摘要
为实时无损监测大田烤烟钾素积累状况,以烤烟品种K326为试验材料,研究不同施氮量条件下成熟期烤烟叶层间钾积累量变化规律及其与冠层光谱参数间的相关关系。结果显示:烟株上层钾积累量除少数波段与光谱反射率相关外,大部分波段两者不相关,中下层钾积累量与可见光波段光谱反射率呈显著负相关,与近红外波段呈显著正相关。适用于不同叶层钾积累量估算的最优光谱参数并非完全一致,其中上层、中层、上中层钾积累量估算的最优光谱参数为比值植被指数RVI(810,680),而下层、中下层、上中下层植株钾积累量则与红边振幅(DλRed)相关性最高。建立的烤烟中层、下层、上中层、中下层、植株叶钾积累量的估算模型分别为:y=-0.002
钾是烤烟生长发育必需的营养元素之一,能促进烤烟光合作用,提高植株的抗寒性、抗旱性及抗病虫害能
随着光谱分析技术的发展,国内外研究者利用光谱技术实现了对苹
本研究考察打顶后烤烟钾积累量的时空分布特征,并分析烤烟各叶层钾积累量与冠层光谱参数间的相关关系,构建出烤烟不同叶层钾积累量的估算模型,旨在为大田烤烟各叶层钾素营养诊断及精准管理提供科学依据。
试验分别于2010年和2021年在广东省烟叶主产区之一的始兴县马市镇进行,供试品种为烤烟K326,试验地为旱坡地,前作为花生,土壤pH 7.40,有机质15.03 g/kg,全氮0.98 g/kg,碱解氮84.04 mg/kg,全磷0.56 g/kg,速效磷6.70 mg/kg,全钾25.91 g/kg,速效钾100.03 mg/kg。
设4个氮肥量处理,分别为纯氮0(N0)、105 kg/h
1)冠层光谱的测定。采用MSR-16R 型多光谱辐射仪(美国 Cropscan 公司)测定冠层光谱,MSR-16R 型多光谱辐射仪主要技术参数如
参数 Parameter | 波段/nm Waveband | |||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
460 | 510 | 560 | 610 | 660 | 680 | 710 | 760 | 810 | 870 | 950 | 1 100 | 1 220 | 1 300 | 1 500 | 1 650 | |
中心波长 Center wavelength | 460.4 | 511.4 | 560.9 | 610.7 | 661.7 | 682.2 | 711.4 | 761.2 | 812.6 | 871.6 | 951.2 | 1 099.5 | 1 222.8 | 1 301.3 | 1 500.2 | 1 669.0 |
带宽 Band width | 6.8 | 7.7 | 9.4 | 10.3 | 11.6 | 11.5 | 12.4 | 10.6 | 11.4 | 12.2 | 13.3 | 16.5 | 11.4 | 12.2 | 14.8 | 200.0 |
2)叶层的分层方法。于打顶定高后,参照王纪华

图1 烤烟叶层分层方法
Fig.1 Leaf layers of flue-cured tobacco
1.打顶位置 Place of tip pruning;2.上层 Upper layer;3.中层 Middle layer;4.下层 Lower layer.
3)钾含量及钾积累量的测定。光谱测定后,每小区随机取3株烟,用园艺剪分别剪下各叶层叶片,经105 ℃杀青30 min,70 ℃烘至恒质量后,测定各叶层叶片干物质量(LLDW)。粉碎机粉样,过孔径0.25 mm网筛,装入自封袋,用于钾含量(质量分数)的测定。采用火焰光度
(1) |
参照前人植物光谱参数计算方法,结合辐射计波段构成(
光谱参数 Spectral parameter | 缩写 Abbreviation | 计算方法 Calculation method |
---|---|---|
比值植被指 | RVI | RNIR/RR |
差值植被指 | DVI | RNIR-RR |
归一化植被指 | NDVI | |
增强植被指 | EVI | |
红边振 | DλRed | (R760R710)/50 |
土壤调整植被指 | SAVI | |
优化土壤调节植被指 | OSAVI |
采用Excel 2010进行数据处理和图形绘制,采用Matlab 2012和SPSS 12.0统计软件进行数据分析。
由

