a pic would sure help us understand ...

but the bottom line.. trees put roots where THEY WANT THEM ...

who in the world do you think you are.. thinking that you can outsmart that tree??? .. lol ...

provide a nice mulch ring of a few feet round ...

trickle the water for an hour or so .. i mean TRICKLE ... it will soak in.. and step away from the tree ...

IT WILL TAKE CARE OF ITSELF ....

w/o the pic.. i can not suggest if pruning for shape might be necessary .... to get it growing up straighter ... but again.. given 10 years.. it will TAKE CARE OF ITSELF ...

if its been heavily shaded.. do not be surprised if its leaves burn a bit ... they arent used to sun ...

and do understand.. it is not a child.. it will NOT need to be fed.. nor diapered.. nor educated .... and.. in fact.. if you are renovating the lawn anywhere within 20 feet.. it will get whatever it might need.. as the years roll by..

the forest of acacia... indicate to me.. that your soil in NOT lacking for anything ... and your oak is not suffering in that regard .. forest trees.. grow in forests ... water competition is probably its only problem... along with lack of sunshine..

and you have solved both those....

now.. dont go killing it with too much love... it simply wont need much from you.. now that you got rid of the competition ...

come back with those pix.. if you want to learn about pruning ...

good luck

ken

Water regularly as nature does in a moist climate or site, rather than trying to impose the deep soaking/deep drying routine - which is not what trees want. Except for desert-adapted trees in arid environments, the majority of roots are near the surface, where the air is. When there is an airless subsoil present, such as on many sites in my region, fallen examples of sometimes quite tall trees are seen to have hit the top of the subsoil and then gone absolutely sideways, their bottoms looking as though exploded against an impenetrable surface. So you do not want to flood most kinds of trees, nor do you want the fine roots to end up in dust. You do want to maintain even moisture, with diligent mulching helping a lot with this. Most kinds of trees and shrubs are not tolerant of sites that have impeded drainage, which is why extensive areas may be forested with the same few species that are, and why cultivation information about so many plants says "needs well-drained soil" or "good drainage essential" etc. Roots grow in the aerated water between the soil particles, rather than in the actual soil particles - that is why hydroponics is possible.

What kind of oak is it? Are you sure the roots are from the oak, most aren't shallow rooted. Mine are young yet so maybe some do root shallowly when mature.

I think poaky1 is on the right track here. Chances are the shallow roots are not from the oak at all, but from the locust, aka false acacia.

Now for the bad news: locust trees are notorious for easily sprouting from the the shallow roots - that's why they are a highly favored species for land reclamation, stabilizing banks along highways, etc. It's not clear when you cut the large locust, but you need to be prepared for an onslaught of root suckering in the future. Herbicide is one option, but would have to be applied repeatedly. Close, frequent mowing is a non chemical option. It may be easier to move the oak or eliminate it entirely until you gain control of this area.