Ron,

It seems to me that the air is simpler, more reliable and lower cost but more difficult to control. Anyone who has tried to change the airbag row unit down pressure on the go knows that is not exactly a quick acting system.

Electric controls on the other hand are far easier to control than air and tie in to the gps and on the go in cab controls much better. A clutch also does not need a lot of force as the row unit down pressure system does. From the sound of it above the row unit clutch is a spring apply/electric release system so it fails on rather than fail off.

Regardless of how they do it, I am amazed at how an integrated gps/row unit shutoff system works.

I was on a 36 row 20" planter this past spring with gps controlled shutoffs. The computer controlled rows in pairs since I think the output is limited to 32 not 36.

We were planting corn into a wheat field that had a creek running diagonally across one corner leaving 4 or 5 acres on the other side of the creek in a triangular shaped area. And we were going to plant this with a 60 ft planter??? In the past many folks would keep a 6 or 8 row (15 or 20 ft) second planter to come back and plant these areas separately.

I was in the cab with this very innovative customer. We made a round 60 ft wide around the outside of this 4-5 acre triangular section of the field driving manually with lots of backing into corners. The operator then put it into autosteer and went back and forth. As we got to the outside headland round it was amazing to see the row units shut off sequentially as we crossed the previously planted headland. And most of this is with no hands on the tractor steering wheel!

On our last pass we were left with a triangular unplanted pass about 8 rows wide on one end and tapering off to nothing maybe 100 yards down.

I will always remember watching a 36 row/60 ft planter end up planting 2 rows at the end and having this weirdly shaped triangular patch planted by a 60 ft planter very quickly with essentially no overlap/double planted area and no unplanted area!

IF this was say 5 acres and at 150 bu yield we just planted 750 bu x say $5 or  $3750. worth of corn that might easily have been skipped altogether or "come back" later (usually much later) with another $20,000 worth of equipment to plant corn that might pollinate and mature a couple days or weeks after the main part of the field. If this happens a couple times a day technology can be paid for pretty quickly.

It was amazing to watch.

Jim at Dawn