蒯婕^,1, 王积军², 左青松³, 陈红琳⁴, 高建芹⁵, 汪波¹, 周广生^,1, 傅廷栋¹1 华中农业大学植物科学技术学院/农业部长江中游作物生理生态与耕作重点实验室,武汉 430070
2 全国农业技术推广服务中心,北京 100026
3 扬州大学/江苏省作物遗传生理重点实验室,江苏扬州 225009
4 四川省农业科学院土壤肥料研究所,成都 610066
5 江苏省农业科学院 经济作物研究所,南京 210014

Effects and Mechanism of Higher Plant Density on Directly-Sown Rapeseed in the Yangtze River Basin of China

KUAI Jie^,1, WANG JiJun², ZUO QingSong³, CHEN HongLin⁴, GAO JianQin⁵, WANG Bo¹, ZHOU GuangSheng^,1, FU TingDong¹ 1 College of Plant Science and Technology, Huazhong Agricultural University/Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, Ministry of Agriculture, Wuhan 430070
2 National Agricultural Technology Extension and Service Centre, Beijing 100026
3 Yangzhou University/Key Laboratory of Crop Genetics and Physiology of Jiangsu Province, Yangzhou 225009, Jiangsu
4 Soil and Fertilizer Research Institute, Sichuan Academy of Agricultural Sciences, Chengdu 610066
5 Institute of Industrial Crops, Jiangsu Academy of Agricultural Sciences, Nanjing 210014

通讯作者: 周广生,E-mail： zhougs@mail.hzau.edu.cn

第一联系人: 蒯婕,E-mail： kuaijie@mail.hzau.edu.cn。
收稿日期:2018-06-26接受日期:2018-07-25网络出版日期:2018-12-26

基金资助:

国家自然科学基金.31671616 湖北省科技支撑计划.2015BBA190 国家科技支撑项目.2014BAD11B03 国家油菜产业技术体系建设专项.CARS-12 高校自主科技创新基金.2013PY001

Received:2018-06-26Accepted:2018-07-25Online:2018-12-26


摘要
长江流域是我国油菜主产区,面积与总产均约占我国油菜总面积与总产的90%左右。但与发达国家相比,我国长江流域直播油菜长期存在着“密度低、单产低、机械化程度低、肥料用量高、人工成本高”的问题。“三低两高”的现状,导致油菜生产成本高,效益低,农户种植油菜积极性不高,面积与总产长期徘徊,阻碍了该产区油菜生产的发展。近年来,各地生产实践均表明,合理密植是提高我国长江流域直播油菜生产效益,提高农户种植油菜积极性,缩小与发达国家差距的一项核心技术。本文根据相关研究,综述了长江流域直播油菜适当增加种植密度后,油菜的籽粒产量、籽粒品质、茎秆抗倒性、角果抗裂角性、肥料利用效率、光能利用率以及菌核病、杂草发生的变化规律及其机理,提出了直播油菜“以密增产、以密补迟、以密省肥、以密控草、以密适机”的“五密”栽培技术,为建立适宜油菜机械化生产的高产抗倒油菜群体提供了理论依据,同时也为油菜绿色轻简高效生产提供了技术支撑。
关键词： 长江流域;油菜;密度;效应;机理

Abstract
The Yangtze River Basin is the main producing area of rapeseed in China, where the rapeseed area and total output accounts for about 90% of those of China. Compared with the developed country, directly-sown rapeseed in the Yangtze River Basin of China had lower density, lower yield, and lower mechanical rate but a higher fertilizer rate and higher labour costs. The high production costs, low economic performance resulted in farmers’ negative attitude toward planting rapeseed, which hindered the development of rapeseed production in this area. In recent years, the production practice all over the place showed that higher plant density was an effective measure to promote plant benefit and narrow the yield gap with the developed country. Based on relevant studies, this article summarized the effects and mechanism of higher plant density on rapeseed yield, seed quality, the resistance of stem lodging and pod shattering, nitrogen and light use efficiency, stem rot caused by Sclerotinia sclerotiorum, and weed occurrence. Based on this summary, the cultivation techniques that “the higher density can increase yield, compensate for late planting, adequately control weeds, lower nitrogen requirement, increase lodging resistance and facilitate mechanized harvesting” were brought forward, which could provide theoretical basis on establishing rapeseed population with high yield and high lodging resistance, and technical support for simple and efficient production of rapeseed in the Yangtze River Basin of China.
Keywords：Yangtze River Basin;rapeseed;plant density;effects;mechanism


PDF (370KB)元数据多维度评价相关文章导出EndNote|Ris|Bibtex收藏本文
本文引用格式
蒯婕, 王积军, 左青松, 陈红琳, 高建芹, 汪波, 周广生, 傅廷栋. 长江流域直播油菜密植效应及其机理研究进展[J]. 中国农业科学, 2018, 51(24): 4625-4632 doi:10.3864/j.issn.0578-1752.2018.24.004
KUAI Jie, WANG JiJun, ZUO QingSong, CHEN HongLin, GAO JianQin, WANG Bo, ZHOU GuangSheng, FU TingDong. Effects and Mechanism of Higher Plant Density on Directly-Sown Rapeseed in the Yangtze River Basin of China[J]. Scientia Agricultura Sinica, 2018, 51(24): 4625-4632 doi:10.3864/j.issn.0578-1752.2018.24.004


油菜是世界四大油料作物、我国第五大作物,是我国最主要的食用植物油来源,发展油菜生产对保障我国食用油供给安全具有极其重要的意义。与发达国家相比,我国油菜生产存在以下几个突出问题：（1）肥料施用量偏高。全国每公顷化肥用量约314 kg,远高于世界作物平均化肥用量（120 kg·hm^-2）;（2）种植密度低。加拿大、欧盟在4.50×10⁵株/hm²以上,我国在1.50×10⁵—3.00×10⁵株/hm²;（3）机械化程度低,人工成本高。加拿大、欧盟每公顷用工4.5个,菜籽成本1.5—2.0元/kg,我国每公顷用工120—150个,菜籽成本3.6—4.0元/kg;（4）单产低。欧盟油菜生育期320 d左右,产量约3 300 kg·hm^-2,我国油菜生育期210 d左右,产量仅为2 100 kg·hm^-2左右^[1,2]。这“三低两高”的现状,导致了我国油菜生产成本高,效益低,农户种植油菜积极性不高,油菜种植面积与总产长期徘徊。

合理密植是提高油菜产量与肥料利用效率的重要途径,也是提高我国油菜生产效益,缩小与发达国家间差距的一项核心技术。近年来,本课题组围绕油菜机械化生产的密度优化开展了系列试验,对优化油菜种植密度后,其产量品质变化,与机械收获密切相关的茎秆抗倒性、角果抗裂性等指标变化,光照、肥料等资源利用率变化以及田间杂草、菌核病发生进行了较为系统的研究,提出了“五密”栽培核心技术,即“以密增产、以密补迟、以密省肥、以密控草、以密适机”。其结果为建立适宜油菜机械化生产的高产抗倒油菜群体提供了理论依据,同时也为油菜绿色轻简高效生产提供了技术支撑。

1 对籽粒产量、品质的影响

1.1 对产量的影响

2000年前后,在我国长江流域油菜主产区,直播栽培模式作为一种轻简化栽培技术开始在各地示范推广。但实际生产中,受传统的育苗移栽技术的影响,农户担心增加种植密度,容易倒伏而减产,因此,油菜种植密度一般仅为1.50×10⁵—2.25×10⁵株/hm²,与欧洲国家4.50×10⁵—6.00×10⁵株/hm²的高密度直播油菜相比,密度偏低,肥料用量高,产量差距大。

与育苗移栽相比,直播油菜的个体相对小。因此,在一定范围内增加种植密度的增产效果比较明显。种植密度对油菜株高、根颈粗、分枝数、分枝高度等农艺性状亦有较大影响^[3],且影响大小存在品种间差异^[4],合理的种植密度可有效减少个体间的竞争,并调节个体生长和群体间的矛盾,充分发挥作物群体效应而增产^[5,6]。本课题组多年多点试验结果表明,长江流域在正常播期条件下,与常规1.50×10⁵—3.00×10⁵株/hm²相比,将直播油菜种植密度增至4.50 ×10⁵—6.00×10⁵株/hm²,每公顷产量可达到2 400— 2 700 kg,增产10%以上,“以密增产”效果显著。研究表明,随着播期推迟,油菜越冬期成苗率不断下降。在湖北省,10月15日以后播种,其成苗率下降更为显著。在9月25日播种时,稻茬直播油菜的越冬期成苗率为35%左右,当播量为4.5 kg·hm^-2时,越冬期可获得4.50×10⁵株/hm²的高产的密度要求,如果播期每推迟5—10 d,则播量依次增加0.30—0.45 kg·hm^-2,高产条件下,播期每推迟5—10 d,则越冬期密度需增加3.00×10⁴—4.50×10⁴株/hm²,可保证较高的产量。在播期较晚,种植密度较高时,直播油菜的单株有效角果数与分枝数减少、株高略降,而有效分枝部位高度、每角果粒数和千粒重变化则不尽一致^[7,8],但是群体角果数显著增加,产量增加,即适当密植后也提高了晚播油菜的稳产性,起到了“以密补迟”的效果。

