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我国东北平原有近30%为半干旱农业区,早春低温和干旱是限制该区域玉米生产的主要因素[1]。近年来,滴灌和地膜覆盖相结合的栽培技术在改善耕层土壤水热状况、促进作物生长发育、提高作物产量和水分养分利用效率等方面发挥了重要作用[2-4],现已广泛应用于东北半干旱区玉米栽培[5]。如何将覆膜滴灌技术与其它栽培措施相结合,进而充分发挥有限水资源的生产潜力,是东北半干旱区覆膜滴灌条件下亟需解决的问题。除品种、气候、病虫草害防控与非生物灾害消减等产量形成与保护因素外,种植密度和氮素管理是玉米栽培学中最为活跃的两大因素[6]。合理的种植密度是玉米利用光热资源构建良好群体结构、优化群体光合生理指标的基础[7-8],适宜的氮肥用量是提高玉米物质生产的营养保障[9],而种植密度与氮肥用量二者协调可提高玉米群体对养分吸收和利用,进而提高单位施氮量所增加的籽粒产量。因此,明确覆膜滴灌条件下合理的施氮量与种植密度,对东北半干旱区构建高产高效栽培体系具有重要意义。目前,针对氮肥、种植密度以及二者互作对作物群体氮素吸收利用、物质生产特征和氮肥利用效率的影响已有大量研究。这些研究表明,增加种植密度可提高玉米光、温、水资源的利用效率,通过协调穗数、穗粒数和粒重,依靠群体发挥增产潜力[10],但密度过大,会引起植株间竞争水、养分、光等限制性资源,使茎秆质量变差,养分吸收量下降,虽然穗数有所增加,但穗粒数和粒重降幅过大,造成减产[11-12];增施氮肥可显著增强玉米生育期的光合作用,提高养分吸收与积累速率,有利于营养器官中有机物的合成及花后保绿,延长花后光合与灌浆时间,提高玉米单株生产能力,但当氮肥用量过高时则导致叶片早衰,叶片光合能力和物质生产能力下降,进而影响玉米产量[13-15];而盛耀辉等[16]研究表明,氮肥与密度间互作效应显著,在一定范围内可以相互促进,但当施氮量或种植密度过高时,氮肥与密度互作表现为负效应,对玉米养分吸收利用有抑制作用。可见,在玉米生产中,氮肥、密度二者之间需要高度协调配合,才有利于优化作物群体结构,提高玉米生育期的光合作用,进一步促进养分吸收与物质生产,使玉米产量和氮肥利用效率协同增加。但是当前关于东北春玉米在种植密度和氮肥互作的研究多集中在雨养条件下,且多为氮密互作条件下玉米对氮素吸收利用的报道。而关于东北半干旱区覆膜滴灌条件下,不同施氮水平下如何与密度匹配提高玉米群体氮、磷、钾养分吸收利用效率方面缺乏研究,由于作物体内氮磷钾养分通过有机物的形成和转化相互联系,不同种植密度和施氮量必将对其有所影响,且地膜覆盖使玉米生育进程发生改变,其养分吸收利用特性势必相应改变,滴灌施肥与常规施肥制度理论上存在差异。因此,本研究在覆膜滴灌条件下,分析玉米种植密度和氮肥用量及二者间的互作对群体玉米养分吸收、转运特征的响应机制,明确产量、养分吸收及氮素利用效率协同提高的最佳施氮量和种植密度,以期为提升东北半干旱区玉米高产高效栽培提供理论依据。
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试验于2016—2017年在吉林省农业科学院乾安实验站进行。研究区域年平均气温5.6℃,年日照时数2866.6 h,全年积温2884.5℃,无霜期146天,年平均降雨量425 mm,年平均蒸发量1500 mm以上,属典型的半干旱区。试验地种植制度为玉米连作,土壤类型为淡黑钙土,2016和2017年试验起始时0—20 cm土壤基础养分状况为:有机质17.39 g/kg、水解性氮102.4 mg/kg、有效磷35.86 mg/kg、速效钾109.4 mg/kg、pH 7.86。玉米生育期气象数据 (平均温度、最高温度、最低温度、降雨量) 通过试验点的自动气象站获取 (图1)。
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本试验采用密度 (D)、氮肥 (N) 两因素随机区组设计,主区为密度处理,设6.0 × 104、7.5 × 104和9.0 × 104株/hm2 3个水平,依次标记为D1、D2和D3;副区为氮肥处理,设N 0、140、210、280和350 kg/hm2 5个水平,依次标记为N0、N140、N210、N280和N350,共计15个处理。各处理磷肥 (P2O5) 和钾肥 (K2O) 用量一致,分别为90和100 kg/hm2。氮肥按20%基肥、30%拔节肥、20%大喇叭口肥、20%抽雄肥、10%灌浆肥施用;磷肥按40%基肥、60%大喇叭口肥施用;钾肥按60%基肥、40%大喇叭口肥施用。供试玉米品种为农华101,小区面积60 m2,重复3次,2016和2017年玉米种植日期分别为5月7日和5月3日。采用覆膜滴灌种植,玉米播种后,铺设滴灌带与覆盖地膜。滴灌带铺设于宽行中间,每条滴灌带浇灌2行玉米。不同处理两年玉米生育期灌水定额均为240 mm,其中在玉米播前、苗期和拔节期分别灌水20 mm,大喇叭口期、开花期和灌浆期分别灌水60 mm,共计6次,各处理单独用水表控制同等灌水量。供试的氮肥为尿素 (N 46%),磷肥以重过磷酸钙 (P2O5 46%) 和液体磷酸 (P2O5 85%) 作为两种磷源,钾肥为氯化钾 (K2O 60%)。每小区单配18 L压差式施肥罐,施肥开始前按各处理所需氮、磷、钾肥放入施肥罐,充满水后搅拌至完全溶解。在施肥前先滴清水30 min,然后打开施肥阀施肥,施肥时间为120 min,施肥后继续滴清水30 min。收获日期分别为9月30日和10月2日。其他田间管理按玉米常规生产田进行。
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分别于玉米苗期 (V3)、拔节期 (V6)、大喇叭口期 (V12)、开花期 (VT)、灌浆期 (R2) 和成熟期 (PM) 采集不同处理具有代表性玉米植株5株,分解为茎秆和籽粒两部分。105℃杀青30 min,70℃烘干至恒重后进行称重并粉碎,采用硫酸—双氧水消煮,凯氏法测定全氮含量。
玉米成熟期,在每小区收取中间2行,测定每小区的穗数,收获后在晾晒场自然风干,当籽粒水分 ≤ 20%时,人工脱粒,用PM-8188谷物水分测定仪测定籽粒含水量,以14%标准含水量计算产量,并按测产面积折算成单位面积产量。收获时选择10个代表性果穗,测定穗粒数和百粒重。
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收获指数 = 籽粒产量/地上部生物量;
植株养分积累量 (kg/hm2) = 各时期干物质量 × 氮 (磷、钾) 素含量 (%);
养分转运量 (kg/hm2) = 开花期植株地上部养分积累量-成熟期植株地上部营养器官养分积累量;
转运率 (%) = 养分转运量/开花期地上部养分积累量 × 100;
转运养分对籽粒贡献率 (%) = 花前营养器官养分转运量/籽粒养分积累量 × 100;
积累养分对籽粒贡献率 = 100% - 花前营养器官养分转运量/籽粒养分积累量 × 100%;
氮素吸收利用效率 (NRE,%) = (施氮区植株地上部氮积累量-不施氮区植株地上部氮积累量) /施氮量 × 100
