魏廷邦¹, 柴强^,2, 王伟民¹, 王军强¹1 甘肃省农业工程技术研究院,甘肃武威 733006
2 甘肃省干旱生境作物学重点实验室,兰州 730070

Effects of Coupling of Irrigation and Nitrogen Application as well as Planting Density on Photosynthesis and Dry Matter Accumulation Characteristics of Maize in Oasis Irrigated Areas

WEI TingBang¹, CHAI Qiang^,2, WANG WeiMin¹, WANG JunQiang¹ 1 Gansu Academy of Agri-engineering and Technology, Wuwei 733006, Gansu
2 Gansu Provincial Key Laboratory of Arid Land Crop Science, Lanzhou 730070

通讯作者: 柴强,E-mail： chaiq@gsau.edu.cn

收稿日期:2018-07-5接受日期:2018-12-28网络出版日期:2019-02-13

基金资助:

国家公益性行业.农业科研专项201503125-3 国家科技支撑计划子课题.2015BAD22B04-03 国家自然科学基金.3156020171,41867013

Received:2018-07-5Accepted:2018-12-28Online:2019-02-13
作者简介 About authors
魏廷邦,E-mail：weitingbang@163.com。






摘要
目的 针对土壤水分、氮肥供应不足以及玉米早衰、种植密度不合理等严重制约绿洲灌区玉米的生产问题,通过研究不同水氮配比及种植密度对玉米光合作用、干物质积累特征和产量的影响,以期为该区玉米高产、稳产提供技术支撑。方法 2016—2017年,于河西绿洲灌区进行大田试验,以先玉335为参试品种,采用裂裂区设计,灌水水平（W₁：4 050 m ³·hm ^-2,W₂：3 720 m ³·hm ^-2）做主区,施氮水平（不施氮N₀：0,低施氮N₁：300 kg·hm ^-2,高施氮N₂：450 kg·hm ^-2）为裂区,种植密度（低密度D₁：75 000株/hm ²,中密度D₂：97 500株/hm ²,高密度D₃：120 000 株/hm ²）为裂裂区,测定光合速率、干物质积累量和产量等指标。 结果 施氮量、种植密度对玉米全生育期净光合速率、干物质最大增长速率及其出现天数、干物质积累量、产量、WUE和氮肥利用率有显著影响。水肥耦合可增强玉米密植条件下的光合作用,提高干物质最大增长速率,提前干物质最大增长速率出现的天数,增大干物质积累量和产量。在减量20%灌水和高施氮水平下,中密度处理的全生育期净光合速率较低密度和高密度分别提高17.31%和11.43%;高密度和中密度处理的干物质最大增长速率及最大增长速率出现天数较低密度处理分别提高21.07%、7.52%和提前6.7 d、4.1 d;高密度处理的干物质积累量较中密度、低密度分别提高4.27%和10.59%,中密度处理的产量、水分利用效率和氮肥利用率较低密度、高密度处理分别提高24.2%、11.4%、29.9%和29.2%、18.4%、13.8%。在减量20%灌水条件下,中密度高施氮处理的全生育期净光合速率、干物质积累量和产量分别较中施氮、不施氮分别提高7.34%、11.63%、14.63%和49.54%、44.53%、69.03%;高密度高施氮处理的干物质最大增长速率及最大增长速率出现天数较中施氮、不施氮分别提高19.07%、54.35%和提前3.9 d、6.8 d;同等密度高施氮处理的氮肥利用率较低施氮处理提高24.5%。综上,减量20%灌水与高施氮耦合主要通过提高密植玉米的光合作用和干物质积累速率,延长干物质积累的持续时间,提高WUE和氮肥利用率,从而对干物质积累量和产量产生调控作用。结论 在绿洲灌区,采用水肥耦合（生育期减量20%灌水（3 720 m ³·hm ^-2）、施氮量450 kg·hm ^-2、中密度97 500株/hm ²）的最优栽培模式,可为进一步发掘密植条件下玉米高产、高效栽培提供技术指导。
关键词： 水氮耦合;种植密度;绿洲灌区;光合作用;干物质积累特征

Abstract
【Objective】 In oasis irrigation agricultural region, some problems has caused serious influenced of maize production, such as soil available water and nitrogen hunger, premature senescence and unreasonable planting density. To provide technical support for high and stable maize yield, the effects of different ratio of application irrigation and nitrogen and planting density on photosynthesis, dry matter accumulation characteristics and maize yield were studied. 【Method】 Photosynthetic ability, dry matter accumulation characteristics and yield were determined under two-years field experiment, which was carried out in Hexi Oasis irrigation region of Gansu province from 2016 to 2017. In this research, the cultivar “Xianyu335” was applied as research material. A split-split plot design was used as this experiment, with two irrigation application amount treatments (namely 4 050 m ³·hm ^-2 (W₁) and 3 720 m ³·hm ^-2 (W₂)) as the main plot, three nitrogen application amount treatments (namely 0 (N₀), 300 kg·hm ^-2(N₁) and 450 kg·hm ^-2 (N₂)) as the split plot, and three plant densities (namely 7.5×10 ⁴ plant/hm ²(D₁), 9.75×10 ⁴ plant/hm ²(D₂) and 1.2×10 ⁵ plant/hm ²(D₃)) as the split-split plot. 【Result】 Nitrogen fertilizer application and planting density had significant influence on photosynthetic rate, maximum dry matter accumulation rate, emergence days of maximum dry matter accumulation rate, dry matter accumulation amount, grain yield, water use efficiency and nitrogen fertilizer use rate in growth stages of maize. The coupling of irrigation and nitrogen fertilizer management increased photosynthesis, the highest dry matter accumulation rate and advanced the days of emergence of the highest dry matter accumulation rate, and enhanced dry matter accumulation amount and grain yield in growth stages of maize. Under the reduced 20% irrigation and the level of higher nitrogen application in growth stages of maize, compared with the low planting density and high planting density treatments, the photosynthetic rate under the medium planting density treatment was increased by 17.31% and 11.43%, respectively. While, compared with the low planting density treatment, the maximum dry matter accumulation rate and days of emergence of the highest dry matter accumulation rate under the treatment with the high planting density and medium planting density was increased by 21.07% and 7.52%, respectively, and advanced by 6.7, 4.1 days, respectively, meanwhile, the dry matter accumulation of the high planting density treatment was increased by 4.27% and 10.59%, respectively; Compared with the low planting density treatment and the high planting density treatment, the grain yield, water use efficiency and nitrogen fertilizer use rate of maize with the medium planting density treatment was increased by 24.2%, 11.4%, 29.9% and 29.2%, 18.4%, 13.8%, respectively. Under the reduced 20% irrigation and same planting density treatment in growth stages of maize, compared with medium nitrogen application treatment and no nitrogen application treatment, the photosynthetic rate, the dry matter accumulation and grain yield of maize under the treatment with high nitrogen application treatment was increased by 7.34%, 11.63%, 14.63% and 49.54%, 44.53%, 69.03%, under the medium planting density treatment, respectively; Compared with medium nitrogen application treatment and no nitrogen application treatment, the maximum dry matter accumulation rate and days of emergence of the highest dry matter accumulation rate of maize with the high nitrogen application treatment was increased by 19.07% and 54.35% and advanced by 3.9 and 6.8 days under the high planting density treatment, respectively. Compared with no nitrogen application treatment, nitrogen fertilizer use rate of maize with the high nitrogen application treatment was increased by 24.50%. The facts showed that the coupling of reduced 20% irrigation and high nitrogen application had regulated dry matter accumulation, grain yield with the improvement of photosynthesis, dry matter accumulation rate, water use efficiency, nitrogen fertilizer use rate and extending the duration of dry matter accumulation. 【Conclusion】 The treatment with application coupling of irrigation and nitrogen (i.e. reduced 20% irrigation amount during growth 3 720 m ³·hm ^-2(W₂) and N application with 450 kg·hm ^-2 at growth stage and medium density of 9.75×10 ⁴ plant/hm ² at growth stage of maize) could be considered as the best feasible cultivation pattern management, which could provide technical guidance for further exploring high yield and efficient cultivation of close planting maize in Oasis irrigation region.
Keywords：coupling of irrigation and nitrogen application;planting density;oasis irrigation region;photosynthesis;dry matter accumulation characteristics


