Investigating the Balance Status of Nutrients in Wheat Plant Using Isometric Log Ratio and Field Validation of Balances

Abstract

Nutrient status of plants is determined by using critical nutrient range and nutrient ratios. The obtained data may not be generally error‐free due to the nature of compositional data is not taken into account Here, nutrient status of wheat (Triticum aestivum L.) in Entisols and Aridisols soils is investigated by isometric log ratio (ILR) technique. Leaf samples collected from 96 fields at booting stage. To validate the obtained ILR balances, two separate filed experiments were conducted employing a factorial experiment based on CRBD design with three replications. Concentrations of N, P, K, Ca, Mg, Zn, Fe, Mn, Cu, and B in the flag leaf tissue were determined at both fields. Nutrients were arranged into ad hoc balances and computed ILR and classified into four groups as balanced, misbalanced, high and low yielders by receiver operating characteristic (ROC) curve. The ROC classification applied to the data from survey fields and validation test respectively showed 4.67 and 4.02 as the critical Mahalanobis distance and 5034 and 6559 kg ha−1 as yield cut‐off for separating balanced and imbalanced samples at area under curve (AUC = 0.83 and 0.88). Comparing nutrient balance between reference (TN) and nonreference (TP) groups in the survey fields by Tukey's test showed that the balances of [Fe,Mn,Zn,Cu|B,Mg,Ca,K,P,N], [B|Mg,Ca,K,P,N], [Mg,Ca,K|P,N], [Mg,Ca|K], and [Mn|Zn,Cu] were negative. The [Fe|Mn,Zn,Cu] and [Zn|Cu] balances were positive. In the low yielding of survey fields, the balances of [Fe|Mn,Zn,Cu], [Mn|Zn,Cu], [Zn|Cu], [Fe,Mn,Zn,Cu|B,Mg,Ca,K,P,N], and [Ca,Mg|K] were imbalanced, but they become balanced through fertilizer treatments in the validation test.Core Ideas Nutrient balances can be interpreted simultaneously using pan balance approach. The values of isomeric log ratio represent the balances between two or more nutrients. Mahalanobis distance was set as a criterion for nutrient misbalance.