When trying to change some aspect of the farm it's usually better to use animals than machines. Putting cows and sheep or pigs onto a patch of goldenrod will turn it to productive pasture over the course of a couple grazing seasons. While not as fast as plowing and planting, this approach also doesn't require machines, diesel, and expensive seeds. A less obvious positive is that shifting the landscape through animal management limits the rate of change. If left in one place long enough pigs will churn sod to dirt as effectively as a plow, but even a large group can't have the immediate impact of a tractor - my swine herd can't go out one day and turn over fifty acres. The time it takes animals to do their work leaves plenty of room for observation, meaning, for example, that I can move the pigs earlier than planned if it looks like they are causing more erosion than I anticipated.
But there are some jobs that require more direct action. The farm is about half woods, and I aim to turn some of this land into silvopasture. While I can theorize about how it might be possible to achieve such a shift in the landscape by using animals to repeatedly damage the roots of particular sections of forest until the trees died, then waiting years until they fell, then waiting still longer for them to rot, it would not be a feasible approach in a human timeframe. I also doubt it would be better from an environmental perspective, since cutting down the trees not only clears the land more quickly, but also provides lumber for farm construction and firewood.
There are other tasks that animals can't do. Pigs need plenty of bedding to keep their hoops warm and clean through the winter, but they don't seem to have the foresight to gather up hay in preparation for the cold. This gets at one of the biggest hurdles to limiting machinery use - there are certain tasks that only a machine is up to, but it makes no financial sense to own something if it's only going to work a day or two each year.
In an ideal world this might be solved by cooperative ownership. If forty like-minded farmers collectively pooled their resources they could have access to quite a lot of specialized equipment, like post pounders, excavators, skid steers, and manure spreaders, at a relatively modest price. But this would take a level of organization, optimism, and a shared vision that are largely absent from American agriculture.
The next best thing is renting, which allocates resources almost as well as an agricultural collective might. Also, by renting I can be sure to get a machine that is big enough to do the job. Here's a video explaining why we like wood chips for bedding and how we make them: