Sodium Bicarbonate Extraction to Estimate Nitrogen, Phosphorus, and Potassium Availability in Soils

Abstract

AbstractThe extractability of NO3‐N, P, and K from five calcareous soils differing in physical and chemical characteristics by NaHCO3 (0.5M, pH 8.5) was studied under laboratory conditions. The extracted amounts of the three ions were related to time since their application to the soils, to the equilibration period of the soils with the extractants, to the concentration of the ions in the soils, and to the clay content of the soils. After about 70 days in the soil, the extractability of each ion at a given application level was independent of time. The recovery percentage of P and K as a function of the applied amounts of these elements depended mainly on the clay content of the soils, while NO3‐N recovery was independent of the factors studied. Linear relationships were obtained between NaHCO3‐and NH4OAc‐extracted K, and NaHCO3‐ and KCl‐extracted NO3‐N. The slopes for NO3‐N were 45° for all soils, but were specific for each soil in the case of K.