Plant Cover Crops

Learning about the benefits of planting cover crops.

Austrian Winter Peas

Prevented Planting Row Crop Acres – Which Cover Crops Can Help?

The following was originally posted on May 27, 2011 when the Eastern Corn Belt was suffering with severe flooding and wet conditions.  In 2013 the Upper Midwest – especially Iowa, Minnesota, and Wisconsin – is flooded and wet.  Many farmers are considering taking the crop insurance for prevented planting.  Even if it would stop raining – which does not appear will happen anytime soon – many farmers will not be in their fields for two weeks.  While locations are different, the recommendations below still apply.  Please keep the farmers in the Upper Midwest in your prayers; they need it!

For other options that might include growing cover crops for forages click here.

More rain tonight on already flooded fields create a tough situation for many Midwestern farmers.
More rain tonight on already flooded fields create a tough situation for many Midwestern farmers.

In 2010 there were wet spots in fields that were never planted,  so some ingenious farmers planted cover crops in those spots after they dried out.  Now in 2011 there are several entire fields that may not be planted to cash crops at all.  I have heard from two friends in Ohio that are working on plans to help northwest Ohio farmers know what to use on their prevented acres.

Maybe this is not an issue where you live.  I hope you never have to face a spring like this year in the Eastern Corn Belt, where many producers in Ohio, Indiana, Illinois, and Michigan are struggling to get their crops in the ground.  The forecast is for many more days of rain to finish out the month of May.

For wet spots in fields there are many good options like these cover crop radishes that were planted later in the season in a field of sweet corn.

For prevented planting the cover crops may not be harvested until after November 1st.

So what are the options for planting cover crops in the prevented planted fields?  Below I will list the options with a few of their benefits and also some disadvantages.

Oats

Advantages

  1. Provides erosion control
  2. Scavenges nitrogen
  3. Grows a deep and fibrous root mass
  4. Promotes mycorrhiza growth
  5. Quick to establish
  6. Relatively inexpensive
  7. Can be broadcast and lightly tilled in
  8. Can be added to other cover crops to add additional value
  9. Can spray with broadleaf herbicides if necessary to control weeds

Disadvantages

  1. While they provide cover and decent root growth they do not provide additional nitrogen to the soil (at the most it would be very minimal)
  2. Best to use seed oats vs. bin run oats for optimum value
  3. If planting wheat after oats there may be some “grass after grass” issues (I’m not confident this will be a problem and would welcome comments)

 

Field Peas or Austrian Winter Peas

Austrian Winter Peas and cover crop radishes were planted into prevented planting acres in Michigan in 2010. These peas were producing nitrogen for the 2011 crop while fields that were sprayed or tilled for weed control had no such benefit.

Advantages

  1. Can provide 60-120 # nitrogen/acre (excellent if following with wheat in the fall)
  2. Can be broadcast and lightly tilled in (1″ or deeper)
  3. Can be added to other cover crops to add additional value (add to oats)
  4. Can spray with broadleaf herbicides if necessary to control weeds

Disadvantages

  1. Slower to establish than oats
  2. More costly than straight oats
  3. Seed MUST be inoculated at the time of planting

 

Crimson Clover

Advantages

  1. Can produce up to 150# N/acre within 100 days (great option if following with fall planted wheat or Winter Barley)
  2. Fairly quick to establish
  3. Relatively inexpensive
  4. Can be broadcast and lightly tilled in (1/4-1/2 inch deep)
  5. Can be added to other cover crops to add additional value (add oats at 1 bu/acre)
  6. Can spray with broadleaf herbicides if necessary to control weeds (This article is for seed production in the northwestern part of the USA)

Disadvantages

  1. More costly than straight oats
  2. Slower to establish than straight oats
  3. Seed MUST be inoculated (it may be purchased pre-inoculated)

 

Cowpea

Advantages

  1. Can produce 60-150# nitrogen/acre
  2. Can be broadcast and lightly tilled in (1″ or deeper)
  3. Can be added to other cover crops to add additional value (add to oats)
  4. Can spray with broadleaf herbicides if necessary to control weeds

Disadvantages

  1. Cost and availability of seed
  2. Slower to establish than oats
  3. Seed MUST be inoculated

Other crops to consider: Berseem Clover, Fava Beans, and others.

For further information, please read this excellent article by Barry Fisher, NRCS Agronomist from Indiana, who wrote on this very topic in 2009.

Fertilizing Cover Crops & Planting Legumes After Soybeans

If you spend any time at all in cover crop meetings, you may have heard that it’s a good idea to add 20-50# of Nitrogen per acre to your cover crop – if you don’t have a legume in the mix or you don’t have manure available. You also probably heard (or participated in) the grumbling that predictably starts from the crowd. Who wants to fertilize a crop that they will not harvest?

