Disc Harrow for 3720

dkhntr04 · Sep 13, 2013

I am in need of a disc harrow to finish prepping some land. The ground is fine sand and has been worked twice with a heavy disk (Wishek) and field cultivated twice. I need to disk it primarily to chop up the sod chunks that are laying on top.

I am leaning towards the Woods DHM6 or DHM7 due to weight and local dealer availability. I know that I should be able to pull the 6', but do you thing I can go with the 7'? I need to cover a lot of ground so the extra foot of width would be nice. Tractor has cab, loader, loaded large R4's, and will have my heavy 500# skidloader bucket on. Total tractor weight with operator will be around 5700#.

wolftree · Sep 13, 2013

The rule of thumb usually is 5hp/per foot of disk. I do not know your drawbar or pto horsepower. If you are 35 HP+ at the PTO or drawbar you should be good for a 7 foot disk.

jenkinsph · Sep 14, 2013

There is only about 80 lbs difference between the two disks so I think you could go with either one. Both are fairly light weight disks and should be an easy pull, still if needed you can adjust the gang pitch to lessen the load.

jeff9366 · Sep 14, 2013

I pull a 16/18", 567 pound, 5'-6" Howse tandem disc harrow behind my Kubota B3300SU over sandy loam without problem.

With your much larger tractor I would think you could pull an 8' Disc Harrow.

What diameter discs are you considering? 20"?

How many discs?

jenkinsph · Sep 14, 2013

jeff,
the op is looking at 800 to 900 lbs with 18" blades, 7.5" spacings.

deere5105 · Sep 15, 2013

An 8' with 20" blades on 9" spacing with a 4" frame will spin all four on my JD 5303 when buried to the axles in soft loose soil. If all you are doing is pulverizing the surface soil either should work. I may be under estimating the 3000 series units, but I would think a heavy 7' unit fully engaged would be quite a load.

Edward. S · Sep 15, 2013

wolftree said:
The rule of thumb usually is 5hp/per foot of disk. I do not know your drawbar or pto horsepower. If you are 35 HP+ at the PTO or drawbar you should be good for a 7 foot disk.

Rule of thumbs aren't really good to go by because I have a 100PTO HP tractor and I only pull a 14 Footer and it doesn't want anymore in certain conditions.

foggy1111 · Sep 15, 2013

HP is not the issue here. You will have plenty of power.....but tires and traction is going to be the issue. Not sure what you have for tires. I have industrial tires which are loaded with rimguard on my 3320. I have a 5.5' box frame KK disc. I pull it fine....but would not like any more disc if I have it set up aggressively and deep in sand.

Just re-read your post with tires and weight. Hmmmm. Any way you could try a disc before buying one? I still think I would play it safe with the smaller disc you mentioned.

wolftree · Sep 15, 2013

Edward S,

I agree, rules of thumb are only a very rough guide at best. Soil type, hills and tractor weight all have to be figured in. Where I grew up, we figured 1 HP / inch of moldboard plow until you reached 4 bottom. After that you added another 10 horse or so to compensate. My clay soil here would push that to 1.5 HP/ inch. Throw in my hills and you better figure 2 HP/inch with lots of front end weights and rear wheel weights.

This probably is why tractors under 100 HP usually are made in increments of 5- 10 HP.

dkhntr04 · Sep 15, 2013

Thanks for all the replies. I'm thinking that I will stick to a 6' disc based on my original thoughts that have been verified by your input. For this project I could probably do fine with a 7' since I will be running in the 7 or 14 degree setting. I do however want to be able to pull this disk in the future at full tilt and sunk to the spools in heavy ground when needed.

Foggy, I don't know of any discs that I could try before buying. What kind of ground are you running that 5.5' disc in?