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 ZnSO4·7H2O (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”.
Highlights
Maize (Zea mays L.), one of the world’s paramount cereal crops, along with wheat and rice
Increased Zn concentrations in maize kernels were positively correlated with the grain yield, increased concentrations in and maize were alsoZinc positively correlated withbeen the grain yield, grainZn weight, cob length, cobkernels diameter fertilization has reported to grain weight, cob length, and cob diameter
Zn and/or the dry-matter accumulation in maize grains is less dependent on exogenous foliar Zn and/or carbohydrate supply, at least under the conditions used in this study
Summary
Maize (Zea mays L.), one of the world’s paramount cereal crops, along with wheat and rice. It is very popular due to its diverse functionality as a food source for both humans and animals [1,2]. Zinc is an essential micronutrient for the survival of plants, animals, and humans [3]. Maize grains do not inherently contain enough Zn to meet daily human requirements, when grown in. Since the 1990s, crop Zn deficiency has been very common worldwide, with 33%. Of the world’s total cultivated area containing Zn-deficient soil [5]. An increased crop yield, imbalanced fertilization, large-scale irrigation practices, and changes in climatic and soil conditions
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