Comparative evaluation of pumice as a soilless substrate for indoor Rubus idaeus L. cultivation

Figures & data

Table 1. Physical properties of four substrate types (Showed as Mean ± SEM, n = 4).

Substrate	Bulk density (g·cm^−3)	Porosity (%)	Water Holding Capacity (%)
Coconut Coir (Control)	0.446 ± 0.024	66.05% ± 0.99%	18.31% ± 0.4%
Pumice	0.993 ± 0.04	45.03% ± 0.79%	15.49% ± 0.31%
Flax + Pumice	0.87 ± 0.027	49.53% ± 1.23%	10.95% ± 0.49%
Coconut Coir + Pumice	0.764 ± 0.012	57.95% ± 0.49%	22.55% ± 0.44%

Figure 1. Regression curves of growth rate over time based on the average cane height (mm) of sel.8 and sel.110 in four substrates.

Figure 2. Regression curves of growth rate over time based on the average cane diameter (cm) of sel.8 and sel.110 in four substrates.

Table 2. Estimated regression equation of plant growth per week (W) based on plant height (cm).

Selection	Treatment	Link Function	Model equation	n	F
sel.8	Coir (Ctrl)	Log	H = e^(0.02935W + 3.9863) ^a	340	593.84
	Pumice	Log	H = e^(0.02314W + 3.9469) ^b	340	399.04
	Pumice/Flax	Log	H = e^(0.02576W + 3.8568) ^ab	340	464.17
	Coir/Pumice	Log	H = e^(0.02871W + 3.7166) ^a	340	516.53
sel.110	Coir (Ctrl)	Log	H = e^(0.02543W + 3.9863) ^a	160	241.38
	Pumice	Log	H = e^(0.02369W + 4.1085) ^a	160	232.57
	Pumice/Flax	Log	H = e^(0.02548W + 3.8631) ^a	160	214.47
	Coir/Pumice	Log	H = e^(0.02116W + 4.032) ^a	160	167.42

n: Number of observations used.

The slopes of regression lines were compared according the 95% CLs.

Table 3. Estimated regression equation of plant growth per week (W) based on cane diameter (mm).

Selection	Treatment	Link Function	Model equation	n	F
sel.8	Coir (Control)	Log	D = e^(0.02022W + 1.4889) ^a	644	52.61
	Pumice	Log	D = e^(0.01771W + 1.613) ^a	662	42.7
	Pumice/Flax	Log	D = e^(0.01894W + 1.5811) ^a	680	48.38
	Coir/Pumice	Log	D = e^(0.02623W + 1.4211) ^a	649	89.8
sel.110	Coir (Control)	Log	D = e^(0.02406W + 1.5687) ^a	298	36.64
	Pumice	Log	D = e^(0.02098W + 1.7622) ^a	320	28.16
	Pumice/Flax	Log	D = e^(0.02177W + 1.6298) ^a	303	28.02
	Coir/Pumice	Log	D = e^(0.0236W + 1.6724) ^a	320	36.51

n: Number of observations used.

The slopes of regression lines were compared according the 95% CLs.

Table 4. Lateral formation of two raspberry selections in four substrates.

Selection	Treatment	Lateral formation (Laterals/Week)
sel.8	Coir (Control)	0.147 ^ab
	Pumice	0.168 ^a
	Pumice/Flax	0.126 ^b
	Coir/Pumice	0.153 ^ab
sel.110	Coir (Control)	0.175 ^ab
	Pumice	0.181 ^a
	Pumice/Flax	0.119 ^b
	Coir/Pumice	0.181 ^a

Tukey HSD multiple comparison method was applied for the analysis, and different letter were used to represent significant differences (p < 0.05).

Table 5. Total number of harvested fruits, bulk fruit weight (g), plant crop load of cane cross section and estimated yield (kg·ha⁻¹) of two raspberry selections, sel.8 (n = 17) and sel.110 (n = 8). Data were bulk collected during the fruiting period, from 27 February to 14 April.

Selection	Treatment	Total Harvested Fruit Number	Bulk fruit weight* (g)	Crop Load** (Fruit·cm^−2)	Estimated Yield*** (kg·ha^−1)
sel.8	Coir (Ctrl)	268	86.47	6.9	7771.5
	Pumice	325	119.7	7.2	9527.1
	Pumice/Flax	184	65.47	4.17	5763.9
	Coir/Pumice	119	43.24	5.71	3517.92
sel.110	Coir (Ctrl)	313	137.81	8.19	14233.3
	Pumice	324	127.03	9.48	12387.9
	Pumice/Flax	125	71.4	8.30	5460.9
	Coir/Pumice	291	176.4	7.97	14969.7

*Bulk yield: average fruit weight × total fruit number / plant number.

**Crop load: fruit number per plant / cane cross-sectional area.

***Estimated yield: (1 ha × yield per plant) / area of single plant.

Figure 3. Pearson’s correlation analysis of vegetative growth and productivity parameters in raspberry plants. * and ** represent significant correlations at the p < 0.05 and p < 0.01 levels, respectively (two-tailed). n.s. denotes not significant.

Figure 4. Fruit size and shape of sel.8 and sel.110 grown in four substrates (Control = Coconut coir). Photo was taken on 19 March 2023, with fruit selected for harvest maturity and representative traits for each treatment.