1.2 对关键品质的影响

油菜生产中,除了产量外,籽粒品质也是影响油菜种植效益的关键指标。众多品质指标中,目前研究较多的依然是籽粒含油量。前人研究认为,当密度从9.00×10⁴株/hm²增加到1.80×10⁵株/hm²,除了可以显著增产外,还可提高籽粒含油量,但蛋白质含量下降^[9];其他研究也表明,密度从2.40×10⁵株/hm²增加到4.80×10⁵株/hm²,油菜籽粒含油量增加。这种变化主要由分枝数量差异所决定,油菜主茎籽粒含油量高于分枝,随种植密度的增加单株分枝数大大减少,群体主茎角果比例增大,因而随密度增大籽粒含油量提高^[10]。不同的观点则认为密度对含油量的影响依赖于施氮量,低中氮（120 和240 kg·hm^-2）条件下,在3.00×10⁵—6.00×10⁵株/hm²范围内,随密度增加,含油量、产油量均增加,高氮条件下（360 kg·hm^-2）,随密度增加,含油量略有下降,产油量则随密度增加而增加。含油量和倒伏指数极显著相关（2013—2014年,R²=0.3783**;2014—2015年,R²=0.5641**）,不同氮肥、密度及其互作下,倒伏指数的差异是影响含油量的决定因素^[11]。低中氮条件下,密度增加,抗倒性增强,冠层通风透光,利于籽粒油分积累;而高氮高密条件下,倒伏指数增加,倒伏发生严重,冠层遮蔽,光照减弱,影响角果光合,而含油量由籽粒充实期的光合产物量决定^[12],倒伏后,光合产物不足阻碍了籽粒脂肪累积,含油量因此下降。

“双低”油菜的籽粒品质除了与含油量、蛋白质相关外,还取决于脂肪酸的组成。油酸是人体最易消化吸收的脂肪酸,亚油酸和亚麻酸是人体必需脂肪酸,倍受重视^[13,14]。双低菜籽油中芥酸含量低于3%,菜饼中硫代葡萄糖甙（简称硫甙）含量低于30 μmol·g^-1,符合国家优质菜油标准,油酸含量达63%,亚油酸含量21%,亚麻酸含量9%,被称为“最健康的食用植物油”^[15]。但是目前针对关键栽培措施,如不同种植密度等对高油酸油菜品种脂肪酸组成和含量的影响及其产量形成机理尚未见报道。

2 对茎秆抗倒性、角果抗裂性的影响

油菜倒伏和裂角由品种特性和外界环境共同作用^[16],两者以遗传因素为主^[17,18],而合理的栽培措施可通过改善植株和角果形态来调控茎秆倒伏和角果开裂^[8,19]。种植密度是作物高产栽培重要途径,也是影响油菜倒伏和裂角的重要因素。

2.1 对茎秆抗倒性的影响

就直播油菜而言,其倒伏主要是茎秆倒伏,根倒发生较少。对水稻、小麦、玉米的研究表明,倒伏与种植密度呈极显著正相关,即种植密度增加,玉米、小麦和水稻的倒伏发生加重^[20,21,22]。就油菜茎秆倒伏而言,其对种植密度的响应与其他作物存在明显差异。低密度条件下,油菜茎秆基部倒伏指数小,抗倒性强;茎秆顶端紧临有效分枝部位的倒伏指数大,抗倒性弱,因此,直播油菜茎秆倒伏往往发生在茎秆顶端紧临有效分枝的部位。在一定范围内增加种植密度,油菜株高降低,倒伏角度降低,茎秆基部倒伏指数增加,而茎秆顶端紧临有效分枝的部位倒伏指数降低,抗倒性增强,即种植密度的增加能够降低紧临有效分枝以下茎秆的倒伏风险,茎秆抗倒性增强。这主要与适宜密植条件下油菜形态及茎秆生理结构相关。从形态学来讲,合理密植后,油菜株高、根颈粗、根干重和地上部干重均显著降低,但根冠比增加,茎秆抗折力变小,倒伏指数显著降低,倒伏发生减轻^[11];从茎秆生理特性来讲,油菜密度增加,茎秆上部木质素合成关键基因（PAL,CCR1和4CL）表达量均增加,木质素含量增加,抗倒性增强^[2]。若种植密度过高,油菜株高降低,但茎秆单位长度抗折力及根颈粗减小过大,倒伏指数则逐渐增大^[23]。

2.2 对角果抗裂性的影响

影响油菜角果开裂的因素很多,如角果干燥程度、成熟度及外界对角果的机械作用。已有研究认为,油菜角果长、宽,每角粒数与抗裂角指数显著正相关,但相关系数较小^[24];但不同的结果则认为抗裂角指数与角果长、宽和每角果粒数不相关^[25]。多数研究认为,在油菜角果各项指标中,角果壳重量对抗裂角指数影响最大^[26]。角果抗裂性除了受到角果形态影响外,角果皮生理组成成分也是重要的影响因素。角果皮木质素、纤维素含量增加,可以增强细胞壁的机械支撑作用而增加角果抗裂能力^[27]。

合理密植可影响油菜植株形态,协调个体、群体生长与环境之间的矛盾,改良角果农艺性状而提高抗裂角能力,提高抗裂角指数的适宜种植密度存在品种间差异^[25]。适宜密度下,油菜群体冠层结构较合理,冠层光合有效辐射增加,有利于角果光合作用,促进了角果壳干物质的累积,进而提高角果抗裂性;此外,角果含水量也是影响角果开裂的重要因素^[28]。本课题组前期研究表明,花后20 d至成熟期,角果含水量下降速率与抗裂角指数呈极显著负相关关系,且在各角果性状中的相关系数最大,表明不同密度下,主要通过影响角果含水量的变化影响裂角性,角果含水量下降速率越慢越抗裂^[8]。

因此,适当增加密度后,油菜茎秆抗倒性及角果抗裂性增强,起到了“以密适机”的效果。

3 对肥料、光能等资源利用率的影响

长江流域是我国油菜的主产区,水稻-油菜轮作模式占该产区油菜总面积的80%左右。稻-油轮作模式下,由于各地水稻收获时间差异较大,导致油菜播期相应变化较大。较多情况下,由于水稻生育期延长,收获时间推迟,导致油菜播期推迟,温、光等资源则无法满足其高产需求^[29]。研究表明,油菜晚播,则营养生长显著抑制,花前期缩短,叶面积指数、收获指数和氮素利用率（NUE）均显著降低,且易早熟,分枝数、单株角果数和千粒重降低,引起产量下降达到30%—70%^[30,31]。播期推迟一周,含油量下降0.5%—1.5%^[32]。油菜生产中,常通过增加种植密度来缓解晚播带来的负面效应。种植密度可调节群体结构、肥料利用和光能利用,影响植株茎秆与生殖器官间碳水化合物的积累与运转及茎秆结构形态的建成,进一步影响茎秆机械强度等抗倒伏关键指标及最终的籽粒产量和品质。

3.1 氮肥利用率

氮肥利用率是评价氮肥施用后被吸收利用的指标。适宜密度下,单位面积角果数多,库容和库强度较大,可进一步促进光合物质源的生产和运转,籽粒对养分的需求反过来促进角果皮光合产物的生产。成熟期油菜氮素积累量达到最高,能够充分满足角果和籽粒的生长发育,源库关系协调,这是油菜高产的重要原因之一^[33]。在相同目标产量下,高密度种植（4.50—6.00×10⁵株/hm²）比低密度种植（1.50×10⁵—3.00×10⁵株/hm²）节约22.9%—30.6%的氮肥用量,NUE显著增加^[2]。苏伟等^[34]研究表明,与3.00×10⁵株/hm²相比,高密度（6.00×10⁵株/hm²）下,整个生育期油菜氮、磷、钾的养分吸收量分别增加了46.7%、53.6%和50.2%,油菜籽产量也提高了43.1%,可见“以密省肥”效果显著。

