Renewable Farming

Biological benefits add to the profits in cover crops

Many of the most compelling benefits of cover crops occur out of sight, underground.

Adding a fresh plant species to your crop rotation dramatically multiples the spectrum of beneficial microbes, fungi and soil life.

USDA-ARS microbiologist Dr. Robert Kremer showed us data on that fact at a seminar last December. And Dr. Jill Clapperton emphasized it again at a Practical Farmers of Iowa seminar in January.

We simply don’t have an easy way to quantify the yield benefits of that biological bloom in our soils.

Dave Larson, founder of AgriEnergy Resources, constantly repeated his essential ingredient of real soil fertility: The soil with the widest range of beneficials in the soil food web has the greatest long-term fertility potential. 

That’s a polar extreme from what I was first told in 1964 by Ralph Wennblom, senior crops editor at Farm Journal: “The soil is just there to hold up the crop. Everything that crop needs, we can provide with fertilizer.”

Flying on cereal rye over standing soybeans

So this morning, Sept. 19, I was enthused to hear a Piper turboprop’s mellow wrooooom over our house, as it scattered cereal rye on Dennis Kruger’s soybean field just across the road. Last fall, Dennis drilled cereal rye after corn harvest, and it barely emerged before a hard freeze. This fall, that entire soybean field will probably green up before the first frost.

The cover feature in the current Wallaces Farmer describes the benefits of cover crops. Two of our pilot friends who do aerial applications, Rick Kettley and Mark Watson, are ardent cover-crop fans: They extend their flying season, and cover-crop farmers seem to have more money for foliar nutrient applications in subsequent seasons. 

Which brings us to a new management scenario:  What can we do to maximize the vigor of cover crops, to “yield” the most of their typical benefits?

The website specifies eight benefits of cover crops:

Increased yields

Improved soil fertility

Reduced inputs

Weed control

Nematode control

Reduced compaction

Increased water retention


That final benefit, increased biological life in the soil, should probably be listed first — as it contributes to all the others.

On our research farm, this is the third season we’ve focused on tillage radish as a cover crop. Cereal rye is promising, along with others, but we haven’t found a non-toxic way to “terminate” cereal rye in spring. No glyphosate or paraquat here. 

Our 2015 corn following 2014 tillage radish is about 10 ft. tall

Where we’ve sown fall tillage radish in previous seasons, the soil is dramatically more mellow and well-structured. Our best corn this season follows last fall’s tillage radish. We should also mention that this benefit is in the context of a ton per acre of calcium sulfate, (gypsum from the ADM plant in Cedar Rapids, via BRT’s service), blended with a ton of ag lime.

This fall, we drilled tillage radish following sweet corn and wheat.  Our intent is to see how we can “amplify” the work of tillage radish in pumping the maximum sugars to that big root, which in turn will maximize the underground bloom of mycorrhiza and beneficial bacteria. 

Research agronomist Jim Porterfield of Arise Research & Discovery, Inc. of Martinsville, IL has literally dug up some evidence on how pumping more sugars to roots leads to more root mass — and thus, logically, more bioactivity in the rhizosphere.

Root sugars can be enhanced with foliar treatment!

In 2012, Porterfied found on a research project for us that foliar feeding corn at V5 with WakeUP, nitrogen and Sea-90-minerals generated 70% higher sugar levels (measured as brix) in lower roots compared with controls. The measuring was done at 45 hours after treatment. The effect continued eight days after treatment. Sea-90 is the product of evaporating seawater and preserving the minerals. It’s mostly salt, but has about 80 other micronutrients.

In 2013, we hired Jim for a similar test using tillage radish and oats as a cover crop.  Porterfield’s summary: “This quick evaluation suggests that foliar application of WakeUP can have a significant impact on increasing growth of Tillage Radishes in a cover crop mixed with oats, especially if the plants are not too crowded. Dissolving and adding the SEA-90 micronutrient fertilizer to the mix also appeared to be beneficial for increasing Tillage Radish growth in crowded conditions.”

The dry weight per tillage radish increased 14.2% when applied to a mixed cover crop of oats and radish. Including Sea-90 in the foliar spray doubled that weight benefit.    You can download Jim’s full report as a PDF at this link.

Because of these brief experiences — blending sea minerals and WakeUP — we’re conducting field trials this fall on tillage radish using WakeUP and another form of sea minerals. We’ll use Sea-Crop, which is a liquid product derived from seawater drawn from a coastal bay in Washington.  All but 5% of the salt has been removed, but the biological components and other minerals are preserved in the liquid.

If we can inexpensively increase the benefits of a cover crop by nurturing it like any other crop, that’s one more “nudge” toward improving soil life and our productive base.