Table 6. The fruit dimension (mm), fruit shape index (FSI) and average weight of a single fruit FW (g) of two raspberry selections under four treatments. Shown as mean ± SEM.

Selection	Treatment	Fruit Diameter (mm)	Fruit Height (mm)	FSI	FW / Fruit (g)	TSS (%)	TA (g/mL)	DM (%)	Firmness (N/mm)	L*	C*	h°
sel.8	Coir (Ctrl)	22.51 ± 0.36^b	23.08 ± 0.36^a	1.03 ± 0.012^a	4.936 ± 0.143^a	8.09%±0.23%^b	2.47 ± 0.09^a	12.16%±0.06%^c	0.2576 ± 0.014^a	29.54 ± 0.45^a	17.08 ± 0.69^a	16.07 ± 0.37^ab
	Pumice	23.79 ± 0.3^a	24.18 ± 0.34^a	1.025 ± 0.02^a	4.977 ± 0.148^a	10.25%±0.33%^a	2.21 ± 0.07^ab	18.28%±0.59%^a	0.2373 ± 0.012^ab	28.38 ± 0.23^ab	15.1 ± 0.66^ab	14.73 ± 0.56^b
	Pumice/Flax	24.13 ± 0.19^a	23.99 ± 0.38^a	0.994 ± 0.014^ab	5.332 ± 0.13^a	8.24%±0.23%^b	2.37 ± 0.09^a	15.48%±0.72%^b	0.2343 ± 0.015^ab	27.71 ± 0.48^b	13.9 ± 0.56^b	11.72 ± 1.0^c
	Coir/Pumice	24.09 ± 0.3^a	23.03 ± 0.46^a	0.957 ± 0.018^b	5.026 ± 0.167^a	8.36%±0.26%^b	1.96 ± 0.07^b	17.03%±0.62%^ab	0.1972 ± 0.008^b	25.18 ± 0.27^c	13.8 ± 0.47^b	17.09 ± 0.53^a
sel.110	Coir (Ctrl)	20.38 ± 0.24^a	21.76 ± 0.29^a	1.07 ± 0.013^a	3.637 ± 0.104^ab	9.22%±0.19%^ab	1.96 ± 0.06^b	15.43%±0.74%^ab	0.2759 ± 0.019^a	28.81 ± 0.41^b	19.44 ± 0.74^a	16.99 ± 0.46^b
	Pumice	19.09 ± 0.35^b	20.17 ± 0.51^b	1.055 ± 0.016^ab	3.058 ± 0.151^c	9.0%±0.22%^ab	2.24 ± 0.08^ab	17.17%±0.41%^a	0.288 ± 0.019^a	29.66 ± 0.47^ab	21.33 ± 0.64^a	19.04 ± 0.49^a
	Pumice/Flax	20.04 ± 0.29^ab	20.17 ± 0.37^b	1.008 ± 0.014^b	3.497 ± 0.134^bc	8.59%±0.14%^b	2.41 ± 0.08^a	13.41%±0.66%^b	0.2748 ± 0.02^a	29.17 ± 0.33^b	20.21 ± 0.54^a	16.73 ± 0.51^b
	Coir/Pumice	21.07 ± 0.38^a	22.16 ± 0.41^a	1.058 ± 0.016^ab	4.108 ± 0.148^a	9.36%±0.23%^a	2.20 ± 0.08^ab	18.40%±0.61%^a	0.2503 ± 0.012^a	30.96 ± 0.60^a	19.82 ± 0.66^a	19.09 ± 0.42^a
Significance
p(Selection)		0.000**	0.000**	<0.001**	0.000**	0.037*	0.341^NS	0.724^NS	<0.001**	<0.001**	0.000**	<0.001**
p(Treatment)		<0.001**	0.412^NS	0.003**	<0.001**	<0.001**	<0.001**	<0.001**	0.005**	0.013*	0.01*	<0.001**
p(Selection*Treatment)		<0.001**	<0.001**	0.03*	<0.001**	<0.001**	<0.001**	<0.001**	0.003**	<0.001**	<0.001**	0.024*

Tukey HSD multiple comparison method was applied for the analysis, and different letters were used to represent significant differences (P < 0.05).

Generalised linear mixed-effects model was used to analyse the effects of selection, treatment and their interaction. **, * and ^NS denote significant differences at the 0.01, 0.05 levels and non-significant difference, respectively.

Figure 5. Proportion of variance and the cumulative contribution rate of principal components.

Figure 6. Three-dimensional component plots for 11 quality parameters of raspberries.

Table 7. Comprehensive score and ranking according to 11 main quality indicators of the two raspberry selections.

		Principal Component Score
Selection	Treatment	y1	y2	y3	Comprehensive Score	Rank
sel.8	Coir (Ctrl)	−0.7174	−2.2283	0.0931	−0.8799	2
	Pumice	−1.5756	1.8031	1.5781	−0.2723	1
	Pumice/Flax	−3.3582	−1.5655	0.4449	−2.1248	4
	Coir/Pumice	−2.7602	1.5115	−1.9529	−1.3784	3
sel.110	Coir (Ctrl)	1.8899	0.9516	−0.7998	1.1498	2
	Pumice	3.2483	0.1737	−0.0762	1.7938	1
	Pumice/Flax	2.0914	−1.5911	−0.4375	0.7284	4
	Coir/Pumice	1.1817	0.9451	1.1504	0.9835	3