高密度种植后,油菜氮肥利用效率提高的主要机理是高密油菜单位面积根系总长、总表面积、总体积和根系活力均高于低密度种植油菜,根直径则低于低密度油菜。同一施肥水平下,高密度油菜根系生物量在0—10 cm土层低于低密度油菜,但在10—20、20—30和30—40 cm各土层中显著高于低密度油菜,即增加密度可以促使根系向土壤深层延伸^[35],高密度油菜群体根系生长优于低密度,群体的养分吸收能力有很大提升,有效弥补了个体生长的不足。

3.2 光能利用率

增加种植密度可通过改变作物株型及冠层结构,增加群体光合面积指数和光能利用率,影响光能拦截与利用^[36],充分发挥作物群体效应^[6]。增加密度,油菜个体生长受限制,单株叶片、角果光合面积较小,光合速率减小,导致单株干物质积累量下降。其原因是增加种植密度后,株距变小,油菜个体之间对光照养分等的竞争激烈,个体发育受限制,但作物冠层结构改变,群体叶面积指数（LAI）/角果皮面积指数（PAI）增大,光能拦截率（LIR）增加,最终光能利用率（RUE）也增加。群体光能截获及RUE是干物质形成的关键,可见,增加种植密度,油菜均可通过增加群体光能截获和RUE的提高,促进光合产物积累,最终达到增产的效果,这与在小麦^[37]、高粱^[38]中的结论一致。

作物不同生育时期的RUE不同^[39],对密度的响应也存在差异。油菜RUE在终花期至成熟期最大,在该时期受密度的影响最大,且相关分析结果表明,该时期RUE与产量极显著正相关。终花期至成熟期为角果发育关键时期,光照充足,角果遮阴少,角果层能够充分利用光能,RUE升高利于角果发育。播种至初花是油菜营养生长旺盛时期,此时RUE升高,有利于油菜壮苗,是油菜高产抗倒形成的基础。因此,高产栽培应重视苗期和花后角果RUE的提高。

除了肥料、光照外,土壤水分也是限制油菜生产效益提高的关键因素,但关于不同密度下油菜水分利用情况的研究尚未见系统报道。

4 对田间杂草及菌核病发生的影响

4.1 田间杂草发生

杂草危害是影响油菜产量的主要因素之一。长江流域油菜产区田间杂草种类多、危害较重,尤其是直播油菜。该产区田间杂草发生高峰主要在冬前,造成油菜在苗期遭受杂草危害。杂草发生后,导致油菜成苗株数减少,且易形成瘦苗、弱苗、高脚苗,抽薹后分枝少,单株角果数下降,一般年份可减产10%—20%,严重时减产50%以上。油菜田间杂草已成为制约直播油菜生产的一大因素^[40,41]。

长江流域稻油轮作区,由于晚播,油菜个体生长受到抑制,加重了田间杂草的发生,前人研究亦表明,晚播后,作物氮素和生物量累积减少导致对杂草抑制效应减弱^[42,43];而生产中过量施用氮肥加重了田间杂草的发生^[44];针对油菜田杂草较多,生产中可以通过施用除草剂和开深沟等加以控制,但这些措施的应用往往会使生产成本增加,前者还容易造成环境污染,在实际生产中农民也难以接受。增加种植密度,油菜冠层加厚,透光率降低,且高密度抑制了杂草对养分的吸收^[2,30],下部杂草因无法截获充足的光照进行光合作用,同时养分供应不足,生长受到抑制,表现为数量和生物量均减少,即增加密度有效抑制了杂草的发生^[11],起到了“以密控草”的效果,前人研究也表明高密油菜可抑制杂草发生^[45]。

4.2 菌核病发病率

油菜菌核病是一种由核盘菌[Sclerotinia sclerotiorum（Lib.）de Bary]侵染引起的病害,分布范围广、发生频率高、预防治理难,是长江流域危害油菜生产的主要病害,从苗期至接近成熟均可发生,但以盛花期发病最盛,茎杆受害最重。长江流域一般年份大面积油菜菌核病发病率为10%—35%,严重年份达80%以上;菌核病一般可减产10%—70%,含油量降1%—5%^[46]。目前生产上对该病害的防治主要采用化学防治为主,辅以农业防治和生物防治。但长期使用单一药剂,可导致抗性菌株产生,药剂防治效果降低。而生物防治相关研究周期长、过程复杂。

研究表明,随着油菜倒伏角度的增加,菌核病发病率增加,原因是倒伏后,冠层通风透光差,温湿度更利于菌核病发生。油菜菌核病发病率受氮肥密度互作影响显著。随着施氮量的增加,油菜菌核病发病率增加。在施氮量为0—180 kg·hm^-2时,增加种植密度,菌核病发生有增加的趋势;而在施氮量为270—360 kg·hm^-2时,增加种植密度,菌核病发病率显著降低,即中、高氮条件下,增加种植密度可有效减轻菌核病发生。增加密度后,茎秆木质素含量增加^[2],木质素作为植物机械组织中重要组成部分和结构抗性物质,在植物防御病原体的过程中发挥重要的作用,而木质化的细胞壁可以增强草本和木本植物的抗菌能力^[47]。杨向东^[48]发现油菜木质素含量与抗菌核病之间存在显著正相关性。密植条件下,茎秆木质素含量增加直接阻碍了菌核病病原体的入侵,同时茎秆木质素增加后,茎秆机械组织增强,抗倒性增加,倒伏发生减轻,间接降低了菌核病的发生。

5 小结

油菜适当密植后,可以有效发挥群体优势,改变了株型及冠层结构,光能利用率提高,群体产量增加,起到了“以密增产”的效果。在茬口矛盾突出的区域,油菜播种晚、产量低,通过增加种植密度,可稳定产量,即“以密补迟”的效果明显。密植后,根系群体总量增加,土壤养分吸收利用能力提高,一定程度上缓解了个体间的养分竞争,肥料利用率提高,起到了“以密省肥”的效果。密植后,冠层紧凑,透光率低,种间竞争加剧,抑制了地表杂草发生,起到了“以密控草”的效果。与其他作物不同,油菜在密植后,株高降低,冠层重量减轻,抗倒性增强,起到了“以密适机”的效果;且抗倒性增强、茎秆木质素增加,可降低菌核病发生,减少农药使用。

在我国推行“减肥减药”绿色栽培的大背景下,油菜采用适当密植的栽培方式,是实现我国长江流域油菜主产区大面积绿色高效生产的重要技术措施,是促进我国长江流域油菜主产区增效、农民增收的重要手段,也是提高我国油菜生产力的重要举措。

参考文献 View Option 原文顺序
文献年度倒序
文中引用次数倒序
被引期刊影响因子

[1] ANGADI S V, CUTFORTH H W, MCCONKEY B G, GAN Y . Yield adjustment by canola grown at different plant populations under semiarid conditions
Crop Science, 2003,43(4):1358-1366.
DOI:10.2135/cropsci2003.1358URL [本文引用: 1]
Establishing a good canola (rapeseed; Brassica napus L.) stand is difficult in the semiarid prairie region of Canada where low temperature, water stress, and soil crusting could result in poor seed bed conditions. A field study was conducted from 1999 to 2001 at Swift Current, SK, Canada, to determine the effect of a range of uniform (5 to 80 plants m(-2)) and nonuniform (seedlings from 1-m lengths from two adjoining rows were removed and retained alternatively; 10 to 40 plants m(-2)) plant populations on yield and yield components of canola. Canola adjusted seed yield across a wide range of plant populations, although it did not compensate completely for the decreasing populations. Environmental conditions played a significant role in the expression of plasticity of canola. For example, in 2000, with slightly above-normal growing season precipitation, canola maintained similar yield levels across a wide range of populations (20 to 80 plants m(-2)), while in 2001, with well below normal precipitation, seed yield declined as populations dropped below 40 plants m(-2). Reducing plant population by half from 80 to 40 plants m(-2) did not reduce seed yield when the reduced plant population was uniformly distributed, but reduced yield when the population was nonuniformly distributed. The primary response of canola to lower plant population was increased pods per plant through increased branching and increased pod retention at each node. The number of pods formed on primary and secondary branches increased as population decreased. Seeds per pod and seed weight were stable across populations.

