Phosphorus and potassium mineralization as affected by phosphorus levels and soil types under laboratory condition.

Nutrients' mineralization‐immobilization in soil is crucial for their management in crop production. An incubation experiment was conducted to study the effects of phosphorus levels on mineralization of phosphorus (P) and potassium (K) under three soil types in laboratory conditions at the National Soil Science Research Center in Nepal with 3 × 4 factorial completely randomized design. Two factors were three soil types (silty clay loam, loam, and sandy loam) and four P levels: 0, 25, 50, and 75 kg P2O5 ha–1. Five incubation periods (1, 30, 60, 90, and 120 d after incubation) were replicated three times with total of 180 experimental units. The P and K mineralization patterns varied with soil types and P levels, with higher fluctuation of P content in silty clay loam soil as compared with loam and sandy loam soil. Phosphorus concentration with application of 25 kg, 50 kg, and 75 kg P2O5 ha–1 after 120 d of incubation were 95.6, 112.2, and 116.6 mg kg–1, respectively, which was 19.65% (25 kg P2O5 ha–1) to 45.93% (75 kg P2O5 ha–1) higher than control. There were four stages of mineralization‐immobilization turnover of Olsen‐P and available K: rapid declining trend up to 30 d, slow rise up to 60 d, rapid mineralization up to 90 d, and then slows down up to 120 d. On average, rapid reduction in soil pH from 6.60 to 5.42 was observed within 120 d of incubation. The study of mineralization of PK and change in pH during incubation could be helpful for predicting nutrient availability and requirement time for crops. Core Ideas: Phosphorus and potassium mineralization patterns varied with soil types and P levels.Four phases of phosphorus mineralization‐immobilization occurred during 120 d incubation.Soil with high levels of phosphorus obtained greater amount of available P compared with control.High mineralization due to temperature and moisture resulted higher reduction in soil pH. Mineralization study is helpful for predicting nutrient availability/requirement for crops. [ABSTRACT FROM AUTHOR]