Figures (3)  Tables (7)

    • Figure 1. 

      The life cycle of black soldier flies in four phases and six stages of larvae in different instars.

    • Figure 2. 

      (a) Colour and texture of undigested substrate (DC and PKE mixture). (b) Colour and texture of BSFL frass after being fed on DC and PKE mixture.

    • Figure 3. 

      Relationship between acid addition and pH of samples. * represents a significant difference at p ≤ 0.05.

    • PropertiesMixture of DC and PKE
      pHwater6.33 ± 0.03
      CEC (cmol kg−1)10.1 ± 1.63
      Exchangeable NH4+ (mg kg−1)3.97 ± 0.62
      Available NO3− (mg kg−1)3.27 ± 0.23
      Total N (%)1.72 ± 0.14
      Total P (mg kg−1)2976 ± 87.9
      TOM (%)82.5 ± 2.09
      TOC (%)47.8 ± 1.21
      C/N ratio28:1
      The values given are based on a dry-weight basis. Mean value followed by ± standard error.

      Table 1. 

      Selected chemical properties of decanter cake and palm kernel expeller.

    • Property Value obtained
      pHwater 4.67 ± 0.25
      CEC (cmol kg−1) 11.67 ± 0.21
      Total N (%) 0.37 ± 0.42
      Total P (mg kg−1) 5.27 ± 0.31
      Available P (mg kg−1) 0.114 ± 0.01
      OM (%) 5.03 ± 1.04
      TOC (%) 2.91 ± 0.60
      Exchangeable NH4+ (mg kg−1) 12.00 ± 2.49
      Available NO3− (mg kg−1) 5.20 ± 1.01
      The values given are based on a dry-weight basis. Mean value followed by ± standard error.

      Table 2. 

      Initial selected chemical properties of Bekenu Series soil for pH buffering capacity determination.

    • TreatmentT1T2T3T4T5
      Ambient temperature (°C)26 ± 0.3026 ± 0.3026 ± 0.3026 ± 0.3026 ± 0.30
      Feeding tray temperature (°C)27 ± 0.4827 ± 0.4127 ± 0.4327 ± 0.4427 ± 0.41
      Mean value followed by ± standard error. No significant difference among the treatments at p < 0.05. T1: 15 g BSFL + 15 kg DC and PKE; T2: 20 g BSFL + 15 kg DC and PKE; T3: 25 g BSFL + 15 kg DC and PKE; T4: 30 g BSFL + 15 kg DC and PKE; T5: 35 g BSFL + 15 kg DC and PKE.

      Table 3. 

      Average temperature of ambient and feeding substrates in 54 d of rearing black soldier fly larvae.

    • BSFL
      weights (g)      		 Weight of DC and
      PKE applied (kg)      		 BSFL frass
      produced (kg)      		 Material reduction
      WRR (%) WRI (d−1)
      T1−15 15 2.43 83.79 ± 0.69 1.55 ± 0.01
      T2−20 15 2.65 82.36 ± 0.64 1.53 ± 0.01
      T3−25 15 2.75 81.69 ± 0.83 1.51 ± 0.02
      T4−30 15 2.66 82.25 ± 0.53 1.52 ± 0.01
      T5−35 15 2.42 83.84 ± 1.56 1.55 ± 0.03
      The weight of DC and PKE are based on a wet-weight basis. The value of the frass given is based on a dry-weight basis. Mean value followed by ± standard error. No significant difference among the treatments at p < 0.05. T1: 15 g BSFL + 15 kg DC and PKE; T2: 20 g BSFL + 15 kg DC and PKE; T3: 25 g BSFL + 15 kg DC and PKE; T4: 30 g BSFL + 15 kg DC and PKE; T5: 35 g BSFL + 15 kg DC and PKE.

      Table 4. 

      Bioconversion of feeding substrates into frass excreted by black soldier fly larvae.

