High phosphate sorption constitutes a critical impediment to agricultural use of Andosols in the volcanic highlands of Central African Great Lakes region. A laboratory experiment was conducted on soil samples collecte...High phosphate sorption constitutes a critical impediment to agricultural use of Andosols in the volcanic highlands of Central African Great Lakes region. A laboratory experiment was conducted on soil samples collected from an Andosol amended with a factorial combination of lime and P （phosphorus） fertiliser to determine the P sorption characteristics and derive parameter estimates relevant in the prediction and management of P in the Andosols. The potential for sorption of additional P and its binding intensity were evaluated by applying the two-surface Langmuir model to sorption isotherms. The calculated P sorption maxima ranged from 1,667 mg·kg^-1 to 10,000 mg·kg^-1 representing about 95% of the P applied to the soil. The external P requirement ranged from 1,492 mgP·kg^-1 to 2,760 mgP.kgl which is further evidence that the studied Andosols are high P sorbers. There was no significant effect of lime and P rates on P sorption capacity of the Andosols. Exchangeable iron was highly correlated with P sorption maxima b2 （r = 0.98） on the high energy sites, whereas cation exchange capacity was negatively correlated with P sorption maxima bl （r = 0.999） and positively correlated with P binding energy K1 （r = 0.998） on the low energy sites.展开更多
文摘High phosphate sorption constitutes a critical impediment to agricultural use of Andosols in the volcanic highlands of Central African Great Lakes region. A laboratory experiment was conducted on soil samples collected from an Andosol amended with a factorial combination of lime and P （phosphorus） fertiliser to determine the P sorption characteristics and derive parameter estimates relevant in the prediction and management of P in the Andosols. The potential for sorption of additional P and its binding intensity were evaluated by applying the two-surface Langmuir model to sorption isotherms. The calculated P sorption maxima ranged from 1,667 mg·kg^-1 to 10,000 mg·kg^-1 representing about 95% of the P applied to the soil. The external P requirement ranged from 1,492 mgP·kg^-1 to 2,760 mgP.kgl which is further evidence that the studied Andosols are high P sorbers. There was no significant effect of lime and P rates on P sorption capacity of the Andosols. Exchangeable iron was highly correlated with P sorption maxima b2 （r = 0.98） on the high energy sites, whereas cation exchange capacity was negatively correlated with P sorption maxima bl （r = 0.999） and positively correlated with P binding energy K1 （r = 0.998） on the low energy sites.
