刘 梦 张 垚 葛均筑,* 周宝元 吴锡冬 杨永安 侯海鹏

不同降雨年型施氮量与收获期对夏玉米产量及氮肥利用效率的影响

刘 梦1张 垚1葛均筑1,*周宝元2吴锡冬1杨永安3侯海鹏4

1天津农学院农学与资源环境学院，天津 300384；2中国农业科学院作物科学研究所，北京 100081；3天津市优质农产品开发示范中心，天津 301500；4天津市农业发展服务中心，天津 300061

为探讨施氮量与收获期对华北平原热量资源限制区夏玉米籽粒灌浆与脱水、产量形成及氮素利用效率的调控效应, 本研究采用二因素区组试验设计, 因素公顷施氮量为0 (N0)、120 kg (N120, 2021)、180 kg (N180)、240 kg (N240)、300 kg (N300)、360 kg (N360)和450 kg (N450, 2020), 因素收获期设为传统收获(normal harvest, NH)和延迟收获(delayed harvest, DH), 测定干物质积累量(dry matter accumulation, DM)、籽粒灌浆与脱水、产量(grain yield, GY)及其构成因素、氮肥偏生产力(nitrogen partial factor productivity, PFPN)和农学利用效率(nitrogen agronomic use efficiency, ANUE)。与干旱年型(2020年)相比, 丰水年型(2021年) DM和粒重(grain weight, GW)显著下降16.3%～81.5%和2.1%～28.1%, 穗粒数(ear grains number, EGN)显著减少44.7%～47.4%, 导致GY、PFPN和ANUE显著降低31.4%～58.3%、27.2%～30.0%和2.9%～18.0%。与N0相比, 施氮显著提高DM, GW提高14.6～82.1 mg grain–1, 最大灌浆速率(maximum grain filling rate,max)及其生长量(weight increment ofmax,max)提高0.2～3.4 mg (grain d)–1和10.4～44.1 mg grain–1, 到达max时期(time reaching themax,max)提前0.4～7.0 d, GY显著提高51.5%～169.5% (<0.01), N240增产效应最优; 增施氮肥导致PFPN和ANUE比N180/N120显著降低11.7%～57.9%和2.5%～54.9%、19.9%～52.6%和4.9%～37.0%。与NH相比, DH处理DM和GW显著提高0.8%～55.7%和3.4%～79.3%, 籽粒含水率(grain moisture content, GMC)显著降低至22.0%～27.9%, GY、PFPN和ANUE显著提高10.6%～18.5%、4.4%～26.8%和1.5%～48.6%。线性加平台模型分析表明, DH处理比NH GY提高11.3%～12.6% (<0.01), 达12.0×103kg hm–2和7.0×103kg hm–2, 但最优施氮量自200～210 kg hm–2增至247 kg hm–2。综之, 华北平原热量限制区夏玉米传统收获情景下减氮至200 kg hm–2, 产量稳定在6.0×103～10.5×103kg hm–2以上; 延迟收获情景下, 降低籽粒含水率, 减氮至240 kg hm–2, 产量达8.0×103～12.0×103kg hm–2以上, PFPN和ANUE最优为19.2～49.6 kg kg–1和15.3～20.8 kg kg–1, 可为区域夏玉米降低籽粒含水率, 实现籽粒机收与减氮稳产高效的生产目标提供理论支撑。