[2] KUAI J, SUN Y, ZHOU M, ZHANG P, ZUO Q, WU J, ZHOU G . The effect of nitrogen application and planting density on the radiation use efficiency and the stem lignin metabolism in rapeseed (
Brassica napus L.). Field Crops Research, 2016,199:89-98.
DOI:10.1016/j.fcr.2016.09.025URL [本文引用: 5]
Using the rapeseed Huayouza 62 as experimental material, yield and lodging related traits were evaluated under various nitrogen applications [120,240 and 360kgha611(N1–N3, respectively)] and planting densities [15×104, 30×104and 45×104plants ha611(D1–D3, respectively)]. Results showed: (1) the increase of nitrogen fertilizer elevated the leaf (and silique) area index (LAI) and light interception rate (LIR), significantly affecting the bud stage. In addition, the radiation use efficiency (RUE) for different growth stages and biomass accumulation were increased, which improved yield by facilitating formation of siliques in both single plants and populations. The increase of planting density significantly elevated the population LAI and LIR in seedlings, and the RUE in various growth stages, increased population biomass accumulation, which may have also improved yield by promoting the formation of siliques in the population. The correlation between LIR/LAI and yield was the highest at the bud stage, while the strongest correlation between RUE and yield was at silique development. (2) More nitrogen increased the lodging angle, base lodging index (LIL) and the upper lodging index (LIU), resulting in elevated whole plant lodging risk. With increases in nitrogen fertilizer, expression of phenylalanine ammonia-lyase (PAL) of lignin biosynthesis decreased in the upper stem, leading to lower lignin content and lodging resistance. However, higher plant density reduced the lodging angle and LIU, but increased LIL. The increase in planting density induced the expression ofPAL, cinnamoyl-CoA reductase 1 (CCR1), 4-coumarate: CoA ligase (4CL) in the stem, which showed their highest expression in the N2D3 treatment, leading to higher lignin content and lodging resistance. (3) In this study, N2D3 achieved relative high yield and the lowest lodging index, which will meet the requirements for mechanized harvest.

[3] 宋稀, 刘凤兰, 郑普英, 张学昆, 陆光远, 付桂萍, 程勇 . 高密度种植专用油菜重要农艺性状与产量的关系分析
中国农业科学, 2010,43(9):1800-1806.
[本文引用: 1]

SONG X, LIU F L, ZHENG P Y, ZHANG X K, LU G Y, FU G P, CHENG Y . Correlation analysis between agronomic traits and yield of rapeseed (Brassica napus L.) for high-density planting.
Scientia Agricultura Sinica, 2010,43(9):1800-1806. (in Chinese)
[本文引用: 1]

[4] 浦惠明, 傅寿仲, 戚存扣, 张洁夫, 伍贻美, 高建芹, 陈新军 . 不同种植密度对杂交油菜若干性状的影响.
江苏农业科学, 2001(3):28-30.
[本文引用: 1]

PU H M, FU S Z, QI C K, ZHANG J F, WU Y M, GAO J Q, CHEN X J . Influence of planting density on several characters of hybrid rape
.Jiangsu Agricultural Sciences, 2001(3):28-30. (in Chinese)
[本文引用: 1]

[5] 王锐, 李京, 胡立勇 . 不同株行配置与密度对油菜产量的影响
中国农学通报, 2011,27(16):273-277.
[本文引用: 1]

WANG R, LI J, HU L Y . Effects of different row spacing and planting density on yield of rapeseed
Chinese Agricultural Science Bulletin, 2011,27(16):273-277. (in Chinese)
[本文引用: 1]

[6] DIEPENBROCK W . Yield analysis of winter oilseed rape (Brassica napus L.): A review.
Field Crops Research, 2000,67:35-49.
[本文引用: 2]

[7] 王翠翠, 陈爱武, 王积军, 张冬晓, 汤松, 周广生, 胡立勇, 吴江生, 傅廷栋 . 湖北双季稻区免耕直播油菜生长及产量形成
作物学报, 2011,37(4):694-702.
[本文引用: 1]

WANG C C, CHEN A W, WANG J J, ZHANG D X, TANG S, ZHOU G S, HU L Y, WU J S, FU T D . Growth and yield formation of no-tillage direct-seeding rapeseed in Hubei double cropping rice area
Acta Agronomica Sinica, 2011,37(4):694-702. (in Chinese)
[本文引用: 1]

[8] 李小勇, 周敏, 王涛, 张兰, 周广生, 蒯婕 . 种植密度对油菜机械收获关键性状的影响
作物学报, 2018,44(2):278-287.
[本文引用: 3]

LI X Y, ZHOU M, WANG T, ZHANG L, ZHOU G S, KUAI J . Effects of planting density on the mechanical harvesting characteristics of semi-winter rapeseed
Acta Agronomica Sinica, 2018,44(2):278-287. (in Chinese)
[本文引用: 3]

[9] 张子龙, 王瑞, 李加纳, 唐章林, 谌利 . 密度和氮素与甘蓝型黄籽油菜主要品质的关系
西南农业大学学报, 2006,28(3):349-352.
[本文引用: 1]

ZHANG Z L, WANG R, LI J N, TANG Z L, ZHAN L . Effects of planting density and N fertilization on seed colour and related quality characters of yellow-seeded rapeseed (Brassica napus L.).
Journal of Southwest Agricultural.University, 2006,28(3):349-352. (in Chinese)
[本文引用: 1]

[10] ZHANG S, LIAO X, ZHANG C, XU H . Influences of plant density on the seed yield and oil content of winter oilseed rape (Brassica napus L.).
Industrial Crops & Products, 2012,40:27-32.
DOI:10.1016/j.indcrop.2012.02.016URL [本文引用: 1]
A field experiment was conducted to investigate the influences of plant densities on the seed yield and oil content of the winter oilseed rape (Brassica napus L.), which included two varieties, Zhongshuang No. 11 (ZS) and Ganyouza No. 1 (GY), and three densities (2.4×104, 3.6×104 and 4.8×104planthm612) treatments in two consecutive growing seasons (2009–2010 and 2010–2011). Results showed that, compared with 2.4×104planthm612, the seed yield per plot of 3.6×104 and 4.8×104planthm612 treatments were significantly increased in both growing seasons, which might be due to the raceme and pod numbers per unit area were significantly increased with the increase in plant densities. And the seed oil content was significantly increased with the increase in plant densities, which might be due to the proportion of seed yield of main raceme significantly increased. Meanwhile, the seed oil content and 1000 seed weight of main raceme were significant higher than branch raceme about 1.0% and 10.0%, respectively. And the influences of plant densities on the seed yield of winter oilseed rape are mainly on the branch raceme and less on the main raceme. These results indicated that increasing the main raceme numbers per unit area and the production capacity of main raceme might be an effective means to increase the seed yield and oil production of winter oilseed rape.

[11] LI X, ZUO Q S, CHANG H B, BAI G P, KUAI J, ZHOU G S . Higher density planting benefits mechanical harvesting of rapeseed in the Yangtze River Basin of China
Field Crops Research, 2018,218:97-105.
DOI:10.1016/j.fcr.2018.01.013URL [本文引用: 3]
Winter rapeseed is an important oilseed crop in the Yangtze River Basin. To optimize its cultivation in this area and improve its production efficiency, a split-plot experiment with various planting dates (25 September and 10 October), nitrogen applications (120, 240 and 36062kg62ha 611 ) and planting densities (3.062×6210 5 , 4.562×6210 5 and 6.062×6210 5 plants ha 611 ) was performed to investigate their effects and interactions on the seed yield of rapeseed, its lodging index and weed occurrence in farmland. Our results indicated that (1) Delay in planting led to the decrease in the net photosynthetic rate ( Pn ) of leaf, nitrogen seed production efficiency (NUE), pod number per plant and yield, but aggravated weed occurrence. The increase in nitrogen fertilization resulted in reduced NUE, elevated Pn of leaves, improved pod number per plant and yield, and facilitated weed growth. The increase of planting density elevated NUE, reduced Pn and yield per plant because of the lowered number of pods per plant, but enhanced the population yield and substantially inhibited weed growth. (2) Delayed planting inhibited rapeseed growth, showing significant reductions in plant height, rhizome diameter, root dry weight, aboveground dry weight and root/shoot ratio, and resulted in lower snapping resistance but a higher lodging index. Although higher nitrogen application improved root dry weight, rhizome diameter and snapping resistance, it resulted in the increase of plant height and aboveground dry weight, which led to a reduced root/shoot ratio and a greater lodging index. The increase in planting density lowered the rhizome diameter, root dry weight and snapping resistance, significantly reduced the plant height and aboveground dry weight, hence increasing the root/shoot ratio, which further decreased the lodging index. A linear relationship was observed between the seed oil content and lodging index (2013–2014, R 2 62=620.3783**; 2014–2015, R 2 62=620.5641**). Oil content was reduced while the lodging index increased, indicating that lodging index was a key factor determining oil content under various planting dates, nitrogen amounts, densities and their interactions.

