| Treatment | Soaking time (minutes) | ||
| 1 | 3 | 5 | |
| Control | 5.75a | 4.56b | 3.77b |
| 9:1 H2SO4 | 0.80def | 0.00ef | 0.60d-f |
| 7:3 H2SO4 | 1.59cd | 0.20d-f | 2.58c |
| 1:1 H2SO4 | 0.60d-f | 0.99de | 0.20d-f |
| 4:6 H2SO4 | 3.97b | 0.99de | 2.78c |
| 3:7 H2SO4 | 3.97b | 0.79d-f | 1.00de |
| 2:8 H2SO4 | 1.59cd | 0.40d-f | 0.99de |
| 1:9 H2SO4 | 2.38c | 1.00 de | 1.59cd |
| SE (±) 0.46 | |||