3.1. Summary of inputs–outputs of the Bokashi and Compost tea methods
Summary of input as raw materials and output as products of the two methods is given in Table 3. For Bokashi method, the amount of input raw material as fresh vegetables ranged from 22.1 to 50.0 kg. A small number of vegetables (< 1% by weight) was lost after milling by the shredder machine. The total volume of milled JWC ranged from 45 L to 102 L which required additional water from 18 L to 23 L depending on the lower or higher amount of raw material.
As a result, a total volume of 76.9 L of Bokashi extract was produced from 249.2 kg of fresh
JWC, consuming 135 L of clean water. An amount of 25 L of Bokashi extract was then additionally produced using the same procedures to supply enough amount of Bokashi extract (101.9 L) used for the field experiment (data not shown in the table).
Table 3. Summary of weight and volume of inputs–outputs of two methods
Bokashi method Run 1 Run 2 Run 3 Run 4 Run 5 Run 6 Run 7 Total
Mr-JCW-in (kg) 50.0 50.0 50.0 32.9 22.1 22.1 22.1 249.2
Mm-JCW-in (kg) 46.6 46.6 46.6 30.6 20.6 20.6 20.6 232.2
VJCW-in (L) 102 102 102 67 45 45 45 508
VH2O in (L) 23 23 23 16 16 16 18 135
VBokashi-out (L) 16.9 17.8 13.5 9.2 7.2 4.8 7.7 76.9
Compost tea method Run 1 Run 2 Run 3 Run 4 Run 5 Run 6 Run 7 Total
MCMRH-in (kg) 0.45 0.90 1.38 1.38 1.38 1.83 1.83 9.15
VH2O in (L) 11 23 34 34 34 46 46 228
VCompost tea-out (L) 228
B and C indicate for bins used for Bokashi and Compost methods, the number of batches for Bokashi and Compost were n = 18 and n = 7, respectively;Mr-JCW-in = weight of fresh vegetable, Mm-JCW-in = weight of vegetable after milling, VJCW-in = volume of milled vegetable; Vin = total volume of water added to each bin, VBokashi-out: total volume of Bokashi extract obtained in the experiment.
For Compost tea method, the amount of input raw material as CMRH compost ranged from 0.45 to 1.83 kg, with a dilution ratio of 1:25 (w/v) that consumed 11–46 L of clean water. As a result, a total volume of 228 L Compost tea was produced in 07 batches using 9.15 kg of compost and the same amount of 228 L of clean water (Table 3). It can be said that the Compost tea method can result in a larger amount of product in a shorter period within 24 hours, however, the composting process in the preliminary research took about 30 days for maturity (Tran et al, 2022).
3.2. The properties of Bokashi and Compost extracts
The Bokashi extract showed the ranges of chemical parameters in the sub-samples as follows:
pH 4.8–6.4, EC 17.0–47.6 dS/m, and salinity 0.9–2.9% (Table 4). The representative sample had the total organic matter of 13,900 mg/L, in which approximately a haft was present in form of humic and fulvic acids (5,800 mg/L). The Bokashi extract was rich in available potassium (12,100 mg/L), followed by total CaO (1,300 mg/L) and total N (1,160 mg/L). Available potassium and total magnesium were found in low concentrations (Table 4).
The properties of Compost extract in seven separate runs and the mixed sample are shown in Table 5. The values of the runs are as follows: pH 5.35–5.90, EC 3.23–5.02 dS/m and NaCl 0.18–0.27%. The mix-sample had a total N, available P2O5, and available K2O of 520 mg/L, 100 mg/L, and 1,100 mg/L, respectively (Table 5). In comparison to the quality of Bokashi, more product was produced following Compost tea method, however, the total nitrogen, available phosphorus, and potassium concentrations were only haft and one-tenth those of Bokashi extract.
