Agronomy Library > Soil Conservation

Adjusting Planting Depth Under Wet Soil Conditions
Author: Murray Green P. Eng.
Date Created: May 15, 2003
Last Reviewed: February 01, 2007

 Issues with initial crop emergence:
Seed placement depth and soil cover will affect several crop stand conditions:
Percentage of seeds to germinate. Seed/soil contact, or how well the seeds are covered and firmed with soil particles, will determine moisture uptake and germination.
Vigor of the plants that emerge. Rapid germination provides maximum energy for the seedling and best protection from soil born diseases.
Number of seed or plants that are delayed in germination but emergence more than a week later. Too many of these and harvest decisions will be more difficult and green kernel content above set limits will down grade the sample.
Setting planting depth:
Recommended depth of planting of some seed types is listed under Seeding Depth. An additional feature of good seed placement is that the seed are about a half inch into moist soil.
A common mistake by direct seed farmers is to tempt to just “scratch” the seed into the surface. The result is frequently poor, as any significant drying after seeding will leave some or all of the seed stranded in dry soil. Or much of the seed is never covered with soil in the first place. Subsequent rain will germinate some of this seed and result in “late comers.” Only broadcast Canola and incorporation and covering with a fertilizer application operation that provides sufficient soil disturbance, has provided satisfactory results in very shallow placement.
Wet soil conditions:
Except for the most forgiving loamy soils, when direct seeding, wet soils break into lumps when a ground opener passes through. Lumps do not make a good seed bed. They cannot easily be pressed or formed into a seal over the seed row. Heavy packing will cause soil density too great for the seedling to break through. (Regarding packing wet soil, ensure there is no traffic on the unseeded part of the field. Trucks or equipment after planting are not a great a problem.)
The deeper the ground opener must penetrate, the wetter the soil and the larger the lumps. Therefore the decision is how deep to place the seed versus how many soil lumps are produced.
What to do:
  • Ensure the depth is great enough to obtain soil cover over the seed.
  • Try to stay out of the very damp soil deeper in the seedbed.
  • Try an opener that does not need to penetrate deeper (fertilizer band) than about an inch below the seed placement depth.
  • If none of the above is possible, one solution is to harrow the field after planting. The objective is to break the lumps and mix the loose surface soil particles, even if they are dry, into the lumpy seedbed. This will fill the air spaces and seal the seedbed.
  • Another solution proven successful by some farmers is to roll the field with the same machine used to roll field peas. The objective is to force the seed row furrow closed from the sides, while not increasing the depth of soil cover above the seed.
  • When harrowing or rolling is likely to be required after planting, reduced the seeding depth slightly to maintain the proper seed cover depth.
  • If the calendar date is near the middle of May, select fields to plant based their dryness, not on the crop type.
Finally, check the seed placement depth and soil cover conditions frequently and in every field. The time taken will ensure the best emergence possible.