Variations in grain yield and nutrient status of different maize cultivars by application of zinc sulfate.

Although maize is sensitive to zinc (Zn) deficiencies, the responses of maize cultivars to the foliar application of Zn sulfate (ZnSO4) may vary significantly. Here, we quantified the responses of grain yields and nitrogen (N), phosphorus (P), and potassium (K) absorption to ZnSO4 using 22 modern maize cultivars. The results revealed that 40.9% of the cultivars were not affected by foliar ZnSO4, whereas only 45.5% of the cultivars responded positively to ZnSO4, which was evidenced by increased grain numbers and shortened bald tip lengths. The impact of Zn fertilizer might be manifested in the dry biomass, from the 8-leaf stage (BBCH 18). For Zn-deficiency resistant cultivars, the foliar application of ZnSO4 enhanced N accumulation by 44.1%, while it reduced P and K absorption by 13.6% and 23.7%, respectively. For Zn-deficiency sensitive maize cultivars, foliar applied ZnSO4 improved the accumulation of N and K by 27.3% and 25.0%, respectively; however, it lowered their utilization efficiency. Hence, determining the optimized application of Zn fertilizer, while avoiding Zn toxicity, should not be based solely on the level of Zn deficiency in the soil, but also, take into consideration the sensitivity of some cultivars to Zn, Furthermore, the supplementation of Zn-deficiency sensitive maize cultivars with N and K is key to maximizing the benefits of Zn fertilization.