Phosphate sorption of some Nigerian soils and its effect on cation exchange capacity

Langmulr phosphate sorption isotherms for several representative Nigerian soils derived from different parent materials were studied. Two straight‐line portions of the isotherm were obtained for each soil studied after 24‐hour equilibration. The number of straight‐line portions or “breaks”; of the isotherm for a soil was found to depend not only on the P concentration range but on the time of equilibration as well.Phosphate sorption capacity of the soil studied follows the order: Alfisols from basalts > Ultisols from sandstone > Alfisols from basement complex rocks (gneisses) ˜ Alfisols from coastal sediments ˜ Alfisols from eolian drift. The sandy forest soils derived from basement complex rocks and from coastal sediments in south‐western Nigeria require relatively low amounts of phosphate for maximum crop yield as determined by the Langmuir isotherm.Phosphate sorption resulted in significant increases in cation exchange capacity of the soils studied. The percentage CEC increase ranged from 17% to 370%

Copper chloride as an extractant for estimating the potentially reactive aluminum pool in acid soils

The reactive Al pool in selected Ultisols, Oxisols, and Histosols from Africa, South America, and North Carolina was estimated by extraction with 1N CuCl2. The Al-saturated clay minerals with and without interlayered hydroxy-Al were used to compare the extractability of Al by 1N CuCl2 and 1N KCl. The 1N solutions of KCl and CuCl2 were equally effective in extracting exchangeable Al from an Al saturated montmorillonite. The 1N CuCl2 solution, however, extracted almost twice as much Al from an Al saturated vermiculite containing a hydroxy Al interlayer as compared with 1N KCl. Generally, more than twice as much Al was extracted from acid surface soils (< pH 5) by 1N CuCl2 than by 1N KCl suggesting that Al bound by organic matter was being extracted by the CuCl2

Adsorption and desorption of paraquat in acid tropical soils

Adsorption of paraquat (1:1′-dimethyl 4:4′-bipyridylium chloride) by six common soil types from southern Nigeria was studied. Adsorption data conformed with linear Langmuir isotherm. Adsorption maximum (b) calculated from the Langmuir equation ranged from 1,200 to 7,500 µg/g of soil. The iron oxide-rich soil derived from basalts adsorbed the highest amount, while the strongly acidic soils derived from sedimentary rocks adsorbed the least amount of paraquat. Desorption data indicated that a substantial portion (40 to 70%) of the adsorbed paraquat could not be recovered by 12 successive extractions with dilute CaCl2 solution

Effets des engrais verts et des rotations de cultures sur la productivité des sols au Mali

Dans IDL-1387