Plant Cover Crops

Learning about the benefits of planting cover crops.

manure

Fall Cover Crop Management

While in southern Minnesota in early September 2013 I was asked when a farmer should plow his cover crop field this fall because he needs the fields to be “black” this winter in preparation for next spring.  I shuddered.  There I was in a beautiful field of cover crops that are jump-starting some biology on a “biologically dead” field and the farmer wants to kill his biology driving mechanism.  UG!  The main reason he wanted to till the field was to have warmer soils in the spring where he had black soil.  I shared that our research sowed much different results.  His thought process sound right but has proven to be a myth, not a fact.

A beautiful stand of Oats, Berseem Clover, and Pasja Hybrid Brassica on prevent plant acres in SO. MN
A beautiful stand of Oats, Berseem Clover, and Pasja Hybrid Brassica on prevent plant acres in SO. MN

I told the farmer to leave the cover crops in all winter and use conservation tillage next spring.  (He’s not a no-tiller.)  We dug some shallow root pits for a field day and we found many problems that I believe can be somewhat rectified if the cover crops are left in all winter.

We found many soil health problems in this prevent plant field

  • Severe compaction– many areas had compaction starting at 2-3″ deep.  Part of that was from spring tillage of wet soils…but the compaction was about 8″ thick as the soil was coming up in blocks the size of cinder blocks!
  • Lack of soil biology – I know this because we found a significant amount of corn fodder 2 foot deep that was not even breaking down.  It would have been buried with the deep ripper 18 months ago.  I could not believe my eyes!
  • Lack of aeration in the soil – the soil was literally rock hard.  We did find a few earthworm channels but it was so dry that worms were small and deep.
  • Low organic matter – I’m not sure how low it was but there was very little soil structure.  I talked with a regional NRCS employee and the local SWCD specialist and both men lamented that many of the soils in that region were “about as bad as this one”.
We found corn fodder two feet deep that had not yet decompose after over 18 months.
We found corn fodder two feet deep that had not yet decompose after over 18 months.

I need to be fair.  The farmer currently renting this field has only farmed it a few years and he is making major strides to improve this farm.  But he has lots to accomplish before he has a healthy field.  Having cover crops are a great first step and he knows it.

Other solutions (instead of cover crops) being proposed to fix the “tight” soils (“unhealthy” soils) in the region

  • Tile – LOTS and LOTS of tile has been installed in prevent plant acres this year.  Farmers know they need aeration and percolation in their “tight” soils.  The regional specialist from NRCS lamented that many farmers don’t believe that cover crops are a solution to make their soils better long term.  Tile is not bad; but tile and cover crops are a much better solution.
  • Deep ripping – this will get air into the soil and break up compaction, but will it build soil health?  No, it will not  (note the corn fodder found 2 foot deep in a root pit).  Let cover crops naturally deep rip the soil.
  • Tillage- and lots of it – many fields in the area had been tilled (disked, field cultivated, etc…) four times already to control weeds…Unfortunately it also reduces organic matter and soil structure and soil health.

So what should happen with the cover crops heading into winter?

  • Leave the cover crop growing into the winter – This will give the best opportunity to help with aeration and percolation.  This also helps build soil structure and reduce compaction.  (See deep ripping, and tiling above…just let the cover crops do this naturally!)
  • Sarah Carlson from Practical Farmers of Iowa recently wrote an article about this topic and you can find it here Prevent Plant, Cover Crops, Now What 2013.
  • Let the cover crops keep putting down deep roots – we found roots of crimson clover, radishes, cereal rye, annual ryegrass, oats, and Pasja all around 24″ deep.  Let them keep growing deeper to open up the soil to get air and moisture deeply into the soil profile.
This 5 week old PileDriver Radish shows the compaction zone starts at around 2-3" seep. Roots on this radish went over 24" deep despite very dry conditions.
This 5 week old PileDriver Radish shows the compaction zone starts at around 2-3″ seep. Roots on this radish went over 24″ deep despite very dry conditions.
This field had very poor soil structure. The regional NRCS specialist told me that many fields in the area had similar issues
This field had very poor soil structure. The regional NRCS specialist told me that many fields in the area had similar issues