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本文引用格式
魏廷邦, 柴强, 王伟民, 王军强. 水氮耦合及种植密度对绿洲灌区玉米光合作用和 干物质积累特征的调控效应[J]. 中国农业科学, 2019, 52(3): 428-444 doi:10.3864/j.issn.0578-1752.2019.03.004
WEI TingBang, CHAI Qiang, WANG WeiMin, WANG JunQiang. Effects of Coupling of Irrigation and Nitrogen Application as well as Planting Density on Photosynthesis and Dry Matter Accumulation Characteristics of Maize in Oasis Irrigated Areas[J]. Scientia Agricultura Sinica, 2019, 52(3): 428-444 doi:10.3864/j.issn.0578-1752.2019.03.004

0 引言

【研究意义】水和肥已成为影响粮食生产的两大关键元素,水、肥协调供应对提高作物产量及综合利用价值意义重大^[1]。大量研究表明,作物干物质积累量的95%左右是来自于光合作用生产的有机物,光合速率的高低是作物产量形成的基础^[2,3],作物的光合作用、干物质积累特征还与土壤水分、养分的供应能力密切相关^[4,5]。种植密度的改变可有效改善作物对水、肥资源的利用状况,是作物增产的重要途径之一^[6,7]。由于不同种植区内适用的水肥配比、栽培密度、种植模式及环境条件差异较大,在资源性缺水地域,针对性研发密植条件下相应的水肥耦合制度,对解决区域性水资源危机和挖掘玉米增产潜力具有十分重要的意义。【前人研究进展】目前,国内外****关于水、肥及互作效应对密植作物群体光合特性、干物质积累特征及产量形成过程均有报道。张旺锋等^[8]和李广浩等^[9]研究表明,作物的产量与叶片的光合速率紧密相关,提高并保持生育后期较高的叶片净光合速率、叶绿素含量,对获得高产十分重要。张秋英等^[10]和JIM ^[11]发现,光合速率的变化趋势与土壤水分和氮素营养的供应多少密切相关,在轻度水分胁迫条件下会降低叶片的光合作用,直接影响生育后期光合产物向籽粒中的转移。但王帅等^[12]研究发现,及时追施氮肥可增大玉米生育期叶片的净光合速率、蒸腾速率和叶绿素（SPAD）值,提高叶肉细胞同化CO₂的能力,充分发挥干物质生产潜力,增大生育后期干物质积累速率和籽粒灌浆速率,促进生育后期有机物积累,利于增加粒重^[13,14]。增施氮肥、磷肥、钾肥可显著增强玉米生育期的光合作用,提高单位面积的干物质积累量和积累速率^[15]。李玉英等^[16]和王宜伦等^[17]发现,生育中后期追施氮肥可显著增大玉米的净光合速率,开花期及时追施氮肥能够显著缩短最大干物质增长速率出现的时间,显著提高干物质最大增长速率和干物质积累量。郭丽等^[18]研究发现,在水肥一体化滴管条件下,增施氮肥增产效果显著,但随着施氮量的增加,氮肥农学效率、氮肥生产效率和氮肥利用效率显著降低。马国胜等^[19]和张吉旺等^[20]研究表明,玉米的净光合速率和干物质积累速率随着种植密度的增加,呈现先增加后减少或持续增加的变化趋势,群体干物质积累量和产量随着密度的增加显著增加,但超过一定密度范围时,叶片衰老加速,进而造成玉米产量降低。肖继兵等^[21]研究表明,适当提高种植密度是提升高粱产量的关键,是实现作物群体结构和植株个体功能协同增益和产量提高的重要途径。因此,合理的种植密度是作物充分利用光热资源构建良好群体结构,改善群体内部通风和光照条件,优化群体光合生理指标的基础,而恰当的土壤水分和氮肥施用量则是作物利用适宜种植密度充分发挥群体优势进行光合生产的营养物质保障^[22]。在作物生产中,水、肥、密度三者之间需要高度协调配合,才有利于优化作物群体结构,提高生育期的光合作用,进一步促进干物质积累和产量增加^[23,24]。【本研究切入点】近年来,资源性缺水及传统水肥管理方式,使得单位耕地产出率降低、生态环境恶化等问题日益显现,开展密植条件下高效节水、节肥理论与技术研究已成为栽培领域的新型方向。随着现代滴灌技术广泛的应用,将滴灌、施氮集成应用在同一种植模式中^[25],使得玉米生长发育水氮需求与土壤水氮供给之间的时空吻合度得以大幅度提高,可促进作物显著增产^[26]。目前,在资源匮乏的条件下,关于不同水肥组合模式对密植玉米光合作用、干物质积累及产量形成特征的协同调控增产机理还鲜见报道。【拟解决的关键问题】本研究通过适度调控玉米种植密度,量化灌水量、施氮量及种植密度三者间的互作效应对密植玉米光合作用、干物质积累特征的响应机理,阐明密植玉米光合生理、干物质积累特征的互利增产机理,以期为提升绿洲灌区密植玉米高产、高效水肥管理提供技术支撑。

1 材料与方法

1.1 试验区概况

本试验于2016年4月至2017年10月,在甘肃省武威市凉州区黄羊镇绿洲农业试验站进行。试验站位于河西走廊东端（37°95′ N,102°63′ E）,平均海拨1 506 m,年平均气温约7.2℃,年平均降水量约156 mm,年平均蒸发量约2 400 mm,年降水分布不均,主要集中在5—9月份。试验区以厚层灌漠土为主,容重1.61 g·cm^-3,0—30 cm土层全氮0.59 g·kg^-1、全磷1.48 g·kg^-1、有机质14.67 g·kg^-1。玉米为该区主栽作物,种植密度为7.5×10⁴株/hm²,显著低于高产农田水平。2016—2017年度试验区3—9月降水量及日平均温度变化如图1所示。

图1

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图12016—2017年试验区3—9月降水量及日平均温度变化

Fig. 1Dynamics of precipitation and daily mean temperature in the experimental station from March to September in 2016-2017

1.2 试验材料

选用密植性品种先玉335为供试材料。2016年4月20日播种,9月22日收获,2017年4月23日播种,9月26日收获。氮肥施用（N 46.6%）尿素,磷肥施用（P₂O₅14%）过磷酸钙,覆膜采用武威市泽瑞嘉农资有限责任公司生产的农用透明地膜（宽140 cm、厚0.08 mm）。

