Effects Of Different Zinc Fertilizer And Application Methods On Grain Yield And Zinc Bioavailability Of Rice

Zinc（Zn）is one of the essential micro nutrients for human.Human cannot synthesize Zn,which is usually taken by food.Rice is the staple food of more than half population of the world.Improving the bioavailability of zinc in rice can effectively improve human zinc nutrition.Zinc biofortification has become a hotspot in the field of rice research.Applying zinc fertilizer is an effective method for zinc biofortification of cereals.However,the efficiency of zinc fertilizer is often affected by the environmental factors,and traditional zinc fertilizer such as Zn SO₄usually fixed by soil,which is difficult to meet the needs of biofortification.To provide a reference for the rational application of zinc fertilizer,field experiments were conducted to study the effects of different zinc fertilizer,different zinc application methods and different zinc spraying stages on rice grain yield and zinc bioavailability.The main results are as follows:（1）The application of different kinds of zinc fertilizer significantly improved the zinc content,zinc accumulation and zinc bioavailability of brown rice and polished rice,and the zinc biofortification effect of chelated zinc fertilizers（EDTA-Zn,sugar alcohol zinc and amino acid zinc）was significantly better than inorganic zinc fertilizers（Zn SO₄ and Zn O）.Compared with the treatment without zinc fertilizer,the number of panicles in the treatment of different kinds of zinc fertilizer increased by 23.53%～33.13%;the rice yield increased by 11.02%～16.69%,and the effect of amino acid zinc treatment was the best,yield increased by 1.39 t/hm²,an increase of 16.69%;compared with inorganic zinc fertilizer treatment,the zinc content,zinc accumulation and zinc bioavailability of brown rice of chelated zinc fertilizer treatment increased by 3.85 mg/kg,34.25 g/hm² and 0.58 mg/d,an increase of 13.10%,15.79%and 12.84%;the zinc content,zinc accumulation and zinc bioavailability of polished rice increased by 5.28 mg/kg,37.32 g/hm²and 0.79 mg/d,an increase of 22.89%,25.73%and 22.69%.（2）Compared with the basal treatment,the foliar treatment could significantly increase the zinc content and zinc accumulation of brown rice and polished rice,reduce the content of phytic acid and improve the bioavailability of zinc;the zinc biofortification effect of chelated zinc fertilizer is better than that of inorganic zinc fertilizer.Compared with the basal treatment,the zinc content,zinc accumulation and zinc bioavailability of brown rice of foliar treatment increased by 11.68 mg/kg,73.64 g/hm² and 1.75 mg/d,an increase of37.49%,33.66%and 36.70%;the zinc content,zinc accumulation and zinc bioavailability of polished rice increased by 10.38 mg/kg,56.32 g/hm² and 1.56 mg/d,an increase of41.29%,34.81%and 40.52%;the phytic acid content of brown rice decreased by 0.69 g/kg,an average decrease of 7.21%;the phytic acid content of polished rice decreased by 0.14g/kg,an average decrease of 9.05%.In foliar treatment,compared with Zn SO₄ treatment,zinc content,zinc accumulation and zinc bioavailability of polished rice treated with amino acid zinc increased by 6.54 mg/kg,38.57 g/hm² and 0.98 g/hm²,an increase of 20.13%,19.25%and 19.99%;the zinc content,zinc accumulation and zinc bioavailability of brown rice increased by 5.16 mg/kg,34.60 g/hm² and 0.77 mg/d,an increase of 12.82%,11.83%and 12.64%.（3）Compared with foliar treatment at tillering stage,foliar treatment at flowering stage and foliar treatment at both tillering stage and flowering stage can significantly improve zinc content,zinc accumulation and zinc bioavailability in brown rice.Compared with the treatment without zinc fertilizer,the zinc content of polished rice foliar sprayed at different stages increased significantly by 9.57～12.43 mg/kg,an increase of 48.80%～62.33%;the bioavailability of zinc in polished rice increased by 1.43～1.86 mg/d,an increase of 47.31%～61.21%;there was no significant difference among treatments of different foliar spraying stages.Compared with foliar treatment at tillering stage,the zinc content of brown rice of foliar treatment at flowering stage and foliar treatment at tillering stage and flowering stage increased by 3.43 mg/kg and 6.63 mg/kg,an increase of 10.20%and 19.70%;the accumulation of zinc in brown rice increased by 15.45 mg/kg and 50.48 mg/kg,an increase of 5.99%and 19.56%;The bioavailability of zinc in brown rice was increased by 0.51 mg/d and 0.99 mg/d,an increase of 10.01%and 19.28%.In conclusion,chelated zinc fertilizer is better than inorganic zinc fertilizer in increasing yield and biofortification;both chelated zinc fertilizer and inorganic zinc fertilizer can effectively increase the zinc content and zinc accumulation of rice,reduce the phytic acid content and improve the zinc bioavailability of rice by foliar treatment;the zinc biofortification effect of foliar treatment at flowering stage was better than that at tillering stage.Foliar treatment at both tillering stage and flowering stage could further improve the zinc bioavailability of rice.