Rising fuel and equipment costs, growers running more acres and a desire to save soil are spurring interest among Wisconsin producers in strip-tillage, say University of Wisconsin soil ccientist Dick Wolkowski, ag economist Thomas Cox and Extension onfarm research coordinator Jim Leverich.
Strip-tillage lets growers capture the production advantages of full-width tillage, while providing the soil-conserving benefits of no-till, they say.
Strip-tillage varies in intensity, but generally no more than 30% of the surface is disturbed. It’s commonly accomplished with a single pass in the fall, creating a strip of soil that’ll warm more quickly come spring.
The researchers say it’s the best of both worlds, with seedbed conditions in the row similar to chisel plowing but with lots of residue undisturbed. Strip-tillage is faster and takes less energy than conventional tillage.
"When strip tillage is coordinated with other field operations, it's controlled-traffic farming that limits compaction," Wolkowski adds. "Some strip-tillers have invested in GPS and tractor auto-steer to ensure planted rows are placed on previously strip-tilled ground."
Strip-tillage is commonly done following soybeans, fall-killed alfalfa or other “fragile” residue crops. However, newer, more aggressive tools can handle corn residue just fine. Some producers also apply fertilizer with their strip-till tool, eliminating another trip and the need for planter-applied fertilizer.
This trio lists several types of strip-tillage:
- Residue clearing using finger or notched coulters, sweeps or brushes to move residue from the row, typically the type found mounted on most no-till planters.
- Shallow (2 to 3 inches) with fluted and notched coulters that cut and move residue, loosen the seedbed and apply fertilizer near the seed. They are typically mounted on the planter, but can be on a separate toolbar. They are good for stony soils.
- Moderate (8 to 10 inches) with cutting coulters, mole knives or ridging coulters that cut and move residue, remove surface compaction, create a seedbed and deep-place fertilizer, as well as form a small ridge that’ll dry and warm quickly.
- Deep (over 10 inches) with a straight-shanked knife with limited soil inversion that takes care of subsoil compaction.
If fields are stony, they say strip-tillage with coulters is better than knives. On high-clay soils, shallow in-row tillage with a mole knife to break up surface compaction and move residue while forming a small ridge to promote drying in the row is likely best.
"This improves seed-to-soil contact and makes for more favorable planting conditions," Wolkowski says. "If deep compaction is a concern, deep strip-tillage may be needed."
The researchers point out that one of the advantages of fall strip-tillage is applying phosphorus and potassium at the same time. Anhydrous isn’t a good idea in the fall, though, because of lower efficiency and potential for leaching.
A 4-year study at the Arlington research station looked at fertilizer placement. Some 200 pounds of 9-23-30 was either fall broadcast or put in a fall-made strip 6 to 7 inches deep with a mole knife, or planter-applied in a 2-by-2-inch location. These were compared with no fertilizer in corn-on-corn and corn/soybean rotations.
While there was minimal difference between placement methods, corn/soybean was more responsive to fertilization than corn-on-corn. Because soil test phosphorus was excessively high and potassium optimum, any fertilizer response was likely from applied potassium, they say.
Long-term research at Arlington compared fall strip-tillage with fall chisel/spring field cultivator and no-till in both continuous corn and a corn/soybean rotation. The strip-tillage tool used was a mole knife that runs 8 inches deep and builds a 2- to 3-inch ridge on which the crop is planted. No-till was without row cleaners for “extreme” minimum tillage.
Both strip tillage and no-till rows were alternated 15 inches between years.
Results showed equal corn grain yield in first-year corn with chisel plowing and strip-tillage averaged over 10 seasons. No-till yields were 5% lower. Yields in continuous corn over the same period were highest in the chisel system and about 4% greater than strip-tillage and 8% better than no-till.
Strip-tillage saves soil and slows runoff versus conventional tillage. From the same Arlington study (1999-2005), chisel tillage of soybean residue reduced the surface residue to an average of 15%, while strip-tillage and no-till left soybean residue in the 55% to 70% range — with the amount left after strip-tillage about 15% to 25% less than no-till.
Passive runoff collectors were installed in a field with both chisel and strip-tillage on 8% slope on the Lancaster, Wis., station, trapping sediment from 100 square feet uphill. Soil loss in a year with substantial rain in the early part of the growing season prior to canopy closure was 4.67 tons per acre where the field was chiseled, but only 0.28 tons with strip-tillage.
In continuous corn, strip-tillage and no-till averaged, respectively, 8 and 15 bushels less than chisel plowing — which averaged 182 bushels over 10 years at Arlington. However, using those 10 years of yield data from the Arlington tillage/rotation study, cost of production per acre (figured for 2007) was lower for both strip-tillage ($23.20 an acre less) and no-till ($25.90 an acre less) than fall chisel plowing with a cultivator in the spring.
Comparing on a per-bushel basis adjusts for cost differences and the possibility of lower yields in reduced-tillage systems. When accounting for the reduced yield in these tillage systems — a 10-year average of 174 bushels continuous corn with strip-tillage and 167 for no-till — the lower costs per bushel for strip-till and no-till resulted in a 2-cents-per-bushel benefit for strip-tillage or an 8-cents-per-bushel loss for no-till vs. conventional tillage.
“The situation changes in the soybean-corn rotation,” Cox says. "In contrast to continuous corn, the first-year soybean/corn-under-strip-tillage yields are virtually identical to chiseling, while no-till came in 9 bushels less than chisel plowing.
Given that costs of production are similar to continuous corn, these more competitive yield differences generate favorable returns for reduced tillage — 12 cents a bushel less for fall strip-tillage versus chiseling and 3 cents per bushel less for no-till in corn following beans.
According to the researchers, this suggests that both cost savings and improved environmental performance are possible with reduced-tillage soybean/corn systems compared to chiseling, with strip-tillage “providing stronger economic gains” than no-till, albeit the planter was equipped without residue managers.
The soybean portion of the corn/soy rotation favors reduced tillage even more. On a per-bushel basis, yield and cost of production differences amounted to 18 cents per bushel less for strip-tillage and 26 cents per bushel less for no-till compared to chiseling.