1.3 试验设计

本研究采用裂裂区设计,以灌水水平做主区,施氮水平为裂区,种植密度为裂裂区。设置常规灌水（W₁,4 050 m³·hm^-2）,生育期灌水减量20%（W₂,3 720 m³·hm^-2）2种灌水水平;设置0（N₀,对照）、300 kg·hm^-2（N₁）和450 kg·hm^-2（N₂）3种施氮水平;设置低密度（D₁,75 000株/hm²）,中密度（D₂,97 500株/hm²）,高密度（D₃,120 000株/hm²）3种种植密度。试验共设置18个处理,每个处理3次重复,各小区随机排列,小区面积为40 m²（5 m×8 m）。

玉米覆膜平作,等行距种植,行距40 cm,通过株距来调控种植密度,D₁、D₂、D₃株距分别为33、26、21 cm。氮肥施用尿素（N 46.6%）,按基肥﹕大喇叭口期追肥﹕灌浆期追肥= 3﹕6﹕1分施,磷肥基施过磷酸钙（P₂O₅ 14%）225 kg·hm^-2,小区间筑埂,以防串水漏肥。W₁、W₂冬储灌量均为1 200 m³·hm^-2,其中常规灌水（W₁）生育期灌水量总计4 050 m³·hm^-2,按拔节期、大喇叭口期、抽雄吐丝期、开花期、灌浆期分别灌水900、750、900、750、750 m³·hm^-2;生育期灌水减量20%（W₂）灌水量总计3 720 m³·hm^-2,按拔节期、大喇叭口期、抽雄吐丝期、开花期、灌浆期分别灌水720、750、900、750、600 m³·hm^-2。所有处理均为膜下滴灌,采用精确度为0.001 m³的水表（宁波市佳佳美水表有限公司生产）控制灌水量。

1.4 测定项目与方法

1.4.1 净光合速率（Pn） 使用Li-6400型光合测定仪（美国Li-COR公司生产）,玉米拔节以后,在各小区中间位置随机选取3株玉米,每隔15 d,选择晴朗天气,于上午9：00—11：30进行测定,结果取平均值^[21]。

1.4.2 干物质积累量 玉米出苗以后,在每小区中间部位每隔15 d随机选取玉米5株（苗期选取10株）,分器官称鲜重后,于105℃下杀青15—30 min,80℃下烘干至恒重,计算干物质积累量^[25]。

植株总干物质积累量=成熟期单株总干重×成熟期实收株数

采用Logistic方程y = k/(1+e^{a - rt})拟合玉米生育期

干物质积累过程,并对Logistic方程求一阶、二阶导数,可得生育期干物质积累速率、各生育阶段干物质积累速率以及积累速率持续天数^[25]。

1.4.3 水分利用效率（water use efficiency,WUE） WUE = Y/ET。式中,Y 为作物籽粒产量,ET为作物全生育期内总耗水量^[23]。

1.4.4 氮肥利用率（nitrogen fertilizer use rate,NUR） NUR（%）=（施氮区地上部吸氮量-空白区地上部吸氮量）/施氮量×100%。

1.4.5 产量 玉米完全成熟后,收获每小区玉米计产量。另在小区中间部位连续取20株玉米,风干后考种,测定穗行数、行粒数、千粒重等产量性状。

1.5 数据处理与分析

采用Microsoft Excel 2007和SPSS 17.0软件进行数据整理、方差分析、相关分析、回归分析以及拟合回归方程。

2 结果

2.1 不同处理对玉米光合作用的影响

灌水量、施氮量和种植密度对玉米净光合速率影响显著（P<0.05）,种植密度与施氮量对玉米净光合速率的互作效应影响显著（P<0.05）,但灌水量与种植密度间的互作效应影响不显著（P>0.05）。

图2

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图2不同处理玉米净光合速率动态

Fig. 2The net photosynthetic rate dynamic of maize under different treatments



通过2年平均净光合速率结果比较（图2）,在相同灌水和施氮水平下,中密度处理的净光合速率优于低密度和高密度处理,W1N2D2处理的全生育期净光合速率分别较W1N2D1、W1N2D3提高13.46%和22.06%,W1N1D2处理分别较W1N1D1、W1N1D3处理提高14.47%和15.33%;W2N2D2处理分别较W2N2D1、W2N2D3处理提高17.31%和11.43%,W2N1D2处理分别较W2N1D1、W2N1D3处理提高18.59%和9.91%。

在相同灌水和种植密度下,W1N2D3处理全生育期净光合速率分别较W1N1D3、W1N0D3提高10.75%和55.68%,W1N2D2处理分别较W1N1D2、W1N0D2处理提高17.21%和57.59%,W1N2D1处理分别较W1N1D1、W1N0D1处理提高18.24%和45.76%;W2N2D3处理分别较W2N1D3、W2N0D3处理提高8.52%和47.29%,W2N2D2处理分别较W2N1D2、W2N0D2处理提高7.34%和49.54%。说明在玉米生育期减量20%灌水条件下,增大氮肥用量可显著提高密植玉米生育期叶片的净光合速率,为有机物的积累和转运奠定基础。

2.2 不同处理对玉米群体干物质积累特征的影响

2.2.1 不同处理玉米群体干物质积累动态 施氮量和种植密度对玉米收获期干物质积累量影响显著（P<0.05）,种植密度和灌水量间、种植密度和施氮量间、灌水量和施氮量间对玉米收获期干物质积累量互作效应显著（P<0.05）,但灌水量、施氮量和种植密度三因素间互作效应不显著（P>0.05）。

收获期2年平均干物质积累量比较（图3）,在相同灌水和施氮水平下,高密度处理干物质积累量优于中密度和低密度处理,其中W1N2D3处理干物质积累量较W1N2D2、W1N2D1处理分别提高5.78%和14.11%,W1N1D3处理较W1N1D2、W1N1D1处理分别提高9.34%和14.21%;W2N2D3处理较W2N2D2、W2N2D1处理分别提高4.27%和10.59%,W2N1D3处理较W2N1D2、W2N1D1处理分别提高12.57%和26.81%。

图3

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图3不同处理玉米干物质积累量动态

Fig. 3The dry matter accumulation dynamic of maize under different treatments



在相同灌水和种植密度下,高施氮处理的干物质积累量优于低施氮和不施氮处理,W1N2D3处理干物质积累量较W1N1D3、W1N0D3处理分别提高2.06%和21.33%,W1N2D2处理较W1N1D2、W1N0D2处理分别提高4.84%和31.55%,W2N2D3处理较W2N0D3处理提高31.23%,W2N2D2处理较W2N1D2、W2N0D2处理分别提高11.63%和44.53%。各处理中,以减量灌水、高氮和中密度处理的玉米干物质积累量最高,说明减量灌水模式下,增大氮肥用量有助于提高密植玉米生育期的干物质积累量,为收获期玉米增产奠定基础。

2.2.2 不同处理玉米群体干物质积累速率变化 2年平均干物质积累速率（图4）表明,不同灌水处理的干物质积累速率在拔节期至开花期差异不显著,在开花期至成熟期,平均干物质积累速率随着施氮量的增加而显著增加,高密度和中密度处理的干物质积累速率与低密度相比较差异显著。

图4

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图4不同处理玉米干物质积累速率动态

Fig. 4The dry matter accumulation rate dynamics of maize under different treatments