    • PropertyTreatments
      T1T2T3T4T5
      pH in water7.77 ± 0.17.68 ± 0.17.46 ± 0.27.70 ± 0.17.98 ± 0.1
      CEC (cmol kg−1)21.00 ± 0.320.63 ±1.520.43 ± 1.020.37 ± 0.420.23 ± 1.2
      OM (%)74.7 ± 2.471.3 ± 2.973.3 ± 2.774.0 ± 0.072.7 ± 0.7
      Exchangeable NH4+ (mg kg−1)101.57± 2.597.14± 6.4113.95 ± 3.1120.72±8.3114.65 ± 5.3
      Available NO3− (mg kg−1)110.68 ± 4.2100.17±1.284.99 ± 5.588.03 ± 9.5103.44 ± 6.5
      Total N (%)2.51 ± 0.22.37 ± 0.22.51 ± 0.32.55 ± 0.22.46 ± 0.3
      TOC (%)43.31 ± 1.441.37 ± 1.742.53 ± 1.642.92 ± 0.042.15 ± 0.4
      Total P (mg kg−1)4896.8 ± 56.24355.3 ± 158.14421.7 ± 236.94607.0 ± 332.25341.7 ± 299.4
      C/N ratio17:118:117:117:117:1
      The values given are based on a dry-weight basis. Mean value followed by ± standard error. No significant difference among the treatments at p < 0.05. T1: 15 g BSFL + 15 kg DC and PKE; T2: 20 g BSFL + 15 kg DC and PKE; T3: 25 g BSFL + 15 kg DC and PKE; T4: 30 g BSFL + 15 kg DC and PKE; T5: 35 g BSFL + 15 kg DC and PKE.

      Table 5. 

      Selected chemical properties of black soldier fly larvae frass fed on mixed DC and PKE.

    • Extractant Concentration Root length (cm) Shoot length (cm) RSG (%) GI (%)
      C Distilled water 1.26 ± 0.15 2.01 ± 0.13 100.0 100
      T1 IE 3.14 ± 0.36 1.54 ± 0.22 80.0 100
      D1 5.91 ± 0.45 2.63 ± 0.25 93.3 100
      D2 4.29 ± 0.32 2.20 ± 0.20 90.0 100
      D3 4.07 ± 0.30 2.19 ± 0.20 93.3 100
      T2 IE 5.13 ± 0.43 2.17 ± 0.24 90.0 100
      D1 4.69 ± 0.38 2.48 ± 0.23 93.3 100
      D2 5.03 ± 0.46 2.14 ± 0.19 86.7 100
      D3 3.05 ± 0.36 1.74 ± 0.21 80.0 100
      T3 IE 4.03 ± 0.44 1.77 ± 0.24 86.7 100
      D1 4.19 ± 0.49 2.42 ± 0.32 80.0 100
      D2 4.19 ± 0.38 2.39 ±0.20 93.3 100
      D3 3.40 ± 0.41 1.79 ± 0.23 80.0 100
      T4 IE 3.36 ± 0.43 1.73 ± 0.28 83.3 100
      D1 4.82 ± 0.47 2.29 ± 0.25 86.7 100
      D2 3.20 ± 0.21 1.93 ± 0.17 96.7 100
      D3 3.20 ± 0.28 2.10 ± 0.18 93.3 100
      T5 IE 3.36± 0.42 1.42 ± 0.20 80.0 100
      D1 4.02 ± 0.40 2.19 ± 0.25 86.7 100
      D2 3.59 ± 0.37 1.74 ± 0.23 83.3 100
      D3 3.47 ± 0.25 2.16 ± 0.18 93.3 100
      Mean value followed by ± standard error. C is distilled water served as control. IE is initial extraction. D1, D2, D3 are three times dilutions. RSG is relative seed germination. GI is the germination index.

      Table 6. 

      Plant bioassay test of treatments in different concentrations of extractants.

    • Treatment code Initial pH pH buffering
      capacity      		 R2
      Soil only (S0) 5.93 ± 0.06 0.6074 0.8670*
      BSFL frass only (F1) 7.94 ± 0.10 2.6212 0.9511*
      Soil + 9 g BSFL frass (F2) 6.50 ± 0.04 0.3444 0.8951*
      Soil + 7.2 g BSFL frass (F3) 6.43 ± 0.02 0.3519 0.8740*
      Soil + 5.4 g BSFL frass (F4) 6.11 ± 0.04 0.3620 0.8552*
      * represents a significant difference at p ≤ 0.05.

      Table 7. 

      Summary of soil pH buffering capacity affected by soil alone, BSFL frass alone and soil with the BSFL frass.