While it’s true that producers will not “harvest” the cover crops, they will have healthier cover crops which should lead to healthier soils and healthier profits.

Manure as the No-Brainer

Obviously if manure is available it is a smart move to put manure where you will have or already have cover crops.  We know from research that cover crops can hold as much as 90% of the nutrients from manure applications.

We have also know that where manure is applied without a cover crop being present (even if worked in) we can lose a significant amount of nutrients into ground water or as surface run-off.

What About Adding Commercial Fertilizer?

The Radishes on the left had manure applied and those on the right did not have any additional nitrogen applied.
The Radishes on the left had manure applied and those on the right did not have any additional nitrogen applied.

But, what if there is no manure to apply and for some reason you do not want to include a legume in your system?

Is it worth applying 50# of nitrogen to produce a cover crop?

Let’s look at what we think we know:

  • Pages 22-24 of Managing Cover Crops Profitably provide formulas to figure out the value of using cover crops as a green manure in a cover crop system –  whether with legumes, manure, or fertilized.

Look especially at the section on “Potential losses” to see that there can be nitrogen losses even in this scenario.

  • Cover crop experts say to count on 50% of the N captured or N produced by a cover crop to be available to the next cash crop.
  • It appears that adding a grass with legumes or brassicas will help “slow down” the release of the N in the spring making it more slowly released to the next crop.

 

Here is a photo of the Ingham County Michigan Cover Crop Plot. Where there was a legume in the mixture there was considerably more growth and earthworm activity
Here is a photo of the Ingham County Michigan Cover Crop Plot. Where there was a legume in the mixture there was considerably more growth and earthworm activity

What can we expect if we plant a cover crop and we don’t add more nitrogen?

How will that cover crop do?

I will utilize work that Dan Hudson did when he was an Extension educator in Ingham County Michigan in cover crop plots he planted back three or four years ago.

  • Radish tubers are considerably smaller and the roots appear to not be as deep  (I have not dug a root pit in this scenario).
  • Grasses have a more shallow root system in forage settings when fertility is lacking.
  • The cover crops were pale green.
  • The “hungry” grass cover crops had less earthworm activity than in the grass + legume mix plots.
  • “Hungry” radishes and turnips had much less tuber and top growth, thus sequestering less nutrients (one of their main functions).
  • Winterhardiness on cover crops is potentially not as good when the cover crop is undernourished.

What can we expect after soybeans?

Do we need a legume in the cover crop mix following the beans or is having a grass and/or brassica to sequester the N from the soybeans good enough?

Let’s investigate the difference between adding a legume to a cover crop mix following soybeans compared to planting scavengers only.  The charts are from our family farm trials.  The charts show the chlorophyll readings of the corn in the year following the soybeans (and then following a cover crop).

It is important to look at the “Y” axis as each chart is slightly different in how it shows the top reading.

When Austrian Winter Peas were added to a scavenger (Radishes) the chlorophyll readings were very favorable compared to the no cover crop check plot and plots with just scavengers.
When Austrian Winter Peas were added to a scavenger (Radishes) the chlorophyll readings were very favorable compared to the no cover crop check plot and plots with just scavengers.
Just like the peas gave us an advantage over the no cover crop check the crimson clover showed very favorably.
Just like the peas gave us an advantage over the no cover crop check  and scavengers, the crimson clover also showed very favorably.

 

While the Oats and Radish showed exceptionally favorable in the early part of the season the plot are "ran out of gas" as the corn was pollinating.
While the Oats and Radish showed exceptionally favorable in the early part of the season the plot “ran out of gas” as the season progressed.
Straight Winter Cereal Rye was impressive early season but also did not fare as well against the check as the mixes with legumes
Straight Winter Cereal Rye was impressive early season but also did not fare as well against the check as the mixes with legumes.

As we looked at the yield of the corn in these plots we saw a considerable difference – suggesting that even after soybeans we might want to add a legume to improve the corn yield the following year.

Yields from the different cover crop plots shown above were:

Check Plot                                    105.24 bu/ac

Winter Cereal Rye                      126.86 bu/ac

Oats and Radish                          138.79 bu/ac

Crimson Clover + Radish           153.99 bu/ac

AW Peas + Radish                        164.82 bu/ac

Conclusion

All indicators seem to point that adding manure, a legume, or additional N might very well pay off when planting a cover crop, even after soybeans.  However, adding a nitrogen source is not necessarily vital to having a successful cover crop system.  I would suggest that you try different scenarios on your own farm and in your own system and see what works best for you.

Cover Cropping North of I-80 After Corn & Soybeans – A Whole New World?

There is a lot of Iowa and Minnesota and Wisconsin above I-80. Is this all part of the “no cover crops works here after corn and soybeans” zone? Maybe not!

Sarah Carlson from Practical Farmers of Iowa reminded me that cover cropping north of I-80 is different than cover cropping in northern Indiana.  She’s right.  But how different is it, and why is it different?

Sarah is quoted in a very good article in Corn and Soybean Digest that helps explain the differences.

Several farmers in Wisconsin and northern Illinois are having cover crops aerial applied with good success. But I agree with Sarah; there are still challenges.

Cover Crop Challenges in the North

This field of Annual Ryegrass is in SE Wisconsin and was aerial applied into standing corn in the fall of 2011 with great success.

I see the following challenges to using cover crops North of I-80 after corn and soybeans:

  • Shorter growing season after corn and soybean harvest
  • The use of “full season” (for the region) soybean varieties and corn hybrids to maximize yield potential
  • Fear using winter cereal rye (their best option after corn and beans) because of potential risks
  • Fewer choices for cover crop species to use
  • Harsh winters and less snowfall to protect smaller cover crop plants

Cover Crop Opportunities in the North

  • More aerial applicators successfully flying on cover crops into standing corn and soybeans
  • Improved yields following winter cereal rye, a crop that can be planted late
  • High yields and profit with shorter season corn allowing timely application of cover crops
  • Annual Ryegrass is working well in southern Wisconsin and southern Michigan and there are many positive results from using it.
  • Dixie Crimson Clover has a good history of surviving the winter even in mid-Michigan and southern Wisconsin.
  • Late planted Austrian Winter Peas are overwintering as far north as the top of the Thumb of Michigan.
  • Winter Barley (winter hardy varieties) is surviving well in southern to mid-Wisconsin and in southern Minnesota and used for a cover crop or haylage before planting corn silage.

While not every producer North of I-80 will have success with cover crops after corn and soybeans, there are a number now that are happy with their results.

My message is to use wisdom and best management practices.

IF you want to try cover crops after corn and soybeans and you are north of I-80, realize that you are not the first person to try it.  Many have gone before you with good results.

Don’t give up before you investigate the possibilities.

Now, if you are north of I-90…

Cover Crops Provide Improved Corn Yields in On-Farm Trial

All of what is reported below was accomplished after only one year of cover crops.  This work was inspired by a conversation Don and I had last winter with Dr. Eileen Kladivko from Purdue University.  As I say in cover crop meetings,

Don’t expect a miracle the first year – but look for one.

Over the exceptionally dry and super hot late-spring/summer months of 2012 my brother Don Robison collected “plant-health” related data on our corn field at Robison Farms near Greenwood, IN.  Don took data on the corn  from each area of the cover crop plot we planted last fall over the top of a soybean field as well in the “check area” (no cover crop area).

The data he took throughout the summer included plant chlorophyll readings, plant height, and compaction readings.  I presented some of the chlorophyll data on the CropLife Webinar and at several cover crop meetings this summer (and more is posted below).

On August 15th Don and I took hand harvested yield checks from each area and from the check area.   The data on the corn yield was almost identical to what we found with the chlorophyll data and compaction data. Where we had the healthier plants all season long (more “green-ness” and deeper roots) we had higher yields.

To figure yield we utilized this formula we found at a Purdue University agronomy website.

Each cover crop treatment out yielded the “no cover crop check”. The top three yielding plots also had the least compaction and highest chlorophyll readings through out the drought stricken summer.  The check plot yield was 105.24 bushels per acre.  The top yield estimate was 164.82 bushels per acre.

 

The area where the plot was had a 24″ water line was installed by the county in 2009; so it was intended to be a “rescue disturbed soil trial”.  The corn was not harvested directly over the water line but it was where the soil from the water line was mixed in with the top soil.  In 2011 the field was in Soybeans and yielded 48 bushels/acre.  In 2010 the field was corn and yielded 198 bushels/acre.  The whole field has been no-tilled for most of the past 20 years (there were some years with conventional tillage done – mainly in the early 90’s).  175 Units of N were applied (100 units (28%) with the chemical burn down application early season and 75 units side dressed (28%) in early May).

Rainfall from May 1 to July 31 was 2.24″ (with only 0.75 from May 1 to July 19).  There were 42 days over 90 degrees and 8 days over 100 degrees during that time.  All time record dry and heat was recorded in July, 2012 in the area.

