Solution:
Required equipment- any mower, any tractor with 110 hp or higher for the John Deere C441R Baler with wrapper. No other balers work for this.
Costs: Baler- $112,500 base, I recommend having the bale turner equiped in the shop menu when you buy it. It adds $1,500.
Map I completed this on was Zeilonka.
-Start a new save in career mode, with $1,000,000 starting money.
-Set your settings the way you like. Save the game.
-Buy the equipment you want to use. You have to have the JD C441R. The mower I used was the Krone Big M450.
-Now, there are two ways to get the extra money you'll need for this. One will be to use Government Subsidy signs located in the in game Mod Hub (Downloadable Content) section. The other way is to create a multiplayer game, using the save you saved in step 1. Once in Multiplayer, create as many farms as you want. You'll want at least 3 extra farms. Total cost for this solution is around $2,500,000. Give or take a few bucks.
-Once the MP farms are created, save the game, and exit.
-Load that save back into career mode. Once loaded in, save the game. Then buy all of the following Farmlands: 40-50. You don't need Farmland 44. So that will save you some money.
-This is the crucial step to get this done quickly (about an hour total). Paint the fields with the longest Meadow Grass in the Build Mode. Cover the roads, as you'll get extra grass for this. Not needed, but don't be too carefull about the painting. We're only using this save for this achievement.
-Good time to save the game. Next, mow one headland around the whole area. You'll only need the one headland.
-After mowing, use the baler to pickup, bale, and wrap the grass. You can miss some if you want. Try not to, or it'll take longer. Once you get to 40 bales, the achievement should unlock.
Any base game map could be used for this. No mod maps released to all platforms at the time of writing this. I used Zeilonka because the fields were in a big group. You don't have to get all of the fields I did. I just got them as I wasn't sure how many fields I needed.
Hope this helps you guys. Works the same on Xbox Series X as well for those Xbox Series X players out there reading this.