“…Predictive factors that influence the above mentioned processes in the soil and the soil-plant system, such as the numerous physical and chemical properties of the soil and the mechanisms of the adoption of TEs by the plants, are used to form the training set. The physical and chemical properties include the content of clay fraction, organic matter (total SOM and/or water-soluble DOM), cation exchange capacity (CEC), total DTPA, EDTA, soluble and water-soluble forms of TEs, iron/manganese/aluminum oxide, pH, texture class, liquid-solid ratio for TEs and chemical speciation TEs [13,18,23,24,36,[41][42][43][44], and have been used in prediction models by many authors [18,40,[45][46][47][48][49][50][51][52][53][54][55][56][57]. The most commonly used quantitative prediction variables are pH, SOM and total content of TEs [36,58].…”