氮肥用量和喷施锌钾肥对小麦籽粒锌含量及生物有效性的影响

Effects of soil N application rate and foliar application of Zn and K on Zn concentration and its bioavailability in wheat grains

【目的】小麦籽粒锌(Zn)含量普遍较低,在没有外源锌施用措施下难以满足以小麦为主食人群健康所需。探索提升小麦籽粒Zn含量,尤其是其加工产品面粉Zn含量和Zn生物有效性的农艺措施,具有实际重要的意义。【方法】于2013、2014年分别在陕西杨凌示范区和三原试验站进行小麦田间试验,两地均为潜在缺锌石灰性土壤,DTPA-Zn含量分别为0.67、0.90 mg/kg,种植制度为小麦-玉米轮作。以氮肥用量为主处理,杨凌试验点为N 0(N_(0))、120(N_(1))和240(N_(2))kg/hm^(2);三原试验点为传统施氮量(N 150 kg/hm^(2),N_(C))、减氮15%(N 127.5 kg/hm^(2),N_(R1))和减氮30%(N 105 kg/hm^(2),N_(R2))。喷施处理为副处理,两地均为灌浆前期喷施清水(CK)、0.5%K_(2)SO_(4)(K)、0.3%ZnSO_(4)·7H_(2)O(Zn)和0.3%ZnSO_(4)·7H_(2)O+0.5%K_(2)SO_(4)(Zn+K)。测定了小麦籽粒及其加工面粉Zn等矿质养分含量、Zn形态及锌生物有效性。【结果】杨凌试验点,中等施氮量N_(1)(120 kg/hm^(2))处理显著增加了小麦籽粒全粒及面粉和麸皮Zn含量,分别较N_(0)提高了8.78%、13.2%和17.3%,而N_(2)(240 kg/hm^(2))降低了全粒及其各组分Zn含量,N_(1)处理显著降低了各加工组分植酸含量;与Zn处理相比,Zn+K处理对小麦全粒Zn含量提升幅度两季平均达13.1%;在中等施氮量条件下,Zn+K处理与Zn处理相比显著增加了面粉Zn含量,特别是增加了可溶性Zn含量,还大幅度降低了全粒和面粉的植酸/Zn摩尔比;氮肥用量与喷肥处理对籽粒Zn形态和Zn生物有效性具有显著的交互作用。三原试验点,小麦全粒、面粉和麸皮Zn含量均在N_(R1)处理下达到最高;与Zn处理相比,Zn+K处理并未显著影响小麦籽粒及其加工组分Zn含量;施氮量与喷施锌钾肥处理的交互作用(N×Zn)对面粉Zn含量两季均有显著影响。【结论】在北方潜在缺锌石灰性土壤上,适宜的氮肥用量和叶面喷施锌肥均可显著提升小麦籽粒和面粉Zn含量,降低植酸/Zn摩尔比,提高锌的生物有效性,且氮肥用量与喷施锌肥对提升小麦锌含量有显著的交互作用。喷施效果以锌与钾肥配合总体好于单独喷施硫酸锌。综合两地两年试验结果,获得高锌小麦的适宜氮肥用量为120 kg/hm^(2)左右,喷施效果以硫酸锌和硫酸钾配合喷施为好。

【Objectives】Wheat grains are generally low in Zinc(Zn)content which does not meet human needs.We studied the optimum nitrogen application rate and Zn fertilizer foliar application way that is effective in improving Zn content and its bioavailability in wheat grain and its milling fractions(especially in consumed flour).【Methods】Two field experiments were conducted in Yangling and Sanyuan City,Shannxi Province in 2013 and 2014.The soil type in two locations was potential Zn-deficient calcareous soil,with DTPA-Zn(soil available Zn)content of 0.67 and 0.90 mg/kg and wheat-maize rotation planting system.The N rates(i.e.,main factor)were N 0(control,CK),120(N_(1))and 240(N_(2))kg/hm^(2)in Yangling,and 150 kg/hm^(2)(N_(c)),-15%N(N_(R1))and-30%N(N_(R2))in Sanyuan.The foliar application treatments(i.e.,the subfactor)in the two sites were spraying of water(control,CK),0.5%K_(2)SO_(4)(K),0.3%ZnSO_(4)·7H_(2)O(Zn)and both Zn and K(Zn+K)at the grain filling stage.The Zn fractions in whole grains and processed flour were determined.【Results】In Yangling,the N_(1)(120 kg/hm^(2))treatment significantly increased Zn contents in whole grain,flour and bran by 13.2%,17.3%and 8.78%respectively,but N_(2)(240 kg/hm^(2))treatment did not increase Zn contents.N_(1)(120 kg/hm^(2))treatment also significantly reduced the phytate concentration in grain milling fractions.Compared with Zn treatment,Zn+K treatment significantly increased grain Zn content by 13.1%on average.Under N_(1)treatment,Zn+K treatment increased flour Zn content,especially the water-soluble Zn content,and decreased the ratio of phytate to Zn in whole grain and processed flour.N rate and foliar application showed significant interaction on Zn fractions and Zn bioavailability of whole grain and milling products.In Sanyuan,Nc treatment recorded the highest Zn contents in whole grains,flour and bran,while N_(R1)treatment did reduce the Zn contents significantly.Compared with Zn treatment,Zn concentrations in whole grains and its milling fractions were slightly affected by Zn+K treatment.N rate and foliar Zn and/or K aplplication had significant interactive effects on flour Zn concentration in both cropping year.【Conclusions】Both the two experiments showed significant increment in Zn content and bioavailability with N rate and Zn foliar application.Moreover,the results revealed that the optimum N rate was 120 kg/hm^(2),and the effective foliar application way was the combination of Zn and K in the potentially Zn-deficient calcareous soil.