夏玉米; 降雨年型; 施氮量; 收获期; 产量; 氮肥利用效率

华北平原是我国夏玉米主产区之一, 在保障国家粮食安全中发挥重要作用[1], 但大部分地区周年热量资源紧张, 两熟制体系中受冬小麦播/收期双重限制, 夏玉米成熟和脱水热量资源紧张, 致使成熟期籽粒含水率较高[2], 难以达到适宜机械粒收含水量(28%或25%)的标准[3], 成为限制区域夏玉米机械粒收技术和全程机械化的瓶颈问题[4]。“双晚技术”推迟夏玉米收获可以在不增加成本前提下, 延长夏玉米灌浆脱水时间, 促进生育后期物质积累及向籽粒转运[5], 研究表明夏玉米生理成熟后田间站秆晾晒使百粒重自23.3～37.4 g提高至22.9～38.4 g[6], 夏玉米延长45 d脱水时间含水量降低至14.4%～17.3%, 周年增产6.7%～7.9%[7], 同时提高籽粒氮素积累量39.0%～57.3%, 实现氮素利用效率提高[8]。周宝元等[9]研究表明, 在华北平原中南部热量资源相对丰沛区夏玉米延迟收获后可以通过冬小麦增大播量提高基本苗数量弥补播期延迟群体数量不足的问题; 但在平原北部热量资源紧张区, 延迟夏玉米收获难以播种冬小麦, 可将冬小麦变革为春小麦, 实现夏玉米粒收技术与周年产量及气候资源协同提高。氮素在玉米器官建成、光合作用和产量形成中发挥关键作用[10]。研究表明, 施氮量增加, 调控干物质积累和产量构成因素[11], 促进光合产物向籽粒的转运, 提高籽粒灌浆速率和粒重[12], 实现增产。但华北平原高度集约化的冬小麦-夏玉米周年体系中大量施氮问题突出[13], 仅夏玉米季农田氮肥投入量平均达276 kg hm–2, 但利用率低于25%[14], 且氨挥发损失较高[15], 导致肥料利用率低和环境生态等问题[16-17]。为破解过量施氮对环境生态的危害, 提高氮素利用效率, 适量减氮能协调氮素积累与转运[18], 促进植株对氮素吸收和利用[19], 增加土壤硝态氮累积并减少N2O的排放[20], 优化施氮使氮肥偏生产力从26 kg kg–1提升至57 kg kg–1 [21]。华北平原地处亚热带季风气候区, 夏玉米生育期处于降雨季, 近年来极端降水如夏季大暴雨日数和平均日降水强度有增加趋势[22], 2021年降雨量近1000 mm, 是平常年份的2倍以上, 显著影响夏玉米生长发育与产量形成。强降雨导致夏玉米发生淹水胁迫, 玉米根系生理性危害加剧, 叶绿体结构破坏, 光系统活性和光合速率显著降低, 叶片失绿早衰, 干物质积累急剧降低, 雌雄穗发育不良, 籽粒物质转运量减少, 籽粒灌浆速率显著降低, 灌浆时间缩短, 穗粒数减少和粒重降低导致减产甚至绝收, 胁迫时间越早, 淹水时间越长影响越显著[23-27]。

如前所述, 优化施氮调控夏玉米产量及氮素利用已有大量研究, 但为实现华北平原夏玉米延迟收获降低籽粒含水量实现机械粒收情境下, 特别是针对2021年长时间强降雨情境下, 施氮量与收获期对后期籽粒灌浆与脱水过程、产量形成与氮肥利用效率的影响未见报道。为此, 本论文针对华北平原北部热量资源限制区, 比较分析2020年和2021年2个代表性降雨年型下, 施氮量与收获期调控夏玉米籽粒灌浆脱水过程与产量形成及氮肥利用的效应, 以期为华北平原延迟收获夏玉米稳产减氮增效与机械粒收技术发展提供理论支撑。

1 材料与方法

1.1 试验设计

于2020年和2021年6月至11月在天津市优质农产品开发示范中心(39°42′N, 117°49′E)进行, 0～20 cm土壤基础养分含量为有机质18.6 g kg–1、全氮1.09 g kg–1、水解性氮77.68 mg kg–1、速效磷64.8 mg kg–1、速效钾296 mg kg–1。试验期间夏玉米生育气象数据如图1, 2020年夏玉米生长季降雨量为287.6 mm, 2021年降雨量为973.5 mm。据天津市1991—2020年统计年鉴年均降水量566.1 mm, 6月至10月平均降水量为451.6 mm, 将2020年认定为干旱年型, 2021年为丰水年型。试验品种选用京农科728, 采用二因素随机区组试验设计, 因素施氮量为0 kg hm–2(N0)、120 kg hm–2(N120, 2021)、180 kg hm–2(N180)、240 kg hm–2(N240)、300 kg hm–2(N300)、360 kg hm–2(N360)和450 kg hm–2(N450, 2020), 2021年施氮量根据2020年试验结果进行优化增加N120而去掉N450处理, 因素收获期为正常收获(normal harvest, NH, 10月5 (13)日)和延迟收获(delayed harvest, DH, 11月8 (6)日)。种植密度75,000株 hm–2, 行距60 cm、株距22.2 cm, 小区长7.0 m, 宽4.2 m, 种植7行, 重复3次, 各小区间设置1 m隔离带。N肥按照50%-30%-20%分别按种肥-拔节肥-大喇叭口期肥施用, P2O5120 kg hm–2和K2O 150 kg hm–2全部作种肥。及时防治病虫草害, 2020年灌水2次, 2021年排水。

图1 2020年和2021年玉米生育期气象数据

1.2 测定指标及方法

1.2.1 干物质积累量(dry matter accumulation, DM) 于拔节期(V6)、吐丝期(R1)和收获期, 每小区取代表性植株3株, 分为营养器官和籽粒(收获期) 两部分, 105℃杀青30 min, 85℃烘干至恒重后称重。

