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Cover crops: Harvest or terminate?
CROPS & WATER

Cover crops: Harvest or terminate?

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Cover crops have been a great tool for many producers across Nebraska as they can be used for managing soil erosion, weeds, moisture accumulation, microbial activity and forage crops for livestock producers.

Every producer has different goals while planting their cover crop, the same message rings true for termination. Some producers may wish to use their cover crop as a cash crop, or sell it as certified seed.

If you do plan to harvest the grain for certified seed, contact the Nebraska Crop Improvement Association to work through this process (http://www.necrop.org/). NCIA is the official seed certifying agency for Nebraska providing field inspections, seed lab testing services and quality assurance for your seed.

Other producers may plan to terminate their cover crop before, during or after planting. Things you need to ask yourself before terminating: What was my goal for this cover crop, and has it been achieved? Is this ground irrigated or non-irrigated, and how much moisture is available for my cash crop? Is wheat stem maggot a problem in my area? How tall do I plan to let the cover crop grow, and which herbicides do I use for effective control? Am I working with the NRCS office, and what do their termination guidelines say? All good questions that each individual producer needs to consider for their operation.

Some guidelines indicate that cover crop termination 14 days before planting can help with moisture conservation and reduce any negative allelopathic effects depending on the cover crop. Rainfall or irrigation can be a concern to ensure enough moisture is available for the cash crop. This will really depend on current soil moisture levels, irrigation potential, weather conditions,and where you farm in Nebraska.

Dry conditions last fall made cover crop germination and growth slow, but recent rain events and warm weather have helped recharge soil profiles and encourage new growth. Many producers utilize starter fertilizer at planting. This has helped mitigate nitrogen tie up as cover crops are gradually dying, so their corn crop doesn’t look as yellow. If wheat stem maggot is a concern in your area, planting into green cover crops and then terminating can potentially lead to issues with infestation in your corn crop. For some producers, wheat stem maggot isn’t a problem, but always consider the risk and scout fields routinely for this pest especially if planting green and then terminating.

Cover crop height is another consideration as some producers want lots of biomass prior to termination. Depending on how large those cover crops are, carefully consider which herbicides to use. Common herbicide active ingredients for termination include glyphosate; 2,4-D; dicamba; paraquat; sulfentrazone; and chlorimuron (plus many more). If the cover crop is taller than 12 inches, control may take longer, and residual products may not reach the soil line to manage future germinating weeds.

In addition, some herbicides take longer for effective control and planting into mushy, dying cover crops may not lead to proper planting conditions, seed placement, or eventual stands. Terminating cover crops when they are less than 12 inches tall can be quite effective when using a good burndown product with residual activity. If the cover crop is too tall, the residual product may need to be incorporated into a postemergence pass to provide in-season control.

Herbicide efficacy will also depend greatly on timing, cover crop species, rate, temperature and other weather conditions. Finally, contact your local NRCS office for termination guidelines for your specific situation. Depending on your program enrollment, location and cover crop species planted, early termination may be required.

For others, terminating at or after planting may be perfectly fine. There’s a lot of considerations when it comes to terminating cover crops this spring, but ultimately it comes down to producer preference and what works best for their operation.

References

Sarah Sivits is the Dawson County Extension educator in crops and water, and serves Dawson, Buffalo and Hall counties. Contact her at 308-324-5501 or by email at ssivits@unl.edu.

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