Phosphorus (P) is an essential nutrient for crop growth but its availability in soils is often limited due to precipitation in secondary minerals, adsorption to clays, or fixation/immobilization with organic matter. Plant available P (Pavail) in young volcanic soils may be high due to rapid weathering of primary minerals. This study assesses the content of plant-available P in agricultural and nonagricultural soils after 26 years of pyroclastic (ash and lahar) deposition from 1991 Mt. Pinatubo eruption. Pavail concentrations of modern soils (56-152 mg/kg) under different land-use types did not differ significantly (Fig. 4). Buried soils from high altitude forest and grassland have deficient Pavail concentration at 5 and 2 mg/kg, respectively. Buried soil of IR-Lahar has significantly higher Pavail (136 mg/kg) even with minimal inorganic fertilizer application compared to IR-Ash (24 mg/kg) applied with 18-27 kg P/ha/yr (as per comm. with farm owners).
Quimbo, M., Delmelle, P., & Sanchez P. (2018). Plant-available phosphorus in young volcanic soils developed on pyroclasts from the 1991 eruption of Mt. Pinatubo, Philippines. Midi de rencontre des étudiants-chercheurs 2018, Louvain-la-Neuve, Belgium. https://hdl.handle.net/2078.5/58190