1.2.2 籽粒灌浆与脱水动态 每小区选取吐丝期一致植株50株挂牌标记, 自吐丝开始每10 d取2个代表性果穗, 每穗取中部籽粒50粒, 测定籽粒鲜重, 105℃杀青30 min后85℃烘干至恒重, 称干重(grain weight, GW, mggrain–1), 籽粒含水率(grain moisture content, GMC, %) = (鲜重−烘干重)/鲜重× 100%。以天数(d)为自变量, 粒重(GW)为因变量, 用Logistic方程GW =(1+e–cd))拟合籽粒增重过程并计算籽粒灌浆参数。用指数方程=e模拟籽粒含水率变化过程, 对方程求导得到=e模拟籽粒脱水速率(grain dehydration rate, GDR, % d–1)变化过程。

1.2.3 产量及其构成因素 收获期每小区连续收获20穗, 带回室内立即考种, 数取穗行数(ear lines number, ELN)、行粒数(line grains number, LGN), 脱粒后称取鲜千粒重和全部粒重, 用PM8188-A谷物水分仪测定含水率后按14%安全含水率计算千粒重(1000-grain weight)和产量(GY)。

1.2.4 氮肥利用效率 氮肥偏生产力(nitrogen partial factor productivity, PFPN, kg kg–1) = 籽粒产量/施氮量, 氮肥农学效率(nitrogen agronomic use efficiency, ANUE, kg kg–1) = (施氮区玉米产量–不施氮区玉米产量)/施氮量。

2 结果与分析

2.1 干物质积累量

由图2可看出, 与干旱年型(2020)相比, 丰水年型(2021)夏玉米V6、R1和收获期DM降低16.3%～64.6%、48.5%～76.8%和47.6%～81.5%, 达极显著水平。与N0相比, 施氮处理在干旱年型下V6、R1、NH和DH的DM显著提高50.3%～91.2%、25.1%～47.0%、61.2%～99.5%和14.3%～29.9%, 丰水年型下增幅分别达103.1%～272.5%、64.8%～203.1%、126.5%～248.8%和121.5%～239.9%, 差异达极显著水平。干旱年型和丰水年型下, DH收获期DM比NH显著提高0.8%～55.7%和1.2%～3.8%, DH显著提高干旱年型下籽粒干重, 但显著降低了丰水年型干物质向籽粒的转运分配。NH处理时, 中高施氮水平收获期DM比低氮水平(N180和N120)显著提高10.8%～23.7%和12.4%～54.0%, 且以籽粒增加(6.0%～28.7%和36.4%～90.7%)为主; DH处理时, 干旱年型施氮水平间DM无显著差异, 丰水年型施氮水平间DM差异达显著水平, N240-N360水平比N120-N180显著提高13.8%～53.5%, 其中营养器官增重3.4%～35.7%, 籽粒增加22.1%～66.9%。

图2 不同降雨年型下延迟收获及施氮量对夏玉米干物质积累量的影响

Stem+Leaf: 茎+叶; Grain: 籽粒。NH: 传统收获处理; DH: 延迟收获处理。N0: 施氮量为0 kg hm–2; N120: 施氮量为120 kg hm–2; N180: 施氮量为180 kg hm–2; N240: 施氮量为240 kg hm–2; N300: 施氮量为300 kg hm–2; N360: 施氮量为360 kg hm–2; N450: 施氮量为450 kg hm–2。V6: 拔节期; R1: 吐丝期。不同小写字母表示不同施氮处理在同一时期达到显著差异(< 0.05)。

NH: the normal harvest treatment; DH: the delayed harvest treatment. N0: 0 kg hm–2; N120: 120 kg hm–2; N180: 180 kg hm–2; N240: 240 kg hm–2; N300: 300 kg hm–2; N360: 360 kg hm–2; N450: 450 kg hm–2. V6: the jointing stage; R1: the silking stage. The different lowercase letters indicated there were significantly different at< 0.05 among different N treatments in the same stage.

2.2 籽粒灌浆动态

夏玉米粒重(GW)随灌浆进程呈S型曲线趋势增长(图3), 多雨导致GW显著降低2.1%～28.1% (2021 vs 2020)。干旱年型下, 施氮后GW在NH和DH处理比N0显著提高26.5%～35.7% (60.9～82.1 mg grain–1)和5.9%～14.8% (18.1～45.6 mg grain–1), 施氮量间无差异, 分别在N300和N360水平下GW最高; 丰水年型下, 与N0相比, 施氮处理GW在NH和DH时显著提高12.0%～23.1% (29.1～56.0 mg grain–1)和6.4%～34.7% (14.6～79.0 mg grain–1), 分别在N240和N300处理GW最高。DH处理在NH处理同天GW无差异, 在干旱年型下DH处理推迟收获25～33 d后GW比NH显著提高9.4%～34.0%, 但丰水年型下DH处理GW比NH提高3.9%～8.7% (>0.05)。

分析夏玉米籽粒灌浆速率参数可看出(图4), 与干旱年型相比, 2021年降雨增加使NH处理到达最大灌浆速率(maximum grain filling rate,max)时间(time reaching themax,max)推迟2.5 d, 但使DH处理max推迟3.5 d, 灌浆速率最大时生长量(weight increment ofmax,max)降低15.7%, 且灌浆持续期(active grain filling period,)缩短14.3 d。比较施氮量间籽粒灌浆参数可以看出, 干旱年型下, 与N180相比, NH处理在N300水平max提高10.7%、积累起始势(initial grain filling power,0)降低12.6%、延长14.4%至46.3 d, DH处理在N360水平max、max提高15.8%和12.4%; 丰水年型下, 与N120相比, NH处理在N240水平max提高12.0%至11.8 mg (grain d)–1, DH处理在N240-N300水平max提高12.5%～12.9%、0降低26.2%～ 31.5%、延长35.5%～45.9%, 显著高于其他施氮量。不同年型下收获期处理对籽粒灌浆速率参数影响趋势恰恰相反, 在干旱年型下与NH相比, DH处理max和0显著降低1.9%～20.0%和11.6%～33.7%,max提高0.7%～22.8%,max和分别推迟1.1～6.6 d和延长5.5～18.7 d; 而丰水年型下, DH处理max和0比NH显著提高1.7%～31.6%和5.6%～47.6%,max降低3.7%～11.1%,max与分别提早0.9～5.0 d和缩短1.9～13.4 d。

图3 不同降雨年型下延迟收获及施氮量对夏玉米灌浆期籽粒干重的影响

NH: 传统收获处理; DH: 延迟收获处理。处理同图2。

NH: the normal harvest treatment; DH: the delayed harvest treatment. Treatments are the same as those given in Fig. 2.

图4 不同降雨年型下延迟收获及施氮量对夏玉米籽粒灌浆速率的影响

NH: 传统收获处理; DH: 延迟收获处理。处理同图2。

NH: the normal harvest treatment; DH: the delayed harvest treatment. Treatments are the same as those given in Fig. 2.

2.3 籽粒含水率及脱水速率

随籽粒灌浆进程, 籽粒含水率(GMC)呈指数方程变化趋势(图5), 不同降水年型下, NH和DH处理收获期GMC均在N240水平时最低, 分别为30.8%～32.4%和23.0%～23.2%; 干旱年型下, NH和DH处理其他施氮水平GMC比N240增加17.5%～ 24.5% (<0.05)和7.0%～13.2% (<0.05); 丰水年型下, NH和DH处理不同施氮水平间GMC均无显著差异。多雨年型下同时期GMC显著高于干旱年型, NH处理收获期GMC分别为30.8%～41.8% (2020)和32.4%～41.4% (2021), 2021年NH处理收获期比2020年推迟9 d, 但GMC降低不显著; 年际间DH处理推迟25～33 d收获GMC比DH显著降低25.2%～ 39.1%和25.9%～40.5%, 达到22.0%～27.9%和23.2%～26.3%。

夏玉米籽粒脱水速率(GDR)随灌浆进程不断降低(图6), 丰水年型下同时期GDR低于干旱年型, 但差异不显著; NH和DH处理收获期丰水年型GDR比干旱年型显著降低11.2%～91.0%和52.5%～80.4%。不同施氮水平间, GDR差异主要表现在灌浆前期(30 d), 在干旱年型下, N240 GDR比其他施氮水平提高6.5%～11.8%; 丰水年型下N360与N240间差异不显著, 但比其他施氮量提高34.7%～75.4%。NH处理下, 脱水速率为(0.031～0.042) % d–1(2020)和(0.046～ 0.059) % d–1(2021), DH处理推迟25～33 d收获GDR显著降低至(0.0030～0.0062) % d–1(2020)和(0.0008～ 0.0025) % d–1(2021)。

2.4 产量及产量构成因素

丰水年型夏玉米产量(GY)比干旱年型极显著降低了31.4%～58.3% (图7), 且降雨导致DH处理比NH的增产幅度显著降低; 干旱年型下N240以上施氮水平DH产量比NH增产10.6%～18.5% (<0.05), 丰水年型下不同施氮水平DH处理比NH增产4.2%～14.7%, 但均未达显著水平; 干旱和丰水年型下, 施氮量与收获期对产量的互作效应均未达显著水平。与N0相比, 丰水年型下施氮后显著增产74.4%～ 169.5%, 显著高于干旱年型的增产效应(51.5%～ 99.1%), 且均表现为同一施氮量对DH处理的增产效应显著高于NH处理。干旱年型下, 不同施氮水平间在NH处理时GY无显著差异, N300最高为11.2×103kg hm–2, DH处理施氮量达N240水平即无显著差异, 比N180增产11.8%～23.0% (<0.05); 丰水年型下, NH和DH处理GY在N240水平以上即无显著差异, 分别比N120-N180显著增产21.7%～ 50.2%和12.6%～54.5%。线性加平台模型分析可知, 干旱和丰水年型下, DH比NH处理最高产量提高12.6%和11.3%, 干旱年型下DH和NH最高产量分别为12.00×103kg hm–2和10.66×103kg hm–2, 比丰水年型提高4.35×103～4.98×103kg hm–2, 但DH最优施氮量比NH增加30.3～36.1 kg hm–2, 分别为247.2～248.6 kg hm–2和201.1～218.3 kg hm–2。

