- The soil thermometer belongs in every tool box this spring
- Variable soil moisture and temperature affect corn emergence
- Once we get to mid- to late April, soil temperature is less important. Go with the best soil conditions.
Soil conditions remain largely cool and wet over much of the Midwest despite eagerness to begin fieldwork. Traditional calendar triggers for Midwestern field activity are often the Easter holiday or mid-April. Dates may have little significance under this year’s current weather conditions. Look to the soil thermometer as a more accurate guide to initiating corn planting.
Resist the temptation to follow the-leader in fieldwork this spring. It will be more important to remember the variability of conditions of each field. Soil drainage is one of the most important considerations. Depending on subsurface and surface drainage modifications, side-by-side fields may warm and drain moisture at vastly different rates. Throughout any un-tiled fields, or in those with old tile systems that could be partially plugged, you might see high soil moisture and temperature variability.
Soil organic matter can also significantly influence water-holding capacity and the speed at which soil warms. Darker soils may warm faster than lighter soils. These darker soils may also be slower to dry, due to the water-holding ability of the mentioned organic matter. Soil texture is also very important. Coarse-textured soils tend to drain more quickly than fine-textured soils - unless a compaction layer, high water table, or something else causes water to perch near the surface.
Tillage practices and crop history can affect soil drainage and temperature. Corn planted at the same time on no-till corn residue, and also on soybean residue, clearly show this affect. In the image, corn on the soybean residue has a clear early growth advantage. In addition, because of surface residue and potentially increased soil bulk density, no-till fields tend to dry and warm more slowly than conventional or reduced tillage.
As late April approaches, soil temperature becomes a lessor concern in a planting decision. Established research shows that yield potential starts to decline rapidly when planting is delayed beyond the first week of May. If the choice comes down to either mud-in the crop now, or wait for better conditions, patience may have the better payoff. When the yield clock starts ticking and planting must be done under less than ideal conditions, warmer soils will encourage faster emergence and fewer lasting problems for the crop.