Rational Application of Fertilizer Nitrogen to Soil in Combination With Foliar Zn Spraying Improved Zn Nutritional Quality of Wheat Grains

Abstract

To alleviate human zinc (Zn) deficiency, it is worthy to develop rational agronomic managements to achieve high yielding and high resource-use efficiency wheat (Triticum aestivum L.) grains biofortified with Zn. Effects of application of three rates of nitrogen (N) fertilizer (75,200 and 275 kg·ha−1) to soil in combination with three foliar applications (deionized water, Zn alone, and a combination of Zn and sucrose) on grain yield, yield components, grain Zn concentration, protein, phytic acid (PA), phosphorus (P), calcium (Ca), and carbon (C), as well as on Zn bioavailability, were investigated in four wheat cultivars (“Jinan 17,” “Jimai 20,” “Jimai 22,” and “Luyuan 502”) under field conditions. Enhanced N increased Zn and protein concentrations as well as bioavailability; excessive N input did not result in further improvements. Zinc spraying was more effective than soil fertilizer N application, the spray of Zn (with or without sucrose) increased grain Zn concentrations by 11.1–15.6 mg·kg−1 (27.1–38.1%), and increased grain Zn bioavailability, estimated using total daily absorbed Zn (TAZ) and molar ratios of PA/Zn) and PA × Ca/Zn, by 0.4–0.6 mg d−1 (28.6–42.9%), 23.1–27.4% and 24.0–28.0%, respectively. Remarkably, increases caused by ‘Zn + sucrose’ were higher than spraying Zn alone. Grain Zn bioavailability was more sensitive to the selection of cultivar than Zn concentrations. Among cultivars, the higher the grain yields and concentrations of antinutritional compounds, the lower the grain Zn nutritional quality would be. 200 kg N ha−1 application rate in combination with foliar spraying of “Zn + sucrose” maximized grain Zn concentrations of “Jinan 17,” “Jimai 20,” “Jimai 22,” and “Luyuan 502” to be 59.4, 56.9, 55.8, and 60.9 mg kg−1, respectively, achieving the target value for biofortification. Additionally, PA/Zn and PA × Ca/Zn of “Jinan 17,” “Jimai 20,” and “Luyuan 502” were <15 and 200, and TAZ was maximized to be 2.2, 2.0, and 2.1 mg d−1, respectively, indicating higher bioavailability. Therefore, optimal soil N and foliar Zn management together with suitable cultivars maintained high grain yield with lower N input and could substantially increase grain Zn nutritional quality simultaneously.

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

“…In the current study, foliar Zn and/or sucrose applications did not affect the yield or other agronomic traits of maize in Quzhou and Licheng (Tables 3 and 4), suggesting that 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. Similar results were previously reported for maize and wheat under pot or field conditions [3,26,27,35,38,50,51]. For Zn, this finding may be attributed to the high Zn concentration in soil and the suitable soil conditions, and thus the good Zn nutritional status of plants.…”

“…In 1953, it was reported that the addition of sucrose to urea sprays reduced the injury of maize leaves, perhaps by reducing the rate of urea absorption and increasing the rate of urea translocation within the plant [62]. In our previous studies, foliar application of sucrose + Zn was associated with greater improvements in the concentration, content, and bioavailability of Zn in wheat (a C3 plant) than the spraying of Zn only [3,35]. As mentioned by Zhao et al (2014) [51], the relatively higher effectiveness of sucrose + Zn may be attributed to (1) the longer drying time of the spraying solution;…”

“…Therefore, in the present study, the molar ratios of PA/Zn, PA/Fe, PA × Ca/Zn, and PA × Ca/Fe were used as predictors of the potential bioavailability of Fe and especially Zn in maize grains treated by different foliar sprays under field conditions. The objectives of this research were (1) to quantify the effects of foliar applications of sucrose only, Zn only, and a mixed solution of both on maize grain yields and other agronomic traits; (2) to quantify their effects on the nutritional qualities of Zn and Fe including their concentrations and bioavailability for humans in maize grains; (3) to quantify their effects on C, N, total and phytate P, and Ca concentrations, and on the ratios of C/N and phytate P/total P in maize grains; and (4) to elucidate relationships between maize grain Zn and Fe concentrations across different foliar treatments and experimental locations. The results from these experiments will be useful for providing guidance on agronomic practices aimed at improving the Zn and Fe nutritional qualities of maize grains in the field, thereby providing health benefits to humans.…”

Exploring phosphorus fertilizers and fertilization strategies for improved human and environmental health

“…The application of Zn can simultaneously increase crop yield and grain Zn content under limited soil Zn availability (Drissi et al 2015;Dimkpa et al 2017aDimkpa et al , b, 2018bDimkpa et al , 2019a. Grain Zn content can be more than doubled, even under sufficient Zn soil supply, through foliar Zn application, while grain P or phytate content is not, or only modestly, affected (Zhang et al 2012;Khan et al 2018;Xia et al 2018). As such, foliar Zn fertilization can significantly reduce the PA/Zn molar ratio and increase the bioavailability of both Zn and P. Wang et al (2015) demonstrated a marked reduction in PA/Zn ratio from over 30 in the control treatment to below 15 with Zn fertilization.…”

Chemical Fractions and Availability of Zinc in Winter Wheat Soil in Response to Nitrogen and Zinc Combinations

“…Zn supply is a direct and effective method to solve the low availability of Zn in soil ( Almendros et al, 2013 ; Guo et al, 2015 ). Furthermore, nitrogen (N) application or N combined with Zn application is beneficial for increasing Zn concentration, enhancing Zn translocation to grain in wheat, especially when wheat is cultured in Zn-deficient soil ( Kutman et al, 2010 ; Li et al, 2015 ). N combined with Zn application can enhance Zn uptake via membrane transport and stimulate root development ( Nie et al, 2017 ).…”