Effects of different forms of selenium fertilizers on Se accumulation

Jan 19, 2017 - Foliar Se fertilizers were applied to investigate the effects of Se forms on Se accumulation and distribution in the wheat−maize rota...
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Article

Effects of different forms of selenium fertilizers on Se accumulation, distribution and residual effect in winter wheat-summer maize rotation system Qi Wang, Yao Yu, Jixiang Li, Yanan Wan, Qingqing Huang, Yanbin Guo, and Huafen Li J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.6b05149 • Publication Date (Web): 19 Jan 2017 Downloaded from http://pubs.acs.org on January 23, 2017

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Journal of Agricultural and Food Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

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Journal of Agricultural and Food Chemistry

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Effects of different forms of selenium fertilizers on Se accumulation, distribution

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and residual effect in winter wheat-summer maize rotation system Qi Wang1, Yao Yu1, Jixiang Li1, Yanan Wan1, Qingqing Huang1, 2, Yanbin Guo1,

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Huafen Li*1

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Key Laboratory of Plant-Soil Interactions of the Ministry of Education, College of

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Resources and Environmental Sciences, China Agricultural University, Beijing

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100193, China

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Key Laboratory of Agro-environment and Agro-product Safety, Agro-Environmental Protection Institute, Ministry of Agriculture, Tianjin 300191, China

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Contact information for Corresponding Author:

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Huafen Li

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E-mail: [email protected]

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Tel/Fax: 0086-10-62731165

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Abstract

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Foliar Se fertilizers were applied to investigate the effects of Se forms on Se

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accumulation and distribution in the wheat−maize rotation system and residual

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concentration of Se in subsequent crops. Sodium selenite, sodium selenate,

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selenomethionine, chemical nano-Se, humic acid + sodium selenite and compound

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fertilizer + sodium selenite were applied once at the flowering stage of wheat (30 g

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ha-1) and at the bell stage of maize (60 g ha-1). Compared with the control treatment,

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foliar Se applications significant increased the grain Se concentration of wheat and

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maize by 0.02−0.31 mg kg−1 and 0.07−1.09 mg kg−1, respectively. Wheat and maize

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grain Se recovery was 3.0%−10.4% and 4.1%−18.5%, respectively. However, Se

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concentrations in the grain of subsequent wheat and maize significantly decreased by

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77.9% and 91.2%, respectively. The change of Se concentration in soil was a dynamic

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process with Se depletion after harvest of maize.

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Keywords: selenium fertilizers; wheat; maize; biofortification; residual effect

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Introduction

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Selenium (Se) is considered as an essential trace element for human and animal

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health because of its critical role in antioxidative defense and anticancer agents.1-2 It

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has been estimated that 0.5−1 billion people globally may have inadequate intakes of

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Se,

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intake of Se by human can cause health disorders, such as Keshan disease,

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Kashin-beck disease, cardiovascular disease, infertility, and even death. 4,7-9 Therefore,

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an adequate daily Se intake is required to maintain human health.

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including those in China, UK, and Australia.

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However, insufficient dietary

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Cereal and its products are a primary source of Se in diets and they contribute to

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70% of Se intake in low-Se intake areas of China. 10 Se-enriched fertilizers by soil or

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foliar application for agronomic biofortification in cereals, provides the best

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short-term solution for improving Se concentrations in crops.

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application is simpler, more practicable and more effective than soil application to

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produce Se-enriching food, especially Se fertilizer application in the acid soil under

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strongly reduced soil conditions. 13-17 Under the strongly reduced soil conditions (pH

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< 4 and Eh < 0), selenate and selenite are easily reduced to selenide or even elemental

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selenium, which is less available for plants. 18,19

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Generally, foliar

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Foliar fertilization with inorganic Se has been used in fruit, vegetable and cereal

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productions. Selenite and selenate are the main inorganic forms of foliar application.

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Foliar application of selenate exhibited higher efficiency in increasing the Se

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concentration in rice products than selenite.

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nano-Se over the past few years because of its potential benefits for improving human

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health and lowering poisoning risk. Nano-Se is bright red, soluble, highly stable,

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nano-size and has a redox state of zero (Se0), and it has been reported to have higher

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efficiency in promoting seleno-enzymes activities and alleviating toxicity, compared

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with selenite and SeMet.

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nutritional supplements and medical therapy. Moreover, a recent work has found that

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the accumulation and translocation intensity of Se nanoparticles in perennial onions

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treated with different forms of Se followed decreased in the order Se+6 > Se0 > Se+4. 23

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Compared with inorganic Se, organic Se (selenomethionine) can easily be taken up

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There has been increasing interest in

As a result, nano-Se has been manufactured for both of

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and translocated to above-ground plant tissues. 24 However, much less is known about

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the effects of nano-Se and SeMet as foliar application.

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Wheat and maize were selected as tested plants in the current study because they 10

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are the major source of Se intake by humans and domestic animals.

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the North China Plain, the winter wheat−summer maize rotation system accounts for

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43.4% of the total national wheat−maize production and 40.4% of wheat−maize

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planting area in China.

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of different forms of foliar Se fertilizers on Se concentration and distribution in crops,

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especially of organic Se and nano-Se, (2) to identify the residual effect of Se on the

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subsequent crops, (3) to test the effect of Se in combination with other chemical

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fertilizers, and (4) to assess the potential environment risk of Se fertilization in the

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local wheat−maize rotation system.

