Cover Crops effect on spring Soil temperatures

May 15 2013

Myths Debunked on Cover Crops and Colder Soil Temperatures? – Final Report

Sometimes apparent myths prove to be true and sometimes they prove to be…myths!

In March 2013 I asked my brother Don Robison from Robison Farms to help me figure out how cover crops might effect soil temperatures. We have looked at data in previous posts trying to answer the question “Do Cover Crops that Survive the Winter Keep the Soil Colder in the Spring than Fall-Tilled Soil?”

Now I have asked Don to chart all of his data that he has taken since late March in fall-tilled soil, no-till soil, no-till soil with cover crop annual ryegrass, and a lawn. Don added a test of taking moisture readings as well because “we know” that no-till soils are “always wetter and colder than fall-tilled soils.” At least that is common “knowledge” from many farmers I talk to from Minnesota to Missouri and points eastward.

Don made some comments that I believe are helpful:

The soil type in the lawn is Miami silt loam, while the fields are Crosby silt loam.
The no-till w/o cover crop test had a compaction layer at ~3-9″ deep in this area in our compaction tests we conducted in 2012. Don’s thought is that where he is doing the tests had a compaction layer closer to the 3″ depth (so there is less percolation).
Don reports “No conclusions yet and maybe there won’t be any, but an interesting trend I’m starting to see is that in this cool wet spring, the conventional tillage does not seem to be living up the reputation of being warmer and easier to till in the spring than no till. That may very well change when the rainfall and temperatures become more like you would expect to see in the planting season.”

Data reveals that cover crops do not appear to be keeping the soil colder.

It appears that our no-till soils with cover crops has consistently been warmer or just as warm as the fall-tilled soils. I am placing the charts below for you to observe the data.

Apr 17 2013

Part 3- Do Cover Crops Keep the Soil Colder in the Spring?

Fact or Fiction? Cover Crops that Survive the Winter Keep the Soil Colder in the Spring than Fall-Tilled Soil – Part 3

As of today (April 17, 2013) there is 0% corn planted in Iowa and Indiana with 1% in Illinois and Ohio. It is now wet and cold…not just cold. As my brother Don takes soil temperature readings in no-till soils with cover crops, no-till with out cover crops, and fall tilled soils, we are trying to get an idea if no-till soils and or no-till soils with cover crops keep the soil colder than fall tilled soils. These trials are being conducted in central Indiana and should be a pretty good measurement for much of the Eastern Corn Belt. I am in northern Wisconsin today where there are snow covered fields with 6-8″ more snow coming in the next 36 hours. The readings from central Indiana don’t mean much in Minnesota and Wisconsin…but, I believe they are still instructive.

April 5-12, 2013 weather data

The temperatures at the local weather station showed that the actual average high for the week was 70.6° (historic average is 61°) and the actual nighttime average was 49.9° (historic average is 40.3°). This was the first week in the past several weeks that have been warmer than average. There was nearly 1 inch of rain during the week.

Soil temperatures increased dramatically during the week

Warm weather really helped increase the soil temperature, almost 10° in some of our trials. It is interesting to see that the no-till soil without a cover crop was the coolest by 1°. It was also the wettest soil last week and certainly appears to be the same on 4-12. The warmest soil was the no-till with cover crop. Not by much but it is warmer than the fall tilled soil by ~0.5°.

With heavy rains in the area this week it will be interesting to see what happens in each soil. We hope to get an idea of what kind of earthworm activity we can find, but that might be difficult in the muddy sites.

Improved water infiltration may be showing springtime benefits

As you look at the photos notice the moisture content on the surface of the soil. There are two observations or reminders that we should consider. When we took compaction readings last summer (2012) we saw a significant benefit where we had cover crops compared to the no cover crop check. These soil temperature tests are taken from those same plots. Another observation is that I have found improved aeration and percolation where we have had cover crops (long-term no-till with cover crop) verses long-term no-till without a cover crops and a spring tilled soil. I believe we are seeing that the cover crop is giving benefit again this spring in these areas.

What are you finding on your farm?

Readers would be interested in knowing what is going on in your area and on your farm. Please comment below and share what you are finding. Thanks, Dave

The soil temperature in the long term no-till soils on 4-12-2013. Note how waterlogged the soil looks. — The soil temperature in the long-term no-till soils on 4-12-2013. Note how waterlogged the soil looks.

The soil temperature in the long-term no-till soil with a cover crop. Note that the soil looks drier and it is also the warmest reading this week.

