Haven't found any case of this being reported so here it goes:
I bought some 100% seeds and can't plant them. My upkeep and amount of seeds are right and I added the initial humus but I still can't plant the seeds on any of the 3 fields I planned for them. I can plant them on some other fields. The only difference seems so be that the fields where I want them have 45+ of the influence I'm boosting and the fields where I can plant them are below 30 on 2 stats.