根据玉米干物质积累规律,可将干物质积累过程分为渐增期、快增期和缓增期3个时期。如表1所示,不同灌水处理比较,干物质积累速率在渐增期和快增期持续时间均无显著差异（P>0.05）,不同施氮水平间比较,高施氮和中施氮处理的快增期和缓增期平均干物质积累速率差异显著（P<0.05）,不同种植密度间比较,高密度和中密度处理的快增期和缓增期干物质积累速率差异显著（P<0.05）。

Table 1
表1
表1不同处理玉米干物质积累阶段特征
Table 1Dry matter accumulation stage characteristics of maize under different treatments

年份 Year	处理 Treatment	渐增期Early stage		快增期Fast stage		缓增期Late stage
		持续时间 Duration (d)	平均积累速率 Average accumulate rate (kg·hm-2·d-1)	持续时间 Duration (d)	平均积累速率 Average accumulate rate (kg·hm-2·d-1)	持续时间 Duration (d)	平均积累速率 Average accumulate rate (kg·hm-2·d-1)
2016	W1N0D1	66.50b	76.13c	32.12b	430.64q	46.37o	85.34o
	W1N0D2	64.77c	88.41bc	33.76b	463.38p	46.45n	116.33c
	W1N0D3	62.79d	92.21b	30.62b	516.46l	51.58f	95.32j
	W1N1D1	65.81bc	100.75ab	35.12b	515.82m	44.06q	100.53g
	W1N1D2	65.45bc	104.36a	32.12b	636.67f	47.43m	108.41e
	W1N1D3	61.26de	111.59a	32.52b	677.32d	51.22g	121.62b
	W1N2D1	64.07cd	102.04ab	30.98b	576.42i	49.94k	70.29r
	W1N2D2	61.33de	109.84a	28.32b	649.74e	55.35c	86.39m
	W1N2D3	60.35e	112.02a	24.16b	742.14b	60.48a	88.13l
	W2N0D1	68.69a	76.62c	37.63b	382.14r	38.68r	70.88q
	W2N0D2	68.79a	78.78c	30.98b	477.79o	45.22p	86.16n
	W2N0D3	66.24bc	86.11bc	30.98b	502.83n	47.77l	100.07h
	W2N1D1	64.33cd	91.13b	29.93b	535.09k	50.74i	81.52p
	W2N1D2	62.26de	107.24a	32.52b	560.97j	50.22j	110.54d
	W2N1D3	61.19d	110.04a	32.12b	624.83h	51.68e	130.56a
	W2N2D1	65.97bc	102.18ab	28.94b	636.24g	50.08h	88.83k
	W2N2D2	62.71d	112.37a	28.32b	679.77c	53.96d	99.16i
	W2N2D3	61.44de	118.15ab	25.82a	768.09a	57.74b	105.34f
2017	W1N0D1	66.85a	97.26n	30.27b	586.77m	27.87o	29.41h
	W1N0D2	82.73a	87.73o	37.09ab	534.56p	25.17q	42.23c
	W1N0D3	73.48a	114.04h	41.15a	556.33n	30.36k	45.06b
	W1N1D1	76.95a	107.41i	33.46ab	674.74i	34.58i	34.72f
	W1N1D2	81.21a	106.13k	35.12ab	670.54j	28.66n	58.69a
	W1N1D3	78.71a	115.14g	35.59ab	695.58h	30.71j	40.03d
	W1N2D1	73.42a	121.35e	34.52ab	705.13e	37.05g	21.12l
	W1N2D2	77.34a	133.04c	40.21a	699.08g	27.44p	5.75o
	W1N2D3	75.55a	139.23a	39.31ab	731.05d	40.13d	13.03n
	W2N0D1	74.97a	75.99q	35.59ab	437.31r	34.43i	27.87i
	W2N0D2	76.51a	85.37p	33.64ab	530.42q	34.86h	33.83g
	W2N0D3	71.01a	102.82l	36.58ab	545.18o	37.42f	23.93k
	W2N1D1	80.54a	97.67m	35.21b	610.42l	29.24l	19.41m
	W2N1D2	79.74a	106.59j	36.08ab	643.61k	29.18m	28.27i
	W2N1D3	71.57a	123.82d	33.01ab	733.65c	40.42c	41.92c
	W2N2D1	71.51a	120.96f	33.77ab	699.91f	39.72e	25.64j
	W2N2D2	67.97a	139.22a	34.16ab	756.88b	42.86b	38.81e
	W2N2D3	71.68b	134.41b	30.98b	849.51a	45.33a	44.42b

Values followed by different letters within a column are significantly different at P<0.05. The same as below
同一列数字后的不同小写字母表示在0.05 水平上差异显著。下同

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快增期,在相同灌水和施氮水平下,W1N2D3、W1N2D2处理的2年干物质积累速率分别较W1N2D1处理提高14.95%和5.25%,W2N2D3、W2N2D2处理分别较W2N2D1处理提高21.06%和7.52%。在相同灌水和种植密度下,W2N2D3处理较W2N1D3、W2N0D3处理分别提高19.07%和54.35%。缓增期,在相同灌水和施氮水平下,W1N2D3处理的干物质积累速率较W1N2D1处理提高10.69%,但W1N2D3处理与W1N2D2差异不显著,W2N2D3、W2N2D2处理分别较W2N2D1处理提高30.83%和20.53%。在相同灌水和种植密度下,W2N2D3处理较W2N0D3处理提高20.77%。纵观整个玉米干物质积累时期,减量20%灌水与高施氮耦合能够显著增大密植玉米快增期和缓增期的干物质积累速率,可提高并保持生育后期较高的干物质积累速率,为产量的形成奠定基础。

2.2.3 Logistic方程拟合不同处理玉米干物质最大增长速率及其出现的天数 不同处理干物质积累速率Logistic方程及干物质最大增长速率出现的天数计算参考魏廷邦等^[25]方法。如表2所示,灌水量、施氮量和种植密度对玉米干物质最大增长速率出现的天数影响显著（P<0.05）,灌水量与施氮量、施氮量与种植密度间对玉米干物质最大增长速率的互作效应显著（P<0.05）,但灌水量、施氮量和种植密度三因素间的互作效应不显著（P>0.05）。

Table 2
表2
表2不同处理玉米干物质积累速率的Logistic 方程回归分析
Table 2Logistic equation analysis on dry matter accumulation of maize under different nitrogen treatments

