Early detection of canopy nitrogen deficiency in winter wheat (Triticum aestivum L.) based on hyperspectral measurement of canopy chlorophyll status

Figures & data

Figure 1  Sketch map of canopy layers at elongation (left) and anthesis (right) stages. At anthesis, the unbroken line is for the modelling experiment, and the broken line for the validation experiment.

Figure 2  Leaf chlorophyll content (mg g⁻¹) in different canopy layers at elongation and anthesis of both erectophile and planophile plant types. Data for erectophile and planophile plant types are averaged from eight erectophile plant type cultivars and seven planophile plant type cultivars, respectively. Letters A, B and C following lines at elongation indicates significance at P < 0.01, and letters A, B and C following lines at anthesis indicates significance at P < 0.0001.

Table 1  Canopy chlorophyll density (CCD, g m⁻²) in different layers at elongation and anthesis.

		Erectophile plant type								Planophile plant type
		4P3	9128	95128	98-100	CA16	CY66	J411	LX201	9428	9507	LA17	LK2	LK502	ND3214	ZM9
	Layer 1	0.71±0.09	1.00 ±0.15	0.93 ±0.09	0.95 ±0.15	1.06±0.08	0.97±0.03	0.79±0.03	0.95±0.01	1.35±0.10	1.08±0.12	1.04±0.06	1.21±0.08	1.07±0.03	1.15± 0.06	1.13±0.04
Elongation	Layer 2	1.02±0.14	0.95±0.09	1.06±0.07	1.06±0.15	1.33±0.08	1.23±0.08	0.97±0.06	1.28±0.06	1.11±0.03	1.08±0.12	1.29±0.03	1.43±0.19	1.02±0.02	1.38± 0.12	1.05±0.14
	Layer 3	0.39±0.05	0.66±0.12	0.47±0.02	0.74±0.13	0.72±0.06	0.72±0.01	0.57±0.03	0.55±0.03	0.63±0.06	0.45±0.02	0.50±0.02	0.70±0.08	0.45±0.05	0.57± 0.11	0.47±0.07
	Layer 1	1.19±0.19	0.96±0.12	1.21±0.11	1.19±0.10	1.18±0.09	1.30±0.28	1.32±0.05	0.91±0.06	1.48±0.18	1.34±0.18	1.42±0.11	1.75±0.29	1.74±0.25	1.56± 0.25	1.65±0.29
Anthesis	Layer 2	1.35±0.04	1.03±0.12	1.32±0.11	1.34±0.17	1.47±0.09	1.62±0.23	1.33±0.02	1.13±0.16	1.64±0.08	1.49 ±0.20	1.47±0.16	1.79±0.33	1.76±0.05	1.86± 0.11	1.68±0.17
	Layer 3	0.88±0.06	0.89±0.05	0.77±0.06	0.80±0.03	0.88±0.07	0.95±0.11	0.78±0.07	0.80±0.06	0.80±0.17	0.80±0.13	0.78±0.20	0.91±0.14	0.72±0.10	0.73± 0.15	0.85±0.23
The number after±represents standard error.

Figure 3  Canopy chlorophyll density (CCD, g m⁻²) in different layers at elongation and anthesis of both erectophile plant type and planophile plant type. Data for erectophile and planophile plant types are averaged from eight erectophile plant type cultivars and seven planophile plant type cultivars, respectively. Letters A, B and C following lines at elongation indicates significance at P < 0.0001, and letters A and B following lines at anthesis indicates significance at P < 0.01. The same letters between layers show no significant difference.

Table 2  The percentage of CCD (canopy chlorophyll density, g m⁻²) in each layer of the whole canopy of erectophile and planophile plant types at elongation and anthesis.

	Erectophile plant type		Planophile plant type
	Elongation	Anthesis	Elongation	Anthesis
Layer 1	34.9%	35.4%	40.0%	38.1%
Layer 2	42.1%	39.7%	41.3%	42.5%
Layer 3	23.0%	24.9%	18.7%	19.4%

Table 3  The coefficient of determination (R²) between CCD (canopy chlorophyll density, g m⁻²) and combined CCD (CCCD, g m⁻²) and DVI (difference vegetation index) in the modelling experiment.

	DVI
	Elongation	Anthesis
CCD in layer 1 (or CCCD1)	0.59**	0.55**
CCD in layer 2	0.71**	0.68**
CCD in layer 3	0.30**	0.52**
CCCD1 + 2	0.73**	0.70**
CCCD1 + 2+3	0.80**	0.74**
** indicates significant regression at P < 0.01.

Figure 4  Comparison of: A, observed CCCD₁ and estimated CCCD₁; B, observed CCCD_{1 + 2} and estimated CCCD_{1 + 2}; and C, observed CCCD_{1 + 2+3} and estimated CCCD_{1 + 2+3} at elongation of the validation experiment. CCCD is combined canopy chlorophyll density. F_0.0(1,22)=0.515.

Table 4  Models established based on the relationship between DVI and CCCD_n. DVI is difference vegetation index; CCCD (g m⁻²) is combined canopy chlorophyll density. The n in CCCD is 1, 1 + 2 and 1 + 2+3, respectively. Data are from the modelling experiment, and data from both planophile and erectophile are used together to develop the model. Chl, chlorophyll; N, nitrogen. The units of leaf N content, leaf chlorophyll concentration are mg g⁻¹ dry leaf weight and mg g⁻¹ fresh leaf weight, respectively.

Elongation		Anthesis
Equations	R^2	Equations	R^2
CCCD1=0.031DVI+0.051(58.3≥Ntop≥41.6, 3.49≥Chltop≥2.12, 43.4≥DVI≥24.0, and 1.53≥CCCD1≥0.59)	0.59**	CCCD1=0.055DVI-0.449(55.3≥Ntop≥46.7, 5.27≥Chltop≥3.04, 45.3≥DVI≥23.5, and 2.23 ≥ CCCD1≥0.72)	0.55**
CCCD1 + 2=0.038DVI-0.071(55.3≥Nmid≥36.2, 3.29≥Chlmid≥1.21, 43.4≥DVI≥24.0, and 1.50≥CCCD1 + 2≥0.72)	0.73**	CCCD1 + 2=0.064DVI-0.636(52.7≥Nmid≥43.2, 4.49≥Chlmid≥2.18, 45.3≥DVI≥23.5, and 2.32≥CCCD1 + 2≥0.79)	0.70**
CCCD1 + 2+3=0.036DVI-0.117(47.4≥Nlow≥32.5, 2.78≥Chllow≥0.89, 43.4≥DVI≥24.0, and 1.41≥CCCD1 + 2+3 ≥ 0.64)	0.80**	CCCD1 + 2+3=0.062DVI-0.710(43.2≥Nlow≥34.2, 3.99≥Chllow≥1.29, 45.3≥DVI≥23.5, and 2.28 ≥ CCCD1 + 2+3≥ 0.80)	0.74**
** indicates significant regression at P < 0.01.