Abstract:
Volcanic soil samples from the provinces of Chiriqui and Cocle in Panama were characterized for their andic soil properties: bulk density, phosphorus retention, and amorphous Fe and Al content. The samples were equilibrated in a 1000 mg-P L-1 solution and extracted with pH3 ammonium oxalate solution. All samples were pretreated and diluted for measurement in Hach TNT844, TNT848, and TNT858 vials on a Hach DR1900 spectrophotometer. The Chiriqui samples showed higher P retention (up to 83.18%), as well as higher amorphous Fe and Al contents, with values equal to or greater than 2%. Bulk densities were less than 0.9 g cm-3. The data confirmed that the Chiriquí soils presented all the requirements for the Andisol soil order (USDA Soil Taxonomy). The Coclé soils presented higher bulk density values, lower P retention (up to 60.2%) and lower amorphous Fe or Al content, with values less than 2%, which showed that they are older deposits of volcanic ash with advanced weathering. The characterization of andic properties provides useful tools to local stakeholders for soil fertility management and land use planning. Hach's wet chemistry vials and spectrophotometric method of determining P, Fe, and Al could reduce reagent costs and analysis time.