Here's a "heads-up" to all those folks thinking about flying on cover crops this fall. The practice of flying on the seed using an airplane is usually done when the leaves are falling off the soybean plants in the field—which is the situation that's occurring with the plants in many soybean fields about now.

"However, we are just not getting the rains needed across the majority of the state right now and we were already dry in many areas," noted Sarah Carlson, on September 15. "At this time, with the soil being as dry as it is, successful establishment of cover crops using an airplane might be risky."

Carlson is the research and policy director for Practical Farmers of Iowa. She has worked with a number of farmers across the state the past several years conducting field research and demonstrations on their farms, using various cover crops and seeding methods, to see what works and what doesn't. 

Establishment of cover crop using a plane is risky in extreme dry weather

"We've seen winter rye cover crop seed sit on the soil surface for up to three weeks and then catch a rain and have good establishment," she says. "But thinking about current rainfall around the state and the low moisture fall we had last year, we need to observe our fields, check the weather forecast and be flexible if conditions are too dry."

Carlson offers the following suggestions for establishing a winter small grain cover crop. "Legume establishment at this time whether the soil is dry or not is risky because there is just not enough heat and sun to get it going for good fall growth compared to winter rye or winter wheat," she says.

Here are cover crop seeding options you can consider:

1) If you've already flown on your cover crop, then following fall harvest you should observe the soil-to-seed contact. Where that needs to be improved, where it is appropriate, you can pack or roll the seed to push it into the soil. That will improve soil-to-seed contact and with what little moisture there is in the soil surface, this packing or rolling will help get the cover crop seed germinated. Then we will just need to hope for rainfall to sustain growth.

2) If you are planning to overseed using an airplane or highboy and you have a shorter season corn hybrid or soybean variety to harvest first, you might want to wait to no-till drill the cover crop seed into the ground following grain harvest. That will improve soil-to-seed contact. To save soil moisture, do not disturb the soil and just plant the cover crop seed directly.

3) If you are planning to overseed using an airplane or highboy and have a while until grain harvest happens (one month or more) then timing with moisture will be critical. If rain is in the forecast, then fly the cover crops on. Or, if your fields already have enough soil moisture, then go ahead and fly the cover crop seed on. However, if you are very dry (no rain since sometime in July) and there is not any rainfall in the forecast, then I would re-think flying the cover crop seed on. If you can irrigate, then the problem is solved and you should plan to do that.

4) If you will be planting the cover crop after grain harvest this fall--and your soil is dry and only limited rainfall is in the forecast---DO NOT till the soil before planting the cover crop seed. By drilling the seed directly you will improve the chances of cover crop establishment by saving any soil moisture there is in the top couple inches of the soil. Last fall, that little bit of soil moisture maintained by not disturbing the soil improved cover crop establishment on a farm in Boone County compared to a neighboring farm that did fall tillage and then planted their cover crop. The tilled field was just too dry to get the seed established but our no-tilled cover crop got up and out of the ground in five days.

What if a cover crop is planted, but with the exceptional dryness, the cover crop seed doesn't germinate this fall?

Carlson says if your cover crop seed (winter rye, winter wheat and usually hairy

vetch) does not germinate this fall, you will have unprotected soils this fall and winter but these seeds can still germinate in the spring right after snowmelt and provide soil protection during spring rains. "The goal is to have a cover crop in the fall and the spring but sometimes Mother Nature changes our plans and we must be patient," notes Carlson.

If you have questions or comments regarding cover crops, varieties to plant, stand establishment or any cover-crop related topic, let Carlson know. She's at [email protected] via email or by phone at (515) 232-5661.