Table 4. The properties of the Bokashi extract
Properties Results Reference
pH 4.8–6.4
EC (dS/m) 17.0–47.6
NaCl (%) 0.9–2.9
Total organic matter (mg/L) 13,900 TCVN 9294:2012
Humic and fulvic acids (mg/L) 5,800 TCVN 8561:2010
Total N (mg/L) 1,160 TCVN 8557:2010
Available P2O5 (mg/L) 200 TCVN 8559:2010
Available K2O (mg/L) 12,100 TCVN 8560:2010
Total CaO (mg/L) 1,300 TCVN 12598:2018
Total MgO (mg/L) 120 TCVN 12598:2018
Results of pH, EC, and NaCl (%) were of sub-samples while the other parameters were of the representative one.
Table 5. The properties of the Compost tea
Properties Run 1 Run 2 Run 3 Run 4 Run 5 Run 6 Run 7 Mix
pH 5.53 5.65 5.63 5.45 5.80 5.90 5.35 5.69
EC (dS/m) 4.82 5.18 4.61 5.02 3.91 3.23 4.83 4.37
NaCl (%) 0.24 0.26 0.23 0.25 0.19 0.18 0.27 0.23
Total N (mg/L) 520
Available P2O5 (mg/L) 100
Available K2O (mg/L) 1,100
3.3. Effects of Compost and Bokashi extracts on the plant growth
The plant height between the treatments was not significantly different (P > 0.05) from 5 to 35 DAP. The nutrient requirements during this period of time could be low, and the difference between fertilizer treatments was not clear. At the harvest time (45 DAP), the highest plant height was recorded at Bokashi treatment-T2 (21.8 cm), not significantly different from Compost tea treatment-T3 (21.4 cm) and chemical fertilizer treatment-T5 (20.6 cm), however, significantly different (P < 0.05) from biofertilizer-T4 (18.8 cm) and water only treatment-T1
(18.1 cm). The order of decreasing plant height of the treatments was: T2 ≥ T3 ≥ T5 >> T4 ≥ T1
(Figure 3A). Thus, since 35 DAP the nutrient demand of Japanese Watercress increased, the Bokashi extract provided more available potassium than the others which can result in a remarkable increase in plant height (Table 2). There was no significant difference between the
treatments in terms of the number of pairs of leaf/main stem and the number of branches/plant (Figure 3B and Figure 3C).
Figure 3. Effects of Compost and Bokashi extracts on plant height (A), number of pairs of leaves/main stem (B) and primary branches/plant (C) of Japanese Watercress
Zaman et al. (2009) studied the effect of Bokashi on plant growth, yield, and essential oil quantity and quality in Patchouli. The plant growth parameters of Patchouli were significantly influenced by Bokashi treatment with the highest plant height, the number of branches, plant spread, leaf size, and leaf area. Tran et al. (2022) reported the results of compost application in solid part on Japanese Watercress vegetables. The results showed that the plant height of the treatment applied with Compost fertilizer was similar to commercial organic fertilizer but significantly lower than chemical fertilizer.
3.4. Effect of Compost and Bokashi extracts on theoretical and actual harvested yield of Japanese Watercress
Table 6. Effect of Compost and Bokashi extracts on theoretical and actual harvested yield of Japanese Watercress
Treatment TY
(kg/1,000 m2)
AHY (kg/1,000 m2)
Water only (T1) 852.5b 741.6c
Bokashi extract (T2) 1,343.4a 1,327.3a
Compost tea (T3) 1,302.5a 1,362.5a
CBF (T4) 1,013.8b 850.8bc
NPK fertilizer (T5) 1,334.2a 1,231.4ab
CV (%) 12.1 19.6
Fvalue 7.6** 5.3*
Values within the same column followed by the same letter are not significantly different according to LSD test at P < 0.05. CBF = commercial bio-fertilizer; NPK = commercial chemical fertilizer as NPK16-16-8; TY: theoretical yield; AHY: actual yield.
The results in Table 6 show that the highest theoretical yield of vegetables was obtained the maximum value at T2, which is not significantly different from T3 and T5, but significantly higher (P < 0.01) than T1 and T4. The actual harvested yield had the highest value in T3 (1362.5 kg/1000 m2), not significantly different from T2 (1327.3 kg/1000 m2) and T5 (1231.4 kg/1000 m2). However, the difference was significant higher (P < 0.05) than T1 (741.6 kg/1000 m2) and T4 (850.8 kg/1000 m2) (Table 6).