Effects of foliar applications of fertilizers containing different zinc sources on grain yield and grain nutritional quality of winter wheat and summer maize
The foliar spraying experiments with different fertilizers were carried out in a winter wheat-summer maize rotation system.This study explored the effects of foliar applications of fertilizers containing different zinc(Zn)sources on grain yield,grain mineral element concentrations,and bioavailability of Zn and iron(Fe)of winter wheat and summer maize.In wheat season,five foliar fertilizer treatments consisted of control(deionized water,CK1),urea solution alone(CK2),urea plus nano-Zn oxide(U+ZnO),urea plus chitosan nano-Zn(U+ ZnCNP),urea plus conventional ZnSO4·7H2O(U+Zn).In maize season,a cocktail solution(including Zn in the form of ZnSO4·7H2O,Fe,Se,and urea simultaneously)was also included,recorded as U+Zn/Fe/Se.Results showed that foliar fertilizer spraying treatments had no significant effects on grain yield but had significant effects on grain micronutrient concentrations of wheat and maize.The biofortified effects of different Zn sources plus urea on wheat grain Zn concentration were increased in U+ZnCNP＜U+ZnO＜U+Zn.Compared with the CK2,the wheat grain Zn concentration was significantly improved by 77.7%(increased from 22.80 mg·kg-1 to 40.52 mg·kg-1),while the molar ratios of phytate acid to Zn(PA/Zn)significantly decreased by 42.1%,and consequently the wheat grain Zn bioavailability(TAZ)significantly improved by 74.5%with treatment U+Zn.For maize,compared with the CK2,the grain concentrations of Zn and Se were improved by 32.3%(increased from 14.93 mg·kg-1 to 19.60 mg·kg-1)and 12.7-folds(substantially increased from 17.66 μg·kg-1 to 242.04 μg·kg-1),respectively,while the molar ratios of PA/Zn significantly decreased by 27.0%,and consequently the grain TAZ significantly improved by 36.9%with treatment U+Zn/Fe/Se.Furthermore,the molar ratios of P/Zn and P/Fe in maize shoot or straw were significantly decreased by treatment U+Zn/Fe/Se.These results suggest that foliar application of conventional ZnSO4·7H2O represented the most efficient form to improve the grain Zn concentration and Zn bioavailability of both wheat and maize,with the Zn-biofortified effects being better for wheat than maize.Foliar application of a cocktail solution(treatment of U+Zn/Fe/Se)represented an effective fertilization strategy to solve the deficiencies of trace elements in the human body or animals by improving grain concentrations of Zn and especially Se as well as bioavailability of Zn and Fe in maize grain,shoot and straw.
winter wheat-summer maize cropping systemdifferent zinc sourcesbioavailability of zinc and ironfoliar applicationmicronutrient concentration
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