[12] MENDHAM N J, SHIPWAY P A, SCOTT R K . The effects of delayed sowing and weather on growth, development and yield of winter-oil- seed rape (italic>Brassica napus).
Journal of Agricultural Science, 1981,96(2):389-416.
DOI:10.1017/S002185960006617XURL [本文引用: 1]
Sowing winter oil-seed rape cv. Victor late in autumn (late September or October) in seven seasons from 1970 to 1977 gave enormously variable seed yields, from 120 to 450 g/m2. All crops made little growth before winter, and yield was related to the size of the crop at flowering, a function of the length of time for radiation interception and growth between the 090004beginning of spring090005, when mean temperatures rose consistently above 5 00°C, and full flower in late May. A late spring in 1970 gave the poorest growth and lowest yield, whereas in 1977 an early spring coincided with late flowering to give exceptional growth, and yields higher than from any early sowing.Crops sown in early autumn (before mid-September) produced more consistent seed yields, 280090009360 g/m2, except in the dry year of 1976. All grew well in autumn, overwintered with a large leaf area, and once temperatures rose in spring, rapidly reached peak area and full flower in early May. They were all large at flowering, and yield was apparently limited more by post-flowering events.With all sowings numbers of pods and seeds were largely determined during a 3-week phase in late May and early June, extending from full flower until most pod hulls had finished growing. Late sowings produced 30000900096000 pods/m2, and the number of seeds retained per pod varied widely, from 7 on a poorly grown crop to 22 on a well grown crop, thus expressing the yield potential determined by crop size at flowering. Early sowings, however, produced apparently excessive numbers of pods (600009000912000/m2) and few seeds per pod (609000910), so that yield varied little, regardless of crop size. Early in the phase, when the number of seeds was determined, the mass of yellow flowers at the top of the crop reflected or absorbed up to 60 % of incoming radiation, and then the large number of pods increasingly shaded each other and competed for assimilate, resulting in heavy seed losses. A high-yielding crop type may therefore need to incorporate the restricted pod production and good seed retention of some well-grown latesown crops with the reliability and desirable agronomic features of early-sown crops.Final seed weight varied more between seasons (300·7090009500·3 nag) than between sowings. Seed growth mainly took place after the number of seeds had been determined, the duration depending on temperature, but rate of growth apparently more on assimilate supply, a function of environmental factors and the number of competing seeds.

[13] 沈金雄, 傅廷栋 . 我国油菜生产、改良与食用油供给安全
中国农业科技导报, 2011,13(1):1-8.
[本文引用: 1]

SHEN J X, FU T D . Rapeseed production, improvement and edible oil supply in China
Journal of Agricultural Science and Technology, 2011,13(1):1-8. (in Chinese)
[本文引用: 1]

[14] 官梅 . 德国油菜高油酸育种简介
中国油料作物学报, 2004,26(1):81-83.
[本文引用: 1]

GUAN M . High oleic acid oilseed rape breeding in Germany
Chinese Journal of Oil Crop Sciences, 2004,26(1):81-83. (in Chinese)
[本文引用: 1]

[15] 熊秋芳, 张效明, 文静, 李兴华, 傅廷栋, 沈金雄 . 菜籽油与不同食用植物油营养品质的比较——兼论油菜品质的遗传改良
中国粮油学报, 2014,29(6):122-128.
[本文引用: 1]

XIONG Q F, ZHANG X M, WEN J, LI X H, FU T D, SHEN J X . Comparation of nutritional values between rapeseed oil and several other edible vegetable oils—Discussion of rapeseed quality genetic improvement
Journal of the Chinese Cereals and Oils Association, 2014,29(6):122-128. (in Chinese)
[本文引用: 1]

[16] PINTHUS M J . Lodging in wheat, barley, and oats: The phenomenon, its causes, and preventive measures
Advanced Agronomy, 1974,25:209-263.
DOI:10.1016/S0065-2113(08)60782-8URL [本文引用: 1]
This chapter discusses the phenomenon of lodging in wheat, barley, and oats. Lodging is the state of permanent displacement of the stems from their upright position, which is induced by external forces exerted by wind, rain, or hail. It may culminate in the plants being laid flat on the ground and sometimes involve breakage of the stems. The severity of lodging and the extent of the losses resulting from it depend on the crop's environment and on the growth stage at which lodging occurs. The chapter describes two types of lodging: stem lodging and root lodging and examines various causes of lodging. It discusses the effects of lodging on crop development and yield, including (1) effects on grain yield, (2) effects on grain quality, (3) effects on culm development and tillering, (4) physiological effects of lodging, (5) impact of lodging on grain harvest, and (6) incidence of diseases in lodging crops. Environmental and Agronomic Factors that affecting lodging and the way lodging should be prevented is also discussed in the chapter.

[17] MORGAN C L, LADBROOKE Z L, BRUCE D M, CHILD R, ARTHUR A E . Breeding oilseed rape for pod shattering resistance
Journal of Agricultural Science, 2000,135:347-359.
DOI:10.1017/S0021859699008424URL [本文引用: 1]
The genetic control of pod dehiscence was studied through the production, field trial and subsequent analysis of a full diallel involving seven parents selected for high and low resistance to pod shattering. Additive gene effects were most significant among the measures of pod shattering resistance with only minor contributions from non-additive gene effects. Genetic variation in measures of the stiffness of the pod wall were, however, determined by dominant gene effects. Genes for increased pod shattering resistance acted recessively. All characters showed high levels of heritability. Correlations among pod shatter resistance characters and other pod, raceme and plant characters were low suggesting that resistance is likely to be independent of other important agronomic traits.

[18] 刘定富, 刘后利 . 甘蓝型油菜数量性状遗传变异的研究
遗传学报, 1987,14(1):31-36.
[本文引用: 1]

LIU D F, LIU H L . Genetic variabilities of some quantitative characters in
Brassica napus L. Acta Genetica Sinica, 1987,14(1):31-36. (in Chinese)
[本文引用: 1]

[19] 陈晓光, 石玉华, 王成雨, 尹燕枰, 宁堂原, 史春余, 李勇, 王振林 . 氮肥和多效唑对小麦茎秆木质素合成的影响及其与抗倒伏性的关系
中国农业科学, 2011,44(17):3529-3536.
[本文引用: 1]

CHEN X G, SHI Y H, WANG C Y, YIN Y P, NING T Y, SHI C Y, LI Y, WANG Z L . Effects of nitrogen and PP₃₃₃ application on the lignin synthesis of stem in relation to lodging resistance of wheat
Scientia Agricultura Sinica, 2011,44(17):3529-3536. (in Chinese)
[本文引用: 1]

[20] 勾玲, 黄建军, 张宾, 李涛, 孙锐, 赵明 . 群体密度对玉米茎秆抗倒力学和农艺性状的影响
作物学报, 2007,33(10):1688-1695.
[本文引用: 1]

GOU L, HUANG J J, ZHANG B, LI T, SUN R, ZHAO M . Effects of population density on stalk lodging resistant mechanism and agronomic characteristics of maize
Acta Agronomica Sinica, 2007,33(10):1688-1695. (in Chinese)
[本文引用: 1]

[21] 王成雨, 代兴龙, 石玉华, 王振林, 陈晓光, 贺明荣 . 氮肥水平和种植密度对冬小麦茎秆抗倒性能的影响
作物学报, 2012,38(1):121-128.
[本文引用: 1]

WANG C Y, DAI X L, SHI Y H, WANG Z L, CHEN X G, HE M R . Effects of nitrogen application rate and plant density on lodging resistance in winter wheat
Acta Agronomica Sinica, 2012,38(1):121-128. (in Chinese)
[本文引用: 1]

[22] YOSHINAGA S . Improved lodging resistance in rice (Oryza sativa L.) cultivated by submerged direct seeding using a newly developed hill seeder.
Japan Agricultural Research Quarterly, 2005,39(3):147-152.
[本文引用: 1]

[23] NOVACEK M J, MASON S C, GALUSHA T D, YASEEN M . Twin rows minimally impact irrigated maize yield, morphology, and lodging
Agronomy Journal, 2013,105:268-276.
DOI:10.2134/agronj2012.0301URL [本文引用: 1]
Twin rows are being promoted as a means to increase maize yield through increased interception of photosynthetically active radiation (PAR) and plant morphology modification. The objective of this research was to explore the interactive effects of maize hybrid, plant population, and row configuration on grain yield and grain yield components, interception of PAR during vegetative growth, plant morphology, and percent lodging. Twin-row irrigated maize produced the same grain yield as single-row production. Small changes in plant morphology and grain yield components and 2.3 to 4.2% increased interception of PAR at the V9 (nine leaves with visible collars) stage were documented for twin rows, but the sum of these did not result in changes in grain yield. Twin-row production increased lodging by 3.5%. Few interactions between row configuration and hybrid and target population were found, leading to the conclusion that twin-row production of maize affords little opportunity to increase maize grain yields. Hybrid and plant population had a much larger effect on grain yield and lodging. Increasing the maize target population to 93,000 plants ha(-1) maximized grain yield at 14.3 Mg ha(-1), and led to small changes in plant morphology that increased lodging from 6.8 to 14.9%. Ear height had the highest direct effect on lodging in both the low (2009) and high (2010) percent lodging years. Based on these results, current promotion of twin rows is not justified for irrigated maize production in the western Maize Belt.

