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

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

Summary

(Note to the reader: This report includes data and tables that could not be posted here. To get a copy of the report with data included, send e-mail to nesare@uvm.edu and reference the 2004 annual report for LNE02-166 in your request.)

This summary covers the third year of a study looking at Brassica green manures. 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. The predominant rotation among potato growers is to plant potatoes followed by oats or barley, and then go back to potatoes. Our initial goal was to grow a Brassica green manure in the same season as a cash crop of barley. However, from results of the first season of the study, this appears to be unworkable in northern Maine. Where the winter rapeseed green manure became well established, it interfered with barley harvest when the grain lodged into the underseeded green manure. Where the green manure was established after barley harvest, the remaining growing season was too short to obtain significant growth from the green manure. Accordingly, the grower cooperators choose to redirect the study and work on evaluation of a Brassica green manure as a sole crop completely replacing the barley crop in northern Maine. Also, it was decided to work on establishing a Brassica green manure after barley further south, in central Maine, where the growing season is longer, and barley is often harvested early as silage. The grower-cooperators also chose to conduct the experiment with large plots (60 feet wide) that better fit their farming equipment. This limited the number of treatments that could be evaluated. It was decided to work with ‘Caliente’ green manure mustard, as this variety has been shown to benefit potatoes in Washington. The growers felt with limited treatments they preferred to work with a variety that had been proven elsewhere.

In the 2004 season the project had a number of different facets encompassing several on-farm trials. Data on potatoes was collected from three on-farm trials where different green manure treatments had been imposed the year before. Also, new trials were initiated in four on-farm replicated trials and in 7 unreplicated on-farm observation blocks. Potatoes grown on these plots will be monitored for disease incidence and yield in the coming season.

Results were mixed from the three on-farm trials where potatoes were grown in 2004 (green manure treatments were imposed in 2003). ‘Caliente’ green manure mustard controlled Rhizoctonia at two of the farms. The third farm did not have much Rhizoctonia incidence. The mustard green manure significantly increased total yield at the Roope farm by about 40 bags per acre; there was a trend for greater yield following mustard at the other sites. Canola also appeared to decrease incidence of Rhizoctonia at the Roope farm. We did not see any effect of the mustard green manure on powdery scab at the Flewelling farm. White mold was a little worse following mustard and canola than after barley at the Roope farm. At the Dorman farm the green manures were left standing over the winter and tilled in the next spring and no treatment effects were noted.

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 (1 acre in size) incorporating a rapeseed green manure into the potato cropping system on other farms by the third year of the project.

Accomplishments/Milestones

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 2003 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.

3) Replicated field trials to evaluate a Brassica green manure as compared to the standard barley rotation were implemented in three on-farm trials in the 2003 season, and on four on-farm trials, and seven on-farm observation blocks in the 2004 season. Growers are interested in continuing this work and we plan to follow through with the 2004 trials by monitoring performance of the following potato crop in 2005. Several farmers have ordered mustard seed (at their own expense) to try on their farms in the 2005 season.

4) Preliminary results from the 2004 potato crop indicate that the mustard green manure controlled rhizoctonia and increased total yield of ‘Russet Burbank’. We did not see control of powdery scab. We did see a trend for white mold to be greater where mustard or canola were grown the previous season.

Impacts and Contributions/Outcomes

This effort is a work in progress.

Collaborators: