What do you think "trim" is here, and why do you think anyone would do it?
How much do you think a hay field would grow in six weeks?
The animals are doing the trimming instead of the mowers. This isn't super complicated logistically; each takes tall grass and turns it into short grass. You can rent goats to clean up shit like poison ivy, even.
> How much do you think a hay field would grow in six weeks?
The one by my house grows maybe a foot in that time, which is why they rotate pastures. Even a handful of horses can keep an acre worth of pasture quite well cropped.
The animals keep the grass and weeds under the solar panels trimmed, saving on mowing. This also provides food to the animals, who love grass, meaning you don’t need as much hay during the spring/summer seasons. The cows get fed, the solar field gets maintained, and the farm gets energy output as a bonus.
Leave a grassy field untrimmed for a few months and guess what you wind up with? A hay field.