I am not a specialist, so this probably won't help, but I found an old John Deere manual for horse drawn ploughs -http://www.scribd.com/doc/53055242/The-Operation-Care-And-Repair-Of-Farm-Machinery-19
On plough suction, begining on the bottom of page 9 (the part that may be most relevant, if relevant at all, is at the bottom in bold.) :
"Setting Shares for Suction. The plow bottom is led into the ground and held to its work by the underpoint suction of the share. Such suction is produced by turning the point of the share down slightly below the level of the underside of the share (see Fig. 14). The amount of suction necessary depends upon the type of plow and existing soil conditions. Stiff clay soils are harder to penetrate than light loam soils and require more suction in the share point.
"Landside suction (see Fig. 17) in a plowshare holds the bottom to its full-width cut and is produced by turning the point of the share toward the unplowed ground. The land suction, as well as the down suction, should be measured when the share is new, so that the same amount of suck can be given the share when it is sharpened.
"The importance of having the correct amount of suck in the share cannot be emphasized too strongly. Too little underpoint suction will cause the plow to "ride out" of the ground and cut a furrow of uneven depth. Too much will cause "bobbing" and heavy draft. In either case, the plow is difficult to handle. If the landside suction is too great, the bottom tends to cut a wider furrow than can be handled properly, and the reverse is true when the landside suction is not sufficient.
"The setting of walking plow shares and of riding and tractor plow shares is dicussed separately, as the shares are different.
"Directions for setting walking plow shares are as follows: Set the point of the share down so there is 1/16- to 1/8-inch suction, or clearance, under landside at point "A" (Fig. 14). The clearance, or underpoint suctionin the throat of the share should be 1/16- to 1/8-inch at point "B" (Fig. 15). All 12-, 14-, and 16-inch walking plow shares should have a wing bearing. The correct wing bearing (point "D", Fig. 16) is as follows: 16-inch plow, 1-1/2 inches; 14-inch plow, 1-1/4 inches; 12 inch plow, 3/4 inch. A straight-edge placed at rear of the landside (point "C") and extending to wing of share should touch back of edge (point "D"). When sharpening the share, care must be taken not to turn point to one side or the other. When fitted to the plow, there should be about 1/4th inch clearance or landside suction at "E" (Fig 17)."
I hope this helps, or something in that manual does.
From Maciej Jaworski
Marcin If you still need help with this. Seem to me like it's similar (or really it is ) horses plow. As I remember to plow you need lift the wheels up - by lowering the metal bars on front of it ( I think). I hope this will help you. To have good result with plowing it's better cut weds (this allow cover it nicely) (for small parts if possible) and let it dry a bit (for ecological reason). So, good luck.
I'm a farmer and mechanical engineer from montana. I've never used that implement before but sometimes unworked earth is so hard you can't get in the ground at all using a standard tilling implement. You have to "break" the ground first using what we call a "ripper" implement. It's usually just a plow like implement only it has spikes instead of shovels. Hopefully thats helpful :D