Effect of sheep manure on decreasing of phosphorus fixation in soils different in the content of calcium carbonate, and determination of Langmuir and Freundlich constants

Abstract

This study was carried out in order to determine the effect of sheep manure on decreasing of phosphorus fixation insoils different in the content of calcium carbonate. Four types of soils were selected (non-calcareous I, a light lime II, medium lime III, and high lime IV). Soils were treated with sheep manure with two reates 25 and 50 ton/ha. Two experiments were carried out, the first one was an incubation of soils and sheep manure and phosphorus in pots (1 kg) and lasted three months, and the second one was phosphate adsorption. Available phosphorus was estimated during the incubation well asa dsorbed phosphate and Langmuir constants (great adsorption capacity (bm), and Freundlich constants (number of adsorption sites (a). The results showed the following:    
Decreasing of available phosphorus values ​​(increasing of fixed phosphate) in the soil IV (high content of calcium carbonate ) from 18.2 mg/kg at time zero to 19.4 mg/kg after a one month of incubation to 9.2 mg/kg at the end of the incubation time. Phosphorus fixationin of  the soil I(non-calcareous) did not happen. The highest available phosphorus concentration was in I₅₀treatment sheep manure (56.4) mg/kg. The IV treatment showed the highest great adsorption (fixation) capacity (bm)was to 1250 mg/kg and (a)was 19. While the lowest (bm) was in  treatment I₅₀ (416) mg/kg and the(a) was 3.5.time, as