Ford 4000: TractorData.com Ford 4000 tractor information
Ford 4000: 3,400 pounds, 55-hp, 2-WD, Cat 1 / Cat 2 3-Pts., 13.6" rear tire.
You should Moldboard Plow as your initial operation. The plow inverts the sod, leaving the roots up so they dry and begin to decompose.
A Disc Harrow is a type of soil mixing tiller. A Disc Harrow will not penetrate as deep as a plow on unbroken ground, nor does it invert the sod. Without plowing first, the existing grasses will return year after year in my experience. You just mix "starts" into the soil.
So a plow is necessary, but only necessary once, provide the soil is tilled annually thereafter to keep it friable.
If you decide to go with a Disc Harrow only, find one with 22" diameter or 24" diameter pans which is the weight you will need. Disc Harrows with 22" and 24" diameter pans may be either Category 1 or Category 2 Three Point Hitch compatible, find one that will be a proper fit to your Ford 4000.
Plows come in various widths, which also determines the depth at which sod will be turned. Plowing will probably improve your soils ability to 'perk' moisture. You do not want to plow so deeply that you turn up sub-soil, so dig a few holes with a garden spade around you land to determine the depth of your top soil and do not plow deeper.
The most common moldboard plow is 12", which can plow 5" to 7" deep. These are always Cat 1. You can pull a 1 X 12", 2 X 12" or 3 X 12" plow, however the more 'bottoms' the more difficult to adjust for perfect soil inversion.
You can pull a 1 X 14" or 2 X 14" plow without loaded rear tires. A 14" plow can plow 6" to 8" deep. These are usually Cat 1, but perhaps Cat 2 sometimes.
You can pull a 1 X 16" or 2 x 16" plow but your 2-WD tractor will grunt pulling a 2 X 16" which will plow from 7" to 9" deep. I believe 16" plows are always Cat 2.
So in terms of rough ground, using 12" as an example, you will have a 6" furrow in the ground and next to it a 6" row of inverted sod, so you field will be a series of 12" bumps = rough.
In order to invert sod properly your right rear tire has to go all the way to the floor of the furrow. Tractordata.com reports your rear tire width as 13.6" but measure, you may have replacement tires. You cannot get a 13.6" tire to the bottom of a 12" furrow so you would need to find a 14" plow, not a 12" plow. (This issue with 13" or 14" rear tires in 12" furrows is OFTEN the issue when ops cannot get their plows to perform.)
Here is a very fairly priced Ford Series 101 2 X 16" plow not far from you: Ford 2 Bottom 16" Plow with Coulters Serial 4923 Model 101 | eBay
Determine if it is Cat 1 or Cat 2, likely Cat 2.
I pull a 2 X 12" Ford Series 101 trip protected plow. They are excellent plows. I paid $1,200 for mine, with coulters and a Landing Lever.
Perfect, Thanks alot. That's a perfect explanation!