图5 不同降雨年型下延迟收获及施氮量对夏玉米灌浆期籽粒含水率的影响

NH: 传统收获处理; DH: 延迟收获处理。处理同图2。

NH: the normal harvest treatment; DH: the delayed harvest treatment. Treatments are the same as those given in Fig. 2.

图6 不同降雨年型下延迟收获及施氮量对夏玉米灌浆期籽粒脱水速率的影响

NH: 传统收获处理; DH: 延迟收获处理。处理同图2。

NH: the normal harvest treatment; DH: the delayed harvest treatment. Treatments are the same as those given in Fig. 2.

丰水年型下, 夏玉米穗行数(ELN)、行粒数(LGN)和穗粒数(EGN)比干旱年型显著减少20.3%～21.0%、30.6%～31.5%和44.7%～47.4%, 千粒重(1000-GW)降低2.7%～3.0% (>0.05) (表1)。干旱年型下, N450水平EGN显著少于其他施氮水平, 但在NH处理时1000-GW随施氮量增加显著增加, DH处理时1000-GW在N240水平以上即无差异; 丰水年型下, ELN和EGN在N240-N360水平下显著多于N120, 而施氮水平间1000-GW无显著差异。DH处理推迟25～33 d收获对ELN、LGN和EGN无影响, 但1000- GW比NH处理显著提高7.8%～17.3% (2020年)和6.4%～15.2% (2021年)。

2.5 氮肥利用效率

由图8可知, 干旱年型下夏玉米氮肥偏生产力(PFPN)比丰水年型显著提高42.8% (NH)和37.3% (DH)。夏玉米PFPN随施氮量增加显著降低, 干旱年型下, 增施氮肥在NH处理和DH处理时比N180分别降低16.6%～57.9%和11.7%～55.3%, 且施氮处理间差异均达显著水平; 丰水年型下, NH处理在N120水平下最高(36.7 kg kg–1,<0.05), 且N360水平下最低(19.4 kg kg–1,<0.05), N240与N180和N300无差异, DH处理下N180处理PFPN显著低于N120但显著高于N240-N360, 在N240-N360水平间无差异。干旱年型下, DH处理在N240以上水平PFPN比NH显著提高10.6%～15.6%, 丰水年型下, DH处理仅在N120-N180水平时比NH显著提高19.6%和26.8%。

由图9可知, 丰水年型下NH处理氮肥农学利用效率(ANUE)比干旱年型显著降低18.0%, 而DH处理ANUE降雨年型间无显著差异。干旱年型下, NH和DH处理ANUE在N180-N300间无差异, 比N360和N450显著提高17.7%～54.9%; 丰水年型下, NH和DH处理在N120-N300水平间无显著差异, N360比N120显著降低28.7%和37.0%。干旱年型下, DH处理ANUE在N180水平下比NH处理显著降低12.4%, 但在N360水平下显著提高12.5%, 其他水平间无差异; 丰水年型下, DH处理ANUE在N120-N180水平比NH显著提高21.6%和48.6%。

3 讨论

2021年华北平原强降雨导致夏玉米受到淹水胁迫, 淹水胁迫导致夏玉米产量降低[23], 不同时期淹水对产量影响不同, 三叶期、拔节期和花后淹水导致减产41.5%、26.5%和15.3%[24], 主要原因在于淹水限制根系发育[27], 导致玉米叶片叶绿素结构破坏, 影响光合特性[23,26]及干物质积累与转运[23], 吐丝后籽粒灌浆持续期缩短, 灌浆速率降低, 最大灌浆速率时间提前, 粒重显著降低导致减产[25,28]。本研究表明, 在大田非可控条件下夏玉米全生育期尤其是生育前期的持续强降雨使其生长发育受到显著抑制, 灌浆后期叶片早衰, 导致干物质积累量显著降低16.3%～81.5%, 同时影响光合产物向籽粒的转运, 丰水年型下穗行数、行粒数和穗粒数比干旱年型显著减少20.3%～21.0%、30.6%～31.5%和44.7%～ 47.4%。淹水胁迫导致夏玉米籽粒灌浆持续期显著缩短5～8 d, 灌浆速率降低且达到最大灌浆速率时间提前3～5 d, 粒重显著降低2.1%～28.1%, 最终夏玉米减产31.4%～58.3%, 且氮肥偏生产力显著降低27.2%～ 30.0%, 氮肥农学利用效率降低3.5%～18.0%。Xu等[29]研究结果也表明多雨年份导致春玉米物质积累与分配失衡引起产量降低, 支持本研究结果; Wang等[30]研究表明丰水年使穗粒数增加19.0%, 粒重提高是影响高密度群体产量的重要因素[31], 主要原因是研究区域在西北干旱区, 与本研究的华北平原有较大的生态差异。

