Table 4. Ratios of total organic carbon to total nitrogen contents at selected periods during frass composting.
| Substrate formulations | Experiment set 1 | Experiment set 2 | ||||||
|---|---|---|---|---|---|---|---|---|
| Time (weeks) | ||||||||
| 0 | 1 | 3 | 5 | 0 | 1 | 3 | 5 | |
| Control | 13.3 ± 0.33d | 15.2 ± 0.48bc | 13.5 ± 0.67b | 12.8 ± 0.12b | 18.5 ± 0.69b | 18.8 ± 0.66bc | 22.2 ± 2.28 | 19.3 ± 1.28 |
| 5Gpysum | 15.4 ± 0.27c | 13.6 ± 0.49c | 13.6 ± 0.30b | 13.7 ± 0.10b | 20.9 ± 0.07ab | 18.0 ± 0.49bc | 17.7 ± 0.66 | 17.4 ± 0.48 |
| 10Gypsum | 16.2 ± 0.43bc | 15.7 ± 0.09bc | 13.3 ± 0.79b | 13.6 ± 1.09b | 20.2 ± 0.03ab | 18.6 ± 0.62bc | 17.4 ± 0.75 | 16.6 ± 0.54 |
| 15Gypsum | 17.1 ± 0.23bc | 15.3 ± 0.65bc | 12.5 ± 0.52b | 13.6 ± 0.52b | 21.6 ± 0.72ab | 17.6 ± 0.55c | 18.0 ± 1.23 | 19.3 ± 1.02 |
| 5Biochar | 15.0 ± 0.43c | 16.7 ± 1.23bc | 16.4 ± 1.07ab | 15.8 ± 1.06ab | 20.9 ± 0.15ab | 22.3 ± 0.46a | 23.1 ± 0.95 | 18.2 ± 0.93 |
| 10Biochar | 15.6 ± 0.19bc | 16.4 ± 1.32bc | 14.2 ± 1.41b | 15.9 ± 0.62ab | 19.9 ± 0.26ab | 21.9 ± 0.21a | 25.4 ± 3.85 | 19.3 ± 1.24 |
| 15Biochar | 15.1 ± 0.33c | 17.5 ± 0.95b | 12.6 ± 0.72b | 15.2 ± 1.02ab | 23.1 ± 1.54a | 20.9 ± 0.55ab | 23.4 ± 1.17 | 20.3 ± 1.08 |
| 20Biochar | 21.7 ± 0.07a | 25.6 ± 0.12a | 19.7 ± 0.33a | 17.9 ± 0.15a | 21.5 ± 0.23ab | 20.6 ± 0.80abc | 22.6 ± 4.00 | 18.7 ± 0.83 |
| p value | < 0.001 | < 0.001 | < 0.001 | 0.0019 | 0.0079 | < 0.001 | 0.148 | 0.235 |
Key: control = unamended substrate, 5Gypsum, 10Gypsum, 15Gypsum = substrate amended with 5, 10 and 15% gypsum, respectively, 5Biochar, 10Biochar, 15Biochar and 20Biochar = substrate amended with 5, 10, 15 and 20% biochar, respectively.