Killing a 100 sq foot area of ants in pasture - ideas?

I have this beautiful back area of pasture that I am reclaiming from Salal and Scotchbroom - the soils is nice and airy, but absolutely INUNDATED with ants. I've stumbled over one big ant hill and think another one is hiding back behind the last section I have to clear. Every few inches there is another little hole with soil piled up indicating they are waking up from winter slumber and getting busy.

Area is roughly 100 square feet, give or take - it's generous. I'm putting corn and moringa in there so need to get the ants out quick because:
1) ew
2) I need to work back there and have to till like crazy
3) ew, again
4) They are still sleeping but soon, with it warming up, they will be EVERYWHERE.

My thoughts:
1) DE spread at intervals between rain showers. Which would be funny because it'll look from the porch as if my pasture has a sever cocaine dependency problem.
2) Burning that big pile of Scotchbroom that I have piled up in strategic locations so as to burn the ants out - would that even work?


Am I missing something? Is there a natural way to get these guys out? I can't even imagine the labyrinthine complex they have tunneled out in the back 40. Between them and the moles, I think I've got some pretty aerated soil back there. I'm in the middle of research about how the ants work in their colonies to understand them better, but thought I would pose the question here, as well...

It's like that old 80's song - "don't go away angry - just go away."

Thanks, all!

Some thing to consider, those ants are likely a big part of the reason the soil is so airy and nice. They have likely been boosting the soil health greatly in their time burrowing back there.

Now I can understand your issue of wishing them not to be there while you work the area. Ants crawling all over you while trying to plant is not so fun.

Sounds like you have the general gist of techniques. DE, and fire should greatly decrease their populations. You could also pour boiling hot water into their holes. While they have systems to move water away from the colony, this can still help reduce their numbers and decrease the colony.

A big question might end up being do you want to actually completely eradicate them or just reduce their population to a more manageable amount? Complete removal will likely be difficult to next to impossible. But management and decrease is highly probable. And ants in the garden can be quite beneficial. They will help with soil fertility and aeration. As well as defend the area against many other insects that can be more damaging to crops. They are often decent pollinators as well.

This article may help.  
http://www.motherearthnews.com/homesteading-and-livestock/get-rid-of-fire-ants-zb0z1307zsor
ETA
https://www.dirtdoctor.com/garden/Organic-Fire-Ant-Control_vq376.htm

Ants act similarly to Earthworms, and in many ecological systems replace them in function.  As well as making myriad tunnels, ants take biological material (insects, spiders, dead mammal parts, not to mention the massive amounts of vegetation) underground where they store it in galleries and usually inoculate it in fungi spores for more delicate consumption.  As you might guess, this process massively boosts soil fertility over time.  Your scotch broom is a nitrogen fixer, and as such might be more valuable growing, if not allowed to go to seed.  Coppice them, or chop and drop.  Plant your corn in circles around it, and gain Broom's nitrogen boost.  The boiling water method works to reduce ant populations, as does massive watering in general, but these will have resulting detrimental effects on your soil systems.  I've heard that they don't like vinegar.  If that is the case, an experiment might be in order of placing some vinegar soaked rags over some of the holes to see what happens.  Salal is a great berry, and is prized also for it's leaf shoots which florist use to dress up arrangements.  As is my usual fall-back response:  try to work with the systems that exist.  Reduce them, and use them to your advantage, while tilting the ecosystem towards what your desire in either a slow process, or trying to get the greatest gains from the least amount of force.

I'm just now trying it, but b-Dahl bluestem supposedly chases ants away. The tests they conducted showed 1 mound per acre vs 38 per acre where it wasn't planted.

Maybe not a test, but they stumbled on it. They think it's when it goes to seed. Has a bad smell to it.

It's also easy to remove. No underground roots shooting out like with bermuda.

I bought a few round bales of it. Horses and cows like it.