图2 施氮量对烤烟叶钾积累量时空分布的影响
Fig.2 The potassium accumulation spatial-temporal distribution of flue-cured tobacco leaf with different nitrogen application rate
施氮量对烟叶钾积累量有较大影响,成熟前期不同施氮量下钾积累量表现为N2>N3>N1>N0;成熟中后期(5月29日之后)烟叶钾积累量随施氮量的提高而增加。一般认为随着氮素量的提高,烟叶中的钾含量呈升高趋势,成熟前期出现N3处理钾积累量小于N2处理,可能跟始兴烟区前期干旱(数据未列出)导致氮素效应推迟有关。
对烤烟叶层进行多种组合(上层、中层、下层、上中层、中下层和上中下层),以便于分析烤烟钾积累量在不同叶层间的时空分布特征及其与冠层光谱反射率的相关性。如

图3 烤烟各叶层钾积累量与冠层光谱反射率的相关关系
Fig.3 Correlation relation between potassium accumulation distribution at each layer and spectra reflectance of flue-cured tobacco leaf
由
叶层 Leaf layers | 比值指数 RVI (810,680) | 差值指数 DVI (810,680) | 归一化植被 指数 NDVI(810,680) | 增强植被指数 EVI810 | 土壤调整植被指数 SAVI | 改进土壤调节植被指数 OSAVI | 红边 振幅 DλRed |
---|---|---|---|---|---|---|---|
上层 Upper layer |
0.6 |
0.5 |
0.5 | 0.38 |
0.5 |
0.5 | 0.29 |
中层 Middle layer |
0.9 |
0.8 |
0.8 |
0.8 |
0.8 |
0.8 |
0.8 |
下层 Lower layer |
0.5 |
0.5 |
0.4 |
0.6 |
0.4 |
0.5 |
0.7 |
上中层 Upper-middle layer |
0.8 |
0.7 |
0.7 |
0.6 |
0.7 |
0.7 | 0.58 |
中下层 Middle-lower layer |
0.7 |
0.7 |
0.6 |
0.7 |
0.6 |
0.7 |
0.9 |
整株 Whole plant |
0.9 |
0.8 |
0.8 |
0.8 |
0.8 |
0.8 |
0.9 |
注: *表示显著相关(P<0.05);**表示极显著相关(P<0.01)。下同。Note:* indicates significant correlation at the level of 0.05;**indicates significant correlation at the level of 0.01.The same as below.
2010年试验烟叶成熟期5次采样获取的1 800组光谱数据和540组钾积累量数据用于模型构建,2021年于打顶后10、30 d随机选取了原试验田附近2块烟田各10株烟进行冠层光谱数据采集,所获得120组光谱数据和36组钾数据用于模型验证。由
叶层 Leaf layers | 光谱参数 Spectral parameter | 模型建立 Model calibration | 模型验证 Model validation | ||
---|---|---|---|---|---|
回归模型 Regression model | 决定系数 | 决定系数 | 回归剩余残差 RMSE | ||
上层 Upper layer | RVI(810,680) |
y=-0.0019 | 0.357 | / | / |
中层 Middle layer | RVI(810,680) |
y=-0.002 |
0.90 |
0.91 | 0.213 |
下层 Lower layer | DλRed |
y=8.8736 |
0.61 |
0.63 | 0.301 |
上中层 Upper-middle layer | RVI(810,680) |
y=0.0856 |
0.74 |
0.73 | 0.314 |
中下层 Middle-lower layer | DλRed |
y=6.6558 |
0.82 |
0.84 | 0.272 |
整株 Whole plant | DλRed |
y=0.2803 |
0.93 |
0.93 | 0.216 |
植物冠层的光谱特性在可见光波段主要受叶绿素影
光谱特征参数将简单的单波段光谱信息转化为组合波段信
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