Winter Plant Protection On Blueberries in Northern Minnesota

BACKGROUND
We have a 70 acre farm in Northern Minnesota on which we raise sheep, blueberries, and board some horses. We use rotational grazing on our pastures, and we have 12 different paddocks of about 3 acres each. We have 1000 half high blueberry plants of 3 different varieties that are irrigated with drip irrigation and fertilized with a minimum amount of nitrogen once a year.

We have always been interested in using sustainable practices on our farm. We use rotational grazing, proper manure management, drip irrigation to conserve water and minimal application of fertilizer. We also are using alternative energy in our home and on our farm with a geothermal heating system, solar domestic water heater and a 10kw wind turbine.

PROJECT DESCRIPTION
The goal of our project was to increase the production of blueberries from our field. One of the problems associated with small fruit growing is winter plant protection. Most people would associate Northern Minnesota with heavy snow cover, but in some recent past years we have seen very little snow cover, with frigid temperatures. If the fragile fruit buds on the plants are not protected over winter, there will be no fruit production the next year. We wanted to investigate the different types of plant coverings to see what was the most reliable, sustainable, and cost efficient. These included different types of row cover, plastic barrels, straw, and making snow. We had the help of Bob Olen from the University of Minnesota Extension Service in Duluth, MN and with other growers including Dave Olafson, Kathleen Anderson and Justin Waldriff.

RESULTS
We only have results from one winter of production and these are listed on the enclosed handout. What we found surprised us in some respects. We thought that plastic barrels would work great for plant protection, but there was no fruit production on those plants, and in fact the plants themselves looked terrible after one winter. Making snow was great for the plants, but it is a time and energy intensive project that needs to be performed in sub freezing temperatures with all parts of the setup working perfectly. I don’t think that this aspect of the project would be easy to adapt to other farms. Row cover seems to hold the best promise of a material that could work on other farms is easy to apply, is reusable and the cost is not prohibitive.

DISCUSSION
We are still learning from this project, and we are going to do it another winter with some different materials. These are talked about in the enclosed handout. We will not be using plastic barrels again, nor will we be using straw and row cover together. We have not made snow yet for this winter, because the temperatures in November were just too warm.
Some things we have learned from our first year of covering plants:

1. Most types of coverings are better than no cover at all
2. Plastic barrels do not work at all, for two reasons. The plants need to breath during the winter, and the barrels do not allow that. Also they act like little greenhouses, and during February for example they will get very warm inside during the day, then at night they will drop down to very cold temperatures.
3. Plants that were covered with both straw and row cover did not do very well as a whole. This might have to do with the breathing issue also.
4. The plants with row cover had the added advantage of protecting the plants from deer browsing. We noticed tracks thru the field and buds that were nipped off by the deer on uncovered plants. We thought deer might be attracted to the plants that had the straw cover, and initially they checked them out, but it wasn’t a problem.
5. Making snow is a labor intensive project that relies on all types of mechanical devices working perfectly (pump, air compressor, power washer, snow gun), otherwise the water stops flowing and everything freezes up; but, the plants that had early snow cover in mid-November did very well.
6. We thought that the straw might attract rodents to nest and chew on the plants, but this was not an issue.
On Feb. 10, 2009 we had almost ¾ “ of rain, which lowered the snowpack over the plants quite a bit, exposing the plants. This was followed by many days of sub zero weather, including at least 3 that were -30 or colder. This might account for production as a whole to be down from the previous year.

For this winter we are doing a few things differently. We are not using plastic barrels, nor are we using both straw and row cover on the same plants. We are using different weights of row cover along with burlap. Here is how the test looks for this winter:

Type of cover Number of Plants
.5 oz. / yd. row cover 8
1 oz./ yd. plant bags 2
1.5 oz./ yd. row cover 32
7 oz./yd. burlap 8
Straw only 12
Test plots 8

If the weather permits we will also try making snow again. In 2008, we made snow on 3 days in November, but November in 2009 was too warm to make snow. We had an average high temp. of 42 degrees which will not work.

We are also setting up the test plots better with mainly one variety, Northblue. This will help out with the varialibility between varieties. We had soil tests done on different parts of the field, and found out that our pH varies somewhat, so our test plots this year will be in areas of the field that have similar pH.

Our blueberry customers enjoyed the poster display of the project when they came to pick, and they learned things as well as us.

PROJECT IMPACTS
After only one winter of results, we have only a small snapshot of results, but they were mostly positive. The straw we used for row cover was expensive, but it seemed to work well and we were able to use it as mulch on an area of our farm. I don’t know if this will be possible every year, and it seems to take a while to decompose in a pile. Many of the row covers were able to be reused this winter, and to get an accurate economic impact we will have to see how many seasons they can be reused. The snow making equipment was expensive, and the time and conditions needed to make snow can be so variable. We were happy to get added fruit production and income from the plants that were covered, and this helped our family out.

OUTREACH
We had two field days this year which were held on July 28 and August 4 and attended by 15 and 8 people respectively. We also had about 135 people come to our farm to pick berries and we had a poster display set up to explain our project. We had plots in the field roped off, so people picking could see firsthand the effects of different types of winter cover. We had 2 newspaper articles about our project, one in the Duluth News Tribune in November 2008 and one in the Lake County News Chronicle in July of 2009. We sent information to other publications, but it seems with budget cutbacks, a small farm project is not high on the list of news to cover.

PROGRAM EVALUATION
We really appreciated being selected to receive a grant. It enabled us to pursue this project, and hopefully improve our berry production and our farm income. I thought the grant process was easy and straight forward and the reporting process was manageable, although it seemed like there were too many individual forms for the final report. Maybe they could all be put together for only one final document? Just a thought.