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

Tea and hazelnut cultivated soils are mainly distributed in Black Sea region of Turkey. Low pH value is a primary problemfor 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 Afsin-Elbistan Coal Basin (estimated reserve is around4.8 billion tons). The aim of this study was to determine the phosphorus (P) sorption characteristics of gyttja, and its efficiency on Pavailability 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 (G(1)P(1)) basedon its b value, and the experiment was set as pot experiment according to a comletely randomized factorial experimental design withfive replications. Applications were control (G(0)P(0)), gyttja + P-0 (G(1)P(0)), sole P (G(0)P(1)), and gyttja + P (G(1)P(1)). The b value obtained fromLangmuir isotherm for gyttja was found as 1.59 mgg(-1). The highest available P was obtained at treatment of (G(1)P(1)). Also, the treatment G(1)P(1) was significantly different (p < 0.01) from the rest of the treatments. Gyttja application increased soil's pH value from 4.86 to 5.74in a 6-month time period. Therefore, gyttja can be recommended for amending soil acidity and increasing available P contents in acidsoils. Further studies should be conducted in field conditions to increase applicability of the results.