Growing Organic Blueberries Using Biochar

View the project final report

Commodities

• Fruits: berries (blueberries)

Practices

• Education and Training: demonstration
• Farm Business Management: you-pick blueberries
• Natural Resources/Environment: carbon sequestration
• Production Systems: transitioning to organic
• Soil Management: organic matter, soil analysis, soil quality/health
• Sustainable Communities: community development, quality of life, sustainability measures, urban/rural integration

Our goal is to raise blueberries sustainably on ½ acre of pasture land. The soil is heavy loess clay on top of a hill. In order to produce blueberries we have amended the soil significantly. We used biochar on ¼ acre along with our usual sustainable practice using mulch and organic amendments. On the other ¼ acre we used the same practice minus the biochar.

Biochar is a type of charcoal that is produced by heating air-dried plant material (biomass) in a setting without oxygen. Biochar can store moisture and nutrients in the soil. Properly produced biochar provides a good environment for essential microorganisms to grow. These microorganisms play a major role in nutrient cycling within the soil environment. Biochar has been proven to have a significant impact when using a holistic approach to sustainable food production.

When I began this project I intended to produce the biochar on site as part of the project. I thought I had an endless source of free woodchips. That source disappeared suddenly and getting the wood chips dry enough became an issue. I found that buying the biochar was a better solution to complete the project in a timely way even though I had already bought the materials needed to produce it myself.

One problem with using biochar in blueberry production is that that biochar has a naturally high pH. This is, of course, the inverse of what is desirable when raising blueberries. Our pH is naturally 6.9. Depending on what medium is used to make the biochar the pH can be between 7-9. I solved this by washing the biochar and then mixing it with compost to charge it before adding it to the beds. The pH is presently 5.9 which is at the high end of acceptable but it does not vary from the area with the biochar so I don't think the biochar is contributing to the acidification of the soil in any way.

In Spring 2017 I plowed 1800 feet of contoured rows leaving 6 feet of turf between the beds. I left the turf between the beds to discourage erosion as the field is fairly hilly. I used a 2 bottom plow and flipped the turf downhill. Then I tilled with a 4 foot tiller driving with the back tire in the furrow. I added sulfur, rock phosphate, green sand and 100 cubic yards of pine bark mulch to the bed and tilled it in. If I did this again I would wait to see weeds and then cover the beds with black plastic until fall. 

I found 16 cubic yards of compost from a local microgreen farm for free. In the fall I added 8 cubic yards to the control beds and mixed the washed biochar with the remaining 8 cubic yards of compost. The compost came in totes and after emptying 8 of them I had 16 totes to mix the biochar with the compost. After mixing I wet it down thoroughly. This activates the biochar. Then I spread it on the biochar beds and tilled it in with the 4 foot tiller.

I planted the blueberry bushes in the fall on a grid which is outlined on my attached poster. The bushes that I planted were challenged by a hot dry fall, followed by a dry warm winter, followed by an extremely cold dry early spring, followed by a hot dry late spring, summer was extreme dry and hot and we didn't get a break until late fall when we got 10 inches of rain which ended the drought. I irrigated throughout the year but still lost over half my plants and many of them struggled. 

I have purchased another 250 plants which will be planted in March and will lay down an additional 75 cubic yards of free wood chips from local arborists or purchase ramial bark to add another 5 inches of mulch which I intend to spread on top of the beds for weed suppression and to gradually break down into the  of the soil. 

Weed suppression was an ongoing issue throughout the summer as I am not using glysophate and the pasture where I put in the blueberries has some fairly relentless grass. Over the summer I put down plastic weed mat and did a lot of hand weeding. I also tilled between the beds and planted clover and rye. I'm planning on continuing to seed the pathways between the beds. I expect the clover to improve the overall water retention but I'm not sure how it will hold up in the summer. I'm looking for something to compete with the weeds, improve the soil, mowable and that is easier to keep out of the beds than the relentless pasture grass and fescue.

The weather was extremely challenging and I didn't expect much data to report by end of this two year project as it takes six months to prepare the soil before planting blueberries and three years before harvest. I will update this report annually. My hope is to see better growth, stable pH, and better production with the plants in the biochar beds.

Our objective is to see if biochar improves blueberry growth and production. Making the biochar proved to take longer than I expected so I bought enough organically produced biochar to use at 3%. After receiving the shipment of biochar I washed it and then added it to the compost.  After letting it stew for a few weeks I added it to the soil and about a month later tested the soil. Our soil pH is presently at 5.9 . I may want to bring that down a bit more and should be able to do that with iron oxide and/or sulfur. 

After the study is over I will report yields and measure plant growth to determine if biochar had a significant effect. At this time I cannot report any benefits but it will be interesting to see the effects throughout the years. Blueberry bushes can live over 25 years and biochar can remain in the soil for up to 1000 years.