氮素农学利用率 (NAE,kg/kg) = (施氮区作物产量-不施氮区玉米产量) /施氮量;
氮肥偏生产力 (NPFP,kg/kg) = 施氮区籽粒产量/施氮量
试验数据采用Excel进行处理,用SAS 9.0软件进行两因素 (种植密度和施肥处理) 方差分析,处理间多重比较采用LSD-test法;用SigmaPlot 14.0软件绘图。
本研究中2016和2017年各指标变化规律一致,因此数据采用2年数据的平均值进行分析。
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由表1可知,种植密度和施肥处理均对玉米产量影响显著,且两因素表现出显著的交互作用。在同一密度下,玉米产量随着施氮水平的增加呈先增后降趋势,其中在D1和D2密度下,以N210处理玉米产量最高;在D3密度中,以N280处理玉米产量最高。施氮水平相同时,以D2密度下玉米产量最高,后依次为D3和D1密度。其中D2处理玉米平均产量较D1和D3处理分别提高了12.7%和3.8%,并与D1处理差异达显著水平 (P < 0.05)。
表 1 不同种植密度和施氮水平处理玉米产量与构成因素
Table 1. Maize yield and its components under varied plant density and nitrogen application rates
密度 Density 氮水平 N level 产量 Yield (kg/hm2) 穗数 Ear number per 穗粒数 Kernel 百粒重 100-kernel weight (g) 收获指数 Harvest index D1 N0 7672 ± 336 d 58000 ± 300 a 467.2 ± 7.6 d 28.6 ± 0.7 c 0.49 ± 0.01 c N140 10126 ± 207 c 58000 ± 300 a 544.1 ± 10.0 c 32.1 ± 0.1 b 0.50 ± 0.02 ab N210 11265 ± 181 a 59000 ± 1200 a 587.9 ± 4.5 a 34.6 ± 0.7 a 0.51 ± 0.01 a N280 11077 ± 222 a 60000 ± 1000 a 582.2 ± 5.6 ab 34.2 ± 0.5 a 0.50 ± 0.01 ab N350 10683 ± 270 b 60000 ± 300 a 568.5 ± 10.5 b 33.8 ± 0.6 a 0.50 ± 0.01 bc 均值 Mean 10165 ± 1460 59000 ± 1000 550.0 ± 49.3 32.7 ± 2.5 0.50 ± 0.01 D2 N0 8571 ± 252 d 74000 ± 1400 a 421.0 ± 9.4 c 26.6 ± 0.8 c 0.48 ± 0.01 b N140 11462 ± 289 c 74000 ± 900 a 501.4 ± 3.7 b 30.2 ± 0.9 b 0.50 ± 0.02 a N210 12662 ± 277 a 75000 ± 1100 a 550.0 ± 6.8 a 32.6 ± 0.9 a 0.52 ± 0.01 a N280 12428 ± 190 ab 75000 ± 700 a 545.1 ± 3.0 a 32.1 ± 1.6 a 0.52 ± 0.01 a N350 12139 ± 177 b 74000 ± 700 a 542.3 ± 10.4 a 31.6 ± 1.1 ab 0.51 ± 0.01 a 均值 Mean 11452 ± 1672 74000 ± 500 512.0 ± 54.4 30.6 ± 2.4 0.51 ± 0.01 D3 N0 8493 ± 286 d 88000 ± 2000 a 397.3 ± 6.6 c 24.3 ± 0.9 c 0.48 ± 0.02 b N140 10878 ± 307 c 87000 ± 1200 a 461.3 ± 8.7 b 29.1 ± 0.3 b 0.49 ± 0.01 ab N210 11475 ± 157 b 88000 ± 1500 a 470.3 ± 5.8 b 29.2 ± 0.5 b 0.51 ± 0.01 a N280 12305 ± 355 a 86000 ± 700 a 493.7 ± 7.2 a 30.7 ± 0.8 a 0.51 ± 0.01 a N350 12014 ± 110 ab 87000 ± 1500 a 473.6 ± 6.5 b 30.2 ± 0.4 a 0.50 ± 0.01 a 均值 Mean 11033 ± 1521 87000 ± 800 459.2 ± 36.6 28.7 ± 2.6 0.50 ± 0.01 方差分析 ANOVA 种植密度 Plant density (D) ** ** ** ** NS 施氮量 N rate (N) ** NS ** ** NS D × N ** NS * NS NS 注(Note):D1—6.0 × 104 plant/hm2;D2—7.5 × 104 plant/hm2; D3—9.0 × 104 plant/hm2. 同列数值后不同小写字母表示同一密度下各处理间在 5% 水平上差异显著 Values followed by different lowercase letters in the same column are significantly different at 5% level at the same density among different treatments; NS—不显著 Not significant; *—P < 0.05; **—P < 0.01. 产量构成中,种植密度对实收穗数、穗粒数和百粒重影响显著,对收获指数无显著影响,施肥处理对穗粒数和百粒重影响显著,对实收穗数和收获指数无显著影响,而两因素仅对玉米穗粒数表现出显著的交互效应。在同一密度下,穗粒数和百粒重随施氮水平的增加呈先增后降趋势,其中在D1和D2密度下,以N210处理玉米穗粒数和百粒重最高;D3密度下,以N280处理玉米穗粒数和百粒重最高。施氮水平相同时,玉米实收穗数随种植密度的增加而增加;玉米穗粒数和百粒重均以D1处理最高,后依次为D2和D3处理。
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随生育进程的推进,植株氮、磷、钾积累量均呈逐渐增加趋势 (图2)。在不同施氮处理中,植株氮、磷、钾积累量在玉米拔节期至开花期随施氮水平的增加而增加,以N350处理最高;灌浆期至成熟期氮、磷、钾积累量则表现为随施氮水平的增加先增后降,其中在D1和D2密度下,以N210处理玉米氮、磷、钾积累量最高;在D3密度下,以N280处理最高。说明过量施氮有利于生育前期氮、磷、钾养分积累,而适宜的氮肥用量可使玉米生育中后期保持较高的氮、磷、钾积累速率,提高开花期至成熟期氮、磷、钾积累量。施氮水平相同时,苗期不同密度下氮、磷、钾积累量无明显差异,拔节期至成熟期以D2处理氮、磷、钾积累量最高,后依次为D3和D1处理。
