Method of Analysis of the Sample Matching of Diagnostic Ranges of Mineral Nutrients in Soil and Cacao Leaves

Abstract

ABSTRACT Nutritional diagnostic ranges (NDRs) for soil mineral nutrients (SMNs) and leaf mineral nutrients (LMNs) were obtained from the response of the relative dry biomass of cacao beans (rDBCB) and the relative dry biomass of cacao pod husk (rDBCH). Using an exploratory approach, the sample matching levels of the NDRs were determined to discriminate the results of the soil and leaf nutritional diagnostics. These objectives have been achieved from two methodological processes: a new approach to the boundary line technique where the two-dimensional graph is divided into class intervals based on the predictor variables to then establish the NDR from second degree polynomial regressions, and the development of a classification system for soil and leaf samples by NDR to later verify the corresponding matching levels. This new graphical analysis approach has also allowed us to observe how the SMNs and LMNs present different diagnostic profiles for the prediction of rDBCB and rDBCH responses. The leaf nitrogen (N), potassium (K), magnesium (Mg), and manganese (Mn) concentrations showed an NDR matching level above 80% as predictors of rDBCB and rDBCH responses. Leaf calcium (Ca) concentration showed a level between 60% and 80%. Soil phosphorus (P) concentration showed more than 80% of the sample matching level classified by NDR, followed by the concentrations of K, Ca, and zinc (Zn) in the soil that showed a level of coincidence between 60% and 80%. The lack of uniformity in the genetic potential of cacao production and management has produced differences between predictions.