張久權(quán)

（中國農(nóng)業(yè)科學(xué)院煙草研究所 青島 266101）

引言，又稱前言、概述、緒論等，是論文主體部分的開端，它向讀者交代本研究的來龍去脈，引導(dǎo)讀者閱讀和理解全文。引言的內(nèi)容應(yīng)包括：本研究工作的背景；相關(guān)領(lǐng)域前人研究的歷史、現(xiàn)狀、知識空白（如結(jié)論存在矛盾等）；研究目的、理論依據(jù)、所作假設(shè)、要解決的問題、目的意義等。撰寫引言時，要注意以下幾點：

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（4）在回顧前人的研究時，不需要面面俱到，應(yīng)引用“最相關(guān)”的文獻(xiàn)以指引讀者，優(yōu)先引用相關(guān)研究中經(jīng)典、重要、最新和最具說服力的文獻(xiàn)。如果作者沒有引用最重要的相關(guān)文獻(xiàn)，或者不恰當(dāng)?shù)卮罅恳米髡弑救说奈墨I(xiàn)，將會使整篇文章的價值大打折扣。

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（6）對不常用的專門術(shù)語或縮寫詞，進(jìn)行解釋或定義，以幫助編輯、審稿人和讀者閱讀稿件；

（7）引言的關(guān)鍵在最后部分，即要明確地陳述該研究的目的和假設(shè)。讀者在閱讀后面的內(nèi)容時，會思索作者是否最終達(dá)到了預(yù)期的目的，假設(shè)是否成立？以什么研究材料和研究方法來驗證這些假設(shè)？邏輯結(jié)構(gòu)上是否合理？這將是整個研究是否科學(xué)、嚴(yán)謹(jǐn)?shù)暮诵摹?/p>

下面是2006發(fā)表在美國農(nóng)學(xué)雜志Agronomy Journal （SCI刊物）上的一篇文章的引言，文章題目為：Boron Fertilization Influences on Soybean Yield and Leaf and Seed Boron Concentrations，供大家參考。為了節(jié)省篇幅，將參考文獻(xiàn)引用格式改成了數(shù)字標(biāo)注式。

Boron is an essential micronutrient for plants.Some plants are more susceptible to B deficiency and toxicity than others.Soybean is considered relatively insensitive to B deficiency[1-2].However, research with soybean has reported negative, positive, or no yield responses from direct applications of B fertilizer[2-8].Oplinger et al[9]reported that 0.28 kg B ha-1applied foliarly numerically increased soybean yields by 3% when averaged across 29 trials conducted on B-sufficient soils in the Midwest.Individual trial results usually showed no significant differences among yields between the unfertilized control and soybean receiving B.Touchton et al[10]noted that soybean yield responded positively and nominally to B fertilization at three of nine site-years in Georgia and suggested that environmental conditions probably influence whether soybean responds positively or not at all to B fertilization.Although environmental conditions may play an important role in soybean response to B fertilization,soybean leaf B concentrations reported by Touchton et al[10]were sufficient (.25 mg B kg-1).Soil chemical (e.g.,soil pH and organic matter content) and physical (e.g., texture) properties also influence B availability to plants and have likely contributed to the inconsistent soybean response to B fertilization[11].

In Arkansas, before 2001, B was not recognized as a growth- or yield-limiting nutrient for soybean production, and no recommendations for B fertilization of soybean were available to growers.In 2001, Bdeficiency of soybean was first diagnosed in several counties in northeast Arkansas[12]and has been observed every year since, making it the most common nutrient deficiency of soybean reported in Arkansas.The soybean-producing areas of Craighead, Cross, Greene, Jackson, Lawrence, Poinsett, Randolph, St.Francis, and Woodruff counties that are west of Crowley’s Ridge produce about 403000 ha of soybean annually[13], which accounts for roughly one third of the Arkansas soybean production area.A large portion of the Arkansas soybean hectarage is irrigated with ground water high in Ca and Mg bicarbonate, rotated with flood-irrigated rice (Oryza sativa L.), and grown on siltloam soils that have low organic matter, low clay content, alkaline soil pH, and shallow topsoil, all of which have been recognized as soil conditions conducive to B deficiency[14].Boron deficiency symptoms have been observed 4 to 6 wk after soybean emergence during vegetative growth and during reproductive growth.The only published record of B fertilization field research with soybean in Arkansas was made by Al-Molla[15], who reported a 15% yield increase from the application of granular B at the R1 soybean stage[16]in Poinsett and Craighead counties.

Several studies have reported that soybean[8], cotton (Gossypium hirsutum L.)[16], peanut (Arachis hypogaea L.)[17], and alfalfa (Medicago sativa L.)[18]yields may respond positively to pre-plant incorporated or postemergence foliar applications of B.Boron application rate, rather than application strategy, seems to be the most important factor determining the response of crops grown on B-deficient soils.Compared with the unfertilized control, Touchton and Boswell[19]reported that soybean yields were increased from 0 to 4% from application of 0.28 to 1.12 kg B ha-1and reduced by 6 to 10% from 2.24 kg B ha-1.Woodruff[20]reported that soybean yields at one site were 77% greater than the unfertilized control when 0.56 kg B ha-1was applied to the soil from the V4 to V8 growth stage.The trifoliate leaves of the unfertilized control contained only 10 mg B kg-1,which is below the critical level of 20 mg B kg-1[21].The literature suggests that soybean with low tissue B concentrations (,20 mg B kg-1) generally respond positively to B fertilization and that B fertilization of soybean with sufficient concentrations of tissue B may have no benefit, slightly increase, or may reduce soybean yields.Much of the B fertilization research conducted with soybean has examined B fertilization for the purpose of increasing soybean yield potential by increasing branching[22], pod set[23-24], and various physiologic processes that may contribute to higher seed yields[23],especially for soybean grown in high-yielding environments[8].Preventing B deficiency has not been cited as a primary reason for studying B fertilization of soybean, presumably because widespread B deficiency of soybean, similar to the recent occurrence reported in Arkansas[25], is uncommon.Because B deficiency of soybean in Arkansas often occurs before the onset of reproductive growth and tissue B concentrations of soybean grown in northeast Arkansas are often low[26], research-based B fertilization recommendations are needed to assess the proper timing and rates of B application for preventing significant seed yield losses.The objective of these field studies was to determine the effects of foliar B application time and rate on soybean growth, B concentration in trifoliate leaves and seed, and grain yield.We hypothesized that (i)soybean yields would increase with B fertilization, (ii) B applied during early vegetative growth would increase soybean yield more than B applied during early reproductive growth on B-deficient soils, and (iii) increasing B rate would increase leaf and seed B concentrations.