[24] 刘婷婷, 孙盈盈, 曹石, 杨阳, 吴莲蓉, 左青松, 吴江生, 周广生 . 油菜抗裂角性状研究进展. 作物杂志, 2014(3):5-9.
[本文引用: 1]

LIU T T, SUN Y Y, CAO S, YANG Y, WU L R, ZUO Q S, WU J S, ZHOU G S . Research advances on traits of resistance to pod shattering in rapeseed.Crops, 2014(3):5-9. (in Chinese)
[本文引用: 1]

[25] 孟倩, 董军刚, 黄伟男, 段海峰, 张博, 解芳宁, 董振生 . 密度和播期对甘蓝型油菜角果抗裂性的影响
西北农业学报, 2013,22(11):37-41.
[本文引用: 2]

MENG Q, DONG J G, HUANG W N, DUAN H F, ZHANG B, XIE F N, DONG Z S . Effects of planting density and sowing date on the shatter resistance of
Brassica napus pods. Acta Agriculturae Boreali- Occidentalis Sinica, 2013,22(11):37-41. (in Chinese)
[本文引用: 2]

[26] 刘婷婷, 蒯婕, 孙盈盈, 杨阳, 吴莲蓉, 吴江生, 周广生 . 氮、磷、钾肥用量对油菜角果抗裂性相关性状的影响
作物学报, 2015,41(9):1416-1425.
[本文引用: 1]

LIU T T, KUAI J, SUN Y Y, YANG Y, WU L R, WU J S, ZHOU G S . Effects of N, P, and K fertilizers on silique shatter resistance and related traits of rapeseed
Acta Agronomica Sinica, 2015,41(9):1416-1425. (in Chinese)
[本文引用: 1]

[27] 向达兵, 郭凯, 雷婷, 于晓波, 罗庆明, 杨文钰 . 磷钾营养对套作大豆茎秆形态和抗倒性的影响
中国油料作物学报, 2010,32(3):395-402.
[本文引用: 1]

XIANG D B, GUO K, LEI T, YU X B, LUO Q M, YANG W Y . Effects of phosphorus and potassium on stem characteristics and lodging resistance of relay cropping soybean
Chinese Journal of Oil Crop Sciences, 2010,32(3):395-402. (in Chinese)
[本文引用: 1]

[28] TYS J . Evaluation of the mechanical properties of winter rape siliques in respect to their susceptibility to cracking
Journal of Public Administration & Policy Research, 1985,115:512-517.
DOI:10.1542/peds.2004-1977URL [本文引用: 1]
ABSTRACT On December 6 th , 1978 the Spanish population implemented its new constitution by means of a referendum and finalised the transition process from the Franco regime to a modern democracy based on a parliamentary monarchy. In the next 30 years the fiscal power and the expenditure autonomy of the 17 regions, called Comunidades autónomas, increased constantly. But on the other hand, in some regions – mainly in the Catalan and the Basque regions – the demand for complete sovereignty has also become stronger, while the central government is currently unwilling to delegate any additional tax sovereignty to the regions. Therefore, this paper presents the German equalization system among the states and concludes with some policy implications to reduce the ill feelings between the central government and its respective regional counterparts in Spain.

[29] 廖桂平, 官春云 . 不同播期对不同基因型油菜产量特性的影响
应用生态学报, 2001,12(6):853-858.
[本文引用: 1]

LIAO G P, GUAN C Y . Effect of seeding date on yield characteristics of different rapeseed (Brassica napus L.) genotypes.
Chinese Journal of Applied Ecology, 2001,12(6):853-858. (in Chinese)
[本文引用: 1]

[30] OZER H . Sowing date and nitrogen rate effects on growth, yield and yield components of two summer rapeseed cultivars
European Journal of Agronomy, 2003,19:453-463.
DOI:10.1016/S1161-0301(02)00136-3URL [本文引用: 2]
Rapeseed ( Brassica napus L.) has potential to become an alternate oilseed crop in eastern Anatolia, Turkey. Information on sowing date and nitrogen rate for rapeseed is not available in this region. Therefore, a study was initiated to investigate the effects of sowing date and nitrogen rate on the yield and agronomic characteristics of two genotypes of spring rapeseed (Tower and Lirawell) in Erzurum, eastern Anatolia, during 1994 and 1995. Four sowing dates were established at about 10-day intervals from mid April to lately May (19 April, 29 April, 9 May, and 18 May 1994; and 29 April, 9 May, 18 May, and 27 May 1995). Four N fertilizer rates established; 0, 80, 160, and 240 kg N ha 1. In both years, there were effects on plant growth, yield, and yield components due to sowing dates, nitrogen rates, and cultivars. Cultivars tended to respond similarly to sowing date and nitrogen rate for seed yield in both years of the study. In general, early sowings gave higher yields than late sowings in both years, except the first sowing (9 April) in 1994 growing season. From this study, it appears that seeding rapeseed from 29 April to 9 May gives a greater assurance for higher yields. The present results highlight the practical importance of adequate N fertilization in yield formation in summer oilseed rape and suggest that the rate of 160 kg N ha 1 will be about adequate for the crop to meet its N requirements. The yield differences measured for both sowing dates and nitrogen rates were primarily due to the changes in branch numbers, pod numbers per plant, and 1000 seed weights.

[31] HOCKING P J, STAPPER M . Effects of sowing time and nitrogen fertiliser on canola and wheat, and nitrogen fertiliser on Indian mustard. I. Dry matter production, grain yield, and yield components
Crop & Pasture Science, 2001,52:623-634.
[本文引用: 1]

[32] KIRKEGAARD J A, LILLEY J M, BRILL R D, SPRAGUE S J, FETTELL N A, PENGILLEY G C . Re-evaluating sowing time of spring canola (Brassica napus L.) in south-eastern Australia—How early is too early?
Crop & Pasture Science, 2016,67(3/4):381-396.
DOI:10.1071/CP15282URL [本文引用: 1]
Optimising the sowing date of canola (L.) in specific environments is an important determinant of yield worldwide. In eastern Australia, late April to early May has traditionally been considered the optimum sowing window for spring canola, with significant reduction in yield and oil in later sown crops. Recent and projected changes in climate, new vigorous hybrids, and improved fallow management and seeding equipment have stimulated a re-evaluation of early-April sowing to capture physiological advantages of greater biomass production and earlier flowering under contemporary conditions. Early–mid-April sowing generated the highest or equal highest yield and oil content in eight of nine field experiments conducted from 2002 to 2012 in south-eastern Australia. Declines in seed yield (–6.0% to –6.5%), oil content (–0.5% to –1.5%) and water-use efficiency (–3.8% to –5.5%) per week delay in sowing after early April reflected levels reported in previous studies with sowings from late April. Interactions with cultivar phenology were evident at some sites depending on seasonal conditions. There was no consistent difference in performance between hybrid and non-hybrid cultivars at the earliest sowing dates. Despite low temperatures thought to damage early pods at some sites (<612°C), frost damage did not significantly compromise the yield of the early-sown crops, presumably because of greater impact of heat and water-stress in the later sown crops. A validated APSIM-Canola simulation study using 50 years of weather data at selected sites predicted highest potential yields from early-April sowing. However, the application of a frost-heat sensitivity index to account for impacts of temperature stress during the reproductive phase predicted lower yields and higher yield variability from early-April sowing. The frost–heat-limited yields predicted optimum sowing times of mid-April at southern sites, and late April to early May at the northern sites with lower median yield and higher yield variability in crops sown in early April. The experimental and simulation data are potentially compatible given that the experiments occurred during the decade of the Millennium drought in south-eastern Australia (2002–10), with dry and hot spring conditions favouring earlier sowing. However, the study reveals the need for more accurate and validated prediction of the frost and heat impacts on field-grown canola if simulation models are to provide more accurate prediction of attainable yield as new combinations of cultivar and sowing dates are explored.

