Adsorption and Desorption of Phosphorus in Andisol at Several Elevation Variations in the Catena of Mount Merbabu and Sindoro

Andisol is a potential soil but has problems related to phosphorus. Amorphous minerals absorb P in Andisol. But in certain conditions, P can be desorbed. This study aims to determine adsorption and desorption patterns and the soil properties in two different catenas, namely Mount Merbabu and Sindoro. This research uses the catena concept with 3 height variations, 800, 1400, and 2000 meters above sea level. Samples were taken on uncultivated land in horizons A and B. Tests were carried out in the laboratory. The data obtained were processed using ANOVA and Fisher’s LSD test, Pearson Correlation, and regression graphs. The results of the P adsorption pattern showed the rate, capacity, and energy of adsorption binding increase with elevation. Despite high adsorption, desorption rates at 2000 masl are also high. However, different results were shown in the Mount Sindoro catena, where the highest desorption rates are found in horizon A at 800 masl and horizon B at 1400 masl. The soil properties most strongly correlated with phosphorus availability are organic matter and organic acids, particularly fulvic acid, as well as the soil’s ability to retain phosphorus due to the presence of amorphous minerals such as allophane, imogolite, and amorphous Al/Fe compounds.