Shallow Tillage Research Brief — KELLY Tillage & University of Illinois Trials, 2019–2023
A single spring pass with a KELLY 30-foot shallow harrow — with no fall tillage at all — produced the same corn yield as full conventional deep-tillage programs across three seasons of University of Illinois field trials (2019–2023), while using roughly one-quarter the tillage fuel. Same yield. Less diesel. More residue and moisture kept on the field. That is the practical case for shallow tillage as a middle ground between deep tillage and no-till — and it is the data that puts KELLY at the center of the shallow-tillage conversation in North American agriculture.
Disclosure: the U of I study was commissioned by KELLY Tillage and is cited here with KELLY's permission. It is independent university testing, and we credit the sponsorship openly.
Key Findings
Yield: no penalty for going shallow
Across three seasons of University of Illinois trials, a spring-only KELLY pass (NONE-K: no fall tillage, KELLY Diamond Harrow in spring) matched the corn yield of full deep-tillage programs — the differences were not statistically significant. In the 2022–23 season, all six treatments landed in a tight 180–195 bu/acre range with no statistical spread between systems. Equal yield at a fraction of the diesel is the economic case for shallow tillage. Note: 2019–20 season yields were significantly reduced by a June 15 planting date and a V7–V8 hailstorm affecting all plots, so absolute yield levels do not compare across seasons — but the relative parity between treatments held. (Source: U of I Dept. of Agricultural and Biological Engineering, Cumulative Report 2019–2023.)
Fuel: upwards of four times less diesel
Counting tillage passes only, a full conventional program (fall disk ripper plus spring field cultivator) burned about 11.6–12.1 liters per acre across the two combined-fuel years measured. A single spring KELLY pass (NONE-K) burned about 2.0 liters per acre — the report's own summary describes deep-tillage fuel as "upwards of four times as much" as spring-only KELLY. At the whole-farm level, USDA-linked data (Hanna et al., 2001, cited by SDSU Extension) puts continuous no-till at about 2 gallons per acre versus about 6 gallons per acre for conventional programs — a 4-gallon-per-acre difference, worth $22.56 per acre at the $5.64/gallon diesel price of spring 2026. (Sources: U of I 2023; SDSU Extension.)
Residue and soil health
In the Illinois trials, the fall-KELLY treatment (K-NONE) held among the highest surface residue — 54% in Spring 2019 and 74% in Spring 2020, comparable to or above the vertical-tillage treatment and roughly triple the residue left by the fall disk-ripper programs, which came in near the bottom of the range. Reduced-tillage practices generally keep 30 to 60 percent of crop residues covering the soil surface, versus less than 15 percent for moldboard plowing — cover that stops crusting, cuts erosion, and holds moisture through a dry August. One study measured moldboard plowing losing over 3,800 pounds per acre of organic matter within 19 days after the primary tillage pass. Less soil disturbance also releases less carbon: disk ripping and strip tillage released 53 and 83 percent less CO2 from the soil than moldboard plowing. (Sources: U of I 2023; UMN Extension.)
Moisture
Illinois spring-KELLY treatments (NONE-K) consistently held some of the highest soil moisture across both measured seasons. The fall disk-ripper programs tended to be drier — especially the DR-FC treatment in Spring 2019, which was among the driest of all treatments — though the moisture gap narrowed in Spring 2020. Broader USDA research: moldboard plowing loses 23 percent more soil moisture than chisel plowing within 80 hours — and twice as much moisture as no-till. Residue on the surface is the difference. (Sources: U of I 2023; UMN Extension.)
Weed control
In Spring 2019, the KELLY Diamond Harrow achieved a 97+ percent weed-elimination rate — just 2.76 percent weed cover remained after the pass, versus 32.4 percent behind a John Deere field cultivator (a 68 percent removal rate) and 6.7 percent behind a Sunflower soil finisher. In Summer 2023, all three tillage tools kept weed cover under 1 percent, while the no-till control plot ran near 20 percent — with the upper confidence bound reaching 32 percent. Shallow mechanical tillage beats no-till badly on weed suppression and can trim early-season herbicide dependence. Honest edge: weeds tended to survive in the center seam of the KELLY pass, so a residual-herbicide plan still matters. (Sources: U of I 2023; UMN Extension.)