年份 Year	处理 Treatment	回归方程 Regression equation	R2	最大增长速率 出现天数 The days of MIR (d)	最大增长速率 Maximum increase rate (kg·d-1·hm-2)
2016	W1N0D1	Y = 23959.28 / (1 + e6.77 - 0.082 t)	0.993	82.56c	491.16b
	W1N0D2	Y = 27102.43 / (1 + e6.370 - 0.078 t)	0.998	81.66c	528.49b
	W1N0D3	Y = 27397.08 / (1 + e6.717 - 0.086 t)	0.994	78.10gh	589.03ab
	W1N1D1	Y = 31376.54 / (1 + e6.253 - 0.075 t)	0.996	83.37c	588.31ab
	W1N1D2	Y = 35421.91 / (1 + e6.684 - 0.082 t)	0.991	81.51d	726.14ab
	W1N1D3	Y = 38148.18 / (1 + e6.279 - 0.081 t)	0.995	77.51h	772.50ab
	W1N2D1	Y = 30937.64 / (1 + e6.763 - 0.085 t)	0.989	79.56f	657.42ab
	W1N2D2	Y = 31873.15 / (1 + e7.020 - 0.093 t)	0.987	75.48i	741.05a
	W1N2D3	Y = 33991.32 / (1 + e7.895 - 0.109 t)	0.996	78.43g	926.26ab
	W2N0D1	Y = 24905.35 / (1 + e6.125 - 0.07 t)	0.998	87.50a	435.84b
	W2N0D2	Y = 25644.27 / (1 + e7.164 - 0.085 t)	0.989	84.28b	544.94ab
	W2N0D3	Y = 26987.54 / (1 + e6.947 - 0.085 t)	0.994	81.72d	573.48ab
	W2N1D1	Y = 27740.45 / (1 + e6.978 - 0.088 t)	0.992	79.29f	610.29ab
	W2N1D2	Y = 31595.12 / (1 + e6.360 - 0.081 t)	0.996	78.52g	639.80ab
	W2N1D3	Y = 34762.66 / (1 + e6.335 - 0.082 t)	0.998	77.25h	712.63ab
	W2N2D1	Y = 31896.55 / (1 + e7.320 - 0.091 t)	0.983	80.44e	725.64ab
	W2N2D2	Y = 33346.21 / (1 + e7.149 - 0.093 t)	0.987	76.87h	775.29a
	W2N2D3	Y = 34354.051/ (1 + e7.584 - 0.102 t)	0.991	74.35j	876.02ab
2017	W1N0D1	Y = 30769.12 / (1 + e7.133 - 0.087 t)	0.906	81.98r	669.22m
	W1N0D2	Y = 34348.66 / (1 + e7.191 - 0.071 t)	0.949	101.28a	609.68p
	W1N0D3	Y = 39656.88 / (1 + e6.020 - 0.064 t)	0.967	94.06h	634.51n
	W1N1D1	Y = 39113.70 / (1 + e7.373 - 0.079 t)	0.970	93.68i	769.56i
	W1N1D2	Y = 40787.85 / (1 + e7.408 - 0.075 t)	0.968	98.77b	764.77j
	W1N1D3	Y = 42882.84 / (1 + e7.141 - 0.074 t)	0.976	96.50f	793.33h
	W1N2D1	Y = 42160.80 / (1 + e6.919 - 0.076 t)	0.959	90.68l	804.22e
	W1N2D2	Y = 45691.69 / (1 + e6.383 - 0.066 t)	0.948	97.45e	797.32g
	W1N2D3	Y = 47778.52 / (1 + e6.379 - 0.067 t)	0.954	95.21g	833.79d
	W2N0D1	Y = 26960.35 / (1 + e6.865 - 0.074 t)	0.940	92.77k	498.76r
	W2N0D2	Y = 30904.47 / (1 + e7.307 - 0.078 t)	0.971	93.32j	604.95q
	W2N0D3	Y = 34544.28 / (1 + e6.429 - 0.072 t)	0.969	89.29m	621.79o
	W2N1D1	Y = 37229.95 / (1 + e7.342 - 0.075 t)	0.964	98.15c	696.20l
	W2N1D2	Y = 40222.45 / (1 + e7.138 - 0.073 t)	0.943	97.78d	734.06k
	W2N1D3	Y = 41942.52 / (1 + e7.029 - 0.080 t)	0.948	88.08o	836.75c
	W2N2D1	Y = 40936.35 / (1 + e6.895 - 0.078 t)	0.973	88.39n	798.25f
	W2N2D2	Y = 44785.55 / (1 + e6.558 - 0.077 t)	0.950	85.05p	863.24b
	W2N2D3	Y = 45594.61 / (1 + e7.410 - 0.085 t)	0.941	83.17q	968.88a
显著性（P值）Significance (P value)
灌水水平W		—	—	*	NS
施氮水平N		—	—	*	*
种植密度D		—	—	*	*
灌水水平×施氮水平W×N		—	—	*	*
灌水水平×种植密度W×D		—	—	*	*
施氮水平×种植密度N×D		—	—	*	NS
灌水水平×施氮水平×种植密度W×N×D		—	—	*	NS

NS和*分别表示无显著差异及在0.05水平上差异显著 NS, * indicate non-significant or significant at P<0.05

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从2年平均结果看,在相同灌水和施氮水平下,W1N2D3、W1N2D2处理的干物质最大增长速率分别较W1N2D1提高20.42%和5.25%,W1N2D3处理的干物质最大增长速率出现天数较W1N2D1提前3.3 d,W2N2D3、W2N2D2处理的干物质最大增长速率分别较W2N2D1提高21.07%和7.52%,W2N2D3、W2N2D2处理的干物质最大增长速率出现天数分别较W2N2D1提前6.7 d和4.1 d。在相同灌水和种植密度下,W2N2D3处理干物质最大增长速率分别较W2N1D3、W2N0D3提高19.07%和54.35%,W2N2D3处理的干物质最大增长速率出现天数分别较W2N1D3、W2N0D3提前3.9 d和6.8 d。说明减量20%灌水与高施氮耦合能够显著增大中密度处理的干物质积累速率,维持生育后期干物质积累高峰期,增大干物质积累量。

2.3 水氮耦合条件下不同种植密度玉米的产量、水分利用效率及氮肥利用率的综合表现

如表3所示,施氮量和种植密度对玉米产量、水分利用效率和氮肥利用率影响显著（P<0.05）,但灌水水平对产量影响不显著（P>0.05）。灌水水平与施氮水平、施氮水平与种植密度对产量、水分利用效率和氮肥利用率互作效应显著（P<0.05）,灌水水平、施氮水平和种植密度对产量、水分利用效率和氮肥利用率互作效应显著（P<0.05）。

Table 3
表3
表3不同处理玉米的产量、水分利用效率及氮肥利用率
Table 3The grain yield and WUE and nitrogen utilization efficiency of maize under different treatments

年份 Year	处理 Treatment	产量 Grain yield	水分利用效率 WUE	氮肥利用率 Nitrogen utilization efficiency
2016	W1N0D1	8015.63c	12.18d	—
	W1N0D2	8599.57c	12.70d	—
	W1N0D3	8406.93c	12.38d	—
	W1N1D1	12211.91b	17.83b	13.10d
	W1N1D2	10725.40b	19.81a	15.33c
	W1N1D3	11008.27b	15.81bc	19.30a
	W1N2D1	12037.13b	17.19bc	17.52f
	W1N2D2	11273.53b	18.68ab	20.64e
	W1N2D3	11403.40c	16.99bc	24.36bc
	W2N0D1	8093.53c	12.66d	—
	W2N0D2	8247.37c	12.69d	—
	W2N0D3	7948.39b	12.19d	—
	W2N1D1	10471.90b	15.55c	12.62c
	W2N1D2	12170.47b	17.80b	13.92bc
	W2N1D3	11161.16b	16.10bc	17.84b
	W2N2D1	11238.43b	16.40bc	20.85f
	W2N2D2	13871.22a	18.99ab	22.28ef
	W2N2D3	11078.11b	15.69c	23.18d
2017	W1N0D1	7159.1c	11.42ef	—
	W1N0D2	7605.8c	10.74f	—
	W1N0D3	7674.9c	12.46ef	—
	W1N1D1	9971.6cb	20.40b	19.29c
	W1N1D2	11329.5ab	20.65a	27.55a
	W1N1D3	11792.6ab	16.02d	23.47b
	W1N2D1	10514.2b	17.26d	18.86c
	W1N2D2	12297.8ab	19.63c	24.18a
	W1N2D3	11930.0ab	16.10d	21.59bc
	W2N0D1	7729.6c	12.14ef	—
	W2N0D2	8063.5c	13.21e	—
	W2N0D3	7708.6c	12.07ef	—
	W2N1D1	9633.7cb	15.31d	16.62c
	W2N1D2	11880.5ab	17.95cd	27.33a
	W2N1D3	12154.3ab	16.09d	20.83bc
	W2N2D1	10956.1b	17.08d	17.42c
	W2N2D2	13699.3a	18.29cd	27.42a
	W2N2D3	10271.2cb	15.80d	20.48bc
显著性（P值）Significance (P value)
灌水水平W		NS	*	*
施氮水平N		*	*	*
种植密度D		*	*	*
灌水水平×施氮水平W×N		*	*	*
灌水水平×种植密度W×D		*	NS	*
施氮水平×种植密度N×D		*	*	*
灌水水平×施氮水平×种植密度W×N×D		*	*	*

