Renewable Farming

Your next crop starts now, as your “littlest livestock” digest 2016 harvest residue

Oct. 20, 2016 — It’s really encouraging to see a growing percentage of farmers in our north central Corn Belt region pushing hard to capture carbon and nutrients from corn and bean residue just as it hits the ground from the combine.

Some farmers have separate crews applying residue-digesting biologicals, running vertical tillage rigs, shredding stalks, seeding cover crops or doing some combination of those effective management moves. 

Total net farm profit is no longer primarily about more acres; it’s getting the most yield and productivity buildup from existing acres.  

Here’s our favored combination of fall activities to nurture soil health.

1. We began realizing the virtues of fall residue digestion back in the 1980s when Dave Larson, founder of AgriEnergy Resources, showed field results at the Renewable Farming seminars which Pro Farmer sponsored then.  Dave’s field trials used their “Residuce” blend of live mycorrhizal fungi, other fungi and beneficial bacteria.  

Today, the proliferation of ag biological products includes many residue breakdown blends of bacteria and fungi. Probably the main aspect to use as a guide is that the primary soil-building benefit of residue decomposition organisms comes from the fungal population. The mycorrhizae and all their relatives grow rapidly, extend their filament tendrils around “raw” carbon in stalks, and build the glomalin which is foundational to a living soil. 

Glomalin is a key component in active humus. It’s the “stickum” that creates a coffee-grounds structure in soil. It helps protect against wind and water erosion. Helps aerobic soil organisms thrive. Creates pore structures for water and air exchange deeper into topsoil. We recommend that you download and read this fascinating Ag Research Report on glomalin, which is a relatively new “discovery” of soil science in the early 1990s. In a healthy soil, glomalin provides the foundational 20% of active humus.  Raw crop residue may be “organic matter” but it’s not useful for crop nutrients until soil microbes convert it into plant-available forms.

You can check out AgriEnergy’s Residuce at this link. The firm makes several formulations for different programs, including a dehydrated version which is easy to ship and incorporate into fall liquid nutrient applications. It’s beneficial to apply digester critters with a readily available energy supply.  Each manufacturer will have recommendations. 

John Kempf at Advancing EcoAgriculture is an example of the innovators in this realm. Here’s a link to their products page. The smaller entrepreneurs have blazed the trail for the big corporate investors like Monsanto, who are moving rapidly into the ag microbiological market. 

2. Cover crops are a huge natural microbial nursery. Dr. Robert Kremer’s USDA/ARS work at the University of Missouri found that each species of plant in your cover crop mix fosters up to 10 species of soil organisms.  So that scrawny green coat of cereal rye out there following soybeans may not look like much, but  a lot is going on underground. 

This fall we picked up another Hagie Highboy, a diesel 4-wd rig which has seen better days and outlived them. Our winter project plan is to strip off the spray equipment and rig up a high-mounted Gandy seeder with drops so we can drive through corn or soybeans, and seed cover crop blends. Our little 40-acre research patches aren’t suited to aerial seeding, and precise strip application suits our research needs. So far our cover crop experiments have primarily followed early-harvest crops like wheat and sweet corn. But we’ve noted, for example, that tillage radish and clover leave a magnificent seedbed with very little weed pressure the following spring.   Here’s how our current tillage radish planting looks as of Oct. 20, barely a month after drilling.  We went for a light population of radish, anticipating larger roots and deeper penetration. The first couple of years,  the big white Dakons would punch down about 8 inches, hit a density layer and push the remainder of their growth upward, above the surface. Now, they keep growing deeper.

It’s fun to see the top-echelon growers around here, like our neighbor Dennis Kruger (founder of Kruger Seeds) flying on cover crops such as cereal rye.  Increasingly our county is turning green in October, with a lot less recreational tillage. 

3. Even purist no-tillers can get cornstalks “down and dirty” without wrecking the habitat for soil organisms. Our cheap favorite is the stalk shredder, which we run so it grazes the soil surface and kicks up a good bit of dirt while pulverizing stalks. 

Getting that layer of shredded stalks smoothly spread and wicking up moisture is probably enough to lay the table for residue decomposing organisms. Usually we can see the white filaments of arbuscular mycorrhizal fungi creeping all over shards of stalks within a couple of weeks after harvest and shredding. 

Growers with the cash and innovative spirit to add vertical tillage to this mulch cover certainly gain moisture and air penetration, again without abrading the soil habitat.  The old Aer-Way and the new Cursebuster vertical tillage units are on opposite ends of the timeline of “discovery” of vertical tillage. There are many rigs with different methodologies in between.  

We’re not even afraid of a very light field-finishing run in the fall, preferably after stalks have started to “melt” and soil conditions are perfectly mellow. Not sticky. No deeper than two inches.

4. Gypsum.  More Gypsum. And next year, repeat. Main challenge here is to find a clean, cheap source. All the arguments for calcium sulfate are out there. Jerry Hatfield at what we used to call the National Soil Tilth Lab at Iowa State is confirming benefits. Something like 10 bu. per acre on corn after one application the previous fall, we’ve heard.

Our own limited experience, four years, has helped us upgrade a neglected horse pasture into fields that produce pretty decent crops, and have soil tilth that’s noticeably different to walk on. 

Since we’re too far from our gypsum source, and our acreage is too small, we don’t have the luxury of custom spreading of the gypsum, which we buy from BRT Ag&Turf based in Ladora, Iowa.  We stockpile the gypsum on a pad, cover it, and put an equal tonnage of high-calcium lime beside the pile. Each fall, preferably after the soil freezes, we have our lime-truck spreading service spin it out this way:

A front-loader bucket of gypsum goes in the high-speed belt loader filling the spreader truck, then an equal  bucket of ag lime. Alternating like that, the blend is pretty well mixed by the time the spinner truck is full. The combination heats up in a few minutes, and the load will turn hard if you let it sit much beyond a half-hour. The gypsum draws enough moisture from the lime so the spreading isn’t dusty as it would be if you spun out gypsum alone.  (Doing that with a spinner truck leaves a white fog for a half-mile downwind.)

All of these fall farming techniques add up, and act with synergism.  The sulfur in the gypsum helps foster late-growing organisms.  Such efforts help achieve what Dave Larson used to describe as the best fertility: “The widest possible array of beneficial soil organisms.”