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不同种植密度和施氮水平下玉米开花前后氮、磷、钾养分积累占整个植株氮、磷、钾积累总量比例 (图3) 表明,在同一密度下,随着施氮水平的增加,开花期至成熟期氮、磷、钾分配比例呈先增后降趋势。在D1和D2密度下,以N210处理开花期至成熟期氮、磷、钾分配比例最高,D3密度下以N280处理氮、磷、钾分配比例最高。施氮水平相同时,不同种植密度处理间开花期至成熟期氮、磷、钾分配比例无显著性差异 (P > 0.05)。
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对玉米开花前 (苗期—开花期) 和开花后 (开花期—成熟期) 地上部氮、磷、钾积累量与产量间进行相关性分析 (图4),结果表明,玉米花前和花后氮、磷、钾积累量与产量间均呈显著正相关,但开花后氮、磷、钾积累量线性方程的相关系数 (r = 0.9224**、0.8137**、0.7689**) 均高于花前 (r = 0.8852**、0.625**、0.7207**),说明玉米开花后群体氮、磷、钾积累量的提高与产量更为密切相关。
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由表2可知,种植密度对养分转运量影响显著,对养分转运率、转运养分对籽粒贡献率和积累养分对籽粒贡献率无显著影响;施肥处理对养分转运量、转运养分对籽粒贡献率和积累养分对籽粒贡献率影响显著,对氮磷钾转运率无显著影响,而两因素仅对氮磷钾转运量表现出显著的交互效应。在同一密度下,与不施氮肥处理 (N0) 相比,施氮显著提高了氮、磷、钾转运量 (P < 0.05),并随施氮水平的增加呈先增后降趋势,其中在D1和D2密度下以N210处理玉米氮、磷、钾转运量最高,D3密度下以N280处理最高。转运养分对籽粒贡献率表现为随施氮水平的增加呈先降后升趋势,而积累养分对籽粒贡献率则随施氮水平的增加先增后降,其中在D1和D2密度下最高值出现在N210处理,D3密度下最高值出现在N280处理。相同施氮水平时,以D2处理玉米氮、磷、钾转运量最高,后依次为D3和D1处理,其中D2处理平均氮、磷、钾转运量较D1和D3分别提高22.5%、13.6%、19.3%和16.7%、2.6%、12.1%,并与D1处理差异达显著水平 (P < 0.05)。而不同密度下氮磷钾转运率、转运养分对籽粒贡献率和积累养分对籽粒贡献率间无显著性差异。此外,不同施氮水平和密度下氮磷钾转运量、转运率、转运养分对籽粒贡献率和积累养分对籽粒贡献率无论增加或减少,均具有明显的一致性。
表 2 不同种植密度与施氮水平处理玉米氮、磷、钾转运及对籽粒的贡献率
Table 2. The translocation of N,P and K in maize under different plant density and nitrogen rate
密度
Density
(plant/hm2)氮水平
N level
(kg/hm2)转运量 (kg/hm2)
Translocation amount转运率 (%)
Translocation rate转运养分贡献率 (%)
Contribution rate of translocated nutrient积累养分贡献率 (%)
Contribution rate of accumulated nutrientN P K N P K N P K N P K D1 0 42.4 ± 2.4 c 9.8 ± 0.7 c 12.4 ± 1.1 c 46.6 ± 2.3 a 81.7 ± 2.9 a 15.1 ± 1.6 a 63.1 ± 0.6 a 57.2 ± 1.6 a 58.4 ± 4.7 a 36.9 ± 0.6 c 42.8 ± 1.6 c 41.6 ± 4.7 c 140 56.4 ± 1.0 b 13.1 ± 0.8 b 15.5 ± 0.9 b 47.9 ± 1.9 a 78.0 ± 1.9 a 14.6 ± 1.5 a 60.4 ± 1.0 b 54.9 ± 0.8 b 53.1 ± 4.3 b 39.6 ± 1.0 b 45.1 ± 0.8 b 46.9 ± 4.3 b 210 62.9 ± 2.0 a 16.1 ± 0.2 a 19.8 ± 0.6 a 47.9 ± 2.2 a 81.5 ± 1.6 a 15.6 ± 0.9 a 55.6 ± 0.2 c 51.7 ± 0.5 c 44.4 ± 2.8 c 44.4 ± 0.2 a 48.3 ± 0.5 a 55.6 ± 2.8 a 280 59.5 ± 1.3 ab 15.7 ± 0.8 a 19.5 ± 0.7 a 44.8 ± 1.2 a 80.7 ± 3.8 a 16.0 ± 0.9 a 55.8 ± 0.4 c 54.1 ± 0.7 b 46.7 ± 2.9 c 44.2 ± 0.4 a 45.9 ± 0.7 b 53.3 ± 2.9 a 350 58.9 ± 2.3 ab 15.2 ± 0.7 a 18.1 ± 1.6 a 43.4 ± 1.3 a 80.9 ± 2.4 a 14.6 ± 1.2 a 59.9 ± 0.4 b 54.6 ± 1.0 b 49.3 ± 3.8 c 40.1 ± 0.4 b 45.4 ± 1.0 b 50.7 ± 3.8 a 均值 Mean 56.0 ± 8.0 14.0 ± 2.6 17.1 ± 3.1 46.1 ± 2.0 80.6 ± 1.5 15.2 ± 0.6 59.0 ± 3.2 54.5 ± 2.0 50.4 ± 5.5 41.0 ± 3.2 45.5 ± 2.0 49.6 ± 5.5 D2 0 55.8 ± 2.2 c 11.8 ± 0.9 c 15.0 ± 0.7 c 57.3 ± 5.0 a 76.0 ± 2.4 a 15.9 ± 1.1 a 65.2 ± 2.1 a 58.4 ± 1.0 a 56.0 ± 0.6 a 34.8 ± 2.1 c 41.6 ± 1.0 d 44.0 ± 0.6 c 140 68.1 ± 2.0 b 15.3 ± 0.6 b 17.5 ± 0.5 b 55.1 ± 2.4 a 80.1 ± 1.8 a 17.2 ± 1.4 a 56.2 ± 0.4 b 55.1 ± 1.1 b 53.6 ± 1.4 b 43.8 ± 0.4 b 44.9 ± 1.1 c 46.4 ± 1.4 b 210 74.9 ± 1.4 a 17.8 ± 1.6 a 24.3 ± 1.3 a 53.8 ± 6.0 a 79.5 ± 2.2 a 16.9 ± 1.2 a 52.5 ± 1.4 c 49.9 ± 1.1 d 49.6 ± 1.1 c 47.5 ± 1.4 a 50.1 ± 1.1 a 50.4 ± 1.1 a 280 73.3 ± 4.6 a 17.5 ± 0.9 a 23.1 ± 0.6 a 52.3 ± 2.2 a 76.8 ± 4.3 a 18.0 ± 1.5 a 53.3 ± 1.3 c 