Corn strip-tilled in the spring of 2009 out-yielded other practices used to grow corn, according to a study from Iowa State University.

The strip-tilled corn yielded 184 bushels per acre,  while the disc-chisel and the disc-ripping produced 167 and 164 bushels per acre, respectively, the university says.

The 2009 research was done at an ISU farm north of Ames that had been planted to corn for two seasons.

Two tillage treatments of disc-chisel and disc-rip were conducted in the fall of 2008 as standard field preparation for planned corn following corn. A third treatment of untilled stalks was left for strip-till.

Treatments were 40-feet wide at 30-inch rows and 1,610 feet long. Treatments were replicated three times across the field.

The middle eight rows of each 16-row treatment were harvested to avoid border concerns from the tillage treatments.

Due to a late harvest and unusually wet conditions following harvest, the strip-till was not done in the fall, nor was any nitrogen applied to any of the treatments in the fall. 

In spring of 2009, anhydrous ammonia was applied directly into standing cornstalks using a Blu-Jet strip-till unit donated by Brokaw Supply Company in Fort Dodge, Iowa.

Anhydrous ammonia was also spring applied to the fall tillage treatments using a standard ammonia unit. The target rate was between

180 and 200 pounds per acre of actual nitrogen. Tillage treatments were worked once with a field cultivator before planting .

The corn hybrid DKC61-69 VT3 was planted at 32,000 seeds per acre. The same herbicide program was applied to the entire trial. Weed control was very good with very little volunteer corn present. 

The Study's Results

The trial was scouted every two weeks from planting to harvest. Population counts were taken at V3.

A slightly higher corn population was observed in the disc chisel vs. the strip-till and disc-rip treatments.  exhibited a zone of horizontal root proliferation at the 4- to-6-inch depth before proceeding downward. This was not observed in the strip-till treatment.

Two strips of four rows each were harvested from the center eight rows of each treatment. This provided six data points from each replication, and a total of 18 data points for the trial. Each strip was weighed separately and moisture determined with a hand-held moisture tester.

Although yields were not different statistically, there was an advantage to the strip-till in this trial. One possibility for the difference was that nitrogen was applied with two different units.

In future trials, the nitrogen in all treatments will be applied with the strip-till unit to eliminate possible inconsistencies due to application equipment.

Another factor might have been the lack of uniform drainage across the field. In this exceptionally wet season, there were two areas of the field that showed signs of yield-limiting wetness that were not distributed evenly across the treatments. No adjustments to yield were made for field variation. 

Application of anhydrous ammonia in the fall is a generally accepted practice to secure lower-cost nitrogen, reduce compaction and distribute workload.

However, the potential for leaching and runoff is greater the longer the product remains in the soil before being used by the crop. Fall-applied nitrogen with strip-till may increase surface residue and reduce soil loosening, thus reducing risk of nitrogen loss.

Spring-applied nitrogen with strip-till will also reduce the risk of nitrogen loss by reducing time in the soil before the crop needs it. However, spring-applied nitrogen with strip-till may increase the risk of compaction in the soils of the Des Moines Lobe because they’re naturally high in clay and poorly drained.

This trial was a single location in a single year. Multiple locations over several years and environments would be necessary to draw long-term conclusions for the feasibility of using strip-till in Des Moines Lobe soils.

Corn Populations for Various Tillage Systems

Tillage and plants/acre

Strip-till: 33,000  

Disc-chisel: 34,000  

Disc-rip: 33,000  

Corn Yields for Various Tillage Systems

Tillage, bushels per acre and moisture percentage

Strip-till: 184; 22%

Disc-chisel: 167; 21%

Disc-rip: 164; 22%