Readily measurable soil properties that affect the phosphorus fertilizer requirement of ultisols

Publisher Website
Google Scholar
Abstract
Phosphorus fertilizer recommendations could be improved mark‐edly if, in addition to the extractable P concentration, some estimate of the P buffering capacity were considered. Measuring the P buffering capacity or its estimate from clay content or surface area, however, is too time consuming for most soil testing laboratories. Soil samples from the southeastern USA and western Spain were analyzed for several properties that either are or could be measured readily. These properties were cation exchange capacity (CEC), sample density (SD), humic matter (HM), and a color index (CHL). Topsoil samples with HM > 20 g/L were eliminated from the set. The P buffering capacity was estimated with a sorption index. This index correlated well with clay content, so clay content was used for comparison with CEC, SD, and CHL. Of these parameters, clay content was best correlated with CHL (r2 = 0.81). Since CHL can be determined very quickly under routine laboratory conditions, it could be utilized for refining the P soil test interpretation and improving subsequent fertilizer P recommendations.