Cold soil tends to prevail under the residue cover in no till and direct seeding systems. The reason is simply because the soil surface does not receive as much sunshine (solar radiation) energy and generally there is more moisture at the soil surface which also has to be warmed.
Is this a problem? Well, not as great a problem as no residue, warm soil, and no soil moisture which is more likely to occur under tilled conditions. The crop year 2002 is a recent example of that!
There are some practices which will help the situation:
Treat the seed to protect it during the slightly longer germination and emergence period.
Harrow cereal stubble to distribute any concentration of residue which would otherwise insulate that area of the field.
Cut taller stubble so that there is less chopped residue insulating the soil surface. Balance the stubble height between a less dense residue thatch and the height which the planter will accommodate.
Select a planting depth that is at an acceptable soil temperature, but will still provide sufficient soil flow over the opener to cover the seed. Often direct seeding equipment is set too shallow resulting in poor initial emergence and then a lot of late emergence. Poor crop emergence is usually a result of planting too shallow rather than at the depth normally recommended for various crops, even if that depth places the seed into colder soil. Shallower placement is acceptable only if there is at least 10 to 15 mm (.5”) of moist soil over the seed and the surface is firmed (no lumps, cracks or open spaces) to prevent moisture loss.
Crops that have to be planted into cold soil in order to get adequate seed to soil moisture contact usually come though fine, although slightly delayed in emergence.
Each year will present a different circumstance as the spring advances. In 2004, the earlier the planting, the better the chances were for crop maturity before poor fall weather occurred.