When should I terminate my cover crop

First and foremost, discuss termination plans with your local crop insurance agent, who should be up to speed on the most recent crop insurance guidelines through the Risk Management Agency (RMA) division of the USDA. See the USDA's RMA Cover Crop website, which contains helpful information. Producers practicing no-till generally have a 7-day extension beyond the permitted termination date as described in the NRCS Guidelines Version 4. The key here is that crop insurance recognizes good management practices for cover crop management. That means that if an agronomic expert suggests a cover crop management strategy or the management strategy is common in your area, RMA will recognize it as meeting their guidelines.

Cover crops are fantastic for improving soil structure and aggregate stability while increasing organic matter. Delaying termination as long as possible and letting those covers grow can improve those characteristics even faster.  Farmers all over the country have reported soil infiltration rates improving from less the 2 inches of water per hour to well over 5 inches in a matter of 2 - 5 years after implementing cover crops and no-till practices.  Imagine the next time you have a 5-inch rainfall in less than an hour, and every ounce of rain is absorbed by your soil. For every 1 percent organic matter added per foot of soil, your water holding capacity will increase by up to 20,000 gallons of water per acre, which is incredibly valuable during a persistent dry spell or drought.  

There are situations where it is not advisable to delay termination and plant green. One example is when unusually dry conditions occur 2 – 4 weeks with no foreseeable accumulating rain for the next two weeks after planting.  If these conditions are common in your area, it may be valuable to terminate your cover crop 10 days to 2 weeks prior to planting, or sooner than planned. This will help preserve moisture for seed germination, especially when new to cover cropping. Veteran cover croppers will likely have a greater buffer due to their soils’ enhanced water holding capacity.

On the flip side, when you are experiencing an unusually wet spring, your best bet is delaying termination as long as possible and planting green where permitted. Living plants transpire and pull moisture out of the soil down to their rooting depth. In addition, live roots act as greater support, like rebar in concrete, when pulling a planter through the field. If cover crops are terminated too early, they can act like a mat, potentially slowing evaporation and soil drying.

Most winter legume cover crops have maximum N production by the mid-bloom stage. Waiting to terminate until this point can be costly, as it would likely delay planting until the last half of May or the middle of June, most years.  However, delaying termination as long as possible could be the difference between 20 and 40 additional units of nitrogen made available through N-fixation to the next cash crop.  

Are you interested in reducing your chemical bill? Roller crimpers can be a great alternative to herbicides for terminating your cover crop. Roller crimpers are generally effective for a limited number of cover crop species and require precise termination timing to achieve an adequate kill. For example, cereal rye is most effectively terminated when it reaches anthesis.  At this point, the stem has elongated to near max height and it is less likely to rebound after crimping. Cereal rye terminated earlier may stand back up and appear unfazed.

Cash crop characteristics