I own a Landpride Scarifier SF77. I bought it new just about 9 months ago from a Landpride dealer (which also sells Kubotas, but I don't think that's relevant). I HATE it. It is by far the worst implement I have, and I would not buy one again. Here goes:
Landpride rates this for up to 50hp. I have exactly 50hp. Snag something, or just pull it really hard in compacted soil - like it is MEANT to be used - and those 3/4" thick plates that mount the draft pins WILL bend. I have one bent, and have destroyed two pins on that side and am working on the third. At least the pins are replaceable - those 3/4" end plates are welded structure and realistically are not replaceable. It bent after I had owned it less than two months, and had at most 15 hours of use on it. I took it back to the dealer for warranty - dealer waited for Landpride rep to look at it - the Landpride factory rep said yep, it's bent, no, we won't fix it or replace it. I did not get any good explanation of why they would not fix or replace it, but they wouldn't, and I'm never buying anything Landpride again. I can still use it, but it's harder to get on and off, and I expect the bent plate to get worse over time and eventually fail. I will probably have my wife's uncle, who is a professional welder, try to fix it when it gets a little worse.
OK, don't buy the Landpride version. Unverferth makes basically the same thing - the Town & Country Ltd. "Freedom Line", except it has stronger clevis-style draft pins, and it's $50 cheaper, and from what I've seen it's slightly better made too. IF you really need a scarifier, that's what I would buy. I had priced that before I bought the Landpride, but it would have been special order and I was in a hurry. How I wish I had waited.
BUT... the scarifier is really a one trick pony. It loosens soil and does a great job of popping out rocks and bringing them up, whether you want it to or not. But it doesn't work quite the same as chisel plow, and isn't good for tillage. What it excels at are two things:
1) Loosening soil that is badly compacted, but only to about 10-12" deep and only with a lot of hp;
2) Popping out rocks and bringing them to the surface.
After use in regular soil, the scarifier leaves a field of basically 80% undisturbed soil and 20% deep cracks with large clods on either side of them. This is because it really isn't meant for tillage use. It is meant for busting up badly compacted soil, like overused and dry pastures, or vehicle tracks and parking areas. It does a great job at busting up badly compacted pastures, and I have had some good use of it from that, but that's its main good use. In badly compacted soil it will typically shatter the soil into a powder, which actually is in fairly useable form - run a drag over that a couple times and it's ready to re-seed. But if your soil isn't compacted, it leaves trenches and undisturbed soil, which isn't nearly ready for seeding. Oh, almost forget to mention, in non-compacted soil it also accumulates large clods between the shanks every couple hundred feet (or less), which renders it basically useless until you get off the tractor and kick the clod out with your boots - it often takes several hard kicks. This is tiresome the first time and extremely tiresome the 10th time. I would guess I have done that over 100 times now. The scarifier is not a good tillage implement.
If I were doing it over again, I would not buy any kind of scarifier (and definitely not Landpride). I would either buy a true subsoiler for loosening compaction, or I would buy a box blade which can do most of the scarifier tasks, but not as deep, and can do a lot more. Ideally I would have one of each, but no scarifier. The only person I think would get decent use out of a scarifier would be someone specializing in pasture renovation. While the plate bending is a Landpride design issue, the other issues are going to be common to all brands of scarifiers, I believe.
For what you describe I think a true chisel plow, with spring-trip shanks, is going to be your best option. My second choice would be a subsoiler, but you'll either need a big tractor to run more than one shank, or you'll be making a lot of passes with just a single shank model.
If, after all that, you still want a scarifier, my two cents are:
1) Get the Unverferth model - better design for less money
2) You will need at least 40hp and either MFWD or loaded R1 tires to get reasonable use out of it. Actually to get full use I would recommend a setup like mine, 50hp, MFWD, and loaded R1 tires. With all that I still can sometimes get the whole tractor stalled with the scarifier deep in the soil, but at least I don't run out of hp. 60hp would not be excessive except that the Landpride model can't take nearly that much power (based on it bending with my 50hp setup), and while the Unverferth looks a bit more solid, I wouldn't run it with more than 50hp either. If you have serious ripping/shattering needs you would want a multishank subsoiler. For more conventional tillage use, a conventional chisel plow is probably a good option.
