Pam's Harvestcraft is a really annoying mod to automate for.
Not in the sense that it's hard or impossible to do, but how the crop mechanics tend to be different depending on the version, modpack configs and external mod interactions (speaking of hunger overhaul).
You can't just jump in to a pack and automate Pam's stuff the same way in every pack/world/server. You have to figure it out by trial and error, becasue in the past I used MFR and it worked like a dream in one pack, but in an other the crops where set to rightclick and yeilded no seeds when destroyed so you couldn't use them. Then there's how certain crops that won't plant from the produce it's self and need to be crafted in to seeds.
I wish the mod was a bit more consistent in it's mechanics, judging by how HarvestCraft handles and the sheer mess that the config is in (Going to be frank here, it's horrendous), It doesn't seem like Pam is a fan of organization. I'd use Agriculture if I wasn't such a derp constantly burning my food... Then again Pam's has a really vast variety that's handy for keeping your hunger filled when using Spice of Life.
So essentially my suggestion is observe how the crops are harvesting, if it's the usual crop needing to be broken to get produce and seeds use MFR or other farmers. If it's the rightclick mechanic used you could get away with a easy row of Autonomous activators clicking the crops or other R-Click simulators.
IF you insist on large plot of crops and have thaumcraft you could try to use golems with a "Use Core", but I'm not sure how you handle them sequentially R-clicking multiple objects. Just don't try harvest golems, they work if the produce is plantable but they ballz up the organization of your crops if you insist on mixing crops in one plot. I once had a plot of Tomatoes, lettus, cucumbers ect turn entirely in to cucumbers as harvest golems attempt to plant what they just gathered in nearby empty farm land. They end up empty because sometimes depending on settings a Pams crop yields nothing leaving the farmland empty.
That being said though this will be dependant on the version of HarvestCraft and the configs of the pack.
You might just need to experiment.