Radish / Pea Mix Video

I have been visiting a  farm in eastern Whitley County Indiana over the past month and have seen a few fields of an Austrian Winter Pea/Radish mixture.  These fields were wheat fields that had dairy manure knifed into them after they had been harvested and deep tilled.  The video shows what a great stand the farmer got and the growth of the radishes!  We found one plant that had a 28+” deep tuber/tap root.  That’s how much was in the soil!  At 4″ below the soil surface I found where there had been quite a bit of compaction.  The radish was “crumpled” or “wrinkled” at the 4″ depth range.  Out of the 15 radishes we dug up only one radish had not bored through the compaction layer.

This GroundHog radish had a 28+" deep tuber/tap root.
The Austrian Winter Peas were growing very prostrate in this field. When I lifted the plants up they measure over 12" tall to up to almost knee high.
The radishes showed where there was compaction that caused some wrinkling of the tuber. The tubers grew through that compaction which shows the powerful ability of the cover crop radish.

Cover Crops and Manure are a Great Combination

Manure was captured by the annual ryegrass cover crop and was available for the following year’s corn crop.

During my past five years with the Midwest Cover Crops Council, I have heard cover crop experts say that “the farmer who has access to manure is the perfect candidate to use cover crops.”

I witnessed this truth up-close and personal this fall when visiting the Leman farm in NW Indiana.  The Leman family has a dairy farm and several acres of corn silage (the acres are usually planted to corn silage each year).  For years they fall applied manure to their fields with little nitrogen value being realized in the spring.

The soil is rather sandy and the manure had little to keep it in the soil root zone (but it had not been running off).  These past three years the Leman’s have been using cover crops in their corn silage fields with impressive results.  This year Scott Leman told me that he will “never stop” using cover crops because of the value they are finding.

Each year they leave sections of 30-36 rows in the silage fields that they leave for grain harvest.  In these areas they did not plant cover crops (until this year).

This fall Mark Perry, from CISCO Seeds, and I went to the farm with Randy Davis (Country Acres in Francesville, IN) and Curt Leman to see what difference we might find between where they had a cover crop planted (N-Vest® Soil Builder Annual Ryegrass Blend) and where there was no cover crop planted. The results were astounding…but not totally unexpected!

Where there was a cover crop there was much better plant health and bigger ears on the corn.  Curt was convinced that there would be a 20 bushel/acre or more advantage where there was a cover crop.

I did not take plant samples to send off to the lab to test forage quality on the silage, but I wish I had.  All I know is that there was more grain on a green stalk where they had the cover crop.  Where there was no cover crop the stalks were pretty dry nearly up to the ear and ~2” less grain per ear of corn.

The Lemans also cut back 50#/acre on their nitrogen application on their fields.  So, they saved $20+/acre on N cost and added 20 bu/acre on yield (at $4.50/acre) = PROFIT.  Save $20/ac — add $90/acre on yield = $110/acre. The seed cost was approximately $30/acre with $10 cost of application.

$110 – $40 = $60/acre added profit from using a cover crop.

Add in the benefits of cleaner water, less wind erosion, improved soil biology, increased soil organic matter, and less potential for manure run-off, I’d say that the Lehman’s are right in using cover crops each year.

The photos below show some of the value. Click on them to see a larger view.

These ears were typical where manure was applied but no cover crop was utilized.
These ears were typical from the area where the Lemans used cover crops. There was approximately 2” of “extra” grain on each ear where they had cover crops.
This photo shows the silage corn where there was no cover crop utilized. The stalks were “firing” up to the ears.
This photo shows Curt Leman in the silage corn where there was a cover crop utilized. The stalks were healthy and green.These stalks were approximately 30’ away from the stalks shown at the left.