| Clue | Source | Date |
|---|---|---|
| Switch with another | Newsday | 30 Jun 2019 |
| Gradually substitute | ||
| Make a switch with | Newsday | 18 Jun 2016 |
| Add gradually to a cycle | ||
| Gradually substitute | ||
| Gradually substitute | ||
| Gradually substitute | ||
| Add gradually during a cycle | ||
| Add gradually, as crops to a field |