Phosphorus Flux in Soil Increased with Organic Acid Complexatoin.

Phosphorus (P) fertilizer is used abundantly to maximize growth of crops and other plants. Reduction of P fertilizer is warranted, as it is the primary source of nutrient pollution in surface waters (eutrophication leading to hypoxia) and is derived from non-renewable mineral resources. A lab study was conducted to determine P flux through soil as a result of combining a humic/fulvic acid (Carbond® P) with P fertilizers. An untreated control was compared to ammonium polyphosphate (liquid APP; 34% P₂O₅), monoammonium phosphate (solid MAP; 52% P₂O₅), and Carbond® P (liquid; 24% P₂O₅) applied either as a band or mixed with three soils at 20 or 80 kg ha^-1 P₂O₅. Mobility of P was evaluated at 24, 48, and 110 days after application by applying two pore volumes of water to 25 cm tall soil columns. For the banded applications, Carbond P consistently had significantly greater phosphorus flux for all soils and application rates. For applications mixed with soil, Carbond® P and mono-ammonium phosphate had greater solubility than ammonium polyphosphate at 24 days after application, but by the later evaluation dates the Carbond P was significantly higher than both. Further work is needed to evaluate the impact of P in other environments, as well as evaluating the plant availability of the Carbond® complexed P and how this may improve fertilizer use efficiency.