Adsorption and transport of nitrate and potassium in an Andosol under banana (Guadeloupe, French West Indies)

A series of batch, soil column and field experiments was carried out in order to study nitrate and potassium transport and to improve fertilizer practices in an Andosol under a banana plantation. The focus of the study was on the influence of the substantial variable charge of the soil on ion transport. Leaching of both K+ and NO3--N through the Andosol were both retarded, as expected, because of the soil's cation and anion exchange capacities (CEC and AEC). Under acidic conditions, the B horizon, with the greater allophane content, developed preferential affinity for nitrate. The A horizon, with both organic and mineral adsorption sites, exhibited a stronger affinity for potassium than the B horizon when the soil solution pH was below the zero point of charge (ZPC). Fast leaching of nutrients occurred under the banana stem due to the abundant stemflow derived from rainfall interception by the banana plant. Intensive leaching under the plant questions the concept of fertilizer application at the plant stem.