Cannot apply retrospectively, if they did what little trust there is would be non existent.That is pointless as anyone who wants to put most or a large % of their land into these options will now plough on and do it before then.
It could actually backfire and they get thousands of applications in before then taking large % of farms out of production.
The new rules either need to apply for all schemes regardless of when they were started or no schemes at all.
You can still put 100% into Legume Fallow IPM2, so I would think any applications after the start date of the Cap would just use that option.