How to plant a LOT of trees efficiently / reforest a field?

Related to this thread https://permies.com/t/97977/Mass-reforestation

How would you go about planting out a large food forest? In the context of a field mowed for hay, so starting from the forested edges and working inward to make it easier for the mechanized mowing to avoid young trees.

I envision starting with easy hardy species for first stage succession. Willows, poplars, pines that can be carried as cuttings or bare root in a bag and slipped into the ground with a tree bar. With that kicked off, start with the more careful plantings and even mulching of guilds like Nitrogen/nut/fruit that will carry on as the pioneer species mature, die out, or are harvested.

I'm not in a hurry, I'm planting trees! Saving money is good and tree nurseries are cool, so I'm working on propagating batches of trees I'd like to plant, and will turn to conservation nurseries to get batches of bare root trees at good prices, adding more to expand the (re)forest edge over time. I'm also hoping planting seeds would have a decent success rate, as I can collect hundreds of great nuts locally pretty easy then densely plant them along forest edges to try and expand the woods as a food forest. I'll need to find good ways to keep the hay operation from wrecking those seedlings though - hopefully it can be mowed by someone's ruminant flock instead of a tractor!

Planting lots of trees is very easy. Willow cuttings can just be stuck in the ground, seeds of many trees start very readily,  it's quite easy to start a lot of trees from cuttings in root pouches or pots to be put it the ground later. I think the biggest issue you will have isn't starting trees, it's protecting them initially. I would recommend fencing the area first, before anything else. You can fence individual trees, but it ends up costing far more than fencing an area. Cheap plastic deer fence is a good way to do a pretty large area.  If the area is too large, you may have to accept heavy losses. I planted 400 trees that i got from the DNR last year, and i lost almost all of them. Only a few hazelnuts survived the deer and rabbits. I have approx 20 trees left of the 400 that I got that way.

I have known a lot of people who have planted a lot of trees to get very few survivors. When looking at input cost, of the trees and labour, I think it's usually best to put more time into each tree, right from digging the hole and fertilizing, then watering and protecting from animals.

One of my brothers gets lots of free trees as a byproduct of his business. On many occasions he has dug something up or had one of his workers dig something up, then stick it into the ground at his place. We have a summer drought. Almost everything died, 10 years in a row. It would have been cheaper for him to buy them at the nursery and then look after a few.

That makes sense Trace. As I think about it more, I agree the establishment and initial maintenance is much harder than the tree propagation at least from what I've seen and experienced so far.

Watering could be a challenge on a site without water. I could use one of those large water tanks in a pickup truck for sensitive trees if needed. Some simple earth works could also help manage water and create needed moisture microclimates, but that might be a stretch if this is not a main focus project.

Browse protection and weeds seem like the major threats.

For general IPM: diverse plant communities nearby, as in adjacent hayed field or current forest, could help along with diverse plantings. Using currants and scent blockers in guilds could also help with browse protection, and I've heard foliar sprays with egg water have worked for others establishing nut groves in my area.

Tree tubes seem feasible to me for sensitive species (e.g. hazelnuts don't need them, hickories and chestnuts might).

Fencing would need to be smaller sections of fencing that get moved as new areas get reforested. That seems like a big project, but it would also help keep hay mowing from damaging trees. Smaller-scale mowing, scything, or even grazing would be another plus for weed management within the fence.

Be sure to include many support species