Zinc-nitrogen interaction effect on wheat biofortification and nutrient use efficiency

Background: The enhancement of zinc (Zn) concentration in cereal crops without compromising yield is a global challenge with crucial health and food security implications. Aims: To achieve Zn biofortification in wheat through the appropriate management of fertilization with both Zn and nitrogen (N), due to the synergistic effect between them, using natural organic sources of Zn. Methods: We carried out a field experiment using a rainfed winter wheat (Triticum aestivum L.) crop fertilized with four Zn sources (Zn-sulphate, Zn-lignosulphonate, Zn-amino acids and Zn-gluconate) and three N application rates under semi-arid conditions. Results: The strategy of increasing the N rate by 50% with respect to the recommended N rate (i.e., 120 kg N ha(-1)) did not improve either wheat yield or grain Zn-N concentration. The combined effect of applying natural organic Zn complexes and the recommended N rate tended to increase grain Zn concentrations (by an average of 14%), although this increase was significantly higher when Zn-sulphate was applied (63%) due to its higher recommended Zn application rate. Natural organic Zn fertilizers achieved the highest grain yields, probably due to the enhancement of N uptake. The natural organic Zn fertilizers resulted in higher Zn utilization efficiency compared with the Zn-sulphate fertilizer. Conclusions: In calcareous Zn-deficient soils, our results suggest that Zn-N co-fertilization involving Zn-sulphate combined with the recommended N application rate would be advisable for obtaining grain Zn biofortification, while the highest yields can be obtained with the application of natural organic Zn fertilizers.