52.4 ± 0.5 c 51.6 ± 1.6 bc 46.7 ± 1.3 a 47.6 ± 0.5 b 48.4 ± 0.5 ab 350 71.0 ± 2.3 ab 17.2 ± 0.5 a 21.9 ± 1.9 ab 49.3 ± 5.0 a 78.4 ± 1.3 a 16.8 ± 1.6 a 55.9 ± 0.9 bc 55.1 ± 1.4 b 53.8 ± 1.2 b 44.1 ± 0.9 ab 44.9 ± 1.4 c 46.2 ± 1.4 b 均值 Mean 68.6 ± 7.6 15.9 ± 2.5 20.4 ± 3.9 53.6 ± 3.0 78.2 ± 1.7 17.0 ± 0.8 56.6 ± 5.1 54.2 ± 3.2 52.9 ± 2.4 43.4 ± 5.1 45.8 ± 3.2 47.1 ± 2.4 D3 0 47.4 ± 1.7 d 11.3 ± 1.1 c 14.5 ± 0.5 c 50.0 ± 2.1 a 85.4 ± 2.1 a 14.6 ± 1.5 a 59.3 ± 1.6 a 60.5 ± 1.2 a 58.9 ± 1.8 a 40.7 ± 1.6 c 39.5 ± 1.2 c 41.1 ± 1.8 c 140 55.5 ± 1.2 c 14.6 ± 0.4 b 16.1 ± 0.9 b 47.5 ± 2.4 a 80.7 ± 2.4 a 15.0 ± 0.9 a 54.9 ± 0.9 b 56.3 ± 1.6 b 54.9 ± 1.9 b 45.1 ± 0.9 c 43.7 ± 1.6 b 45.1 ± 1.9 b 210 60.3 ± 1.4 b 17.0 ± 0.5 a 17.6 ± 1.1 b 47.4 ± 1.5 a 81.4 ± 2.8 a 14.8 ± 1.3 a 53.2 ± 0.8 bc 55.8 ± 1.2 b 50.9 ± 1.3 c 46.8 ± 0.8 ab 44.2 ± 1.2 b 49.1 ± 1.3 a 280 66.0 ± 2.3 a 17.4 ± 0.6 a 22.1 ± 1.4 a 48.5 ± 3.4 a 82.4 ± 3.1 a 15.6 ± 0.9 a 51.3 ± 2.0 c 51.5 ± 1.1 c 49.1 ± 1.6 c 48.7 ± 2.0 a 48.5 ± 1.1 a 50.9 ± 1.6 a 350 64.9 ± 1.7 a 17.3 ± 0.9 a 20.5 ± 1.0 a 48.8 ± 4.0 a 79.4 ± 3.5 a 16.1 ± 1.1 a 53.8 ± 1.4 bc 57.2 ± 1.4 b 52.0 ± 1.2 bc 46.2 ± 1.4 ab 42.8 ± 1.4 b 48.0 ± 1.2 ab 均值 Mean 58.8 ± 7.6 15.5 ± 2.6 18.2 ± 3.1 48.4 ± 1.1 81.9 ± 2.3 15.2 ± 0.6 54.5 ± 3.0 56.3 ± 3.2 53.2 ± 3.8 45.5 ± 3.0 43.7 ± 3.2 46.8 ± 3.8 方差分析 ANOVA 种植密度 Plant density (D) * * * NS NS NS NS NS NS NS NS NS 施氮量 N rate (N) ** ** ** NS NS NS * ** * * * * D × N * * * NS NS NS NS NS NS NS NS NS 注(Note):D1—6.0 × 104 plant/hm2; D2—7.5 × 104 plant/hm2; D3—9.0 × 104 plant/hm2. 同列数值后不同小写字母表示同一密度下各处理间在 5% 水平上差异显著 Values followed by different lowercase letters in the same column are significantly different at 5% level at the same density among different treatments. NS—不显著 Not significant; *—P < 0.05; **—P < 0.01. -
种植密度和施肥处理均对氮素吸收利用率、农学利用率和偏生产力影响显著,且两因素间表现出显著的交互作用 (图5)。总体而言,在相同密度下,氮素吸收利用率、农学利用率和偏生产力均随施氮水平的增加呈下降趋势,相同施氮量时,以D2处理玉米平均氮素吸收利用率、农学利用率和偏生产力最高,后依次为D3和D1处理。其中D2处理氮素吸收利用率、农学利用率和偏生产力均值较D1和D3处理分别高出8.9%、15.7%、12.8%和16.9%、16.7%、5.0%。
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对于禾谷类作物而言,产量构成因素之间的协调发展是实现高产的基础[15]。张仁和等[17]指出,增加穗粒数和穗密度扩大库容是提高玉米产量的重要途径,而适宜的种植密度有利于玉米单位面积穗数、穗粒数和粒重的协调发展[18]。同时适量施氮则可较好协调密植群体内玉米的形态生理特性,通过调控株型、维持光合性能、减少籽粒败育等保证生育后期相对较高的物质转化效率,最终获得较高的群体产量[19]。本研究中,提高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,穗粒数和百粒重呈下降趋势,当种植密度为75000株/hm2时获得最高产量。而在同一密度下,通过增施氮肥可以增加玉米穗粒数和百粒重,但当氮肥过量施用,玉米穗粒数和百粒重呈下降趋势。说明增密主要是截获更多的太阳辐射,使得群体生产力较高而增产[20],但超过适宜密度后,会引起玉米群体养分竞争加剧,影响叶片的光合生产能力,个体生长率、光合物质向籽粒分配率降低,使穗粒数和粒重的下降程度大于单位面积穗数的增加,最终导致玉米产量较最适密度群体有所降低[21];而适宜的氮肥用量可提高植株体内活性氧清除酶的代谢合成量[15],使叶片光合性能维持在较高水平,为籽粒形成提供充足的光合碳量,促进光合产物向籽粒的运转,使库容 (穗粒数) 和充实度 (粒重) 增加,进而增加玉米产量。另外,相关研究表明覆膜滴灌模式可较传统灌溉提高种植密度[22],而本研究在覆膜滴灌条件下确定的适宜密度也高于前人在该区域常规模式下确定的适宜密度[23],究其原因,主要是由于覆膜增加了土壤温度,促进玉米根系生长,改善根系在土壤中的分布和增加根系活性[24],同时滴灌施肥根据作物根系特征及需水规律精确调控土壤水分和养分,进一步促进了作物根系的生长,使作物处于最佳的生长状态,达到最优根冠比[25],抗倒伏能力增强,进而提高玉米种植密度。
