Planting a summer cover crop in wheat stubble
One thing about living in Kansas is if you don’t like to current weather, don’t worry, because it will change to the other extreme on the pendulum.
A year ago, we all struggled to get fall crops planted and the wheat harvested due to the extremely wet conditions.
This year it’s the opposite, where many of us planted crops in a dry seedbed with the hope and a prayer that the rain in the forecast happens.
The majority of western Kansas is in a moderate to extreme drought, with some counties in the far southwest in exceptional drought. Some forecast models are indicating that these conditions could persist through the growing season.
Given the current dry conditions and the prospect that this may continue you may think that the last thing I would be wanting to talk about is planting cover crops.
But cover crops can provide as many benefits in dry periods as they can wet periods, especially in fallow systems where there will not be a cash crop planted until next spring.
Much of this year’s wheat crop will be shorter and thinner due to the dry conditions. Some of the late spring freezes also set the wheat back and reduced the number of tillers on the plant.
As a result, soil water evaporation rates will be significant in this thinner, shorter wheat stubble.
Yes, cover crops will use some soil moisture like any other living growing plant, including weeds. But a cover crop, that is properly designed with the right species in the mix, and planted and terminated timely, can mitigate that moisture use by reducing soil water evaporation, improving water infiltration and increasing organic matter.
So, when the rains do come, we can capture and store more water in the soil then we would of without the cover crop.
I typically like to get a cover crop established in wheat stubble within a day or two after harvest.
It’s been my experience that there is typically enough moisture near the soil surface for the seeds to germinate and emerge. But after losing the canopy that the mature wheat provided the moisture evaporates quickly.
This year may be the exception where there simply is no soil moisture close to the surface to get anything to come up. We may have to delay the cover crop planting until we get some decent rain. This would not necessarily be a bad thing.
Likely there would then be a flush of weeds and volunteer wheat that we could eliminate before planting the cover.
I would stick with predominately low water use species in the mix. Millets work well in this situation.
They are shallow rooted and grow and mature quickly and very drought tolerant once established.
Seed costs is reasonable because the seed is small and just a few pounds is all that is needed in a mix.
Because of the small seed size planting depth should be no more then about an inch deep.
I would also add a small amount deep rooted species like sunflowers turnips or radishes. They can really help with breaking compaction layers that almost all cropped fields have.
Some of these species can also be great habitat for beneficial insects and pollinators.
Adding a legume, like sunn hemp can also be beneficial in the mix if allowed to grow long enough the nodulate and fix nitrogen. If the planting is delayed until after early-August, oats could be added to the mix.
The oats really help feed the soil biology that is critical to building and maintaining soil aggregates, which in turn increases soil porosity.
Most summer planted cover mixes will frost terminate once temperatures get cold enough in the fall. But if dry conditions persist through late summer it may be appropriate to terminate the cover early so it doesn’t continue to use moisture that may be needed for the next cash crop.
This is really a judgement call based on current conditions at the time and long-term weather forecasts.
If you used an herbicide in the growing wheat herbicide carryover could be a concern.
Many post wheat herbicides provide long term residual weed control have long plant back restrictions.
These herbicides could inhibit the germination and growth of many cover crop species.
Always check your herbicide label and if in doubt consult with your supplier or crop advisor.
The Risk Management Agency (RMA) has recently adjusted the crop insurance provisions regarding cover crops and termination guidelines, easing many of the prior restrictions.
I would suggest that you contact your crop insurance agent before planting the cover crop to make sure you are meeting all the insurance requirements.
For more information about cover crops or other soil health practices you can contact me at email@example.com or any local NRCS office.
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