Foliar Zn Spraying Simultaneously Improved Concentrations and Bioavailability of Zn and Fe in Maize Grains Irrespective of Foliar Sucrose Supply

Abstract

Zinc (Zn) deficiency is a global nutritional problem that is reduced through agronomic biofortification. In the current study, the effects of foliar spraying of exogenous ZnSO 4 ·7H 2 O (0.2% in Quzhou and 0.3% in Licheng, w/v) and/or sucrose (10.0%, w/v) on maize (Zea mays L.) agronomic traits; concentrations of Zn, iron (Fe), calcium (Ca), total phosphorus (P), phytic acid (PA) P, carbon (C), and nitrogen (N); C/N ratios; and Zn and Fe bioavailability (as evaluated by molar ratios of PA/Zn, PA × Ca/Zn, PA/Fe and PA × Ca/Fe) in maize grains were studied under field conditions for two years at two experimental locations. The results confirmed that there were no significant differences in maize agronomic traits following the various foliar treatments. Compared with the control treatment of foliar spraying with deionized water, foliar applications of Zn alone or combined with sucrose significantly increased maize grain Zn concentrations by 29.2-58.3% in Quzhou (from 18.4-19.9 to 25.2-29.6 mg/kg) and by 39.8-47.8% in Licheng (from 24.9 to 34.8-36.8 mg/kg), as well as its bioavailability. No significant differences were found between the foliar spraying of deionized water and sucrose, and between Zn-only and "sucrose + Zn" at each N application rate and across different N application rates and experimental sites. Similar results were observed for maize grain Fe concentrations and bioavailability, but the Fe concentration increased to a smaller extent than Zn. Foliar Zn spraying alone or with sucrose increased maize grain Fe concentrations by 4.7-28.4% in Quzhou (from 13.4-17.1 to 15.2-18.5 mg/kg) and by 15.4-25.0% in Licheng (from 24.0 to 27.7-30.0 mg/kg). Iron concentrations were significantly and positively correlated with Zn at each N application rate and across different N application rates and experimental locations, indicating that foliar Zn spraying facilitated the transport of endogenous Fe to maize grains. Therefore, foliar Zn spraying increased the Zn concentration and bioavailability in maize grains irrespective of foliar sucrose supply while also improving Fe concentrations and bioavailability to some extent. This is a promising agricultural practice for simultaneous Zn and Fe biofortification in maize grains, i.e., "killing two birds with one stone".

Combined application of zinc and silicon alleviates terminal drought stress in wheat by triggering morpho-physiological and antioxidants defense mechanisms

“…Zinc (Zn) and silicon (Si) are mineral nutrients which aids in improving water use efficiency of plants [ 44 , 45 ]. Foliar application of Zn and Si improved chlorophyll contents and leaf water contents both under terminal drought stress and well-watered conditions.…”

Agronomic Bio-fortification of Rice and Maize with Iron and Zinc: A Review

“…According to Zou et al [27], foliar spray was found to enrich maize grains with Zn more effectively than soil application. Compared with the control, foliar spray of ZnSO and enhanced the Fe concentration significantly by 25.0% (Table 4) [41]. Even though the relationship between Zn and Fe concentrations in major cereal crops is still uncertain, but in the aforementioned study, foliar Zn spraying simultaneously improved the concentrations and bioavailability of Zn and Fe in maize grains to some extent.…”

“…Maize is one of the popular cereal crop due to its diverse functionality as source of food for humans and animals as well [4,41]. It is an exhaustive crop that requires major nutrients as well as micronutrients particularly Zn for better yield [12].…”

Biofortification of Diverse Basmati Rice Cultivars with Iodine, Selenium, and Zinc by Individual and Cocktail Spray of Micronutrients

“…It depicts that it was foliar application of I, as KIO 3 alone and I, was contained in the cocktail, and not Se and Zn, which had a minimal negative effect on Ca concentration in rice grains. Xia et al [82] have reported that the foliar application of 0.2-0.3% ZnSO 4 •7H 2 O solution did not affect the Ca concentration in grains of maize. Although Mangueze et al [54] have reported a decreasing trend in Ca concentration of rice with foliar application of Se, their dose of foliar-applied Se was too high, and they had recommended decreasing the dose for the Se biofortification of rice.…”