氮、磷、钾养分积累是作物物质生产的基础,与作物产量密切相关。齐文增等[26]研究表明,籽粒产量的高低很大程度上取决于玉米生育后期养分积累与光合能力,姜涛[27]的研究也证实了提高玉米开花至成熟期养分积累是提高玉米产量的关键。但也有研究指出,虽然花前物质积累对玉米最终产量的贡献率低于花后,但玉米拔节至开花阶段是穗分化的重要时期,很大程度上影响穗分化质量,尤其是单位面积粒数的贡献更大[28]。可见在花前建立一个高效群体结构,对增加作物抗逆能力,提高玉米花后物质生产至关重要。本研究结果表明,增施氮肥可提高玉米开花期至成熟期氮、磷、钾积累量和玉米花后氮、磷、钾养分所占比例,并随施氮水平的增加呈先增后降趋势,而增密仅提高了玉米地上部氮、磷、钾总积累量,对玉米开花前后氮、磷、钾养分分配比例影响不显著。说明适宜的氮肥用量使玉米在营养体建成期间获得高效的群体结构,同时可提高玉米花后植株光合生理活性及花后保绿,促进玉米养分吸收能力[29],而氮肥过量施用则导致玉米生育前期生长过旺,生育后期叶片早衰及光合能力下降,最终使成熟期养分积累量下降[30]。而在不同种植密度条件下玉米地上部养分积累量随种植密度的增加先增后降,这与增密后群体生产力增益大于单株生产力损失有关。
当玉米进入灌浆期,植株吸收的养分主要供给穗部,同时营养体中的养分也大量向穗部转运,但这两部分营养源对籽粒养分贡献率在不同品种特性、生态环境及栽培措施条件下存在很大差异[12, 17, 19, 21, 26]。较高的产量需要叶片保持持久的光合活性,而这依赖于花后养分积累和转运的平衡[31];同时,养分累积、转运和物质生产相互联系。因此,提高花前营养体养分转运量和花后养分积累均有利于提高玉米产量[32]。本研究结果表明,氮肥与密度互作均显著影响春玉米养分向籽粒的转运量,并随种植密度和施氮水平的增加先增后降,其中以D2和N210条件下氮、磷、钾转运量最高。说明适宜的氮肥用量或群体结构均可促进玉米花前储存更多的养分向籽粒转运[33]。本研究还发现,施氮降低玉米转运养分对籽粒贡献率的同时,提高了玉米花后积累养分对籽粒贡献率,并随施氮水平的增加先增后降。说明氮肥供应不足会促使营养体中养分加速运出,而氮肥供应过量则会导致营养体氮素代谢过旺,两者均会提高营养体花前储藏养分对籽粒养分贡献率,而花前储藏养分贡献率过高则会引起叶片衰老进程加快、光合能力下降[34],进而限制产量的提高。
养分利用率是衡量施肥合理性的指标之一,相关研究表明,适宜的群体结构可提高氮肥利用效率,但随着氮肥用量增加,氮素利用效率呈下降趋势[35]。往往作物获得最高产量和经济效益的施肥量,其肥料利用效率并不是最高[12, 17]。本研究结果也表明,随着种植密度的增加,玉米氮肥利用效率呈先升高后降低的趋势,其中种植密度为75000株/hm2时氮素利用效率最高。说明适宜的群体结构通过增加养分积累而促进了肥料利用效率的提高。在相同密度下,与N140处理相比,N210处理的氮素吸收利用率、农学利用率和偏生产力均有所下降,而产量却显著提高,主要原因是N210处理氮素投入量远高于N140处理;而与N280和N350处理相比,N210处理氮肥利用效率和产量均有所提高。可见,施氮不足虽然可使氮肥利用效率维持在较高水平,但其代价是严重损耗土壤肥力;而过量施氮不仅无法增加产量,同时氮肥利用效率也显著降低,收益下降,还会影响玉米品质[36],对环境也会造成严重的破坏[37]。因此合理的种植密度与适当控制氮肥用量,可促进玉米氮素的吸收利用,增加籽粒产量,提高氮肥利用率,进而实现玉米高产高效和环境友好的目标。
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在东北半干旱区玉米覆膜滴灌模式下,当种植密度达到75000株/hm2,施氮量达到210 kg/hm2时,玉米产量最高,植株对氮、磷、钾的总吸收量和转运量均达到最高值,并且氮素利用效率也维持在较高水平。当超过该密度和施氮量时,会导致产量降低以及氮肥利用率显著下降;而密度过低或施氮不足则会降低玉米产量。因此,密度为75000株/hm2、施氮量210 kg/hm2可作为东北半干旱区覆膜滴灌下高产、节氮的最优栽培模式。
覆膜滴灌下氮肥与种植密度互作对东北春玉米产量、群体养分吸收与转运的调控效应
Interaction between nitrogen fertilizer and plant density on nutrient absorption, translocation and yield of spring maize under drip irrigation in Northeast China
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摘要:
【目的】 和谐的氮素和密度互作是提高东北玉米产量和效益的关键。研究覆膜滴灌条件下氮肥用量、种植密度及其互作对春玉米产量、养分吸收转运及利用效率的影响,以期为东北半干旱区春玉米高产高效栽培提供理论依据。 【方法】 2016—2017年,在吉林省西部半干旱区乾安县开展田间试验,以紧凑型玉米品种农华101为供试材料,在覆膜滴灌条件下,分别设置氮肥用量 (0、140、210、280和350 kg/hm2,分别以N0、N140、N210、N280和N350表示) 和种植密度 (6.0 × 104、7.5 × 104和9.0 × 104株/hm2,分别以D1、D2和D3表示) 2个因子,分析不同处理玉米地上部群体养分积累动态、转运与分配特征、产量及氮肥利用效率。 【结果】 施氮和增加种植密度均可显著增加玉米产量,并随施氮水平和种植密度的增加呈先增后降趋势,以D2和N210条件下玉米产量最高。在相同种植密度下,玉米苗期至开花期群体氮、磷、钾积累量均随施氮水平的增加而增加,而在灌浆期至成熟期则表现为随施氮水平的增加先增后降。在相同施氮水平下,玉米群体氮、磷、钾积累量均以D2密度下最高。不同施氮量与种植密度组合中,以D2和N210条件下玉米成熟期群体氮、磷、钾积累量最高。与不施氮肥处理相比,施氮提高了玉米开花后氮、磷、钾积累量占总生育期积累量比例,并随施氮水平的增加先增后降,而不同种植密度间玉米开花后氮、磷、钾积累量占总生育期积累量比例差异未达显著水平 (P > 0.05)。玉米养分转运量随施氮水平和种植密度的增加先增后降,以D2和N210条件下玉米养分转运量最高,而不同种植密度间养分转运率、转运养分贡献率和花后积累养分贡献率均无显著性差异。随施氮水平的增加,不同种植密度下氮素吸收利用率、农学利用率和偏生产力均呈下降趋势,其中以D2密度下氮素吸收利用率、农学利用率和偏生产力维持在较高水平。相关分析结果表明,玉米开花前后氮、磷、钾素积累量与籽粒产量均呈显著或极显著正相关 (r = 0.6250~0.9224),其中开花后氮、磷、钾积累量与产量的相关性高于开花前。 【结论】 合理的种植密度和施氮水平提高了玉米花后养分积累与分配比例,促进养分转运量和花后积累养分对籽粒贡献率的协同提高,进而提高了玉米产量和氮肥利用效率。综合考虑玉米产量、养分积累与转运及氮素利用效率等因素,在东北半干旱区覆膜滴灌条件下,以种植密度为75000株/hm2,施氮量为210 kg/hm2较为适宜。 