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2年平均产量表明,在相同灌水和施氮水平下,玉米产量随着种植密度的增加表现出先增加后下降的变化趋势。在各处理中,中密度处理的产量显著优于其他处理,W1N2D2处理较W1N2D1处理提高4.52%,但与W1N2D3处理差异不显著;W2N2D2处理较W2N2D1、W2N2D3处理分别提高24.2%和29.2%,W2N1D2处理较W2N1D1、W2N1D3分别提高19.6%和3.2%。W2N2D2处理的水分利用效率较W2N2D1、W2N2D3处理分别提高11.4%、18.4%,W2N2D2处理的氮肥利用率较W2N2D1、W2N2D3处理分别提高29.9%、13.8%。

在常规灌水和相同密度下,高施氮处理的产量优于低施氮和不施氮处理,W1N2D3处理较W1N1D3、W1N0D3处理分别提高2.34%和45.1%,W1N2D2处理较W1N1D2、W1N0D2分别提高6.88%和45.45%;在减量20%灌水和相同密度下,W2N2D2处理产量显著高于其他处理,分别较W2N1D2、W2N0D2提高14.63%和69.03%,W2N2D1处理较W2N1D1、W2N0D1处理分别提高10.39%和40.27%。W2N2D2处理的水分利用效率较分别较W2N1D2、W2N0D2处理提高4.3%、43.9%,W2N2D2处理的氮肥利用率较W2N1D2处理提高24.5%。由此说明,合理的氮肥用量与生育期减量灌水耦合有助于玉米根系对水、肥等营养物质的吸收和利用,促进中密度下玉米的生长和发育,显著提高密植玉米的水分利用效率和氮肥利用率,最终实现增产。

2.4 水氮耦合条件下不同密度玉米主要指标间的相关性分析

在玉米密植条件下,水肥耦合通过直接调控玉米生育期内的光合速率和干物质积累速率,从而优化玉米的干物质积累量、水分利用效率,最终通过各指标的综合效应来影响产量。光合速率、干物质积累量、干物质积累最大增长速率和水分利用效率（WUE）与籽粒产量之间的相关关系如表4所示。

Table 4
表4
表4水氮耦合条件下不同密度玉米主要指标间的相关分析
Table 4The correlation analysis of maize with different density under coupling of irrigation and nitrogen application

指标 Item	光合速率 Pn	干物质积累量 Dry matter accumulation	干物质积累最大增长速率 Maximum increase rate	水分利用效率 WUE	籽粒产量 Grain yield
光合速率Pn	1	-0.5	0.647**	0.919**	0.855**
干物质积累量 Dry matter accumulation		1	-0.2208	-0.259	0.178*
干物质积累最大增长速率 Maximum increase rate			1	0.641**	0.669**
水分利用效率WUE				1	0.898**
籽粒产量Grain yield Grain Yield					1

**表示在0.01水平上差异显著 ** indicates significant at P<0.01

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籽粒产量与光合速率（0.855**）、干物质积累最大增长速率（0.669**）和水分利用效率（0.898**）呈极显著正相关,与干物质积累量（0.178*）呈显著正相关。说明水氮耦合通过调控密植玉米生育期的光合作用和干物质积累最大增长速率,直接影响密植玉米的干物质积累量和水分利用效率,促进光合产物的积累,为生育后期光合产物向籽粒中转移及粒重的增加奠定基础。

光合速率与干物质积累最大增长速率（0.647**）、水分利用效率（0.919**）均呈现极显著正相关,说明水氮耦合通过影响密植玉米生育期的光合作用,直接调控玉米生育期的干物质积累速率,从而提高密植玉米的水分利用效率和产量。

3 讨论

3.1 水氮耦合及种植密度与玉米光合特性、干物质积累特征的关系

研究表明,光合作用是农作物生物产量形成的物质基础,其功能效率的高低直接影响籽粒产量的高低^[27]。在作物的各生育时期,通过膜下滴灌、水肥一体化、交替灌溉、增施氮肥以及增加种植密度等一系列农艺措施优化作物的光合特性和干物质积累过程是获得高产的重要方式之一^[28,29]。灌水量、施氮量和种植密度对作物光合产物的影响是多方面的。曹倩等^[30]、张银锁等^[31]研究发现,水分胁迫下作物的光合速率及干物质积累量显著降低,但及时增加灌溉量能够显著提高夏玉米的光合速率、产量及WUE。魏廷邦等^[25]研究发现,在灌水量和施氮总量不变的情况下,玉米拔节期氮肥后移20%（拔节肥10%+花粒肥30%）可延长拔节期至灌浆期玉米干物质积累持续期,利于提高产量和收获指数。马国胜等^[19]研究发现,种植密度能够显著影响玉米生育期内叶片的光合速率和干物质积累速率,在低密度条件下,干物质积累速率随种植密度的增加而显著增大,但当种植密度增大到一定峰值后,干物质积累增长速度呈下降趋势。本研究结果表明,通过玉米关键生育时期减量20%灌水与高施氮耦合能够显著增大密植玉米光合作用、干物质最大增长速率和干物质积累量。在生育期减量20%灌水和高施氮条件下,中密度处理的全生育期净光合速率较低密度和高密度处理分别提高17.31%和11.43%,高密度和中密度处理的干物质最大增长速率较低密度处理分别提高21.07%和7.52%,高密度处理的干物质积累量较中密度、低密度处理分别提高4.27%和10.59%,且光合速率（0.855**）与籽粒产量呈显著正相关关系。在正常生长条件下,生育期限量供水对玉米光合特性和干物质积累特征的影响大于施用氮肥的作用,但通过种植密度的改变能够调控玉米各生育时期的光合作用和干物质积累特征,恰当比例的水肥互作能够显著促进密植玉米生育期地上部分的生长,利于光合产物的积累,为生育后期增加粒重奠定基础。

