Phosphorus sorption by gyttja and its effect on the pH value and phosphorus in acidic soils

Authors: KADIR SALTALI, AHMET NEDİRLİ

Abstract: Tea and hazelnut cultivated soils are mainly distributed in Black Sea region of Turkey. Low pH value is a primary problem for those soils; therefore, farmers apply lime once every 3-4 years to raise the pH value of soil. Gyttja is highly rich in organic matter (40.59%) and lime (45.67%), and it is a low cost and considerably abundant in Afşin-Elbistan Coal Basin (estimated reserve is around 4.8 billion tons). The aim of this study was to determine the phosphorus (P) sorption characteristics of gyttja, and its efficiency on P availability and soil's pH value. Optimum P sorption conditions (pH, temperature, particle size, amount of sorbent and shaking time) and maximum sorption capacity (b) for gyttja were determined in laboratory condition. Phosphorus was sorbed to gyttja (G₁ P₁) based on its b value, and the experiment was set as pot experiment according to a comletely randomized factorial experimental design with five replications. Applications were control (G₀ P₀), gyttja + P₀ (G₁ P₀), sole P (G₀ P₁), and gyttja + P (G₁ P₁). The b value obtained from Langmuir isotherm for gyttja was found as 1.59 mgg^-1. The highest available P was obtained at treatment of (G₁ P₁). Also, the treatment G₁ P₁ was significantly different (p < 0.01) from the rest of the treatments. Gyttja application increased soil?s pH value from 4.86 to 5.74 in a 6-month time period. Therefore, gyttja can be recommended for amending soil acidity and increasing available P contents in acid soils. Further studies should be conducted in field conditions to increase applicability of the results.

Keywords: Acidic soil, gyttja, phosphorus, pH, sorption

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