John, about your statement concerning the JD single disk drill family:

"...it is hard to get the seed slot closed up behind the opener and if closed it will tend to open back up when the soil dries."

 We have a lot of customers in heavy soils that use our Dawn Curvetine II closing wheel on the JD 750-1890 series drill. The curved teeth on the CT-II "chip in" the slot and smeared sidewalls sometimes left by any disc opener working in heavy wet clay soils. These also work well in tilled ground with the shoulder controlling tooth depth.  They are also becoming more popular on the Case SDX drill family.

The Curvetine II gives good seed to soil contact and does not require a seed firmer although you can use one if you wish. Here is a photo of a JD 750 equipped with them in a heavy clay hill area.

The way these chip in the sidewall it does NOT open up again when the soil dries. Seed depth is also more uniform. Because the closing is concentrated on the teeth rather than a wide wedge shaped surface, much less closing arm spring force is required, usually increasing arm bushing life. Less pressure usually means better performance in sticky clay also.

Jim at Dawn

(Dawn Curvetine II on JD 750 drill IMG_2351A.JPG)

Dawn Curvetine II on JD 750 drill IMG_2351A.JPG (98KB - 80 downloads)