Could you postpone completion of the project (or that part of it) and return in the spring with that in mind? Working with "nature" often entails delays like this.
I will be back as it's on my doorstep and I might well revisit the theme to try to make a set of more consistent pictures. The problem with that is is that when I am deliberately trying to make pictures to a plan either they don't work out or I get bored with the process. If I get an idea and carry it out while the it still excites me things tend to succeed, when I revisit an idea after the initial thrill has gone it become a chore.
I've also planned out a number of projects based around a series of preconceived pictures and given up after taking two or three because it's like box ticking. It's the element of not knowing what will appear before me that I find inspiring in photography. The chance to be surprised by what the world throws at me.
There are lots of people for whom the planning and execution of an idea works really well. They have the patience to wait for the right conditions and so forth. While I'm waiting I start wandering off (in my mind and physically) and start taking photos of other stuff, then forget what it was I was supposed to be photographing!
It's possible that if I revisit my files I might find a more visually coherent set of pictures as one thing I do is to take variations of compositions - on the basis that I don't know how I'll end up using the pictures and one version might work better than another. I know some people think you should only try to take the one composition as taking more suggests you haven't got it right, but when I used to write for fishing mags I always tried to get horizontal and vertical pictures and pictures with lots of negative space to help with page layouts.(Early on I was told that the more picture options you provide the better the chance of getting an article published.

) This has carried over into my general photography. More so since I have started making zines and things.
On the whole I think I might just start again and see if I can make a larger book/zine with a wider variety of pictures. I can see how a larger page size with small grids combined with the more documentary pictures could work. Although I am hoping to expand the documentary side next year now I've got to know a few farmers. So it might end up as a work in progress.
Incidentally, do you know of a book that discusses the preparation of one's work for a photo book?
I've not come across anything like that yet, but it would be useful. I have seen a few bits and bobs on various websites but they've not really told me much I hadn't worked out for myself. It might be worth having a search.