The Phosphorus Compositional Nutrient Diagnosis Range for Potato

Abstract

Leaf analysis could assist in adjusting the P fertilization of potato (Solanum tuberosum L.) to specific soil–plant systems to achieve high yield conditions. Our objective was to derive and validate Compositional Nutrient Diagnosis (CND) norms and ranges for a potato cultivar (Superior) and to compare CND to Diagnosis and Recommendation Integrated System (DRIS) and the Critical Value Approach (CVA). Survey data were obtained from 563 field observations and validated using 100 independent samples and across four P fertilizer trials. The databases included tuber yield and analyses (N, P, K, Ca, and Mg) of the upper fully expanded leaf collected at beginning of bloom. Yield cutoff between low‐ and high‐yield subpopulations, selected from cumulative variance functions across survey data, was 34.1 Mg ha−1. The sum of squared values of CND indexes was distributed like a chi‐square value. The critical chi‐square value was 4.2. The critical CND P index range was between −0.80 and 0.80. Similar critical values were obtained for the validation population and fertilizer trials. The CND P index appeared symmetrical about the zero nutrient balance and was more closely related to yield compared with DRIS and CVA. The CND provides an inferential (as chi‐square) and symmetrical (about zero balance) diagnosis at low cost, could provide nutrient index ranges adjusted to yield goal, and could thus be developed advantageously for specific soil–plant systems.