[33] 唐瑶, 冷锁虎, 左青松, 葛云龙, 晋晨 . 种植密度对稻茬直播油菜氮素吸收与利用的影响
广东农业科学, 2012,39(17):14-16.
[本文引用: 1]

TANG Y, LENG S H, ZUO Q S, GE Y L, JIN C . Effect of density on nitrogen absorption and utilization of direct sowing rapeseed in paddy rice field
Guangdong Agricultural Sciences, 2012,39(17):14-16. (in Chinese)
[本文引用: 1]

[34] 苏伟, 鲁剑巍, 周广生, 李小坤, 韩自航, 雷海霞 . 免耕及直播密度对油菜生长、养分吸收和产量的影响
中国农业科学, 2011,44(7):1519-1526.
[本文引用: 1]

SU W, LU J W, ZHOU G S, LI X K, HAN Z H, LEI H X . Effect of no-tillage and direct sowing density on growth, nutrient uptake and yield of rapeseed (
Brassica napus L.). Scientia Agricultura Sinica, 2011,44(7):1519-1526. (in Chinese)
[本文引用: 1]

[35] 朱珊, 李银水, 余常兵, 谢立华, 胡小加, 张树杰, 廖星, 廖祥生, 车志 . 密度和氮肥用量对油菜产量及氮肥利用率的影响
中国油料作物学报, 2013,35(2):179-184.
[本文引用: 1]

ZHU S, LI Y S, YU C B, XIE L H, HU X J, ZHANG S J, LIAO X, LIAO X S, CHE Z . Effects of planting density and nitrogen application rate on rapeseed yield and nitrogen efficiency
Chinese Journal of Oil Crop Sciences, 2013,35(2):179-184. (in Chinese)
[本文引用: 1]

[36] DORDAS C . Dry matter, nitrogen and phosphorus accumulation, partitioning and remobilization as affected by N and P fertilization and source-sink relations
European Journal of Agronomy, 2009,30(2):129-139.
DOI:10.1016/j.eja.2008.09.001URLMagsci [本文引用: 1]
Durum wheat ( Triticum turgidum subsp. durum L.) is being increasingly grown in many areas of the world, but there is a lack of information about the physiological processes limiting grain yield. In this study, different rates of N and P fertilization were applied and the source:sink ratio was manipulated to examine the factor(s) limiting grain filling under rainfed conditions. Plants exposed to four fertilization treatments (control, 80 kg N ha 611 (N), 50 kg P ha 611 (P) and 80 kg N ha 611 and 50 kg P ha 611 (N–P)) and were artificially modified to obtain a range of different source:sink ratios. The treatments were (I) control; (II) half of the spike was removed; (III) all the spike was removed. The cultivar Cosmodur was used, which is widely grown in Greece and other Mediterranean countries and is quite productive especially under rainfed conditions. The distribution of dry matter, N and P among grains, stems and leaves was analyzed at anthesis and harvesting. Dry matter accumulation and partitioning into different plant parts was different between the fertilization treatments and the control. At anthesis, leaf + culm dry matter was higher than the chaff dry matter. Total aboveground biomass increased after anthesis in both years and at all fertilization treatments. N fertilization affected N concentration at the whole plant level at anthesis and at maturity. There was an average increase of 20% in N concentration with N application at anthesis in both years relative to the control. N content was affected by the fertilization treatments and it was increased by 33% over the 2 years of the study compared with the control. In addition, P fertilization affected P concentration both at anthesis and maturity in every plant organ, and there was also a significant effect of the change of P concentration at the two different growth stages. P accumulation was also affected by the fertilization regime and by the spike halving treatment. Dry matter translocation was an average of 22% higher at the fertilized treatments compared with the control, which indicates that fertilization led plants to translocate higher amount of dry matter. N and P translocation were affected by the fertilization treatment and in some treatments by the sink reduction. The spike reduction treatment increased the pre-anthesis contribution to seed indicating that the N and P remobilization from vegetative tissues were very important for grain development. The present study indicates that N and P fertilization and sink size can affect dry matter, N, and P accumulation, partitioning, and retranslocation of durum wheat which can affect seed yield.

[37] OLESEN J E, BERNTSEN J, HANSEN E M, PETERSEN B M, PETERSEN J . Crop nitrogen demand and canopy area expansion in winter wheat during vegetative growth
European Journal of Agronomy, 2002,16(4):279-294.
DOI:10.1016/S1161-0301(01)00134-4URLMagsci [本文引用: 1]
The effect of nitrogen (N) on crop growth and productivity is mediated through effects on both light interception (green crop area) and radiation use efficiency (RUE). The effects of N nutrition on these factors were studied using data on green area index (GAI), above-ground dry matter and N uptake from growth analysis measurements in winter wheat from a number of experiments in Denmark with different application rates of N. Only measurements taken prior to anthesis were used in the statistical analyses. The N uptake was found to be proportional to GAI, and to have an additional curvilinear response to dry matter implying decreasing N concentration with increasing dry matter. This supports the hypothesis that nitrogen is associated with both the green surfaces of the crop canopy and with the dry matter component. A model of GAI expansion is presented incorporating three limiting factors: an exponential increase in GAI in thermal time, a minimum leaf area ratio, and a minimum ratio of GAI to N content in above-ground dry matter. This simple function has potential to be used as a tool for targeting timing and rates of N fertilisation in relation to a desired development of GAI. Such N application strategies should also consider the nitrogen nutrition index (NNI), which was defined based on the relationship between N uptake and both GAI and dry matter. The response of RUE to NNI showed a curvilinear response with a tendency for saturation at high NNI. The design of N application strategies should therefore ensure that low NNI is avoided during the most productive periods in the growing season.

[38] BORRELL A K, HAMMER G L . Nitrogen dynamics and the physiological basis of stay-green in sorghum
Crop Science, 2000,40(5):1295-1307.
DOI:10.2135/cropsci2000.4051295xURL [本文引用: 1]
Sorghum [Sorghum bicolor (L,) Moench] hybrids containing the stay-green trait retain more photosynthetically active leaves under drought than do hybrids that do not contain this trait. Since the Longevity and photosynthetic capacity of a leaf are related to its N status, it is important to clarify the role of N in extending leaf greenness in stay-green hybrids. Field studies were conducted in northeastern Australia to examine the effect of three water regimes and nine hybrids on N uptake and partitioning among organs. Nine hybrids varying in the B35 and KS19 sources of stay-green were grown under a fully irrigated control, post-flowering water deficit, and terminal water deficit. For hybrids grown under terminal water deficit, stay-green was viewed as a consequence of the balance between N demand by the grain and N supply during gain filling. On the demand side, grain numbers were 16% higher in the four stay-green than in the five senescent hybrids. On the supply side, age-related senescence provided an average of 34 and 42 kg N ha(-1) for stay-green and senescent hybrids, respectively. In addition, N uptake during grain filling averaged 116 and 82 kg ha(-1) in stay-green and senescent hybrids. Matching the N supply from these two sources with grain N demand found that the shortfall in N supply for grain filling in the stay-green and senescent hybrids averaged 32 and 41 kg N ha(-1) resulting in more accelerated leaf senescence in the senescent hybrids. Genotypic differences in delayed onset and reduced rate of leaf senescence were explained by differences in specific leaf nitrogen and N uptake during grain filling. Leaf nitrogen concentration at anthesis was correlated with onset (r = 0.751**, n = 27) and rate (r = -0.783**, n = 27) of leaf senescence ender terminal water deficit.

[39] SHIMONO H, HASEGAWA T, IWAMA K . Response of growth and grain yield in paddy rice to cool water at different growth stages
Field Crops Research, 2002,73(2/3):67-79.
[本文引用: 1]

[40] 朱文达, 张朝贤, 魏守辉 . 农作措施对油菜田杂草的生态控制作用
华中农业大学学报, 2005,24(2):125-128.
[本文引用: 1]

ZHU W D, ZHANG C X, WEI S H . Ecological weed control by agronomic practices in rape fields
Journal of Huazhong Agricultural University, 2005,24(2):125-128. (in Chinese)
[本文引用: 1]

[41] 朱文达, 魏守辉, 刘学, 张朝贤, 张宏军, 张佳, 喻大昭 . 油菜田杂草发生规律及化学防除技术
湖北农业科学, 2007,46(6):936-938.
[本文引用: 1]

ZHU W D, WEI S H, LIU X, ZHANG C X, ZHANG H J, ZHANG J, YU D Z . Occurrence rule and chemical control of weed community in rape field
Hubei Agricultural Sciences, 2007,46(6):936-938. (in Chinese)
[本文引用: 1]

[42] FAJRI A, MAKOTO K, FUJIO N, KAZUTOSHI K, YOSHIHIRO T . Effect of the sowing date on the growth of hairy vetch (Vicia villosa) as a cover crop influenced the weed biomass and soil chemical properties in a subtropical region.
Weed Biology & Management, 2009,9(2):129-136.
DOI:10.1111/j.1445-6664.2009.00330.xURL [本文引用: 1]
Weeds emerge throughout the year in agricultural fields in subtropical regions. The weed suppression and improved soil fertility resulting from a living mulch of hairy vetch were investigated. Hairy vetch was sown in October and in December 2006. The fallow condition was without the sowing of hairy vetch, with the weeds allowed to grow naturally. The biomass of the top parts (BOT) of hairy vetch increased from February to April and then decreased in May on both sowing dates. The BOT of hairy vetch sown in October was significantly higher in February, March, and April than that sown in December. Hairy vetch sown in October and harvested from February to April varied from 372090009403 0103 10 0908083 kg m 0908082 , with weed suppression percentages of 62.8% in comparison with the fallow plots. The fixed C, N, P, and mineral uptake of hairy vetch showed similar patterns to its biomass. The nitrate (NO 3 -N) content increased from February to May for the soils in the October and December plots, in contrast to the fallow plots. Moreover, the NO 3 -N and available N of the October and December soils sampled from February to May were higher than that of the fallow soils. In subtropical agriculture, hairy vetch should be sown in October in order to achieve a higher biomass for suppressing weeds effectively and improving the soil fertility, mainly N.

