Characteristics of phosphorus sorption under different land use systems at Agarfa, South Eastern Ethiopia

Abstract

Determination of the Phosphous (P) sorption characteristics of soils is important for a better understanding of P,
economic fertilizer application and to recommend appropriate management strategies for high P-fixing soils. The
phosphorus adsorption-desorption behavior of soils from four land use patterns of central Ethiopia was studied. The
study was conducted to determine the effects of land-use systems on selected soil physicochemical characteristics and
soil P sorption capacities. Five major representative land-use systems (forest, grazing, homestead, traditionally
cultivated land, and mechanized land) were identified. Composite soil samples were collected at 0-20 and 20-40 cm
depth. Sorption data were obtained by equilibrating 3.0 g of each sample with 25 mL of 0.01 M CaCl2 containing various
amounts of KH2PO4. The resulting data were fitted with Langmuir and Freundlich equations. Sorption maxima (Xm) and
The Freundlich coefficient (Kf) values of soils ranged from 104-295mg P kg-1 and 44-70.5 mg P kg-1 based on Langmuir
and Freundlich models, respectively. The SPR values ranged between 11 to 22 mg P kg-1 and 14 to 28 mg kg-1 based on
Langmuir and Freundlich models, respectively in 0-20 cm depth. In general, P-sorption models can effectively be used
to discriminate soils based on P-fixation ability. Moreover, the amount of fertilizer based on EPR estimation is greater
than the amount of fertilizer practiced both by traditionally cultivated and mechanized land uses. Thus, it is recommended
that this dose of P fertilizer should be revised and the proper amount of fertilizer based on EPR values estimated for
each soil be applied