Abstract

Most iron nodules have micropores as a result of isomorphous substitution of aluminum (Al) for Iron (Fe). Hadejia-Jama’are wetlands is currently facing serious threat of rapid growing weeds associated with poor phosphate management. The objectives were to study the concentrations of dithionite and oxalate Fe and Al oxides, degree of aluminum substitution and phosphate sorption index of Hadejia-Jama’are wetlands. Three wetland locations and corresponding drylands (control) were selected. On each of the six research fields, soil samples were collected at 0 to 35, 35 to 70, 70 to 105 cm soil depth, replicated three times and composited. Oxides of Fe and Al were extracted. Phosphate sorption experiment was also conducted with 0, 100, 200, 400 and 800 mg P kg-1. Phosphate ions sorbed were estimated as P applied minus P in the filtrate. Phosphate sorption index was established as PSI = S/logCt. From the results obtain, the iron fraction extracted with acid ammonium oxalate (Feo) was discovered to be an effective P sink. All the surface soils in the wetland areas revealed higher degree of Al substitution compared to the subsurface soils. About half of the added P in the wetland surface soils was released into the soil solution and more than half of the added P in the surface soil of the northern dryland was released into the soil solution and two-third of the added P in the surface soils of western and southern dryland locations were released into the soil solution. Hadejia-Jama’are soils sorb very little P when applied in small doses.

Key words: Phosphate, extractable-fe and Al oxides, isomorphism, sorption, wetlands.