Controlled release and soil phosphorus distribution of calcium phosphate nanofertilizers in a calcareous soil: a column study

The use of calcium phosphate (Ca-P)-based nanofertilizers is a promising approach to improve phosphorus (P) use efficiency under calcareous soil conditions where P fixation and losses limit its availability. This study investigated the controlled release and leaching behavior of hydroxyapatite (HA), dicalcium phosphate dihydrate (DCPD), and polyphosphate-modified DCPD (DCPD-PolyP) using soil columns, compared with soluble triple superphosphate (TSP). Cumulative P and Ca leaching were monitored over 30 days and fitted to kinetic models. The Korsmeyer-Peppas model best described cumulative P leaching (R 2 > 0.96), consistent with predominantly diffusion-controlled behavior and slower apparent leaching from DCPD-PolyP nanomaterials than from TSP. DCPD-PolyP also showed the most balanced P dynamics, combining low P mobility with higher Olsen-P availability than HA. Principal component and correlation analyses revealed that P leaching was governed by Ca-P phase solubility and soil physico-chemical properties interactions. Overall, Ca-P nanofertilizers tended to reduce P mobility relative to TSP, with 26% of the applied P remaining Olsen-extractable and concentrated in the surface layer after leaching, while sustaining gradual nutrient supply under the conditions evaluated. These results highlight the potential of DCPD-PolyP as a controlled-release P source for alkaline soils and provide a basis for designing nanofertilizers optimized for carbonate-rich environments.