Don took chlorophyll readings weekly (one week missed in July due to a family vacation).  He took 30 chlorophyll readings per plot per sampling date.  He also took multiple plant height readings each time as well.  He followed the manufacturers instructions on the chlorophyll readings and penetrometer tests.  Don spent a lot of time in this field so we could all have this data!  Thanks to The CISCO Companies for providing the seed, equipment, and Don’s labor to collect this data.

 

This chart shows the percentage above the no cover crop area (the “check”) compared to the different cover crop mixes. The two comparisons on the far right are from a soybean study we ran where we had cover crops two consecutive years compared to one year (more data and a post coming soon on this study).

Observations:

  • The plot areas that rated healthier (more green-ness and taller) yielded the best.
  • The plots areas where there was less compaction yielded the best
  • The plots with annual ryegrass did not fare as well as some others in this drought year – yet was still considerably above the check.
  • Not all plots with radish were “top” yielding – however two of the top three yielding plots had legumes plus radish.
  • Plots with legumes were generally healthier all season long and their yield reflected that.
  • I doubt that the whole field will average over 100 bushels/acre.  As with all hand yield tests they are estimates but I believe that the comparison is very accurate.
  • The Austrian Winter Peas, Crimson Clover, and Appin Turnips overwintered “beautifully” and were growing aggressively when sprayed at burndown.
  • There was a considerable amount of earthworm activity in the cover crop area but only a few earthworms were found in the “check” area. That is unfortunate because 2 acres were covered and 48 acres were not!
  • There were more corn roots in the plot areas we dug vs. the check area (watch for a new post coming on this soon).
  • There was more moisture in the soil where the cover crop plots were compared to the check area.
  • The soil structure was considerably better in each cover crop plot vs. the check area.
Don recorded over 180 chlorophyll readings in each cover crop plot and check plot over the summer.

 

The check plot had 175 units of nitrogen plus the whole field had been soybeans the previous year. While the annual ryegrass blend plot was above the check all season long it was not up to the desired level until after the July 19 rain event.

 

The plot with the Oats and Rye and Appin Turnips was impressive most of the spring and summer. It was at or above the desired rating until August. It was very impressive right after the July rain event and that is possibly why it had the second highest estimated yield. By the way, the turnips did live through the winter.
All season long I was convinced that the plot where the Austrian Winter Peas and Radish were was going to have the highest yield based on the data shown above (and plant height readings). It beat the second place entry by less than 1/2 bushel in the yield estimate.

Inoculating Cover Crop Legumes Pays Off

Several farmers have asked me why they need to spend an “extra” 4-6 cents per pound to inoculate the legume seed they are planting for producing nitrogen with their cover crops.  I get asked this especially about Austrian Winter Peas and Cowpea.

However, if you are planting Crimson Clover, Berseem Clover, Kura Clover, Alsike, Hairy Vetch, Sunn Hemp, or Medium Red Clover it’s just as important inoculate!  Why?  I’ll list a few reasons below:Inoculated peas are significantly better at producing nitrogen

  • Legumes are planted as cover crops most specifically to produce nitrogen.
  • Legume seed is relatively expensive; if it does NOT produce nitrogen, then it is exceptionally expensive.
  • The inoculant is a species specific bacteria that allows that plant to fix nitrogen.  If there are not enough bacteria there is limited nitrogen production from the legume plants.
  • A healthy legume cover crop can produce nearly 200 units of nitrogen
  • Even if you have produced a similar crop in your field within a two year time period, it still pays to inoculate each year since many of the bacteria prove to be “weak” and unable to perform like a healthy and vigorous bacteria.
  • If inoculating Peas or Cowpea you will need to do a “seedbox” treatment.  There are not yet inoculants that can be pre-applied that will allow you to have healthy bacteria. Therefore, most inoculant companies suggest putting the inoculant on within hours of putting the seed in the ground.

Be sure to get very good coverage on all of the seeds.

Do not hurry. Each seed needs coverage to actually be inoculated. I know that sounds silly, but I have seen many fields and plots where only some of the pea or vetch  plants were performing well.  The ones that looked poor had no nodules.

Many companies sell pre-inoculated clover seed.  If yours does not, then either find another supplier or purchase the correct inoculant from your current seed supplier.  Do not waste a great opportunity to produce as much nitrogen as possible. It is  less expensive to produce nitrogen than it is to purchase it.

A well inoculate Austrian Winter Pea nodule will be pink inside like the one above.
This photo shows a mixture of well inoculated and poorly inoculated Austrian Winter Pea plants. It is important to inoculate each seed with the nitrogen fixing bacteria.