Study the effect of fulvic acid, humic acid and phosphate fertilizer on the kinetics and adsorption of phosphorous in calcareous soil

Abstract

This study was conducted to evaluate the efficiency of fulvic and humic acids in the kinetics of phosphorus liberation and adsorption in calcareous soils, as they were added at levels of 20 and 40 kg.h-1 with three levels of phosphorus in the form of triple superphosphate fertilizer, 0, 50 and 100 kg. h-1 , the five kinematic equations were used: the zero order equation, the first order equation, the exponential function equation, the diffusion equation and the Eloveg equation. The results showed the superiority of the exponential function equation, as it gave the highest values of the determination coefficient R2 was 0.953 and the lowest standard error value SEe amounted to 0.0584, and the superiority of fulvic acid over humic acid in increasing the speed of release of the added phosphorous at both levels and with an increase rate of 72.0, 45.5 and 25.0% at Level 20 kg.ha-1 , 41.2, 7.1 and 19.7% at 40 kg.ha-1 And the levels of added phosphorous were 0, 50 and 100 kg h-1 , respectively. The results showed in the adsorption experiment that the type of acid affected the values of binding energy k and maximum adsorption Xm, as fulvic acid outperformed humic acid in reducing them, and the percentage of decrease in energy values was Binding 38.7, 41.5 and 52.2%. As for the maximum adsorption values, the decrease percentage was 44.2, 46.2 and 44.7%. An increase in the maximum adsorption values with time was also observed, as they were 1714, 2075 and 2083 µgP.gm-1 soil. The average binding energy values were 1.55, 1.83 and 2.34 µg P.gm-1 in the case of humic, while in the case of Volvic, the maximum adsorption values were 955.5, 1079.5 and 1151.5 µg P.gm-1 in soil, while the binding energy values were 0.95, 1.07 and 1.11 ml. µg P-1 during three time periods. Adding acids to the soil takes 20, 60 and 100 days, respectively. Keywords: humic acid; kinetics; fertilizer; superphosphate.