Looking for an air drill.

Old concord. With the new case air tank that can push 650lbs of product no problem.

If you weren't happy with the Flexi 5000 in wheat I'm assuming you're looking at disc drills mainly. They are likely the best option for narrow spacing/accurate placement but are basically all single shoot under 10" spacing. Atom Jet makes granular and liquid double shoot boots for Case SDX drills and liquid ones for the newer 500/P2080 drills, not sure how high of rates you can safely put down but should be able to get a good shot down safely. 40ft SDXs can be found pretty reasonably it seems, add a bit for fixing up some wear points and a double shoot conversion and you'd be running for a lot less than anything close to new. For a cereals only drill I'd be more inclined to get the narrowest spacing with the most accurate placement you can get and not worry about trying to piece together a one pass fertilizer system and sacrifice efficiency or seed placement/spacing. Get the best stand possible with a good starter blend and add the rest in crop, cereals really respond well to top dressing.

Why wouldn't you inject fertilizer into irrigation water and top dress that way? The potato guys do it that way here.

Moving tanks around, especially if the water outlet is at the pivot point, monitoring tank levels and getting them filled on time. Dealing with plugged filters, stuck check valves, ruptured hoses, leaking fittings (even brand new stuff) etc. Trying to get enough fertilizer on early enough when the crops don't need much moisture is also an issue, especially when trying to time it around spraying. We normally do put 30 or so lbs through the pivots but generally it is later in the season. Was looking through the manual for my fc 3450 tank and it shows that it can deliver 400lbs per acre per meter (coarse roller) but it does not state at what speed or how many foot of drill per run it is capable of doing it at. Anyone know where I should look for more information?

My cart is variable rate but only single fan. Right now it is on a 57 foot single shoot fc 5000 with 7.2 inch spacing. Can put down 450lbs of product at 6mph without issues using all 8 runs. My question is will it work on a 40 foot drill with 7.5 inch spacing and midrow banders using only 4 runs? So about 150lbs down the seed tube and 400lbs down the banders. Could add more towers but costs money and I'm having trouble justify the expense as it is. Would like to increase my speed to 7mph or more under the right conditions.

Is the dual fan necessary to supply enough air or is it just not possible to balance the airflow with a single fan? My old drill has 8 towers with 12 openers each. The drill I am looking at has 4 towers with 16 openers for seed and 4 towers with 8 openers for fertilizer. Each drill has 96 seed/fertilizer tubes so the total amount of air needed should be the same, no? On a side note why are bourgault seed carts so expensive in comparison to fc/case/nh? They seem so simple.

What kind of pumps are you using?  I use piston pumps that suck through a very coarse screen that I haven't checked in years because I'm lazy. Probably don't even need a screen.  Stainless injector/check valve in the water pipe.  I've never experienced any plugging.  I know the tank is often full of flies, dirt, etc, but it all goes through the pump and into the water.  I did have problems with the plastic 30 gph injectors. They are rubbish. I use the stainless 100s and there's no way you could plug those.  I rarely go much over 40 gph.  We have tanks at most pump sites permanently that we use so it makes that part easier. I do have to shuttle my pumps around, which is a bit of pain, but the timing between winter wheat, spring wheat, and canola makes that easier.  I don't lose too much sleep on the accuracy of the rate.  I measure what I put out on that run and adjust the pivot speed to change the rate for the second and third shots.

We usually wait until after herbicide to do the first shot so we're not causing problems for the sprayer.

Some guys around here do fungicide through the pivot (Lance in particular).  I'd have to worry about the rate a little more with that one, and keep it agitated.

Since water does not come on until may, we do rely on ESN for the Winter wheat so we don't have to top dress in April.  I feel ESN works very well, although I recently talked to an agronomist who doesn't feel like ESN is a good fit for western Canada.