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Rye Cover Crop Planted this Fall? Here’s Some Options for the Spring

Fall planted rye as a cover crop will germinate in 34-degree soil and grow peach fuzz until it snows as long as the ground is not frozen. It’s a great starter cover crop for that reason alone. In spring, as snow melts and the sun warms the soil above freezing and lengthens the day, that cereal rye will get back to work again and grow. Despite what you were planning when you planted it, come spring you will have plenty of choices of how you want to manage it if weather throws you a curve. Let’s look at a few of those choices and figure them out.

Seeding rates in fall can vary from 20 lbs to 100 lbs per acre. Seeding rates impact soil coverage and will impact spring growth and yield. Another driver of spring yield, however, is determined by when you plant it and how big and robust the root system became before winter set in. Fields planted early in fall might accumulate over a ton per acre of bio-mass and be 14 inches tall. These plants will take off in spring because they have such an extensive root system already. You can expect 1-2 times the plant growth below ground as you see above ground. That’s pretty impressive. Imagine root hairs getting down over 30 inches on a plant just over a foot tall!

You can certainly terminate that big, growthy spring crop and plant corn into it. Be careful on timing though. If that rye starts to go down, it can be a real monster to plant into with hair pinning, shallow seed depth and open seed trenches in the wake of the planter. It might be better to terminate that big rye plant closer to corn planting time and run your planter through a standing cover crop. You can follow up corn planting with a mechanical rolling down of the rye. Corn will emerge and work its way through that flattened rye and never look back. Corn that has to compete with standing rye or “half standing” rye will cry like a baby and leave you with a very uneven stand.

You may come into spring and decide to burn down that rye when it’s still small. Maybe 8-10 inches tall. That leafy material will shrivel up pretty quickly and not create much grief to plant into. Burn down with residual herbicide can give solid season long weed control while also giving that ground a bit of cover and relief from the drying effects of sun before corn canopies over.

Ok, let’s discuss the elephant in the room. Do cover crops keep the ground colder and wetter and delay corn planting? Yeah, there’s some truth to that but it’s a bit more complicated than that. Anyway, you always have the option of working that rye cover in with light tillage to open up that soil and help warm it up and dry it out. For some, this is a great insurance plan and peace of mind option. That rye worked in should break down faster and release more nutrients to that corn crop in season than rye just rolled and left on the surface. In 2022, those corn acres planted into a terminated cover crop had more complete ear fill than corn planted to open, uncovered fields. Why might this be? Rye roots gave better pathways for corn roots to follow. Rye bio-mass can help protect the soil from heat and drying out before corn canopy. Rye material breaking down releases important ear fill minerals to the corn plant like sulfur.

Another option is to harvest the rye crop as forage in spring. Then terminate with burn down and or tillage before planting corn. Rye can make great cow feed but you might want to start scissor clippings a lot sooner than you think to hit that high digestibility window. I suggest testing every four days once you start because it can “turn” on you really quickly once stem elongation takes off.

For more experienced “cover croppers”, rye can kick start a series of benefits after a spring termination before corn. Inter seeding a mixture into your corn at V2-V3 right into that burn down rye keeps the whole soil system working. There would be just enough pause to get corn out of the ground and ahead of the competition. Young inter seeding plants will benefit from the rye shade as they emerge and grow. As corn canopies, the right mixture of species will survive until silage harvest and explode with growth when they get full sun again.

A common concern is how much moisture the rye takes (and any inter seeding for that matter) from the corn crop. The simple answer is in spring you can always stop the rye growing if it gets very dry. Generally, the amount of moisture lost due to exposure to sun and wind on bare soil far exceeds the moisture taken up by the rye or an inter seeding.

Rye will use nitrogen to break down the following year. If you fall applied manure onto a robust rye crop, the plant will take up a significant amount of nitrogen and hold it until spring. If that crop is terminated early, that nitrogen is there in the plant to help break down the crop residue. The bigger the rye crop at termination, the less nitrogen is readily available to break down the residue and more supplemental N will be required in spring. If no manure was applied in fall, or the crop was very immature at freeze up, then spring rye will take up soil nitrogen in spring and you will need additional nitrogen for the corn crop. A forage analysis and yield estimate will help determine nitrogen tied up in the rye. Many fields do not have the soil biology to breakdown and release that surface bio-mass nitrogen during the crop year.

The ground is desperate to remain covered and alive with roots that feed soil biology. Covered soil is healthy soil. The value of fall planted rye cover crop is to protect the soil from erosion in fall and spring for sure. But the value to the row crop is multiplied when we consider root channels to follow, shade protection and mineral release from root and bio-mass decomposition. Rye is a great cover crop with almost limitless options for spring management.

Bill Powel-Smith

Posted December 26, 2022



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