The soil temperature in the fall-tilled soil on 4-12-2013. The soil doe not look as wet as the no-tilled soils. Maybe the water went down the cracks! — The soil temperature in the fall-tilled soil on 4-12-2013. The soil does not look as wet as the no-tilled soils. Maybe because the water went down the cracks…

Apr 09 2013

Part 2- Do Cover Crops Keep the Soil Colder in the Spring?

Fact or Fiction? Cover Crops that Survive the Winter Keep the Soil Colder in the Spring than Fall-Tilled Soil – Part 2

On Friday April 5, 2013 my brother Don recorded the temperatures in soils on our home farm near Greenwood, IN (central Indiana). The previous week Don took soil temperatures coming out of a colder than normal March. The results showed very similar temperatures in soils at approximately 4″ deep in fall tilled soil, long term no-till soil, and soil covered with an annual ryegrass cover crop.

April 2013 is off to a chilly start in central Indiana

The first week of April saw chilly day and nighttime temperatures in the area. The average daytime temperature was 53.5 degrees (normal is 58.71 degrees) and the nighttime temperatures were 30.8 (average 38.29 degrees). The soil temperatures gained a few degrees in each area.

Soil temperatures did increase during the week

While the soils are not warm enough to plant corn in yet they are getting closer. No one in the area has started any planting yet but the soil temperature readings show that all of the soils tested are getting close to being warm enough to make sure the planter is ready and seed is in the shed ready to go to the fields.

Don’s observations

The long-term No-till area had the most surface soil moisture (not wet but definitely quite moist)
The fall tilled soil was crusted over and had cracks in the soil
The soil covered with Annual Ryegrass was not “wet” and it had no cracks in the soil
Don told me that he heard from Barry Fisher at a recent cover crop field day that soil biology starts becoming active at around 38 degrees soil temperature. Each of the soils are well above that temperature.
During the next testing session Don will also be testing for soil moisture and taking some earthworm counts in each of the soils.

Soil temperature in the fall tilled soil 4-5-2013

Soil Temperature in the long term no-till plot (check plot) 4-5-2013

Soil temperature in the Annual Ryegrass cover crop plot 4-5-2013

Mar 30 2013

Do Cover Crops Keep the Soil Colder in the Spring?

Fact or Fiction? Cover Crops that Survive the Winter Keep the Soil Colder in the Spring than Fall-Tilled Soil

This is a question I get over and over again. And most of the time it’s not really a question. It’s actually someone stating to me why they are not going to plant cover crops. But is it really true that a surviving cover crop will keep my soil colder than a conventionally tilled soil?

Several years ago in March I stopped at a cover crop test plot on the Indiana/Ohio border. While I was there I checked the soil temperature where cover crops had survived (Annual Ryegrass and Winter Cereal Rye) to see if it was indeed colder than the tilled soil that surrounded the plot.

Surprising Results

What I found was a bit surprising considering the conventional “widsom” I commonly heard. The soil temperature at 4″ depth was warmer by 1-2 degrees where we had a surviving cover crop than in moldboard plowed dark soil. I sampled on a sunny day when the temperatures were in the 40’s.

Since then I have taken comparative soil temperatures in many locations where no-till was done, where there was no-till with cover crops, and where there was fall tilled soil. In nearly every instance the area where there was a cover crop the soil temperatures were equal to or above the fall tilled soil temperatures. Each of these samples were just taken one time – a snapshot test in time.

More Testing

This spring my brother Don Robison is taking soil temperatures and photos of a soil thermometer from our home farm near Greenwood, IN. He started taking these photos on March 29, 2013. The plan is that Don will take soil temperatures for four or five consecutive Fridays – in annual ryegrass, in no-till soil (that has some winter annuals present), and in fall tilled soil. And since March of 2013 has been quite cold when compared to recent years, the results should be interesting.

Results Will Be Recorded

Each week I will post the temperatures as Don send them to me. Below you can see the temperatures from March 29. Be sure to check back weekly for the results.

Do Your Own Experiment

Send me temperature readings and photos (phone camera quality is fine) and I’ll compile some data from different parts of the country (world) and pass the data along. Please let me know your soil types and general weather conditions when you send in your reports.

Myths Debunked on Cover Crops and Colder Soil Temperatures? – Final Report

Don made some comments that I believe are helpful:

Data reveals that cover crops do not appear to be keeping the soil colder.

Part 3- Do Cover Crops Keep the Soil Colder in the Spring?