旱地石灰性土壤长期施氮提高小麦籽粒中铁铜锌含量

Long-term nitrogen application increases the content of Fe,Cu and Zn in wheat grains on calcareous soil in dry land

【目的】明确氮肥用量引起的小麦籽粒铁、锰、铜、锌含量变化及土壤作物营养机制,为优化氮肥管理,实现小麦优质丰产提供理论依据。【方法】利用2004年在黄土高原南部陕西杨凌开始的氮肥用量长期定位试验,在施磷(P_(2)O_5) 100 kg/hm^(2)的基础上,设0、80、160、240和320 kg/hm^(2) 5个氮水平,在2013—2016年3个小麦收获期采集小麦植株和土壤样品,测定各器官生物量、铁锰铜锌含量及土壤有效铁锰铜锌含量,采用回归分析方法分析施氮量、小麦籽粒产量和微量元素含量之间的关系,计算获得最高籽粒产量和铁锰铜锌含量及其收获指数的氮肥用量。【结果】与不施氮相比,施氮提高了小麦产量和籽粒铁、铜、锌含量,降低了锰含量。籽粒铁含量与施氮量呈二元一次方程关系,小麦产量达最高(6116 kg/hm^(2))时的施氮量为212 kg/hm^(2),籽粒铁含量达最高(43.9 mg/kg)时施氮量为218 kg/hm^(2),铁收获指数最高时的施氮量为92 kg/hm^(2)。锌铜含量及其收获指数均与施氮量呈线性关系,施氮量每增加100 kg/hm^(2),籽粒铜和锌含量分别提高0.4和3.5 mg/kg。籽粒锰含量与施氮量呈负线性加平台关系,施氮量为57 kg/hm^(2)时,籽粒锰含量达最低37.5 mg/kg。与不施氮相比,施氮处理耕层土壤有效锰含量提高7.8%,有效铁、铜、锌含量无显著变化,平均为5.9,1.3和0.54 mg/kg。【结论】在黄土高原旱地石灰性土壤上,长期施用氮肥提高了冬小麦籽粒铁、铜、锌含量和吸收量,降低了锰含量和吸收量,主要归因于作物吸收量提高及铁向籽粒的分配增强,籽粒锰含量降低主要与产量提高引起的养分稀释效应有关。综合考虑产量和籽粒铁锰铜锌养分含量,该地区实现小麦高产目标5810 kg/hm^(2)时,氮肥用量应为122 kg/hm^(2),在最高产量施氮量212 kg/hm^(2)基础上可减施氮肥42%,此时籽粒铁、锰、铜、锌含量较高,分别为42.1、37.5、4.0和25.1 mg/kg。

【Objectives】Understanding changes of iron(Fe),manganese(Mn),copper(Cu)and zinc(Zn)contents in wheat grains under different nitrogen application levels is of great significance in optimizing nitrogen(N)fertilizer management and realizing high yield and quality of wheat in dryland area.【Methods】The research was based on the long-term field experiment located in the south of the Loess Plateau,Shaanxi Province,and started since 2004.There were five N application rates in total,as 0,80,160,240 and 320 kg/hm^(2) on the basis of P2O5100 kg/hm^(2).At wheat harvest season during 2013 to 2016,wheat plant samples were collected to determine the biomass,contents of Fe,Mn,Cu and Zn in different wheat organs,and soil samples were collected at the same time for determination of available Fe,Mn,Cu and Zn concentrations.The relationship between grain Fe,Mn,Cu and Zn contents,yield,and nitrogen application rate was studied,and the optimal nitrogen application rate was proposed.【Results】Compared with no N application,N fertilization increased grain yield and grain Fe,Cu and Zn content,but decreased Mn content.Regression analysis showed that the N rate was 212 kg/hm^(2) for the maximum grain yield of 6116 kg/hm^(2),218 kg/hm^(2) for the maximum grain Fe concentration(43.9 mg/kg).Grain Cu and Zn contents had a linear relationship with N rate,and their contents would be increased by 0.4 and 3.5 mg/kg with every extra N application of 100 kg/hm^(2).The grain Mn content had a negative linear plus plateau relationship with N applying rate,the minimum Mn content(37.5 mg/kg)appeared at the N rate of 57 kg/hm^(2).N application increased soil available Mn concentration in 0-20 cm layer by 7.8%,did not change the available Fe,Cu and Zn concentration significantly.【Conclusions】On calcareous soil in dryland of the Loess Plateau,N application could increase wheat grain Fe,Cu and Zn contents mainly due to the increased Fe,Cu and Zn uptake and Fe distribution from shoot to grains,while decrease grain Mn concentration due to the nutrient dilution effect caused by the increased grain yield.Comprehensively considering the yield and the grain Fe,Mn,Cu and Zn contents,the N fertilizer application rate 122 kg/hm^(2) is recommended for target wheat yield 5810 kg/hm^(2),and higher grain Fe,Mn,Cu and Zn contents of 42.1,37.5,4.0 and 25.1 mg/kg.