Effects Of Foliar Zn Combined With Pesticides,KH₂PO₄ And Biostimulants On Zn-enrichment Of Wheat Grain

Dietary deficiency of Zn has attracted worldwide attention in recent years.Wheat is the one of the most important staple crop for many inhabitants and also the main source of zinc.While the main wheat-growing area in China overlaps with Zn deficient or potentially Zn deficient soil region,leading to the average grain Zn concentration less than 30 mg/kg,which is lower than that of satisfying human zinc nutritional and health.Moreover,wheat grains are rich in phytic acid and other anti-nutritional factors,which will decrease the bioavailability of Zn in wheat grains.Therefore,it is of great significance to improve the zinc content and bioavailability of wheat grain for improving human health.In the potentially Zn-deficient calcareoussoilin northern China,foliar Zn application is an effectively and rapidly agronomic method to improve the concentration and bioavailability of Zn in wheat grain.However,foliar Zn application need 2³ times of field operation,which requires extra investment of labor and time.In recent years,foliar pesticides,KH₂PO₄ and biostimulants has been widely used in the late stage of wheat production in China.Therefore,it’s necessary to explore the effect of foliar Zn application combined with pesticides,KH₂PO₄ and biostimulants on the Zn biofortification of wheat grains and its mechanisms.By analyzing Zn concentrations in grain and vegetative tissues of wheat,the influences of foliar Zn combined with pesticide,KH₂PO₄,and biostimulants on Zn distribution,and the relative contributions of Zn remobilization and post-anthesis shoot Zn uptake to grain Zn accumulation were evaluated.The main results were obtained as below:（1）By analyzing Zn concentration in vegetative tissues（leaf,glume and stem）of field-grown（2016.10-2018.06）wheat under single wheat plantation,the influences of combined foliar application of Zn（ZnSO₄ and Zn（Gly）₂）with pesticides,KH₂PO₄ on Zn distribution,and the relative contributions of Zn remobilization and post-anthesis shoot Zn uptaketo grain Zn accumulation were evaluated.The results show that:foliar Zn treatments（Zn1 and Zn2）significantly increased grain Zn concentration compared to the Zn0treatment,with grain Zn concentration increased from 35.7³9.8 mg/kg to 51.9⁶4.1mg/kg under foliar NY treatment,and increased from 33.0³8.2 mg/kg to 46.0⁴9.0 mg/kg under foliar PK treatment.These results indicate that combined foliar application of Zn,pesticide and PK can be an effective agronomic approach to enhance grain Zn concentration.Compared with the NY0 treatment,foliar NY treatment had no significant influences on Zn concentrations in vegetative tissues,so did the post-anthesis shoot Zn uptake and its mobilization to grain.Therefore,the increase of grain Zn concentration through foliar Zn applications were not affected by foliar NY application.However,compared with the PK0 treatment,foliar PK treatment reduced the post-anthesis shoot Zn uptake and its mobilization to grain by 64 and 47 g/ha,respectively.Thus,foliar PK application significantly decreased the grain Zn response to foliar Zn applications,and the decrement of grain Zn was lower under Zn2 treatment（16.7%）than under Zn1 treatment（20.3%）.（2）By analyzing Zn concentration in vegetative tissues（leaf,glume and stem）of field-grown（2016.10-2018.06）wheat under single wheat plantation,the influences of combined foliar application of Zn（Zn,Zn+NY and Zn+NY+PK）with biostimulants（FA,AA）on Zn distribution,and the relative contributions of Zn remobilization and post-anthesis shoot Zn uptaketo grain Zn accumulation were evaluated.The results show that:foliar application of AA or FA resulted in 6.6%and 9.6%increase in grain Zn concentration during the second experimental season（2017-2018）,respectively,under different foliar Zn treatments（Zn,Zn+NY and Zn+NY+PK）.Also,foliar AA and FA application increased the post-anthesis shoot Zn uptake and its mobilization to grain in2017-2018 by 15.3 and 11.7 g/ha.（3）On the basis of wheat grain samples obtained from the previous two field experiments,investigate the effects of foliar Zn combined with pesticides,KH₂PO₄ or biostimulants on zinc,iron and protein concentration and Zn bioavailability in wheat grain and its milling fractions.The results showed:foliar ZnSO₄（Zn（Gly）₂）combined with pesticides,KH₂PO_4,the zinc content and its bioavailability of wheat grain and its processing components would be decreased;but compared with foliar ZnSO₄ combined with pesticides and PK,foliar Zn（Gly）₂ combined with pesticides and pk could significantly increase the zinc concentration and bioavailability of wheat grain and its processing products.Therefore,compared with ZnSO₄,Zn（Gly）₂ can inhibit the antagonism of P-Zn and improve the zinc content and bioavailability of wheat grains.In addition,biostimulant can improve zinc bioavailability by reducing phytic acid content and phytic acid/zinc molar ratio in wheat grain and flour.