4 foot implements match a 186D very well. They will do more, in some conditions, but you'll be able to use the implements to their full capacity. One nice thing is the Powershift transmission does a good job at transmitting power efficiently but giving some flexibility in speed. I have 4' box blade, disk, and brush mower behind my 186D, and have run a 2 bottom plow and 5 1/2' disk. They work, but require slow speeds, and are a bit too much implement.
My 186D has cast iron weights in the rear, water filled tires front and rear, side/belly mount cultivators, and up to around 250lbs in front weights. I've never weighed it, but it must weigh around 2000 lbs without me on it: The published weight for the tractor alone is 1538 lbs per Yanmar, and estimating 250 lbs of water in the tires, another 175lbs of wheel weights and another 100 lbs for the cultivators, it's over 2000 lbs before the operator is on or the front suitcase weights are added. Barring a few freak occurrences, my tractor always runs out of power before traction. My tractor is also ballasted more than normal.
With so much mass, this little Yanmar does an admirable job pulling ground engaging implements much larger than it has any business handling, but the size of the implement itself sometimes works against the tractor, with pins too high, for instance. For moving loose fill, I'm sure the tractor would handle a 5' or 6' box, especially of light construction, but you won't be able to lift or work the box if it's full of spoil, or budge it if the rippers are down in hard soil. Basically, it's more productive (faster) for me to use a weighted-down 4' implement like the disk and go at a faster ground speed than it is to use the larger implements. My soil is likely heavier than yours, though.
If you found a light 5' disk, you'll probably be able to use it just fine, but I doubt it will break fresh ground as well as you would like. Using a ballasted 4' disk will give better results for you in that respect. California talks some about the differences between using a bigger disk vs a smaller disk of otherwise identical characteristics with his 186D
here and
earlier in the thread, comments 2 and 5 specifically. He has since added 150lbs of wheel weights, and has remarked that the tractor pulls much better,
even in 2wd (which more mirrors my results).
You'll be able to handle a 12" plow in your sandy soil, or any 4' disk quite well. I doubt you'll have a problem pulling a 5' (or even an angled 6') rake for collecting loose limbs and debris. With the 4' disk, I expect you will be able to add sufficient weight to freshly break and cut up any soil that will grow crops without irrigation. Using a plow first may let you use a 5' disk, but I doubt you would save much time, if any. If your food plots are small anyway (say, 150' square) the 4' disk will be all you ever need anyway: Just ballast it to cut deep enough, and go for it. A potato plow/middle buster may be cheaper or easier to find than a plow.
Comparing the 186 to your ATV with the Groundhog on it: I've never actually used one, but have seen their videos. The main appeal seems to be speed: Getting into a place quickly with the ATV, then ripping around with the disk down. It appears to do an adequate job in soft soil, and it seems like the ability to put the machine's weight down onto the implement will let it cut ok, but it doesn't process the soil anywhere near as much as my 4' disk will with 100 lbs of weight on. The tractor implements will do more, although it will seem much slower. You're going to process the soil more with the tractor; I'm not sure it will matter for your plots. What do others in your area use?
You'll enjoy using your new tractor. Post up some photographs of the work you do with it!
