Accurate depth placement can be compromised if planter units are loose or wobbly. You should not be able to easily lift up a planter unit or move it sideways. Look across your planter units from the side. Are they all at the same height? If one unit is either up or down compared to the others, it needs work. A common problem is that some bolts are loose or additional bushings are needed. You also need to replace cracked or broken seed hoppers.
Seed opener disks
Seed opener disks need to have a minimum diameter (check operator manual) or they will not place the seed at the appropriate depth. Seed opener disks also need to come together in the front (they should touch for 3” for old blades but only 1-1.5 inches on newer blades). Stick two business cards between the openers and move them as close together as possible to check this. If opener disks are worn too much you will get a “W” shaped seed slot instead of the desired “V” slot.
Seed tubes
The end of seed tubes may wear to the extent that they curl inwards, catching seeds. There is often a hook halfway up that can easily break off. Seed tube guards need to have their minimum width and be fastened correctly or damage to the seed tube is likely. Clean seed sensors if you have them.
Seed firmers
These help to press the seed down in the furrow, guaranteeing more accurate depth placement of the seeds. The tension can be adjusted with a bolt. If the seed firmers are worn too much they need to be replaced.
Depth wheels
Depth wheels should run tight against disks. Change washers from in- to outside (or vice versa) of depth wheel if necessary. If this doesn’t resolve the problem, the depth wheel arm needs to be replaced.
Coulters
Check the diameter of the coulters and replace them if needed. You should adjust the depth setting of worn coulters that are still usable.
Row cleaners
Check for wear. Adjust to compensate for wear or replace if worn too much.
Closing wheels
Closing wheels need to have an intact spring and need to be checked for damage or wear. Bearings cannot be wobbly or too tight. The bottoms of rubber or cast-iron closing wheels need to be 1.5”-2” apart. The closing wheel arm cannot have too much play. If so, bushings or the entire arm may need replaced.
Alignment of coulters, opener disks, and closing wheels
Take a rope and pull it straight from the front coulter to the closing wheels. The firming wheels, seed openers, and coulters should all be in line. Closing wheels should not run on top of the seed furrow.
Insecticide boxes
The insecticide boxes should have no holes or cracks. Tubes should be blown out with air as well as the slot on bottom of meter.
Fertilizer unit
Fertilizer opener disks should have a minimum diameter (check manual). The bearings should not be wobbly or too tight. Hang a bucket below the tube of the unit and do a test run of 175 feet in the field. Weigh the fertilizer in the bucket, multiply by 100, and you have the fertilizer you’ll put on in pounds per acre (at 30” row spacing). Adjust as needed.
Chains and sprockets
Check all chains and their sprockets. If they are worn or chain links are stiff, they need to be replaced. Chains need to have the appropriate tension and should be lubricated properly.
Tire pressure
Inflate tires to correct pressure.
Source : psu.edu