Variation of phosphorus pools as affected by land use in acidic soil of eastern Himalayan region of India

Soil phosphorus (P), an essential major element is mostly low in many tropical and sub-tropical soils and its characterization into different pools and relationship with other soil properties is crucial in understanding the adsorption chemistry and its release to available forms. Three soil depths (0-15, 15-30 and 30-45 cm) from six major land use were studied to elucidate the effect of land use on different pools of soil P and its relationship with other soil properties. The studied soils were acidic in nature (pH: 5.03-6.33) and land use significantly increased the soil pH for lowland rice (LR: 6.1), the higher soil pH in LR soil also significantly increased the available P forms (available P: P and Mehlich P: M-P) while the higher clay content in Teak (T) plantation decreased the available P forms implying that P was fixed. In addition, soil pH was positively related to the labile inorganic pool (NaHCO3-PI) and stable pool (HCL-P). The moderately labile pool, NaOH-P (16-44%) was higher compared to labile pool, NaHCO3-P (11-15%) and stable, HCL-P (2-13%) due to the acidic soil pH where Fe and Al oxide dominates in sub-tropical weathered soils. The organic P pools (NaOH and NaHCO3) which is important for long term P cycling were higher than the inorganic pools in T, F and R land uses. Management strategy for increasing SOC is important to maintain organic P cycling to supply available P for long term.