Published Jan 16, 2018

RESEARCH REPORT: Corn Leaf Architecture for Interseeded Cover Crops
By Stefan Gailans

In Iowa, cover crops are typically either aerially seeded into standing corn around the time of physiological maturity in late summer or drilled immediately following corn harvest in the fall. However, the earlier one can seed a cover crop, the more potential for growth and biomass production. An earlier seeding date also opens up the opportunity for more diverse cover crops like brassicas and legumes that need more time and heat units to grow than common cover crops like cereal rye.

Farmer researchers Jack Boyer and Jeremy Gustafson interseeded cover crops (cowpeas, annual ryegrass, rapeseed) into corn at the V4 stage in June. Corn hybrids chosen exhibited vertical and horizontal leaf orientations to test whether more light penetrating the corn canopy would encourage successful cover crop establishment and growth.

Read the full report here: Corn Leaf Architecture for Interseeded Cover Crops.

Interseeding cover crops cover shot

How Was the Trial Conducted?

  • Corn planting date (both hybrids): Boyer = Apr. 25; Gustafson = May 5
  • Cover crop mix interseeding date: Boyer = June 14; Gustafson = June 16
  • Cover crop mix seeding rates: Cowpeas (60 lb/ac); annual ryegrass (22 lb/ac); rapeseed (7 lb/ac)
  • Corn harvest date (both hybrids): Boyer = Nov. 4; Gustafson = Oct. 25

 

Findings

Aboveground biomass of the cover crop mixes was not sampled but photographic evidence shows that cover crops persisted beneath the corn canopy into early fall at both farms.

Cowpeas emerging in corn on June 19, five days after being seeded at Jack Boyer's farm near Reinbeck.
Cowpeas emerging in corn on June 19, five days after being seeded at Jack Boyer’s farm near Reinbeck.
Cowpeas in corn shortly after a frost in October at Jack Boyer's farm near Reinbeck.
Cowpeas in corn shortly after a frost in October at Jack Boyer’s farm near Reinbeck.
Cowpeas in corn at Jeremy Gustafson's farm near Boone in mid-September.
Cowpeas in corn at Jeremy Gustafson’s farm near Boone in mid-September.

Corn yields at Boyer’s were affected by the hybrid (horizontal leaf architecture vs. vertical leaf architecture) and the interseeding. See figure below.

Corn yields at Jack Boyer’s farm (Reinbeck) as affected by corn leaf orientation (horizontal vs. vertical) and the interseeded cover crop mix in 2017. If the difference in yield between any two treatments is greater than the least significant difference (LSD), the treatments are considered significantly different with 95% certainty.
Corn yields at Jack Boyer’s farm (Reinbeck) as affected by corn leaf orientation (horizontal vs. vertical) and the interseeded cover crop mix in 2017. If the difference in yield between any two treatments is greater than the least significant difference (LSD), the treatments are considered significantly different with 95% certainty.

At Jeremy Gustafson’s, corn yields were not affected by hybrid or planting population. All strips were interseeded. See figure below.

Corn yields at Jeremy Gustafson’s farm (Boone) as affected by corn leaf orientation (horizontal vs. vertical) and planting population 2017. All treatments were interseeded with the cover crop mix.
Corn yields at Jeremy Gustafson’s farm (Boone) as affected by corn leaf orientation (horizontal vs. vertical) and planting population 2017. All treatments were interseeded with the cover crop mix.

“The seed germinated well,” Gustafson said, seeing mostly cowpeas by mid-September. “Not much made it into fall, though. Leaf architecture didn’t seem to matter and lack of rain really played havoc with this trial.”

“This technique requires more testing before wide spread adoption,” Boyer said. “I need to understand what caused the yield hit. The cover crop species I interseeded worked with both corn varieties, so I will probably try another interseeding with just one variety.”

For more details on this trial, read the full report: Corn Leaf Architecture for Interseeded Cover Crops.

This project was supported by the Walton Family Foundation.

For more information about this study and other studies as part of PFI’s Cooperators’ Program, contact Stefan Gailans at [email protected]