本研究还发现,在减量20%灌水条件下,中密度高施氮处理的玉米全生育期净光合速率较中施氮、不施氮处理分别提高7.34%和49.54%,高密度高施氮处理的干物质最大增长速率及其出现天数分别较中施氮、不施氮处理提高19.07%、54.35%和提前3.9 d和6.8 d,中密度高施氮处理的干物质积累量较中施氮、不施氮处理分别提高11.63%和44.53%。说明生育期减量20%灌水与高施氮水平的组合为最优水肥耦合模式,生育期适量减少灌水量的条件下,增施氮肥可显著提高密植玉米生育后期叶片的光合能力,保持生育后期较高的干物质积累速率,增大干物质积累量和玉米产量,对提高密植作物的抗旱性及产量具有积极意义。水氮配施可显著提高密植玉米的光合生理活性,其主要原因是水分对生育期叶片的生理活性具有重要影响,适量增加灌水使得玉米生育前期穗位叶的光合速率、蒸腾速率显著增大,可有效延缓穗位叶叶绿素值降低的幅度,水分供应不足时,及时追施氮肥可显著增大叶片的SPAD值和气孔导度,增强生育期的净光合速率,显著促进光合产物积累和转移^[32,33]。另有****研究认为,适量增施氮肥可显著改善定量灌水条件下叶片中叶肉细胞的生理活性,有利于增加叶片中RuBP羧化酶活性,提高水分亏缺条件下叶片抗氧化酶和保护酶系的活性与含量^[34],减缓叶片中SPAD值的降低幅度,延长生育后期叶片光合生理功能的持续期^[35],协调根系与水、肥间的关系,提高其对干旱环境的适应能力,增大生育期干物质积累速率,使得籽粒“库”对有机物质的竞争能力增强,提高成熟期干物质积累量和粒重^[36,37]。

3.2 水氮耦合及种植密度对玉米产量、水分利用效率及氮肥利用率的影响

作物的产量除了主要受到遗传因子的影响外,还受到生态环境、栽培措施、气候条件和种植密度等方面的影响。长期以来,相关领域的研究大多侧重对密度、灌水量或施肥量单个因子对玉米产量的影响,而对关于水氮耦合效应对玉米生长特性及产量性能的调控作用研究较少。在众多农艺措施中,灌水、施肥和种植密度对农作物产量和品质的影响最为突出,在恰当的水肥耦合模式下,通过增加种植密度是提高农作物光合生理特性、干物质积累特征、产量及水肥利用效率的关键措施之一^[38]。研究表明,在常规灌水和定量施肥条件下,增大玉米种植密度可显著增加单位面积的有效穗数,但随着密度的增加,穗粒数和千粒重呈先增加后减小的趋势^[39,40],当种植密度为8.25万株/hm²时获得最高产量^[41]。不同的水氮配施比例对玉米籽粒产量的调控存在互补效应,玉米关键生育时期供水量的不足一定程度上会导致产量和WUE的降低,及时追施氮肥可补偿因水分亏缺导致的产量降低。在一定施氮范围内,施氮量与产量呈显著正相关,合理施氮可促进玉米生育后期营养器官中有机物的合成及防止叶片早衰,保证碳氮代谢的顺利进行,提高作物的WUE和氮肥利用率,有利于作物增产^[42,43]。有****研究发现,氮肥施用过量时会导致有机物水解,叶片光合能力降低,植株倒伏严重,产量及氮肥利用率显著降低;当氮肥施用量较少时,仅补充灌水,增产潜力无法充分发挥;当灌水量严重不足时,增施氮肥小麦收获期产量和WUE急剧下降;当水分轻度亏缺时,及时施肥有利于增大群体叶面积指数,提高水分利用效率和氮肥利用率;当水氮合理配施时,小麦干物质积累量显著增加,增产效果显著^[44,45]。另有研究表明,施肥时期对玉米生育期植株干物质生产影响较大,在定量灌水条件下,追施拔节肥可促进生育前期干物质积累,追施穗肥可提高玉米生育后期干物质积累速率和籽粒灌浆速率,利于光合产物向籽粒中转移,提高粒重^[46]。

本研究发现,在生育期减量20%灌水和高施氮条件下,中密度处理的2年平均产量较低密度、高密度处理分别提高24.2%和29.2%,中密度处理的水分利用效率较低密度、高密度分别提高11.4%、18.4%,中密度处理的氮肥利用率较低密度、高密度分别提高29.9%、13.8%;在中密度条件下,高施氮处理的产量较低施氮、不施氮处理分别提高14.63%和69.03%,高施氮处理的水分利用效率分别较低施氮、不施氮分别提高4.3%、43.9%,高施氮处理的氮肥利用率较低施氮提高24.5%。结果说明,水氮协调供应可同步提高密植玉米水氮需求与供给之间的时空吻合度,在中密度水平下,采用生育期减量20%灌水与高施氮的最优耦合模式能够显著提高玉米的WUE和氮肥利用率,获得高产。但种植密度较大时,水氮耦合对密植玉米产量的作用机理不显著,其主要原因是种植密度过大,导致个体植株对光、水、肥的竞争加剧,严重影响群体冠层的透光率和群体结构,使得玉米生育后期穗位叶净光合速率、叶绿素含量大幅度下降,同时过量的水肥供给,使得玉米营养生长过快,导致茎秆细长而软弱,生育后期遇到风雨天气容易发生根倒、茎倒、茎折断等倒伏情况,易造成严重减产。因此,在生育期减量20%灌水条件下,通过高施氮与中密度处理的最优组合模式,能够改善玉米群体植株内的生理和生态特性,同步协调提高玉米密植条件下的光合速率和干物质积累速率,改善密植玉米生长对土壤有效水分和养分的需求,解决传统灌溉模式下玉米生长后期遇到雨水易倒伏的难题,为提高玉米稳产性奠定基础。

4 结论

生育期减量20%灌水与高施氮耦合可显著增大密植玉米生育期的净光合速率,提高干物质最大增长速率,提前干物质最大增长速率出现的天数,提高水分利用效率和氮肥利用率,优化干物质积累特征,最终实现玉米高产。因此,在河西绿洲灌区,采用生育期减量20%灌水（3 720 m³·hm^-2）、施氮量450 kg·hm^-2、中密度97 500株/hm²组合的最优栽培模式,可为发掘该区密植条件下玉米高产、高效栽培提供技术指导。

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作物生产的最主要的过程就是光合产物的积累、分配、转移及最终经济产量的形成。为研究环境条件和栽培管理对这一过程的动态影响 ,1998至 1999年 2年共进行了 19个处理的田间试验 ,系统地测定了不同播期、不同密度、不同施肥、灌溉水平以及不同含盐量的灌溉水质下 ,包括地下部分的夏玉米各器官干物质动态。本文以有效积温表示的相对发育期为时间变量 ,分析了各处理下干物质积累、分配和转移的动态变化 ,并比较了最终产量水平及收获指数。在计算同化物分配和转移系数时考虑了活体维持呼吸的消耗
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作物生产的最主要的过程就是光合产物的积累、分配、转移及最终经济产量的形成。为研究环境条件和栽培管理对这一过程的动态影响 ,1998至 1999年 2年共进行了 19个处理的田间试验 ,系统地测定了不同播期、不同密度、不同施肥、灌溉水平以及不同含盐量的灌溉水质下 ,包括地下部分的夏玉米各器官干物质动态。本文以有效积温表示的相对发育期为时间变量 ,分析了各处理下干物质积累、分配和转移的动态变化 ,并比较了最终产量水平及收获指数。在计算同化物分配和转移系数时考虑了活体维持呼吸的消耗

