Published Mar 30, 2017

RESEARCH REPORT: Effect on Corn of Green Manure Cover Crops
By Stefan Gailans

Green manure cover crops best fit into extended and diversified crop rotations between the small grain and corn phases of the rotation. Farmer-cooperator Wade Dooley compared corn following two green manure strategies: a red clover + sweet mix interseeded with a cereal rye seed crop vs. a mix of oats + sorghum-sudangrass + peas + rapeseed mix (OSPR mix) established after cereal rye seed harvest.

The objective of this research project was to quantify the agronomic effect on corn yields of green manure cover crops frost-seeded with a small grain or seeded following small grain harvest. Wade lists gaining knowledge, improving soil quality and improving profitability as goals for this on-farm project.

You can read the full report here: Effect on Corn of Green Manure Cover Crops Established with Cereal Rye Seed Crop

On left, a strip of the red + sweet clover mix. On right, the oats + sorghum-sudangrass + peas + rapeseed mix. Photo taken on Nov. 6, 2015.

On left, a strip of the red + sweet clover mix. On right, the oats + sorghum-sudangrass + peas + rapeseed mix. Photo taken on Nov. 6, 2015.

Here’s how Wade conducted this randomized and replicated strip trial:

  • Apr. 4, 2015: Red clover (8 lb/ac) and sweet clover (8 lb/ac) were drilled into existing cereal rye seed crop that was seeded in Fall ’14.
  • Early Aug.: Oats (60 lb/ac), Sorghum-Sudangrass (15 lb/ac), field peas (75 lb/ac) and rapeseed (2 lb/ac) were drilled into cereal rye stubble following cereal rye seed and straw harvest.
  • Apr. 16, 2016: Both green manure cover crops are chemically terminated.
  • May 6: Corn was planted to all strips in 30-in. rows at a population of 33,000 seeds/ac.
    • 100 lb N/ac total applied as UAN(32%) as carrier during green manure burndown and early season weed control within 1 week of corn planting.
  • Oct. 13: Corn harvested from all strips.

Key Findings

  • The two green manure mixes produced similar amounts of biomass and N.

Dooley_biomass table

  • Corn yields were greater by nearly 30 bu/ac following the clover mix (corn in both treatments received 100 lb N/ac as purchased N fertilizer).
Corn yields for the clover mix and oats+sorghum-sudangrass+peas+rapeseed (OSPR) mix treatments from each Rep at Wade Dooley’s in 2016. Mean yields and the least significant difference (LSD) at the P ≤ 0.05 level are indicated in the inset table. Because the mean difference is greater than the LSD, the treatments are considered different with 95% certainty.

Corn yields for the clover mix and oats+sorghum-sudangrass+peas+rapeseed (OSPR) mix treatments from each Rep at Wade Dooley’s in 2016. Mean yields and the least significant difference (LSD) at the P ≤ 0.05 level are indicated in the inset table. Because the mean difference is greater than the LSD, the treatments are considered different with 95% certainty.

  • Financial returns on investment per acre were greater by $123.90 with the clover mix treatment.

Dooley_ROI table

For more details on this trial, read the full report: Effect on Corn of Green Manure Cover Crops Established with Cereal Rye Seed Crop. Support for this trial was provided 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 stefan@practicalfarmers.org.