Spring Spacers are available for John Deere 50 series such as the 750 and the 1850. They are 1/2″ thick and easily install in the spring assembly to increase the opener down-pressure by 75-90 lb.
They are required in the openers behind the tractor wheel tracks and/or air-cart wheel tracks, to increase the down pressure in these lower/compacted areas (relative to all other rows), to increase down pressure and maintain a more consistent seeding depth.
Most drills and air-seeders require 3 spring spacers per tire on 7.5″ spacing and around 2 per tire on 10″ spacing, but measure the tires to be sure.
See the YouTube video below. Compare the left opener (with spring spacer added) to the right opener (without the spring spacer added). Note that everything else is set the same and the openers are both on the same rockshaft with the same down pressure. Also note the openers are using the alternate position to run the gauge wheels either side of the corn rows, when no-tilling into cornstalks using RTK and controlled traffic. Lastly, please see the weight package added to ensure the openers are engaged consistently into the soil, despite the heavy residue.