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Sweetening My Fruit Tree Soils; Blueberry Blues #889918

Asked November 16, 2024, 11:38 AM EST

Greetings: I'm writing for guidance on my fruit trees and on our blueberries: Fruit Trees: Please see S24-01389, attached. I have seven (remaining) fruit trees in my back field, from an original planting of 14 trees in 2012. They are on somewhat higher ground in a characteristically wet field. I think the mortality has been mostly from too wet Soils, and certainly in part from neglect! This is the first time I have tested the Soils, and no surprise, they are acid and low in nutrients. I plan to add three more trees to this orchard. I have a scheme to surface apply dolomitic limestone beneath the seven trees and in the three areas where I will add new trees. These are dwarf trees, so I'm considering only applying the lime to a 10-foot radius at each of the 10 locations (3200 sf). At an application rate of 400lb/1000sf, my calcs indicate that I will need about 3,200 pounds of dolomitic limestone in total. Please let me know if this makes sense. The P, K and Mg levels are low to very low. Should I amend the soils for these chemicals or wait to see if the increased pH will take care of things? If my approach is right, I'll need 26 - 50lb bags of lime. I could borrow a trailer and pick this up in bulk, which I would think would be cheaper. If you know of a source, I'd appreciate guidance. Blueberries: Please see S24-01388. Note that the sulfur level is high. My wife has applied sulfur to these 10 bushes in the past. I've also added sawdust a few times. I need to lower the pH, and my big question is how to do that without adding more sulfur. The soils appear to be low in K and high in P. I'm not sure whether I should add amendments for potassium. This area is well away from streams and surrounded with grass, so the high P should not migrate to surface waters. Many thanks for your assistance!, Dean Grover

Chittenden County Vermont

Expert Response

Hello Dean,

Thank you for reaching out to the EMG helpline!

If the area containing your existing trees is going to remain a wetter area, you might try to find a more ideal site to plant your new trees. 

Dwarf fruit trees typically have a root zone that ranges between 10-12 feet in diameter or a radius of 5-6 feet around the trunk. If you wanted to apply your fertilizers over the root zone, the total area would be about 1000 square feet for all 10 dwarf trees. Considering this area and the recommendations on your soil report for your fruit trees, you could purchase 200 lbs of dolomitic limestone, 1 lb of nitrogen, 2 lb of phosphate, and 3 lb of potash and distribute under the drip line (spread of the branches) of the trees. You can amend the soil with all of recommended items. Here are a few general care resources for fruit trees, which might be helpful! 

Maine Extension, Early Care for Fruit Trees

Cornell Guide to Growing Fruit at Home


University of MN Extension, Growing Apples in the Home Garden

The primary way to reduce soil pH is by adding elemental sulfur. I see that your sulfur value found in the sample was 39 ppm, higher than the typical values found in Vermont samples. It's not necessarily too high. Your organic matter and CEC results indicate that you have a heavier clay soil. More sulfur may be necessary to lower the pH in a clay soil and it does take time for the chemical reactions that change soil pH to occur. The maximum annual application of elemental sulfur is 10 lb / 1000 square feet. Your soil report recommends adding 1 lb of potash per 1000 square feet to increase potassium. Potash may increase your pH further. You could consider using a sulfate of potash, which is more balanced. Here are a few local general resources that cover blueberry care. 

UVM Blueberry Fact Sheet

UNH Blueberry guide

Please feel free to reach out to us if you have any additional questions. 

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