[43] STURM D J, KUNZ C, PETEINATOS G, GERHARDS R . Do cover crop sowing date and fertilization affect field weed suppression?
Plant Soil & Environment, 2017,63:82-88.
[本文引用: 1]

[44] MAZZONCINI M, SAPKOTA T B ,BàRBERI P, ANTICHI D, RISALITI R. Long-term effect of tillage, nitrogen fertilization and cover crops on soil organic carbon and total nitrogen content
Soil & Tillage Research, 2011,114(2):165-174.
DOI:10.1016/j.still.2011.05.001URL [本文引用: 1]
No-tillage, N fertilization and cover crops are known to play an important role in conserving or increasing SOC and STN but the effects of their interactions are less known. In order to evaluate the single and combined effects of these techniques on SOC and STN content under Mediterranean climate, a long term experiment started in 1993 on a loam soil (Typic Xerofluvent) in Central Italy. The experimental variants are: conventional tillage (CT) and no-tillage (NT), four N fertilization rates (N0, N1, N2 and N3) and four soil cover crop (CC) types (C – no cover crop; NL – non-legume CC; LNL – low nitrogen supply legume CC, and HNL – high nitrogen supply legume CC). The nitrogen fertilization rates (N0, N1, N2 and N3) were: 0, 100, 200, 300 kg N ha 611 for maize ( Zea mays, L.); 0, 60, 120,180 kg N a 611 for durum wheat ( Triticum durum Desf.); 0, 50, 100, 150 kg N ha 611 for sunflower ( Helianthus annuus L.). From 1993 to 2008, under the NT system the SOC and STN content in the top 30 cm soil depth increased by 0.61 and 0.04 Mg ha 611 year 611 respectively. In the same period, the SOC and STN content under the CT system decreased by a rate of 0.06 and 0.04 Mg ha 611 year 611 respectively. During the experimental period, N1, N2 and N3 increased the SOC content in the 0–30 cm soil layer at a rate of 0.14, 0.45 and 0.49 Mg ha 611 year 611. Only the higher N fertilization levels (N2 and N3) increased STN content, at a rate of 0.03 and 0.05 Mg ha 611 year 611. NL, LNL and HNL cover crops increased SOC content by 0.17, 0.41 and 0.43 Mg C ha 611 year 611 and 610.01, +0.01 and +0.02 Mg N ha 611 year 611. Significant interactions among treatments were evident only in the case of the N fertilization by tillage system interaction on SOC and STN concentration in the 0–10 cm soil depth in 2008. The observed SOC and STN variations were correlated to C returned to the soil as crop residues, aboveground cover crop biomass and weeds (C input). We conclude that, under our Mediterranean climate, it is easier to conserve or increase SOC and STN by adopting NT than CT. To reach this objective, the CT system requires higher N fertilization rates and introduction of highly productive cover crops.

[45] RATHKE GW, BEHRENS T, DIEPENBROCK W . Integrated nitrogen management strategies to improve seed yield, oil content and nitrogen efficiency of winter oilseed rape (Brassica napus L.): A review.
Agriculture Ecosystems & Environment, 2006,117(2/3):80-108.
DOI:10.1016/j.agee.2006.04.006URL [本文引用: 1]
Winter oilseed rape ( Brassica napus L.) is the dominant oilseed crop in northern Europe. Generally, it requires high amounts of nitrogen (N) but is characterized by low N-efficiency, which is defined as produced seed dry weight per unit of accumulated N-fertilizer. Consequently, there is a strong need to resume all the relevant information on N in relation to cropping of winter oilseed rape and environmental impact to improve the efficiency of rape production. To enhance the productivity of winter oilseed rape cropping, integrated N-management strategies are needed including optimized N-supply due to varied crop rotations or fertilization, best soil and crop management practices. This paper reviews various N-management strategies in relation to seed yield and N-efficiency of winter oilseed rape. Comparing different previous crops, winter oilseed rape yielded considerably lower after cereal crops than following legumes. The seed yield is not only affected by the position within the crop rotation but also by the length of the break between two winter oilseed rape crops and type of cultivar. The use of N-efficient cultivars with reduced N-demand led to lower N-balance surpluses. Since the optimal N-treatment varies with cultivar, year and site condition, the maximum quantity of N-fertilizer for highest seed yield are discussed. A comparison of N-fertilizers reveals that N-fertilizers work different due to their chemical composition. Moreover, rate of N-recovery varies among methods and timing of N-application. Adjusted to the timing of optimum N-demand of the crop, timing of N-doses effectively increases production efficiency of winter oilseed rape. Apart from these integrated N-management strategies soil cultivation, seeding, application of plant protection agents and plant growth regulators as well as soil fertilization and harvesting are closely interacting with N-efficiency of winter oilseed rape. Altogether, amount and timing of N-fertilizer as well as cultivar selection had the strongest influence on productivity followed by smaller effects due to previous crop and type of fertilizer. Using N-efficient management strategies like choice of variety, form and timing of N-application adapted to site conditions, a remarkable reduction in fertilizer N-demand (up to 50% of fertilizer input) is possible leading to lower N-balance surpluses in winter oilseed rape production, thus minimizing environmental pollution.

[46] 孙正祥, 邓乐, 张长青, 周燚 . 不同药剂及其混配剂对油菜菌核病菌的毒力
湖北农业科学, 2015,54(7):1606-1608.
[本文引用: 1]

SUN Z X, DENG L, ZHANG C Q, ZHOU Y . Toxicity of several fungicides and chemical mixture against Sclerotinia sclerotiorum.
Hubei Agricultural Sciences, 2015,54(7):1606-1608. (in Chinese)
[本文引用: 1]

[47] DUSHNICKY L G, BALLANCE G M, SUMNER M J, MACGREGOR A W . The role of lignification as a resistance mechanism in wheat to a toxin-producing isolate of Pyrenophora tritici-repentis.
Canadian Journal of Plant Pathology, 1998,20(1):35-47.
DOI:10.1080/07060669809500443URL [本文引用: 1]
Brightfield, fluorescence, and scanning microscopy were used to observe the cellular effects of by a toxin-producing isolate (86-124) of , which causes tan spot of (). Disruption of mesophyll surrounding or within close proximity to the intercellular hyphae was recognizable macroscopically as a distinct tan-brown lesion on the leaf surface. In a susceptible plant, spread of intercellular hyphae within the leaf was limited laterally only by the larger midveins. In a resistant plant, secondary hyphae were restricted to the infected epidermal and/or to a localized area of mesophyll at the site. Intercellular spaces of the mesophyll tissue surrounding the site were filled with material, confining the of the fungus. Histochemical staining of these regions indicated the presence of or -like material. Occlusion of the intercellular space and lignification appeared to be a response in the resistant . Lesions in resistant were observed as small brown necrotic spots. These observations are discussed in relation to the physical presence of the hyphae in the mesophyll tissue and the possible effect of the fungal toxin in the -pathogen interactions of the susceptible and resistant .

[48] 杨向东 . 木质素合成调控及其与甘蓝型油菜抗菌核病和抗倒伏性关系研究
[D]. 武汉: 华中农业大学, 2006.
[本文引用: 1]

YANG X D . The study on relationship between lignin biosynthesis manipulation and Brassica napus’ resistance to Sclerotinia sclerotiorum and lodging
[D]. Wuhan: Huazhong Agricultural University, 2006. ( in Chinese)
[本文引用: 1]