Wheat possesses inherently low concentrations and bioavailability of the essential micronutrients (EMis) zinc (Zn), iron (Fe), manganese (Mn), and copper (Cu), limiting its capacity to sufficiently address human nutritional requirements. Biofortification of wheat with EMis through agricultural methods is a strategy aimed at addressing EMi deficiencies in human populations that emphasize cost-effectiveness and sustainability. All EMis are usually applied foliarly as sulfates, which indicates sulfur (S)-assisted biofortification. The formation of EMi complexes provides solubility as well as protection during long-distance transport. Several small molecules are possible candidates as ligands—the S-containing amino acids cysteine and methionine among them—linking EMi homeostasis to S homeostasis, which represents another aspect of S-assisted biofortification. In this study, we delve into the S-assisted agronomic biofortification strategy by applying sulfate micronutrients coupled with a sulfur-containing amino acid and we explore the effect of the selected accompanying cation (Zn, Fe, Mn, or Cu) on the EMi metallome of the grain, along with the biofortification effectiveness, whilst the type of the incorporated surface active agent seems to affect this approach. A field experiment was conducted for two years with durum wheat cultivation subjected to various interventions at the initiation of the dough stage, aiming to biofortify the grain with EMis provided as sulfate salts coupled with cysteine or methionine as potential biofortification enhancers. The mixtures were applied alone or in combination with commercial surfactants of the organosilicon ethoxylate (SiE) type or the alcohol ethoxylate (AE) type. The performance of two relevant preparations, FytoAmino-Bo (FABo) and Phillon, has been studied, too. The interventions affected the accumulation of the EMi metallome into the grains, along with the interactions of the EMis within this metallome. Several interventions increased the EMi metallome of the grain and affected the contribution of each EMi to this metallome. Many interventions have increased Zn and Fe, while they have decreased Mn and Cu. An increase in Zn corresponded (i) to a decrease in Cu, (ii) to an increase or no increase in Fe, and (iii) to a variable change in Mn. Cys increased the metallome by 34% and Zn and Fe within it. ZnSO₄ and FeSO₄ increased the metallome by 5% and 9%, whilst MnSO₄ and CuSO₄ increased the metallome by 36% and 33%, respectively. The additives improved the contribution to increasing the metallome in most cases. Without surfactant, the efficacy ranking proved to be MnSO₄ > CuSO₄ > ZnSO₄ > FeSO₄. The use of SW7 sustained the order CuSO₄ > MnSO₄ > ZnSO₄ > FeSO₄. The use of Saldo switched the order to CuSO₄ > ZnSO₄ > FeSO₄ > MnSO₄. In the case of Phillon, the order was CuSO₄ > FeSO₄ > ZnSO₄ > MnSO₄. The effect of Cys or Met was case-specific. The differentiations in the intensity of both the agronomic performance (grain weight, grain weight per spike, and yield) and the biofortification performance (concentrations vs. accumulations of each EMi within the grain) among the various combinations of EMis and additives are depicted by adopting a grading scale, which highlighted the intensity of the acclimation reaction of the biofortified grain to the applied intervention.

A cultivation of durum wheat that established in a field with soil poor in micronutrients received foliar applications at the initiation of the dough stage towards biofortifying the spikes with micronutrients. The morphology of the spike is crucial in determining grain yield, and the spikelets, the components of the inflorescence, influence each other. The number and arrangement of these spike components affect spike length, spike weight, spike chaff (the non-grain biomass in the spike), grain number per spike, grain weight per spike, and spikelet number per spike, and all contribute to final grain yield per spike. The spike’s developmental program responded to the interventions regarding the morphological traits; this response was analyzed for each spike component, and an acclimation program seemed to be activated by each intervention. Cysteine or methionine has been added as a potential enhancer of the biofortification process, and the application mixtures were coupled with selected surfactants, an organosilicon ethoxylate or an alcohol ethoxylate one, while products with targeted composition for biofortification with micronutrients have also been studied. Their effect on the developmental acclimation program of the treated spike is presented and discussed. The action of this program provided grains of similar weight, regardless of the intervention.