Published on Tuesday, March 6, 2018
Planting season is almost here which means many of you are probably thinking about all of the decisions that need to be made before the planter ever hits the field. Questions like “when should I start planting?”, “how deep should I plant?” and “should I wait for perfect conditions?” are all valid questions you may have. But answering them may require some planning and preparation to ensure you start your crops off in the best possible situation.
Let’s first look at planting date. Historically, we have found that yields are optimized when planting corn or soybeans between April 15 and May 15. Last year proved to be an exception to the rule, as we saw the highest corn yields later than usual at each of our Practical Farm Research (PFR)® sites. However, when thinking back to 2017, some areas of Illinois and Indiana received large amounts of precipitation during the spring, which delayed planting and caused replant scenarios. Most everything in agriculture is based off of averages, and when planning the date at which you’ll plant your first field, a long-term average is the best place to start.
When it comes to determining how deep to plant, soil mechanics play a very large role in planting depth. Whether you have sand with a moisture line at 3 to 4 in. or you have heavy clay fields that are prone to crusting, proper planting depth is critical for achieving uniform stands and emergence. An adequate planting depth will also expose your seed to consistent soil moisture and temperatures and ensure good seed-to-soil contact. In our PFR research we’ve found that in optimal conditions, corn yields are maximized at a 2 in. planting depth. Soybeans have provided the highest yields at 1.5 in. Remember, soybean nodules require temperatures between 68 to 74° F to optimize their function. Planting at an adequate depth helps maintain a soil temperature closer to that range without the nodules being exposed to major swings in temperature caused by too shallow of planting depths. Planting depths will likely vary between fields with different levels of soil moisture, varying soil temperatures, and different soil textures.
Your end goal is to achieve an even stand and even emergence and getting all of the plants up within a short window has shown to provide maximum yield potential. For example, say you’ve decided to start planting corn on April 18, when the soil temperature is at 56°F and the extended forecast shows warm, sunny weather for the next 7 days, followed by some light precipitation. When you pull the planter in the field, you notice it’s “a little wet”. Mud is sticking to your gauge wheels, and your tractor spins a little as you try to pull the planter across the ground. But overall, conditions are manageable and you are able to put seed in the ground.
What does this cost you? Other than the potential increase in compaction caused by the spinning tires on the tractor, your gauge wheels aren’t able to keep consistent depth with mud building up on the them. Also, the closing wheels aren’t able to do the best job when it comes to closing the seed trench. The image below illustrates how soil conditions can affect plant emergence. Regardless of soil type, planting when it’s just “a little too wet” spreads our window of emergence out 2 to 3 times what it would be if we would have waited just a few days until soil conditions were optimal.
The 2017 data below is from our Ohio PFR site and illustrates just how much we sacrifice, even within the first 24 hours of emergence. Consistent emergence is critical to maintaining maximum yield potential, especially later in the season.
I know it can be very hard to hold back the reigns when the season begins and your neighbors may be moving full steam ahead. However, if you wait to plant into optimal conditions at an adequate depth, you will give your seed the best chance for success!
Miles McGovney | PFR Agronomist and Operator
Author: Jim Schwartz
Categories: PFR, PFR Reports
Tags: Practical Farm Research, Planting Depth, PFR, PFR Report, Planting Date
3/8/2018 10:46 AM
Would a GDU calculator be helpful with planting decisions? Maybe on Farmserver tied to the weather forecast.
3/22/2018 8:47 AM
Here is Miles' response to your question:
The Farmserver weather forecasting model would be the better tool to use when making planting decisions. Looking ahead at the 10 day forecast is a better indicator of whether you should be pulling the trigger on planting or not. A GDU calculator is a great tool to use once the seed is in the ground, since it tracks historical/accumulated heat (fyi: it takes roughly 100-120 GDU’s for corn to emerge).