In September, any summer resident objectively has a lot of work: there are a lot of important things that need to be done.
Therefore, there is no point in wasting time on useless tasks.
Sometimes you can hear recommendations about using yeast fertilizers for a number of crops in September. You shouldn't listen to them.
Yeast will be useless at this stage of plant development.
This remedy works as a preventative measure against late blight in combination with other methods. But at the moment it makes no sense to use it: it will do no good.
A concentration that does not harm the tops will be absolutely useless in the fight against the disease.
It makes sense to use fertilizer only if you are fertilizing crops that have already finished fruiting.
But if you are waiting for the harvest, you should not use superphosphate: it simply will not have any effect.