2,437. You Can't Nullify Chadash

Maachalos Assuros 15:10

The previous halacha also applies when the current crop of grain (chadash) gets mixed with the previous crop of grain (yoshon) before the omer is brought, i.e., even the smallest amount renders the whole mixture prohibited because the prohibited item will ultimately become permitted. Once the omer has been brought, the whole mixture becomes permitted. Similarly, whenever there’s a way to render a prohibited thing permitted – such as things that were consecrated, second tithe, etc. – the Sages didn’t set a volume for nullification. Rather, even if one of these gets mixed in a ratio of thousands to one, it isn’t nullified because there’s a way to permit the prohibited thing. This is also true of rabbinic prohibitions like muktzeh or animals born on yom tov.

Maachalos Assuros 15:11

As far as orlah (the fruit of a tree’s first three years), the mixed species of a vineyard, fat, blood, etc., the Sages set volumes for their nullification; they also did so for trumah, which has no means to permit it for non-kohanim.