Crops with similar N status and canopy cover can be grouped together.
Table 1: Grouping Options for grains.
| CROP | GROUPING CATEGORY | COMMENTS |
| Barley (spring) | Spring cereal | |
| Oats (spring) | Spring cereal | |
| Wheat (spring) | Spring cereal | |
| Wheat (autumn) | Autumn cereal | |
| Oats (autumn) | Autumn cereal | |
| Maize (short, medium and long) | Maize | The only difference between these maize’s is the duration of their growth differs by about 2 months from short to long. If this loss of precision can be tolerated then a medium maize could be used to represent them all. |