图7 不同降雨年型下延迟收获及施氮量对夏玉米产量的影响

NH: 传统收获处理; DH: 延迟收获处理。不同小写字母表示不同施氮处理收获期产量达到显著差异(< 0.05)。处理同图2。

NH: the normal harvest treatment; DH: the delayed harvest treatment. The different lowercase letters indicated the GY were significantly different at< 0.05 among different N treatments. Treatments are the same as those given in Fig. 2.

表1 不同降雨年型下延迟收获及施氮量对夏玉米产量构成因素的影响

NH: 传统收获处理; DH: 延迟收获处理。不同小写字母表示不同施氮处理收获期产量构成因素达到显著差异(< 0.05)。处理同图2。

NH: the normal harvest treatment; DH: the delayed harvest treatment. The different lowercase letters indicated the GY components were significantly different at< 0.05 among different N treatments. Treatments are the same as those given in Fig. 2.

图8 不同降雨年型下延迟收获及施氮量对夏玉米氮肥偏生产力的影响

NH: 传统收获处理; DH: 延迟收获处理。不同小写字母表示不同施氮处理氮肥偏生产力达到显著差异(＜0.05)。处理同图2。

NH: the normal harvest treatment; DH: the delayed harvest treatment. The different lowercase letters indicated the PFPN were significantly different at< 0.05 among different N treatments. Treatments are the same as those given in Fig. 2.

图9 不同降雨年型下延迟收获及施氮量对夏玉米氮肥农学利用效率的影响

NH: 传统收获处理; DH: 延迟收获处理。不同小写字母表示不同施氮处理氮肥农学利用效率达到显著差异(< 0.05)。处理同图2。

NH: the normal harvest treatment; DH: the delayed harvest treatment. The different lowercase letters indicated the ANUE were significantly different at< 0.05 among different N treatments. Treatments are the same as those given in Fig. 2.

华北平原周年冬小麦-夏玉米生产中, 由于热量资源紧张且受冬小麦播/收期双重限制, 夏玉米脱水时间短, 难以达到适宜机械粒收含水量(28%或25%)标准[3], 适当延迟收获延长籽粒灌浆脱水期, 降低籽粒含水量及籽粒破碎率, 提高机械粒收质量[32]。本研究结果表明, 华北平原北部夏玉米延迟23～33 d收获籽粒含水率可降至22.0%～27.9%, 比传统收获降幅达25.2%～40.5%, 基本满足玉米机械粒收含水率的标准。李璐璐等[6]研究表明, 黄淮海南部夏玉米生理成熟后延迟收获16～52 d, 籽粒含水率自21.5%～33.1%降至12.9%～24.4%, 籽粒含水率显著低于本研究结果,但降幅低于本研究结果。分析差异产生的可能原因为: (1) 本试验所在华北平原北部夏玉米延迟收获的10月中下旬与11月上旬气温整体低于南部地区, 限制了籽粒脱水速率[33]; (2) 由于丰水年份下, 空气湿度较大, 影响籽粒脱水速率, 丰水年份籽粒含水率显著高于干旱年份。另外, 脱水速率低于干旱年份也能证明这个猜测。最重要的是华北平原北部热量限制下为实现冬小麦-夏玉米周年生产, 夏玉米收获及冬小麦播种时间不能晚于10月10日, 导致了夏玉米在传统收获时间籽粒刚刚甚至尚没有达到生理成熟期, 含水率高达30.8%～ 41.8%, 所以延迟收获可使籽粒含水率的降幅高于华北平原南部。本研究结果表明, 延迟收获在干旱年型下通过显著提高夏玉米粒重及干物质积累量9.4%～34.0%和0.8%～55.7%,实现增产10.6%～18.5% (<0.05), 但丰水年型下由于延迟收获对粒重和干物质积累量影响未达显著水平, 实现增产4.2%～14.7%, 但不显著。在华北平原南部的研究也表明夏玉米生理成熟后延迟收获百粒重自23.3～ 37.4 g提高至22.9～38.4 g[6], 籽粒容重提高可实现增产9.72%[8], 大跨度延迟夏玉米收获期可实现冬小麦- 夏玉米周年增产6.7%～7.9%[7], 实现周年光温及氮素的高效利用[5]。本研究条件下, 尽管延迟收获阶段日均温度为11.8℃和10.1℃低于籽粒灌浆15℃要求, 但日均最高温为18.9℃和16.7℃, 同时积温量达到400.9 ℃ d和241.7 ℃ d, 因此分析延迟收获提高粒重的原因一猜测可能是传统收获情境下夏玉米尚未达生理成熟, 满足≥10℃可维持籽粒灌浆活性[34]; 原因二猜测可能是日均最高温大于15℃满足籽粒灌浆的温度需求, 同时日均最低温4.5～5.9℃显著抑制干物质转移, 较高的昼夜温差提高了籽粒干物质积累能力; 年际间延迟收获阶段日均最高温与积温量差异导致2021年延迟收获粒重显著低于2020年也验证了这个猜测, 另外Liu等[34]通过纬度试验也表明灌浆期日均最高温和积温量与粒重呈显著正相关也可以验证本猜测。因此, 在华北平原北部夏玉米延迟收获后期光照、温度和空气湿度等生态资源调控籽粒灌浆和脱水速率的效应值得进一步研究。

