Influence of Different Retting on Hemp Stem and Fiber Characteristics Under the East of France Climate Conditions

Figures & data

Figure 1. Daily weather conditions (minimum and maximum temperatures and rainfall) during the eight weeks of dew-retting from the cutting in October (W0) to the last retting week in December 2020 (W8).

Figure 2. Stem distribution in the different transformation stage.

Table 1. Stem characteristics and confidence intervals estimated for different retting methods and stages based on data from multiple retting durations.

Method	Stage	Diameter (mm)	Mass (g)
Dew	After-retting	7.65 ± 0.23 ab	6.68 ± 0.41 c
	After-drying	7.43 ± 0.19 ab	4.66 ± 0.26 d
Water	After-cutting	7.86 ± 0.29 a	9.57 ± 0.76 b
	After-retting	7.22 ± 0.27 bc	20.80 ± 1.56 a
	After-drying	6.82 ± 0.24 c	3.69 ± 0.29 e
p-value		<0.001	<0.001

The letters a to d correspond to the comparison of the impact of the method coupled to the drying in the same column on the stem characteristic according to an ANOVA analysis.

Figure 3. Impact of the retting method and duration on the hemp stem moisture rate.

Table 2. Stem characteristics and confidence intervals estimated for different retting methods and durations based on data from after-drying stage.

Method	Week	Diameter (mm)	Mass (g)
Dew	W1	7.62 ± 0.38 a	5.11 ± 0.66 ab
	W2	7.78 ± 0.52 a	5.31 ± 0.78 a
	W3	7.37 ± 0.46 a	4.25 ± 0.57 ab
	W4	7.05 ± 0.60 ab	4.12 ± 0.71 ab
	W5	7.68 ± 0.63 a	5.36 ± 0.99 a
	W6	7.73 ± 0.71 a	5.15 ± 0.96 ab
	W7	6.83 ± 0.57 ac	3.66 ± 0.58 ac
	W8	7.27 ± 0.50 a	4.14 ± 0.72 ac
Water	W1	7.94 ± 0.81 a	5.06 ± 1.14 a
	W2	7.27 ± 0.59 a	4.22 ± 0.73 ab
	W3	5.81 ± 0.55 bc	2.88 ± 0.62 bc
	W4	6.99 ± 0.48 ac	4.08 ± 0.75 ac
	W5	5.59 ± 0.54 c	2.32 ± 0.43 c
	W6	6.81 ± 0.74 ac	3.51 ± 0.79 ac
	W7	6.96 ± 0.73 ac	3.72 ± 0.86 ac
	W8	7.22 ± 0.73 a	3.70 ± 0.90 ac
p-value		<0.001	<0.001

The letters a to c correspond to the comparison of the impact of the method coupled to the duration in the same column on the stem characteristic according to an ANOVA analysis.

Table 3. Stem chemical composition and machine accuracy estimated for different retting methods and durations.

