Table 1 The experimental factors and levels
From: Green construction and release mechanism of lignin-based double-layer coated urea
Variable | Code | Range and levels | ||||
|---|---|---|---|---|---|---|
− 2 | − 1 | 0 | 1 | 2 | ||
Lignin content (%) | A | 10 | 30 | 50 | 70 | 90 |
–CNO/–OH molar ratio | B | 0.85 | 1.00 | 1.15 | 1.30 | 1.45 |
Amount of EP (%) | C | 5 | 20 | 35 | 50 | 65 |
Coating ratio (%) | D | 1 | 3 | 5 | 7 | 9 |