Abstract:【Objectives】 An optimum interaction between nitrogen fertilizer and plant density is pertinent to increasing the growth and productivity of maize in Northeast China. This study aimed at investigating the influence of nitrogen application rate, plant density and their interaction on maize yield, nutrient absorption, translocation and utilization efficiency under drip irrigation and plastic mulching condition. The research could provide theoretical basis for high yield and high efficiency cultivation of spring maize in semi-arid region of Northeast China. 【Methods】 The field experiment was conducted using compact ‘Nonghua101’maize cultivar in Qian’an County in western Jilin Province in 2016 and 2017. The imposed nitrogen rates included 0, 140, 210, 280 and 350 kg/hm2 (N0, N140, N210, N280 and N350 respectively) and plant densities were 6.0 × 104, 7.5 × 104 and 9.0 × 104 plants/hm2 (D1, D2 and D3 respectively). The dynamics of aboveground nutrient accumulation maize where translocation, yield and nitrogen utilization efficiency with different plant population were analyzed. 【Results】 The results showed that maize yield increased but later decreased with increasing N- application rate and plant density. The highest yield was obtained from D2 under nitrogen rate of N210. Under the same plant density, the accumulation of N, P and K increased from seedling stage to flowering stage, however, this surged initially and then declined from filling to mature stage with increasing nitrogen application rate. Accumulated N, P and K of maize was highest with D2 × N210 at the matured stage than other treatment combinations under the same nitrogen application. Compared with no nitrogen treatment, maize N, P and K composition after flowering stage was increased at first, however these later decreased with increasing N-rate, but there was no significant differences in the trends under different plant density. Nutrient translocation amount of maize increased but later decreased with increasing N application rate and plant density, and it was highest with D2 × N210. There were not significantly different in nutrient translocation rate, contribution rate of translocated nutrient and contribution rate of accumulated nutrient after flowering stage under different plant density. The N-utilization efficiency, agronomic efficiency and partial factor productivity decreased with increased rate of applied nitrogen at varied plant density, with the highest values obtained under D2. Correlation analysis showed that the relationship between yield and the amounts of N, P and K accumulated was significant or highly significant (r = 0.6250−0.9224) around flowering stage, whereas higher values were obtained before the flowering stage. 【Conclusions】 The reasonable plant density and nitrogen application level enhance the proportions of nutrient accumulation and distribution after flowering stage of maize, promote nutrient translocation amount and contribution rate of accumulation nutrients after flowering stage synergistically, improve higher yield and nitrogen utilization efficiency of maize. Considering maize yield, nutrient accumulation and translocation, and nitrogen utilization efficiency under drip irrigation system and mulching condition, the plant density of 75000 plant/hm2 and nitrogen application rate of 210 kg/hm2 appear optimum in semi-arid region of Northeast China. -