Method	Week	Potassium (mg)	Calcium (mg)	Phosphorus (mg)	Magnesium (mg)	Boron (µg)	Copper (µg)	Manganese (µg)	Zinc (µg)
	W0	206.6 ± 16.6	210 ± 16.9	24.1 ± 1.9	22.4 ± 1.8	232.4 ± 23.4	94.7 ± 14.3	588.8 ± 88.7	172.2 ± 25.9
Dew	W1	263.1 ± 21.2	313.3 ± 25.2	45.4 ± 3.7	23.9 ± 1.9	377.9 ± 37.9	120.5 ± 18.1	1171.9 ± 176.3	73.7 ± 11.1
	W2	169.1 ± 13.6	233.8 ± 18.8	39.8 ± 3.2	17.4 ± 1.4	271.1 ± 27.2	129.8 ± 19.5	614.4 ± 92.4	94.0 ± 14.1
	W3	29.9 ± 2.4	123.4 ± 9.9	13.9 ± 1.1	10.0 ± 0.8	144.7 ± 14.5	73.9 ± 11.1	312.5 ± 47.0	65.3 ± 9.8
	W4	38.6 ± 3.1	250.6 ± 20.2	34.7 ± 2.8	15.4 ± 1.2	219.7 ± 22.1	83.8 ± 12.6	857.8 ± 129.1	74.6 ± 11.2
	W5	45.2 ± 3.6	306.6 ± 24.7	47.7 ± 3.8	15.1 ± 1.2	261.3 ± 26.2	112.3 ± 16.9	1223.7 ± 184.0	105.0 ± 15.8
	W6	36.2 ± 2.9	205.1 ± 16.5	21.7 ± 1.7	12.1 ± 1.0	185.3 ± 18.6	83.2 ± 12.5	460.9 ± 69.3	89.0 ± 13.4
	W7	17.1 ± 1.4	171.5 ± 13.8	13.7 ± 1.1	8.6 ± 0.7	138.5 ± 13.9	97.4 ± 14.7	399.5 ± 60.2	72.9 ± 11.0
	W8	44.6 ± 3.6	286.8 ± 23.1	31 ± 2.5	15.5 ± 1.2	244.2 ± 24.5	108.9 ± 16.4	730.6 ± 110	137.8 ± 20.7
Water	W1	33.2 ± 2.7	284.3 ± 22.9	14.2 ± 1.1	11.8 ± 0.9	241.6 ± 24.3	402.7 ± 60.6	689.3 ± 103.7	1075.4 ± 161.8
	W2
	W3	3.5 ± 0.5	102.1 ± 8.2	3.5 ± 0.3	3.5 ± 0.3	123.8 ± 12.5	440.3 ± 66.3	225.4 ± 33.9	1549.8 ± 233.4
	W4	8.5 ± 0.7	169.9 ± 13.7	18.9 ± 1.5	13.2 ± 1.1	190.6 ± 19.2	556.8 ± 83.8	479.4 ± 72.2	1457.2 ± 219.4
	W5	1.5 ± 0.5	62.5 ± 5.0	1.5 ± 0.1	1.5 ± 0.1	72.3 ± 8.8	252.8 ± 38.1	93.1 ± 17.5	758.3 ± 114.3
	W6	7.8 ± 0.6	79.8 ± 6.4	3.9 ± 0.3	1.9 ± 0.2	103.7 ± 11.7	324.9 ± 48.9	187.4 ± 28.2	953.4 ± 143.5
	W7	1.6 ± 0.5	54.7 ± 4.4	1.6 ± 0.1	1.6 ± 0.1	68.6 ± 9.7	421.8 ± 63.5	75.3 ± 19.4	1001.4 ± 150.8
	W8	3.7 ± 0.6	95.0 ± 7.7	3.7 ± 0.3	1.9 ± 0.2	114.0 ± 11.5	897.5 ± 135.1	191.8 ± 28.9	1845.2 ± 277.8

Table 4. Fiber chemical composition and machine accuracy estimated for different retting methods and durations.

Method	Week	Soluble fraction (%)	Hemicellulose (%)	Cellulose (%)	Lignin (%)
	W0	0.0 ± 0.0	4.0 ± 0.6	76.5 ± 11.5	19.5 ± 2.9
Dew	W1	3.8 ± 0.6	0.9 ± 0.1	78.5 ± 11.8	16.7 ± 2.5
	W2	6.3 ± 0.9	6.8 ± 1	78.5 ± 11.8	8.4 ± 1.3
	W3	4.5 ± 0.7	6.1 ± 0.9	81.3 ± 12.2	8.2 ± 1.2
	W4	1.1 ± 0.2	4.5 ± 0.7	83.9 ± 12.6	10.6 ± 1.6
	W5	3.2 ± 0.5	6.1 ± 0.9	83.6 ± 12.5	7 ± 1.1
	W6	3.2 ± 0.5	5.2 ± 0.8	86.2 ± 12.9	5.5 ± 0.8
	W7	5.2 ± 0.8	2.8 ± 0.4	83.6 ± 12.5	8.4 ± 1.3
	W8	4.1 ± 0.6	5.6 ± 0.8	81.1 ± 12.2	9.2 ± 1.4
Water	W1	1.4 ± 0.2	2.6 ± 0.4	85.6 ± 12.8	10.3 ± 1.5
	W2	7.2 ± 1.1	4.5 ± 0.7	81.7 ± 12.3	6.7 ± 1
	W3	5.7 ± 0.9	5 ± 0.8	84.8 ± 12.7	4.5 ± 0.7
	W4	0.3 ± 0.04	2.6 ± 0.4	85.6 ± 12.8	11.5 ± 1.7
	W5	5 ± 0.8	4.6 ± 0.7	86.3 ± 12.9	4.1 ± 0.6
	W6	3.4 ± 0.5	5.1 ± 0.8	88.3 ± 13.2	3.2 ± 0.5
	W7	4.1 ± 0.6	4.2 ± 0.6	86.9 ± 13	4.7 ± 0.7
	W8	2.5 ± 0.4	2.6 ± 0.4	84.2 ± 12.6	10.6 ± 1.6