Speed and capacity
At the same operating speed, the 30-foot KELLY covers ground about 27.5 percent faster than a 21-foot 9-inch soil finisher — more acres per hour, which matters most in a tight spring window. Combined with lower fuel consumption per acre, this is the operational core of the KELLY value proposition. (Source: U of I 2023.)
Adoption trend
Conservation tillage now covers roughly 76 percent of U.S. corn acres and 74 percent of soybean acres (68 percent of wheat, 43 percent of cotton). No-till alone on corn climbed from 16 percent in 2001 to 36 percent in 2021, including a jump from 28 percent in 2016. Only about a fifth of those conservation-tillage acres are continuously no-till — most farmers flex their tillage year to year. That flex-farmer, looking for a lighter pass without going full no-till, is exactly the shallow-tillage buyer. (Source: USDA ERS, Rosenberg and Wallander, October 2022.)
Honest Tradeoffs
"Deep tillage gives me a better seedbed."
True — the deep disk-ripper plus field-cultivator program had a slight edge on seedbed uniformity in the Illinois trials. KELLY still delivered one of the smoothest seedbeds and, critically, the same yield. A hair more uniformity does not help if it costs four times the fuel for no extra bushels.
"What about compaction?"
Compaction results in the Illinois study were mixed across years and depths. Where shallow-till plots read more compacted, yield did not suffer. If a farmer has a deep compaction layer, shallow tillage will not fix it — that is a different tool and an honest conversation.
"Residue will keep my ground cold and wet."
Real tradeoff. Heavy surface residue can keep soils cooler and wetter in spring. That is exactly where a shallow pass helps — sizing and moving residue so the seedbed can warm, without burying it all.
"Less tillage means more weeds."
Fair. Reduced tillage concentrates weed seed near the surface and rewards a good residual-herbicide plan. Shallow tillage is a mechanical assist, not a silver bullet — but the trial data shows it beats no-till badly on weed suppression.
Where KELLY Sits
KELLY is purpose-built for high-speed shallow tillage. The Illinois findings map cleanly to what the platform is designed to do:
· Fewer passes, lower fuel: one shallow spring pass can replace a fall-plus-spring deep-tillage program.
· Capacity: full-width, 6–9 mph shallow tillage covers more acres in a tight window.
· Residue and moisture: kept up top and in the ground — measured, not claimed.
· Mechanical weed control: a shallow pass knocks down weeds and can trim early-season herbicide spend.
Talk to Hood & Company
Hood & Company is the U.S. manufacturer's representative for KELLY Tillage. If you are considering shallow tillage for your operation, start with your local KELLY dealer — they are the fastest path to a quote and a hands-on look at the system. If you do not have a local dealer or need help sizing a KELLY system for your acres and residue conditions, contact Hood directly at 417-865-2100 or sales@hoodco.com. We work with farmers and dealers across an 11-state territory covering Iowa, Missouri, Illinois, Indiana, Kentucky, Tennessee, Arkansas, Louisiana, Mississippi, eastern Kansas, and northern Alabama, and have represented KELLY since 2006.
Sources
University of Illinois at Urbana-Champaign, Dept. of Agricultural and Biological Engineering — "Evaluation of the performance of the 30' Kelly Tillage Diamond Disc in relation to common Midwestern tillage practices," Cumulative Report 2019–2023 (Grift, Lecher, Barber, December 20, 2023). Commissioned by KELLY Tillage; cited with permission.
USDA Economic Research Service — "Adoption of conservation tillage has increased over the past two decades on acreage planted to major U.S. cash crops" (Rosenberg and Wallander, October 25, 2022). https://www.ers.usda.gov/data-products/charts-of-note/105042
University of Minnesota Extension — "Reducing tillage intensity." https://extension.umn.edu/natural-resources/conservation/agricultural-soil-and-water/reducing-tillage-intensity
SDSU Extension — "The Economic Advantages of No-Till: Diesel Fuel" (Winter and Bly). https://extension.sdstate.edu/economic-advantages-no-till-diesel-fuel
AgWeb — "Shallow Tillage: A Strategic Reset Tool for Conservation and Conventional Systems." https://www.agweb.com/news/machinery/shallow-tillage-strategic-reset-tool-conservation-and-conventional-systems