I want to "save" 3/4 acre of grass from weeds

Keep cutting it and hope that the weeds will give up.

I find regular/frequent mowing is a must when the grass is growing not too short a cut, Scarifying with a wire scarifyer (but not deep) before mowing and not in spring - just rake lightly in spring. I find applying a feed/weed killer in spring and again in the summer is of benefit and is not expensive.
If the grass is impacted you can fork over to airiate it but I do not do this to mine too much like hard work. I found this improved my lawns quite quickly.
If you want to do more there are plenty of lawn care advice on the internet. All grass will improve with care and weeds will reduce if the grass is mown. good luck it will improve and will not kill you or the bank.
Having said all this just realised its 3/4 acrea borrow a ride on mower or some sheep

are there any animals like farm animals that eat this kind of thing? maybe this may help and then what they produce will also benefit the ground?

just a thought?

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