由于氮素在作物产量形成过程的重要作用[10], 生产中农户为追求产量常进行过高施氮[13], 华北平原夏玉米农田氮肥投入量平均为276 kg hm–2 [14], 引起肥料利用率低和环境生态问题[14-17], 优化施氮能够协调氮素积累和转运, 促进植株光合产物积累, 显著提高地上部生物量实现增产[12,18,35-36]。本研究表明, 夏玉米施氮量达240 kg hm–2以上时在正常收获和延迟收获处理情况下干物质积累量增加均不显著,但可提高干物质向籽粒的转运, 而且表现为在丰水年型下施氮量对干物质分配的影响效应更加显著。施氮量增加促进光合产物向籽粒转运改善籽粒灌浆特性[12], 最大灌浆速率及其生长量显著提高, 灌浆活跃期延长[37], 粒重提高且穗粒数增加[36], 实现增产; 但随施氮量增加玉米氮肥偏生产力和氮肥农学利用效率显著降低[38-39]。本研究结果表明, 施氮提高夏玉米籽粒灌浆速率, 且延长灌浆持续期, 正常收获和延迟收获条件下均在施氮量240 kg hm–2以上时处理间粒重无显著差异, 且在240 kg hm–2水平时灌浆前期脱水速率高于其他施氮水平, 收获时籽粒含水率显著降低; 240～360 kg hm–2处理行粒数和穗粒数显著高于低氮量处理, 施氮240 kg hm2时产量增加不显著。通过模型分析表明, 传统收获优化减氮至200～220 kg hm–2, 保证夏玉米稳产6.0 × 103～ 10.5×103kg hm–2水平, 延迟收获条件优化施氮量在240 kg hm–2水平, 可实现高产8.0×103～12.0×103kg hm–2, 模型优化施氮后夏玉米氮肥偏生产力和农学利用效率可达49.6 kg kg–1和20.8 kg kg–1。在丰水年型下, 氮素利用效率低于干旱年型, 施氮量增产效应显著下降, 分析原因可能是多雨淹水胁迫下氮素淋溶比例升高, 氮损失加剧, 同时玉米根系活性下降, 氮素利用能力显著降低[16,20,39]。本研究结果表明, 丰水年型下施氮量对干物质积累、产量的调控效应显著高于干旱年型, 这与张元红等[31]在西北旱区丰水年份提高密度对春玉米的增产效应相似, 说明丰水年型下玉米高产更应该关注密度和氮肥的管理。

4 结论

华北平原北部由于热量资源限制, 夏玉米传统收获时籽粒含水量高达30.8%～41.8%, 只能机械穗收难以机械粒收, 而通过延长夏玉米收获时期23～33 d, 可以实现籽粒含水量降低至22.0%～27.9%, 基本满足玉米机械粒收含水率的标准。丰水年型导致夏玉米穗粒数减少, 粒重和干物质积累量均降低, 产量比干旱年型显著降低31.4%～58.3%, 延迟收获通过提高干物质积累量及粒重实现增产, 施氮提高最大灌浆速率及其生长量, 延长灌浆持续时间提高粒重而实现增产。综之, 华北平原北部夏玉米传统机械穗收情境下, 优化减氮至200 kg hm–2, 产量稳定在6.0×103～10.5×103kg hm–2; 延迟20～35 d可达机械粒收标准, 优化施氮240 kg hm–2, 产量达8.0×103～12.0×103kg hm–2, 氮肥偏生产力和农学利用效率为19.2～49.6 kg kg–1和15.3～20.8 kg kg–1。在华北平原中南部热量资源相对丰沛区夏玉米延迟收获后可以通过冬小麦增大播量提高基本苗数量弥补播期延迟群体数量不足的问题[7]; 但在北部热量资源紧张区, 延迟夏玉米收获难以播种冬小麦, 能否将冬小麦变革为春小麦, 实现夏玉米粒收技术与周年稳产减氮提效及气候资源协同提高值得深入研究。

