• Agronomic Insights

6 Tips for Determining Planting Dates

Tractor pulling a planter in a farm field against blue sky.

As temperatures rise and spring inches closer, it gets more tempting to fire up the tractor and get in the field. However, deciding when to plant is one of the first (of many) management choices that will impact your crop’s performance this season. It pays to be patient and make sure you’re planting at the most optimal time in the most optimal conditions. Here are six tips to help you decide when to put your corn and soybean seeds in the ground.

1. Monitor Soil Moisture.

When evaluating whether a field is ready for planting, the first thing you should consider is soil moisture: Is it too wet or too dry? If the soil is too wet, don’t push it. You can cause compaction, smear the sidewall of the seed trench and even cause the seed to rot and die. These effects will impact the rest of your season.
If the field is dry, consider increasing planting depth to reach more moisture. Corn kernels must absorb approximately 30% of their weight in water before germination begins. Less than optimum water volume can slow or stop germination.
Equally important to moisture presence is moisture consistency. If it’s not spatially consistent at seed depth, it can cause uneven germination, which leads to uneven emergence. Several factors can cause uneven soil moisture in the seed zone, but the number one culprit is variable planting depth.

2. Pay Close Attention to Soil Temperature.

Planting at a suitable soil temperature is critical, especially for corn. You want to maximize the growing season by starting early, but you should aim for soil temperatures of at least 50 F. If you plant corn in soil conditions cooler than that, you run the risk of imbibitional chilling.
When corn seeds imbibe (take up) water, cell membranes stretch and cells expand. When water around 39 F is absorbed, it can cause membrane damage, which often results in cell solute and sugar leakage. This, in turn, is likely to reduce the plant’s growth rate and interfere with the emerging seedling’s development.
Debate exists about what specific temperature and timing cause imbibitional chilling. However, corn plants that imbibe cold water in the low 40s in the first 48 hours after planting undoubtedly are affected. Planting when soil temperatures are above 50 F alleviates concerns of imbibitional chilling affecting corn emergence.
For best results, begin planting corn when soil temperatures are in the high 40s, and the short-term forecast calls for warm days that will continue pushing soil temperatures higher. If soil temperatures are in the high 40s and the weather forecast calls for cold, wet conditions within the next 48 hours, that will likely reduce soil temperatures, so refrain from planting.
In soybeans, the seed is most susceptible to imbibitional chilling in the first 24 hours, when the seed takes up water very fast. Therefore, it’s a good idea to plant your soybeans once you are confident that soil temperatures won't be cold (less than 50 F) for at least 24 hours. There should be no imbibitional injury due to cold temperatures if you planted two or more days before a cold rain.
There are online resources to help you monitor whether conditions are fit for planting. Our seed stress map tracks local soil moisture and temperatures to help you make more informed planting decisions.

3. Choose Your Planting Depth Wisely.

Always check your planter depth. Planting too shallow can have substantial impacts later in the season. In the Midwest, 1.5 to 2.5 inches deep for corn is typically the recommended range. The sweet spot for no-till corn is around 2 inches. Tilled ground will settle so 2.5 inches is an appropriate planting depth on those acres. Any shallower than that, however, you can run into issues with inconsistent soil moisture causing uneven emergence and early-season root lodging.

4. Ensure Good Seed-to-Soil Contact.

For adequate moisture to be held and maintained around the seed, the soil must be firmed around it. This helps ensure that seeds can absorb moisture evenly and emerge uniformly. Planting at proper soil moisture, temperature and depth all support good seed-to-soil contact, while open planter furrows, trash in the seed furrow, or cloddy seedbeds can diminish it.

5. Use Starter Fertilizers and Plant Growth Regulators.

Especially in soybeans, earlier planting dates tend to correlate to higher yields, so growers tend to push the planting window earlier and earlier. This can be good because it allows the plants to capture even more sunlight, and we can use later maturing hybrids and varieties that tend to yield more. However, additional caution should be taken because early planting also brings additional risks.
If you’re going to push for earlier corn planting, I highly recommend providing your crop some extra support. For corn, consider applying chelated zinc and a plant growth regulator like Ascend in the furrow. Ascend2 PGR contains an auxin-dominant formulation to promote vigorous emergence and root development in corn. When combined with a starter fertilizer, Ascend2 offers a simple, convenient way to enhance early-season crop growth and stress tolerance. If you’re planting CROPLAN® corn hybrids, they’ve already been treated with Fortivent® Plus seed treatment, which includes zinc along with insect and disease control to promote early-season growth and root development. 

6. Adjust to Delays.

If the spring ahead is cold and wet and keeps you from your ideal timing, consider adjusting corn maturities to avoid any frost damage in the fall. However, with soybeans, I recommend holding to your original maturity selection as much as possible.
Soybean maturity tells you how much vegetative growth the plant will put on after flowering. When planting gets delayed, the plant has less time to develop before flowering. Unlike corn, soybeans will always flower around the summer equinox, no matter the maturity, because it’s a day-length-controlled plant. Earlier maturities don’t put on as much vegetative growth after flowering, so the risk you have in backing down your maturity is reduced development after flowering, resulting in stunted beans and lower pod counts.
As you begin to assess fields for planting, remember to consider these factors and carefully balance the benefits of planting early with the risks. When in doubt, don’t push it. For more information on determining optimal planting dates, talk with your local WinField United retailer.
All photos are either the property of WinField United or used with permission.

© 2023 WinField United. Important: Before use always read and follow label instructions. Crop performance is dependent on several factors many of which are beyond the control of WinField United, including without limitation, soil type, pest pressures, agronomic practices and weather conditions. Growers are encouraged to consider data from multiple locations, over multiple years and to be mindful of how such agronomic conditions could impact results. Ascend2, CROPLAN, Fortivent and WinField are trademarks of WinField United. All other trademarks are the property of their respective owners.