By DALE YOUNKER
Natural Resources Conservation Service
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, and sometimes that can happen quickly. Just a couple of weeks ago we were struggling to get fall crops planted because of the wet conditions. Now we are hoping that the hot and dry conditions we are currently experiencing isn’t a trend that will last through the summer. Thankfully, we do have some decent sub-soil moisture conditions that will keep the fall crops going through this dry period.
Given the current dry conditions 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, especially in fallow systems where there will not be a cash crop planted until next spring. These cropping systems only capture and store about 15 to 25% of the moisture received during the fallow period and the rest is just lost to evaporation, runoff and deep percolation.
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 the soil moisture losses during the fallow period. 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 I 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 usually enough moisture near the soil surface for the seeds to germinate and emerge because the soil surface is shaded by the mature wheat. But once the wheat is harvested the moisture evaporates quickly. Another option is to delay the cover crop planting later into the summer after a rain or two. Typically, a flush of weeds and volunteer wheat has come up by that time, which can be terminated before planting to cover crop.
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 mid-August, oats could be added to the mix. 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 and 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 soil health practices you can contact me at [email protected] or any local NRCS office.
Dale Younker is a soil health specialist with the USDA Natural Resources Conservation Service, Jetmore.