Table 5. Technical fiber color parameters and confidence intervals estimated for different retting methods and durations.

Method	Week	L*	a*	b*
	W0	71.9 ± 0.9 a	3.7 ± 0.2 ab	28.2 ± 0.8 a
Dew	W1	71.1 ± 1.0 ab	3.5 ± 0.4 bc	27.9 ± 0.6 a
	W2	70.4 ± 1.6 ac	3.6 ± 0.3 b	27.4 ± 0.5 ab
	W3	54.4 ± 1.4 d	1.8 ± 0.1 f	18.2 ± 0.3 f
	W4	49.2 ± 0.4 f	2.1 ± 0.1 f	17.0 ± 0.5 gh
	W5	54.1 ± 0.6 d	2.1 ± 0.1 f	18.0 ± 0.3 f
	W6	50.1 ± 0.6 ef	1.7 ± 0.1 f	16.3 ± 0.5 h
	W7	51.6 ± 1.5 e	2.1 ± 0.1 f	17.7 ± 0.7 fg
	W8	50.0 ± 1.8 ef	1.8 ± 0.1 f	16.8 ± 0.6 gh
Water	W1	71.1 ± 0.6 ab	3.2 ± 0.3 cd	26.2 ± 0.7 c
	W2	69.6 ± 0.6 bc	2.9 ± 0.2 de	24.2 ± 0.7 de
	W3	69.1 ± 0.8 c	2.7 ± 0.2 e	23.7 ± 0.4 e
	W4	71.7 ± 0.8 a	2.8 ± 0.5 e	24.8 ± 0.6 d
	W5	70.9 ± 0.4 ab	4.1 ± 0.2 a	27.5 ± 0.6 ab
	W6	71.7 ± 0.4 a	3.6 ± 0.1 bc	26.9 ± 0.2 bc
	W7	71.3 ± 0.6 ab	3.3 ± 0.3 cd	26.1 ± 0.3 c
	W8	70.2 ± 0.4 ac	3.6 ± 0.2 bc	26.6 ± 0.5 bc
p-value		<0.001	<0.001	<0.001

The letters a to h correspond to the comparison of the impact of the method coupled to the duration in the same column on the color parameter according to an ANOVA analysis.

Figure 4. Impact of the retting method and duration on the fiber linear density distribution.

Table 6. Fiber characteristics and confidence intervals estimated for different retting methods and durations.

Method	Week	Linear density (dtex)	Tenacity (cN/tex)	Breaking strain (%)	Young’s Modulus (cN/tex)
	W0	18.08 ± 2.22 b	68 ± 7 a	2.44 ± 0.18 a	3045 ± 226 a
Dew	W1	23.43 ± 2.67 a	53 ± 6 b	2.05 ± 0.19 bc	2928 ± 247 a
	W4	17.60 ± 2.61 b	47 ± 6 b	1.76 ± 0.19 c	2826 ± 266 a
	W8	15.63 ± 2.47 b	59 ± 7 ab	1.98 ± 0.15 bc	3014 ± 235 a
Water	W1	15.42 ± 1.87 b	70 ± 7 a	2.30 ± 0.18 ab	3228 ± 240 a
	W4	19.50 ± 1.96 ab	51 ± 6 b	1.84 ± 0.15 c	2998 ± 252 a
	W8	17.71 ± 2.26 b	48 ± 5 b	1.77 ± 0.16 c	2896 ± 247 a
p-value		<0.001	<0.001	<0.001	0.40

The letters a to c correspond to the comparison of the impact of the method coupled to the duration in the same column according to an ANOVA analysis.