Integration of a Brassica Green Manure into the Potato-Barley Rotation

2002 Annual Report for LNE02-166

Project Type: Research and Education
Funds awarded in 2002: $77,503.00
Projected End Date: 12/31/2006
Region: Northeast
State: Maine
Project Leader:
Peter Sexton
University of Maine Cooperative Extension

Integration of a Brassica Green Manure into the Potato-Barley Rotation


The objective of this project is to assist New England potato farmers in determining the most efficient way to integrate a Brassica green manure in their current potato–small grain rotation. Some members of the Brassicaceae have been reported to suppress soil pathogens when incorporated as green manures. Our goal is to maintain cash flow from the grain crop while decreasing incidence of soil-borne diseases in the following potato crop, and to increase the amount of organic matter added to the soil.

Towards this end, two on-farm trials were conducted in northern Maine in 2002 to assess the potential for intercropping a winter rapeseed green manure crop with a barley grain crop. In the trial area, winter rapeseed was sole cropped, undersown with barley, and relayed into barley at tillering, at soft dough, and within 10 days of grain harvest. Winter rapeseed was also planted post-harvest using a no-till drill. At one of the farms, the whole field was undersown to annual ryegrass, while the other field was not. Data on stand and biomass were taken in early October, approximately six weeks after barley harvest. Winter rapeseed relayed at tillering did not survive competition with the barley crop. Rapeseed relayed towards the end of the season showed greater stand establishment, but did not produce much biomass–less than 900 lbs per acre. Winter rapeseed undersown in barley at barley planting did survive the season and produced significant amounts of biomass (ca. 4300 lbs per acre), but it also interfered with barley harvest in areas that were lodged.

At this point, intercropping winter rapeseed with barley does not look promising in the short cool growing season of northern Maine. A parallel trial conducted at the University of Maine Rogers Farm in Orono also did not show promising results for intercropping winter rapeseed with barley grown for grain.

Objectives/Performance Targets

1) The feasibility of intercropping and the optimum time of planting will be well-defined by the third year of the project.

2) The farmers working with the project will be planting a rapeseed (or other Brassica) green manure on a production scale (either intercropped or sole cropped – depending on results) on fields outside the study area by the third year of the project.

3) We will have large demonstration/observation strip plots (an acre in size) incorporating a rapeseed green manure into the potato cropping system on other farms by the third year of the project.


1) Trials to evaluate intercropping a Brassica green manure with barley were implemented and evaluated with growers in the 2002 season.

2) Based on the outcome of these trials, growers decided that it would be good to focus the trial work in the coming year on evaluating the benefit of sole-cropped Brassica green manures in northern Maine. They are particularly interested in evaluating the ‘Caliente’ oriental mustard used by potato growers in the Columbia Basin of Washington. Based on grower input, the trial for next year will be modified to work with 60’ wide plots, to evaluate only the ‘Caliente’ oriental mustard, and to include canola grown for grain as a second check plot, if possible.

Impacts and Contributions/Outcomes

This effort is a work in progress.


Steve Johnson

Crops Specialist
University of Maine Cooperative Extension
Presque Isle, ME
Bruce Flewelling

Potato Farmer
Flewelling Farms
Easton, ME
Andrew Plant

IPM Professional
University of Maine Cooperative Extension
Presque Isle, ME
Dave Lambert

Plant Pathologist
University of Maine, Orono
Orono, ME
Fred Flewelling

Flewelling Seed Potatoes
Crouseville, ME
Brandon Roope

Mayfield Farms
Presque Isle, ME
John Jemison

Soil and Water Quality Specialist
University of Maine Cooperative Extension
Orono, ME
John Dorman

Potato Farmer
Exeter, ME