Improvement of salinity in sewage sludge compost prior to its utilization as nursery substrate

Figures & data

Table 1. Composition of sewage sludge compost-based substrate

	Material proportion (w/w)
Treatment	Sewage sludge compost (g)	Raw soil (g)	Dilution ratio
D1	10	90	10
D2	20	80	5
D3	30	70	3.3
D4	40	60	2.5
D5	50	50	2
Control (CK)	Peat/perlite mixture in 3:1

Table 2. Content of soluble salts in saturated extract of sewage sludge compost and background soil

Parameter	Sewage sludge compost	Background soil	Ratio of sewage sludge compost/soil
EC (dS cm^−1)	5.01	0.20	25.1
Na (mg L^−1)	935	12.21	76.6
K (mg L^−1)	753	24.29	31.0
Ca (mg L^−1)	3684	131	28.1
Mg (mg L^−1)	658	29.9	22.0
Cl (mg L^−1)	1083	53.25	20.3
Mn (mg L^−1)	0.32	0.04	8.0
Si (mg L^−1)	39.46	21.59	1.8
Zn (mg L^−1)	0.19	0.15	1.3
Cu (mg L^−1)	0.25	0.30	0.8
Fe (mg L^−1)	0.42	1.27	0.3

Figure 1. Comparison of germination rate, seed shoot length and GI (germination index) of tomato and lettuce cultivated in sewage sludge compost extract with different EC values.

Table 3. Content of soluble salts in saturated extract of sewage sludge compost and background soil after water elution

Parameter (mg L^−1)	Without water elution (T0)	Onefold water volume with elution (T1)	Twofold water volume elution (T2)	Threefold water volume elution (T3)	CK (background soil)
Na	935	609	421	329	12.21
K	753	544	404	313	24.29
Ca	3684	2308	1615	1188	131
Mg	658	401	278	206	29.9
Cl	1083	682	408	320	53.25

Figure 2. Comparison of stem diameter, seedling height, and above-ground biomass of tomato and lettuce cultivated in sludge compost prepared as nursery substrate using different volumes of water eluted.

Figure 3. Effect of water elution of sewage sludge compost used as nursery substrate on seedling growth of tomato (a) and lettuce (b).

Table 4. Effect of mixing sewage sludge compost with raw soil as nursery substrate on biological indices of tomato and lettuce

	Stem diameter (mm)		Seedling height (cm)		Above-ground weight (g)
Treatment	Tomato	Lettuce	Tomato	Lettuce	Tomato	Lettuce
D1	3.21 a*	1.85 a	12.13 a	8.93 a	0.22 a	0.15 a
D2	3.15 a	1.80 a	11.45 a	8.32 ab	0.21 a	0.11 ab
D3	3.02 ab	1.69 b	9.98 ab	7.27 b	0.16 ab	0.12 ab
D4	2.76 b	1.63 b	9.60 b	6.77 c	0.14 b	0.09 b
D5	2.87 ab	1.63 b	9.52 b	6.98 bc	0.15 b	0.08 b
CK	3.11 a	1.76 ab	10.48 a	8.25 ab	0.20 a	0.15 a

Note: *Means with the same letter are not significantly different for p ≤ 0.05.