomic perspective. Commercial fertilizer performed better than struvite due to struvite’s lower solubility in alkaline soil conditions.