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Materials and methods

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Description of field experimental site

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Moreover, in

The objectives of this study were: (1) to examine the effect

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Two field experiments were conducted from November 2013 to October 2015 at

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Huantai Experimental Station of China Agricultural University, located at Huantai

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county, Zibo City, Shandong province, in north China (36°56′N, 117°50′E). This area

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has a warm temperate continental monsoon climate, with an annual mean temperature

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of 13.4℃ and annual precipitation of 604 mm. According to the soil genetic types,

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soil type of this field is classified as lime concretion black soil. The physical and

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chemical properties of the soil (0−20cm) were: pH (H2O), 7.82; organic matter, 25.70

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g kg−1, total N, 1.06 g kg−1; available P, 9.07 mg kg−1; available K, 191.00 mg kg−1;

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and total Se, 0.46 mg kg−1.

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Experimental design

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A common local rotation system of winter wheat (Triticum aesticum L.) and

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summer maize (Zea mays L.) was carried out in the field experiments; the two crop

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varieties were Luyuan 502 (wheat) and Zhengdan 958 (maize). Before planting, both

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wheat and maize were fertilized with base fertilizer which consisted of 90 kg N ha−1,

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90 kg P ha−1 and 90 kg K ha−1, with a topdressing rate of 103.5 kg N ha−1 at the

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jointing stage. Herbicide (tribenuron-methyl) was sprayed once at seeding time of

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wheat and maize in November and June, respectively. Pesticide (melamine

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chrysanthemum ester) was applied once at the flowering stage (April) of wheat and

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twice at the small bell stage (July) and large bell stage (August) of maize.

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The aim of Experiment 1 was to investigate the effects of four foliar Se fertilizers

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on the Se accumulation in plants and retention in soil in the wheat−maize rotation

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system. This field experiment was conducted from November 2013 to September

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2014, including five foliar treatments with three replications in a completely

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randomized block design. These treatments were: (1) control (CK, water without Se);

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(2) sodium selenite (SeIV); (3) sodium selenate (SeVI); (4) selenomethionine (SeMet);

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(5) chemical nano-Se (Nano-Se). Wheat seeds were sown about 3.0 cm deep in

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November 2013 and harvested in June 2014. The maize seeds were sown just one

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week after the harvest of wheat and maize crops were harvested in September 2014.

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Foliar Se fertilizers were applied both at the flowering stage of wheat in April 2014

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and at the bell stage of maize in August 2014. The application rates were 30 g Se ha−1

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and 60 g Se ha−1 for wheat and maize, respectively. Foliar Se fertilizer was applied

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with a motorized backpack sprayer. Analytical reagents of Se were dissolved in water

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and the solutions were applied at a rate of 400 L ha−1. The plot size was 50 m2 with a

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1 m long buffer zone on each side. The Se reagents (Na2SeO3 and Na2SeO4) were

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obtained from Sigma (St Louis, MO, USA); SeMet was provided by Shanxi

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University. Chemical nano-Se was prepared using the method described by Lin and

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Wang (2005)

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were dissolved into deionized water, assuring the final the concentrations of those

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reagents were 5 mM, 20 mM, 10 mM and 10 mM respectively. Suspended nano-Se

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particles form from these solutions after each reaction proceeds for a sufficient time (6

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h). The sizes distributing within the selenium nanoparticle dispersion were measured

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by transmission electron microscopy (TEM-EDAX, Hitachi HT7700, Japan). The

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particle size was 142.8 ± 9.1 nm.

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. In brief, Na2SeO3, Na2S2O3·5H2O, lauryl sodium sulfate and HCl

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The aim of Experiment 2 was to examine the residual effect of Se applied in

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2014 on the wheat and maize planted in 2015 (no Se application in 2015) and to test

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the effect of Se in combination with other fertilizers. Four treatments were arranged in

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the this experiment, including control (water), humic acid (without Se), humic acid +

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sodium selenite and compound fertilizer + sodium selenite, which are referred to as

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CK, HA, HA+SeIV and CF+SeIV, respectively. The planting method, Se application

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time, Se dosage and frequency were all the same as in Experiment 1. After the harvest

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of maize, wheat seeds were sown in November 2014 and harvested in June 2015, just

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one week after the harvest of wheat; then maize crops were harvested in September

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2015. The HA, HA+SeIV and CF+SeIV fertilizer were provided by Sino International

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Ltd (Hong Kong, China). The effective components in the liquid compound fertilizer

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were humic acid ≥ 4.0% and N+P2O5+K2O ≥ 20%.

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Sample and analysis

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For the calculation of yield, all the above-ground plants in 7.5 m2 of each plot

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were entirely collected and divided into unpolished grain, husk, straw or cob at the

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mature stage. The yield of every part of the plant was weighed, calculated and

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expressed in ton per hectare (t ha−1).

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For the determination of elements in wheat and maize, five samples of plants

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(divided into straw, grain, husk or cob and root) and the corresponding rhizosphere

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soil samples (0−20cm) were collected in an S shape from each plot. Plant samples

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were rinsed with deionized water, dried at 105℃ for 30 min and then at 75℃ for 48

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h. All dried soil and plant samples were sieved to