Key words:
- nitrogen rate /
- plant density /
- spring maize /
- nutrient partitioning /
- nitrogen utilization efficiency /
- semi-arid area /
- yield
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表 1 不同种植密度和施氮水平处理玉米产量与构成因素
Table 1. Maize yield and its components under varied plant density and nitrogen application rates
密度 Density 氮水平 N level 产量 Yield (kg/hm2) 穗数 Ear number per 穗粒数 Kernel 百粒重 100-kernel weight (g) 收获指数 Harvest index D1 N0 7672 ± 336 d 58000 ± 300 a 467.2 ± 7.6 d 28.6 ± 0.7 c 0.49 ± 0.01 c N140 10126 ± 207 c 58000 ± 300 a 544.1 ± 10.0 c 32.1 ± 0.1 b 0.50 ± 0.02 ab N210 11265 ± 181 a 59000 ± 1200 a 587.9 ± 4.5 a 34.6 ± 0.7 a 0.51 ± 0.01 a N280 11077 ± 222 a 60000 ± 1000 a 582.2 ± 5.6 ab 34.2 ± 0.5 a 0.50 ± 0.01 ab N350 10683 ± 270 b 60000 ± 300 a 568.5 ± 10.5 b 33.8 ± 0.6 a 0.50 ± 0.01 bc 均值 Mean 10165 ± 1460 59000 ± 1000 550.0 ± 49.3 32.7 ± 2.5 0.50 ± 0.01 D2 N0 8571 ± 252 d 74000 ± 1400 a 421.0 ± 9.4 c 26.6 ± 0.8 c 0.48 ± 0.01 b N140 11462 ± 289 c 74000 ± 900 a 501.4 ± 3.7 b 30.2 ± 0.9 b 0.50 ± 0.02 a N210 12662 ± 277 a 75000 ± 1100 a 550.0 ± 6.8 a 32.6 ± 0.9 a 0.52 ± 0.01 a N280 12428 ± 190 ab 75000 ± 700 a 545.1 ± 3.0 a 32.1 ± 1.6 a 0.52 ± 0.01 a N350 12139 ± 177 b 74000 ± 700 a 542.3 ± 10.4 a 31.6 ± 1.1 ab 0.51 ± 0.01 a 均值 Mean 11452 ± 1672 74000 ± 500 512.0 ± 54.4 30.6 ± 2.4 0.51 ± 0.01 D3 N0 8493 ± 286 d 88000 ± 2000 a 397.3 ± 6.6 c 24.3 ± 0.9 c 0.48 ± 0.02 b N140 10878 ± 307 c 87000 ± 1200 a 461.3 ± 8.7 b 29.1 ± 0.3 b 0.49 ± 0.01 ab N210 11475 ± 157 b 88000 ± 1500 a 470.3 ± 5.8 b 29.2 ± 0.5 b 0.51 ± 0.01 a N280 12305 ± 355 a 86000 ± 700 a 493.7 ± 7.2 a 30.7 ± 0.8 a 0.51 ± 0.01 a N350 12014 ± 110 ab 87000 ± 1500 a 473.6 ± 6.5 b 30.2 ± 0.4 a 0.50 ± 0.01 a 均值 Mean 11033 ± 1521 87000 ± 800 459.2 ± 36.6 28.7 ± 2.6 0.50 ± 0.01 方差分析 ANOVA 种植密度 Plant density (D) ** ** ** ** NS 施氮量 N rate (N) ** NS ** ** NS D × N ** NS * NS NS 注(Note):D1—6.0 × 104 plant/hm2;D2—7.5 × 104 plant/hm2; D3—9.0 × 104 plant/hm2. 同列数值后不同小写字母表示同一密度下各处理间在 5% 水平上差异显著 Values followed by different lowercase letters in the same column are significantly different at 5% level at the same density among different treatments; NS—不显著 Not significant; *—P < 0.05; **—P < 0.01. 表 2 不同种植密度与施氮水平处理玉米氮、磷、钾转运及对籽粒的贡献率
Table 2. The translocation of N,P and K in maize under different plant density and nitrogen rate
密度
Density
(plant/hm2)氮水平
N level
(kg/hm2)转运量 (kg/hm2)
Translocation amount转运率 (%)
Translocation rate转运养分贡献率 (%)
Contribution rate of translocated nutrient积累养分贡献率 (%)
