Interactions between\nStruvite and Humic Acid and Consequences\non Fertilizer Efficiency in a Nonacidic Soil

The effect of humic acid extracted from peat (AHt) on\nimproving\nthe struvite (STR) fertilizing efficiency is explored. To this end,\na soil incubation study is correlated to plant assays comparing STR,\nSTR-AHt, and superphosphate (SSP). Characterization techniques confirm\nthe incorporation of the AHt into the STR. The P-pool distribution\nof STR and SSP is similar in the soil incubation, with STR-AHt presenting\na higher labile P at 90 days passing from 10 to 15% P from SSP and\nSTR to 25% P with STR-AHt. However, when applied to barley and tomato,\nSTR yields more shoot P content, aboveground biomass, and residual\nP in soil than SSP. STR-AHt does not improve the STR results. The\npoor correlation observed between soil incubation and plant trials\nhighlights the role of the rhizosphere in testing the fertilizer efficiency\nof STR. Mechanistic assays indicate the key role of rhizosphere pH.\nFinally, molecular modeling reveals a higher stabilization of STR\nwith AHt, which could reduce P release decreasing the fertilizing\npotential of STR-AHt, as observed in the pot trials.