A review and meta-analysis of the agricultural potential of struvite as a phosphorus fertilizer

The low water solubility of struvite is thought to limit its agronomic utility as a phosphorus (P) fertilizer compared with highly soluble P fertilizers. Furthermore, struvite's fertilizer potential is complicated by its hypothesized soil pH-dependent solubility, crop-specific interactions, and limited availability of struvite-derived N, which may explain conflicting reports of crop responses to struvite compared with conventional P fertilizers. A systematic literature review and meta-analysis was conducted to evaluate the effects of soil pH, soil test P (STP), P rate, struvite particle size, and struvite-derived N on crop aboveground biomass, P concentration, P uptake, and N uptake. Struvite-fertilized plants yielded higher biomass, P concentration, and P uptake compared with ammonium phosphates, and superphosphates in soils with pH < 6 and crop responses decreased with increasing pH. Crop responses to struvite were inversely related to experiment duration to soil mass ratios (d kg⁻¹) used in greenhouse studies, opposite to the hypothesized benefit of more roots per unit soil on struvite dissolution. The proportion of total N applied derived from struvite increased with increasing struvite-P application rate and was inversely related to total N uptake, likely due to the increased crop reliance on slowly available struvite-N. Crop responses were potentially overestimated by high STP and/or P rates and underestimated due to N limitation from large proportions of total N applied derived from struvite. Evaluations of struvite collectively indicate its efficacy as a P fertilizer is affected by soil pH and its contribution to total N application.