Renewable Farming

Strongest profit signal from 2018 field test results: Shift dollars from NPK to soil biological vigor

Here’s the main message we’re gathering from random-rep trials and farmers’ field observations after the 2018 season’s weather stress: If you need to constrain costs, transfer some crop-budget dollars from NPK fertilizer to biological fertility

January 7, 2019 — There’s a difference between just fertilizer and robust soil fertility. Ken Musselman of AgriEnergy Resources emphasized that it’s fertility which keeps crops growing through seasons like 2018’s too-wet, too-dry extremes. Many of our friends who devoted weeks of time and many dollars on 2018 field trials sifted through wildly variable yield data after harvest, but found no statistically significant signals of what actually worked

In our 30 seasons of field tests — our own and friends’ research — we’ve learned that yield variability across a field amplifies greatly under weather stress. But this year’s rainfall extremes across the upper Midwest revealed a more fundamental fact: Soils with diverse, abundant soil life yielded the most consistently, and thus generated the greatest opportunity for net profit.

Veteran field researcher Dave Schwartz, who manages dozens of field trials on his farm west of Guthrie Center, IA, said this morning that he plans to focus dollars on strategies that “turn on the ground” — build up soil life by enhancing beneficial bacteria and fungi. “I’ll probably back off starter fertilizer by 20% and invest the savings in biologicals,” he said.

That echoes the main message recommended by AgriEnergy Resources founder Dave Larson more than 30 years ago. The strategies include far more than bugs-in-a-jug. Solving cover-crop challenges in the upper Midwest is an important ingredient, as each type of cover crop plant stimulates growth of about 10 different beneficial microbe species. 

Dave Schwartz, a marketing manager for Verdesian Life Sciences, said that in general, his 2018 field tests and client experience showed yield benefits from several Verdesian products designed to enhance nutrient efficiency, such as NutriSphere, which helps hold nitrogen later into the season. He also tests many products not sold by Verdesian. He told us that Biodyne USA’s in-furrow blend of live biologicals — Environoc 401 — again showed profitable yield response. “Also, I’ll probably include Biodyne’s new BD-Biocast on my commercial corn acres in 2019,” he added. He observed that calcium silicate generated wider, thicker leaves, adding to yields. He’s referring to a product called Mainstay Si, a blend of calcium and silica, from Redox. This report offers a background on silicon in a summary presented by John Kelly of Redox.

Dave has also tested Bio Empruv for several seasons, and said it “showed up fairly well again” in 2018 by helping keep corn green and kernels filling late in the season. 

Schwartz no-tills continuous corn on the highly rolling fields of his test farm, shredding stalks and applying residue-digesting products as soon as possible after harvest. Building soil biology has already enabled him to raise 300 bu. and even 400+ bu. corn on roughly a half-pound of nitrogen fertilizer per bushel. His N is metered to the crop through the season, and he seldom sees signals of N deficiency.

This link takes you to a report on Dave Schwartz’ field results following the 2017 season. 

Iowa crop consultant Bob Streit coordinates with Dave on research projects, so we also checked in with him for a summary of what he saw through the season and at harvest on the Schwartz plots and main fields.  He confirmed that six weeks of virtually no rain during the heart of the growing season imposed serious variability in corn and beans. 

“Dave and I spent six hours in his standing test plots of corn, making notes, weighing ears, measuring leaf thickness and so on,” he said. “But definitely, the highest average yields occurred where the full array of biologicals and nitrogen enhancers were applied — including in-furrow Environoc 401, NutriSphere, Bio Empruv, and Mainstay Si.”

Corn yields in Dave’s test plots varied from 332 bu. down to 189 bu., heavily influenced by soil variations in the creek bottomland where he operates field trials. 

Bob Streit found ears of corn weighing up to 14 ounces in the 2018 plots, but on average, ears were not as heavy and large as in 2017. 

We assembled the table of Dave’s yield results below based on Dave’s field notes. The seed was Pioneer 1197, treated with takeoff and Tuxedo. On May 2, the test field was dry spread with 150 lbs. per acre of 0-0-60 plus 250 lbs. per acre of pellitezed lime. The entire plot area was sprayed premerge May 12 with 50 gal. per acre of UAN blended with NutriSphere HV. 

We sorted the plots in this table in order of descending yields, in hopes of seeing some kind of general trend. Clearly, extreme weather overwhelmed the ability of plot trials to show moderate responses you’d anticipate, such as 5 to 10 bu. from a treatment variable. Ironically a control plot showed the highest single yield adjusted to 15.5%. 

It is clearly notable that the second and third highest yields had Bio Empruv, Biodyne 401, Ensure, O2YS and Mainstay Si — a “stack” of five biologicals and biostimulants. 

The effort demonstrates again: It’s not easy to tease out accurate readings of response to a test product. We greatly admire growers who patiently study a wide array of field trials and assemble the combinations that work most consistently on their own soils, most seasons.

Dave emphasizes another logical conclusion from his many research efforts: “We need to search out the management strategies and product blends which result in the widest consistent profit margin per acre — not just the highest yields.”





Here’s how corn in Dave’s plots looked in early August, 2018.


For years we’ve encouraged farmers to run on-farm strip tests for evaluating products and techniques. The strip trial protocol developed by Practical Farmers of Iowa can fit into most row-crop management systems. The two forms below offer you the how-to for setting up your field trials.  


Download data collection form here