I have a 4-5 acre area that I converted from corn/soy field to grass around 8-10 years ago. One end is VERY sandy soil, the other isn't. It's a gradual change over ~1,000ft length.
I've used broadleaf killer every other year (sometimes every year) and used crabgrass preventer + feed this year. I've also over-seeded twice, though without any tilling/prep of the surface.
The grass has never completely filled in / has always been sparse. It's definitely more sparse in the sandy areas.
What can I do to help promote grass growth to give make thicker grass to look/feel better and and hopefully crowd-out some of the weeds? If it were a small yard, I could probably come up with solutions, but at this scale, I'm just not sure.
I have a large mower available, and can tow a small sprayer or spreader, but I don't have a tractor.