Plant Cover Crops

Learning about the benefits of planting cover crops.

Cover Crop Challenges

Cover Crop Selection – What to plant after wheat or other cereal grains?

I was in a meeting yesterday and the gentlemen from SWCD asked me:

“What should we recommend for our producers to plant as a cover crop after the wheat comes off?”

After running through a number of scenarios I determined that I’d better make sure I don’t confuse folks with too many ideas.  So, here are a few scenarios that I hope you find useful.

If you want to scavenge Nitrogen and other nutrients, then a good choice would be Oats and Radishes mixed together.  This mix generally should be planted at 1 1/2 bu Oats and 2-5# of Oilseed radish/acre.  This mix also requires manure or around 40# N applied for it to be the ideal mix for this situation.  This mixture will die in the winter and provide excellent winter annual weed control.  Best planting time is Mid August…so you have plenty of time to get weeds killed and manure applied.

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Sudangrass and Sorghum-Sudangrass are excellent crops after wheat if you need animal feed.

If you have livestock to feed, other great nutrient scavengers to plant after wheat are Sudangrass, Pearl Millet, or Sorghum-Sudangrass. These summer annual grasses require 100+# of N or equivalent manure. Tonnage of 4 1/2 tons Dry matter/acre have been common in northern Indiana following wheat the past three years. These grasses are excellent soil builders as well. Mycorrhizae fungus find the roots of these plants a very good place to multiply and build soil structure.

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Oats and Radish Mixture following wheat. Hog manure was nitrogen source.
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When properly inoculated, Austrian Winter Peas are prolific producers of nodules (and nitrogen).
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Oilseed Radishes are "nutrient sorage facilities"! These big tubers take in significant amounts of nitrogen and other nutrients.

If you want to produce nitrogen and also scavenge nutrients as well, then an excellent choice will be Austrian Winter Peas mixed with Oilseed Radish .  This mixture works very well without the addition of additional nitrogen.  Count on the peas to deliver 60-120# of N and the oilseed radishes to keep most all of it in the top soil root zone. This mixture does a great job of controlling weeds.  The radishes will die in the winter and the peas will “probably” die too…depending on your location, planting time of the mixture, and snow cover.  If they overwinter they are easily killed in the spring.

If you are looking mainly for nitrogen production with a species that will winterkill, then choose cowpeas.  The past few years cowpeas have been very expensive to plant.  Be sure to check pricing and also be sure to inoculate the seed at planting time.  Sow 60-100#/acre of cowpeas.

If you want the nitrogen production with a crop that will overwinter, then crimson clover is a top choice.  Excellent new varieties have come on the market the past few years.  Be sure to inoculate this seed as well. Sow 20-25#/acre of crimson clover.

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Crimson clover planted after wheat is an excellent nitrogen producer.

There are several other options but these will certainly give you a good start in making selections.

When to aerial apply cover crops into corn

Corn should be dried "up to the ear" for best results when utilizing aerial application.
Corn should be dried "up to the ear" for best results when utilizing aerial application.
Approximately 50% of the sunlight should reach the ground in the field when aerial applying cover crops into corn.
Approximately 50% of the sunlight should reach the ground in the field when aerial applying cover crops into corn.

A few years back many said “August 15-25” was the right date to aerial seed cover crops into corn.  However, we found out very quickly that “dates” cannot be set…but timing can be.  While we know that August 15-25 often can be correct, we also know that following the calendar (like in the 2009 crop) can be a mistake.  So let’s set a few guidelines that should help all of us have better success when aerial applying cover crops into standing corn.

 

 

Guidelines for success when aerial applying cover crops into standing corn:

  • Aerial apply cover crops when the corn plant is dried approximately to the ear.

 

  • Aerial apply cover crops when approximately 50% of the sunlight can reach the ground between the rows.  (Walk in the field a few rows to determine this).

 

  • For success, do not fly cover crops into corn that is immature (still very green).  The seeds will most likely germinate and then mold (not enough sunlight to conduct photosynthesis and too moist of conditions).

 

When is it too late to aerial apply cover crop seed into standing corn?

  • You need 5-6 weeks of growing time for cover crops going into the winter for best winterhardiness and performance.

 

  • Winter Cereal Rye is more “flexible” than annual ryegrass or other cover crops when it comes to the lateness of application.

 

  • If corn will be harvested soon after an aerial application can be made, consider the cost of other types of cover crop applications (i.e. drilling the cover crop in after harvest).  Utilize the lesser expensive application.

Cover Crop Seeding rates DO matter

As an agronomist I try real hard to recommend the correct seeding rates.  For instance the “recommended” seeing rate on radishes has been 10-12#/acre but in reality only 3-5#/acre does a lot of good in mixes and 10-12 is WAY too thick (and expensive).   Annual Ryegrass rates for cover crops is 1/2 that for forage. In fact, some producers use 12-15#/acre now and achieve very nice stands. Cutting seeding rates helps save the producer money and that is almost always a good thing, right?

GroundHog Radish by itself at 5#/acre is not thick enough to stop erosion.
Radish by itself at 5#/acre is not thick enough to stop erosion. But 10-12#/acre is expensive. 3-5#/acre in mixes seems to be just right.

However, there is another side of the coin.  We do need to achieve adequate coverage to reduce erosion.  Thin stands of cover crops might provide some purpose but they may also give a false sense of “security” that you’ve actually “done enough” to help.  I guess the question is “what IS enough to help?”  I’d suggest that 50% ground cover is not enough to give erosion control.

With the help of NRCS, past experiments in MI and OH, and other cover crop friends  we determined that 35#/acre was going to be thick enough for Austrian Winter Peas and Radishes.  Crimson Cover with Radishes seeded at 17-20#/acre looks just right.

So how do we know what the right seeding rate is?  As I said earlier, I work with NRCS experts and do a lot of test plot work.  In the fall of 2009I helped plant over 15 different cover crop test plots in OH, MI, and IN.  Most of the plots are identical but in some of the plots we are experimenting on new mixes and different seeding rates.  We take notice of plots that look thin and determine why.  Did we get a good catch?  Were the legumes inoculated so they can grow aggressively?  Or, did we just plant too low of a rate?

In the plots in Southern Illinois I wrote about previously there were some plots that were quite thin.  I wish I had taken photos of them.  They had about 30% ground cover.  The Hairy Vetch was not  inoculated and it had few nodules and it was growing very slowly compared to the other inoculated legumes.  I did not put those entries in the plot, but I wondered if they’d be thick enough when I saw the seeding rates they used.

It’s one thing to try to save money for the producers…and I’m all for that, IF the savings are actually savings. I guess it depends on the producers goal.  Would producers plant their corn crop at 1/2 or 3/4 rate to save money?

What do you think?