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Effects of nitrogen application and harvest time on grain yield and nitrogen use efficiency of summer maize under different rainfall years

LIU Meng1, ZHANG Yao1, GE Jun-Zhu1,*, ZHOU Bao-Yuan2, WU Xi-Dong1, YANG Yong-An3, and HOU Hai-Peng4

1College of Agronomy and Resources and Environment, Tianjin Agricultural University, Tianjin 300384, China;2Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081, China;3Tianjin High-quality Agricultural Products Development Demonstration Center, Tianjin 301500, China;4.Tianjin Agricultural Development Service Center, Tianjin 300061, China

To investigate the effects of nitrogen application and harvest time on summer maize grain filling and dehydration, yield formation, and nitrogen use efficiency in thermal resource restricted area in the North China Plain, we adopted a two-factor randomized block area experiment design, one factor was nitrogen application rate per hectare [0 kg (N0), 120 kg (N120, 2021), 180 kg (N180), 240 kg (N240), 300 kg (N300), 360 kg (N360), and 450 kg (N450, 2020)], and another factor was harvest time [normal harvest (NH) and delayed harvest (DH)]. Dry matter accumulation (DM), grain filling and dehydration processes, grain yield (GY) and its components, nitrogen partial factor productivity (PFPN), and agronomic nitrogen utilization efficiency (ANUE) were investigated. Compared to the dry year (2020), DM, grain weight (GW), a%, respectively, resulting in GY, PFPN, and ANUE significantly reduced by 31.4%–58.3%, 27.2%–30.0%, and 2.9%–18.0%, respectively. Compared with N0, nitrogen application significantly enhanced DM, and GW were 14.6–82.1 mg grain–1higher than N0, while the maximum grain filling rate (max) and its weight increment (max) were enhanced by 0.2–3.4 mg (grain d)–1and 10.4–44.1 mg grain–1, meanwhile the time reachingmax(max) were earlier by 0.4–7.0 d. The GY of nitrogen application treatments were dramatically raised by 51.5%–169.5% than N0, and in the N240level it was the optimized nitrogen application. Compared with that of N180/N120,with the increase of nitrogen application rate, the PFPN and ANUE in two years were significantly reduced by 11.7%–57.9% and 2.5%–54.9%, 19.9%–52.6% and 4.9%–37.0%, respectively. Compared with NH treatment, the DM and GW of DH treatment were increased significantly by 0.8%–55.7% and 3.4%–79.3%, and dramatically reduced grain moisture content to 22.0%–27.9% at harvest stage. The GY, PFPN, and ANUE of DH treatment were remarkable higher than NH treatment by 10.6%–18.5%, 4.4%–26.8%, and 1.5%–48.6%, respectively. The linear plus platform model showed that the highest GY of DH treatment obtained to 12.0×103kg hm–2and 7.0×103kg hm–2, which were significantly higher than NH by 11.3%–12.6% , whereas the optimal nitrogen application rate were reached to 247 kg hm–2form 200–210 kg hm–2, increased by 13.9%–22.9%. In conclusion, in thermal resource restricted area in the North nd ear grains number (EGN) under rainy year (2021) were significant decreased by 16.3%–81.5%, 2.1%–28.1%, and 44.7%–47.4 China Plain, the nitrogen application rate could reduce to 200 kg hm–2and GY stabilized above 6.0×103–10.5×103kg hm–2under normal harvest time, meanwhile the nitrogen application rate could optimized to 240 kg hm–2and achieved higher GY above 8.0×103–12.0×103kg hm–2with higher PFPN and ANUE at 19.2–49.6 kg kg–1and 15.2–20.8 kg kg–1levels under delayed harvest. In conclusion, the results revealed that the theoretic support for reduced summer maize grain moisture content, achieving the production goal as grain machine harvesting, nitrogen reduction, high yield and high nitrogen use efficiency of summer maize in the North China Plain.

summer maize; rainfall year types; nitrogen application rate; harvest time; grain yield; nitrogen use efficiency

10.3724/SP.J.1006.2023.23014

本研究由国家自然科学基金项目(31701378)和国家重点研发计划项目(2017YFD0300410)资助。

This study was supported by the National Natural Science Foundation of China (31701378) and the National Key Research and Development Program of China (2017YFD0300410).

葛均筑, E-mail: gjz0121@126.com.

E-mail: m15222312583@126.com

2022-02-18;

2022-06-07;

2022-07-14.

URL: https://kns.cnki.net/kcms/detail/11.1809.S.20220713.1910.002.html

This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).