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[Objective] The aim was to study on effects of N fertilizer on yield, N absorption and utilization of different cultivars of super high-yielding summer maize, in order to provide reference for reasonable N fertilization in accordance with different cultivars. [Method] Field experiment was conducted to study on effects of different N fertilizers on yield, N absorption and use efficiency of Zhengdan 958 and Xundan 20, in order to learn the effect differences at different N fertilizer levels. [Result] After N was applied, yields of the two summer maize increased significantly. Zhengdan 958 achieved the highest in yield and proceeds at 12 051.18 kg/hm2 and 1 722.40 yuan/hm2, respectively in low N level. In contrast, Xundan 20 achieved the highest at 13 166.00 kg/hm2 and 1 343.92 yuan/hm2 in the above two aspects in high N level. Compared with Zhengdan 958, Xundan 20 increased by 9.90%, 5.20% and 12.00% in N levels of 0, 240, and 450 kg/hm2, respectively. When N fertilizers were applied, protein yield of Xundan 20 was significantly higher than that of Zhengdan 958, so that higher N fertilizers contributed higher protein yield for Xundan 20. In high N level, N efficiency, N-fertilizer utilization and partial productivity of Xundan 20 were significantly higher than that of Zhengdan 958. [Conclusion] Lower N-fertilizer was suitable for Zhengdan 958 and Xundan 20 would get a good harvest if more N-fertilizers were applied. The results provided references for reasonable N fertilization.

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DOI:10.1016/S0378-4290(03)00002-9URL [本文引用: 1]
Maize crop management involves decision making on several cultural practices aimed to maximize grain yield, like plant population and row spacing. These practices affect the light environment perceived by plants and the post-flowering source–sink ratio, but there is scarce information on the way they influence plant leaf senescence. The objectives of our research were to: (i) characterize the development of leaf area senescence for contrasting canopy architectures (i.e. plant population×row spacing), and (ii) analyze the response of leaf senescence to changes in the light environment and the post-flowering source–sink ratio. Field experiments were conducted in Argentina between 1997/1998 and 2000/2001. Four hybrids were grown at a wide range of plant populations (3, 9, 10 and 12 plants m 612), row spacings (0.35, 0.7 and 1 m) and pollination treatments (natural and restricted pollination). Senescence development was well described ( r 2=0.61–0.99, P<0.05) as a bilinear process, starting always at around 500 °C day (base temperature of 8 °C) before silking. Senescence progressed at a lower rate during the first phase of the process than during the second one (651.4 vs. 655.5 cm 2 per plant per °C per day). The second phase always started between silking and 400 °C day after silking. Increased plant population increased senescence rate during the whole plant cycle, but never affected the ontogenic stage when senescence was initiated or accelerated in all hybrids. Increased plant population promoted: (i) an enhanced light attenuation within the canopy ( k coefficient=0.43, 0.55, 0.53 and 0.65 for 3, 9, 10 and 12 plants m 612, respectively), (ii) an augmented post-flowering source–sink ratio (11.6 cm 2 of green plant leaf area per kernel at 9 and 12 plants m 612 compared to 8.3 cm 2 per kernel at 3 plants m 612), and (iii) a decreased grain protein concentration. Senescence was reduced by kernel set restrictions that enhanced post-flowering assimilate availability, indicating the process was accelerated by assimilate starvation at high plant populations independently of the green leaf area established per growing kernel. Row spacing altered light quality (red:far-red ratio) perceived at the lowermost leaf stratum at the highest plant populations, but had no effect on senescence development. Senescence during grain filling was related to the local light quantity perceived by leaves and to N availability for actively growing kernels. Although senesced leaf area was influenced by crop growing conditions, senescence initiation and the onset of increased senescence rate were not.

[43] 刘战东, 肖俊夫, 于景春, 刘祖贵, 南纪琴 . 春玉米品种和种植密度对植株性状和耗水特性的影响
农业工程学报, 2012,28(11):125-132.
[本文引用: 1]

LIU Z D, XIAO J F, YU J C, LIU Z G, NAN J Q . Effects of varieties and planting density on plant traits and water consumption characteristics of spring maize
Transactions of the Chinese Society of Agricultural Engineering, 2012,28(11):125-132. (in Chinese)
[本文引用: 1]

[44] 王海茹, 张永清, 董文晓, 闫江艳, 冯晓敏, 李鹏 . 水氮耦合对黍稷幼苗形态和生理指标的影响
中国生态农业学报, 2012,20(11):1420-1426.
[本文引用: 1]

WANG H R, ZHANG Y Q, DONG W X, YAN J Y, FENG X M, LI P . Effect of irrigation and nitrogen supply on physico-morphological indices of broomcorn millet at seedling stage
Chinese Journal of Eco-Agriculture, 2012,20(11):1420-1426. (in Chinese)
[本文引用: 1]

[45] 任中生, 屈忠义, 李哲, 刘安琪 . 水氮互作对河套灌区膜下滴灌玉米产量与水氮利用的影响
水土保持学报, 2016,30(5):149-155.
[本文引用: 1]

REN Z S, QU Z Y, LI Z, LIU A Q . Interactive effects of nitrogen fertilization and irrigation on grain yield, water use efficiency and nitrogen use efficiency of mulched drip-irrigated maize in Hetao irrigation district, China
Journal of Soil and Water Conservation, 2016,30(5):149-155. (in Chinese)
[本文引用: 1]

[46] DING K J, WANG G M, JIANG D K, BISWAS H, XU L F, LI Y H . Effects of nitrogen deficiency on photosynthetic traits of maize hybrids released in different years
Annals of Botany, 2005,96(3):925-930.
DOI:10.1093/aob/mci244URLPMID:16103036 [本文引用: 1]
61 Background and Aims New maize (Zea mays) hybrids outperformed old ones even at reduced N rates. Understanding the mechanisms of the differences in performance between newer and older hybrids under N deficiency could provide avenues for breeding maize cultivars with large yield under N deficiency, and reduce environmental pollution caused by N fertilizers. 61 Methods N deficiency effects on grain weight, plant weight, harvest index, leaf area and photosynthetic traits were studied in the field for six maize hybrids released during the past 50 years to compare their tolerance and to explore their physiological mechanisms. 61 Key Results N deficiency decreased grain yield and plant weight in all hybrids, especially in the older hybrids. However, there was no significant difference in harvest index, rate of light-saturated photosynthesis (P sa t) 20 d before flowering, leaf area or plant weight at flowering between the N-deficient and control plants of all hybrids. Dry matter production after flowering of the N-deficient plants was significantly lower than that of the control plants in all hybrids, especially in the older hybrids, and was mostly due to differences in the rate of decrease in photosynthetic capacity during this stage. The lower Psat of the older hybrids was not due to stomatal limitation, as there was no significant difference in stomatal conductance (gs) and intercellular CO60 concentration (Ci) between the hybrids. N deficiency accelerated senescence, i.e. decreased chlorophyll and soluble protein contents, after anthesis more for the earlier released hybrids than for the later ones. N deficiency decreased phosphoenolpyruvate carboxylase (PEPCase) activity significantly more in older hybrids than newer hybrids, and affected the maximal efficiency of PSII photochemistry (Fv/Fm) only in the old hybrids and at the late stage. 61 Conclusions Compared with older (earlier released) hybrids, newer (later released) hybrids maintained greater plant and grain weight under N deficiency because their photosynthetic capacity decreased more slowly after anthesis, associated with smaller non-stomatal limitations due to maintenance of PEPCase activity, and chlorophyll and soluble protein content.