Contribution rate of accumulated nutrientN P K N P K N P K N P K D1 0 42.4 ± 2.4 c 9.8 ± 0.7 c 12.4 ± 1.1 c 46.6 ± 2.3 a 81.7 ± 2.9 a 15.1 ± 1.6 a 63.1 ± 0.6 a 57.2 ± 1.6 a 58.4 ± 4.7 a 36.9 ± 0.6 c 42.8 ± 1.6 c 41.6 ± 4.7 c 140 56.4 ± 1.0 b 13.1 ± 0.8 b 15.5 ± 0.9 b 47.9 ± 1.9 a 78.0 ± 1.9 a 14.6 ± 1.5 a 60.4 ± 1.0 b 54.9 ± 0.8 b 53.1 ± 4.3 b 39.6 ± 1.0 b 45.1 ± 0.8 b 46.9 ± 4.3 b 210 62.9 ± 2.0 a 16.1 ± 0.2 a 19.8 ± 0.6 a 47.9 ± 2.2 a 81.5 ± 1.6 a 15.6 ± 0.9 a 55.6 ± 0.2 c 51.7 ± 0.5 c 44.4 ± 2.8 c 44.4 ± 0.2 a 48.3 ± 0.5 a 55.6 ± 2.8 a 280 59.5 ± 1.3 ab 15.7 ± 0.8 a 19.5 ± 0.7 a 44.8 ± 1.2 a 80.7 ± 3.8 a 16.0 ± 0.9 a 55.8 ± 0.4 c 54.1 ± 0.7 b 46.7 ± 2.9 c 44.2 ± 0.4 a 45.9 ± 0.7 b 53.3 ± 2.9 a 350 58.9 ± 2.3 ab 15.2 ± 0.7 a 18.1 ± 1.6 a 43.4 ± 1.3 a 80.9 ± 2.4 a 14.6 ± 1.2 a 59.9 ± 0.4 b 54.6 ± 1.0 b 49.3 ± 3.8 c 40.1 ± 0.4 b 45.4 ± 1.0 b 50.7 ± 3.8 a 均值 Mean 56.0 ± 8.0 14.0 ± 2.6 17.1 ± 3.1 46.1 ± 2.0 80.6 ± 1.5 15.2 ± 0.6 59.0 ± 3.2 54.5 ± 2.0 50.4 ± 5.5 41.0 ± 3.2 45.5 ± 2.0 49.6 ± 5.5 D2 0 55.8 ± 2.2 c 11.8 ± 0.9 c 15.0 ± 0.7 c 57.3 ± 5.0 a 76.0 ± 2.4 a 15.9 ± 1.1 a 65.2 ± 2.1 a 58.4 ± 1.0 a 56.0 ± 0.6 a 34.8 ± 2.1 c 41.6 ± 1.0 d 44.0 ± 0.6 c 140 68.1 ± 2.0 b 15.3 ± 0.6 b 17.5 ± 0.5 b 55.1 ± 2.4 a 80.1 ± 1.8 a 17.2 ± 1.4 a 56.2 ± 0.4 b 55.1 ± 1.1 b 53.6 ± 1.4 b 43.8 ± 0.4 b 44.9 ± 1.1 c 46.4 ± 1.4 b 210 74.9 ± 1.4 a 17.8 ± 1.6 a 24.3 ± 1.3 a 53.8 ± 6.0 a 79.5 ± 2.2 a 16.9 ± 1.2 a 52.5 ± 1.4 c 49.9 ± 1.1 d 49.6 ± 1.1 c 47.5 ± 1.4 a 50.1 ± 1.1 a 50.4 ± 1.1 a 280 73.3 ± 4.6 a 17.5 ± 0.9 a 23.1 ± 0.6 a 52.3 ± 2.2 a 76.8 ± 4.3 a 18.0 ± 1.5 a 53.3 ± 1.3 c 52.4 ± 0.5 c 51.6 ± 1.6 bc 46.7 ± 1.3 a 47.6 ± 0.5 b 48.4 ± 0.5 ab 350 71.0 ± 2.3 ab 17.2 ± 0.5 a 21.9 ± 1.9 ab 49.3 ± 5.0 a 78.4 ± 1.3 a 16.8 ± 1.6 a 55.9 ± 0.9 bc 55.1 ± 1.4 b 53.8 ± 1.2 b 44.1 ± 0.9 ab 44.9 ± 1.4 c 46.2 ± 1.4 b 均值 Mean 68.6 ± 7.6 15.9 ± 2.5 20.4 ± 3.9 53.6 ± 3.0 78.2 ± 1.7 17.0 ± 0.8 56.6 ± 5.1 54.2 ± 3.2 52.9 ± 2.4 43.4 ± 5.1 45.8 ± 3.2 47.1 ± 2.4 D3 0 47.4 ± 1.7 d 11.3 ± 1.1 c 14.5 ± 0.5 c 50.0 ± 2.1 a 85.4 ± 2.1 a 14.6 ± 1.5 a 59.3 ± 1.6 a 60.5 ± 1.2 a 58.9 ± 1.8 a 40.7 ± 1.6 c 39.5 ± 1.2 c 41.1 ± 1.8 c 140 55.5 ± 1.2 c 14.6 ± 0.4 b 16.1 ± 0.9 b 47.5 ± 2.4 a 80.7 ± 2.4 a 15.0 ± 0.9 a 54.9 ± 0.9 b 56.3 ± 1.6 b 54.9 ± 1.9 b 45.1 ± 0.9 c 43.7 ± 1.6 b 45.1 ± 1.9 b 210 60.3 ± 1.4 b 17.0 ± 0.5 a 17.6 ± 1.1 b 47.4 ± 1.5 a 81.4 ± 2.8 a 14.8 ± 1.3 a 53.2 ± 0.8 bc 55.8 ± 1.2 b 50.9 ± 1.3 c 46.8 ± 0.8 ab 44.2 ± 1.2 b 49.1 ± 1.3 a 280 66.0 ± 2.3 a 17.4 ± 0.6 a 22.1 ± 1.4 a 48.5 ± 3.4 a 82.4 ± 3.1 a 15.6 ± 0.9 a 51.3 ± 2.0 c 51.5 ± 1.1 c 49.1 ± 1.6 c 48.7 ± 2.0 a 48.5 ± 1.1 a 50.9 ± 1.6 a 350 64.9 ± 1.7 a 17.3 ± 0.9 a 20.5 ± 1.0 a 48.8 ± 4.0 a 79.4 ± 3.5 a 16.1 ± 1.1 a 53.8 ± 1.4 bc 57.2 ± 1.4 b 52.0 ± 1.2 bc 46.2 ± 1.4 ab 42.8 ± 1.4 b 48.0 ± 1.2 ab 均值 Mean 58.8 ± 7.6 15.5 ± 2.6 18.2 ± 3.1 48.4 ± 1.1 81.9 ± 2.3 15.2 ± 0.6 54.5 ± 3.0 56.3 ± 3.2 53.2 ± 3.8 45.5 ± 3.0 43.7 ± 3.2 46.8 ± 3.8 方差分析 ANOVA 种植密度 Plant density (D) * * * NS NS NS NS NS NS NS NS NS 施氮量 N rate (N) ** ** ** NS NS NS * ** * * * * D × N * * * NS NS NS NS NS NS NS NS NS 注(Note):D1—6.0 × 104 plant/hm2; D2—7.5 × 104 plant/hm2; D3—9.0 × 104 plant/hm2. 同列数值后不同小写字母表示同一密度下各处理间在 5% 水平上差异显著 Values followed by different lowercase letters in the same column are significantly different at 5% level at the same density among different treatments. NS—不显著 Not significant; *—P < 0.05; **—P < 0.01. -
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