In May, 2010 I decided to take on the responsibility of filling an open pit out at the Nursery with a soil concoction suitable for growing blueberries, cranberries and lingonberries. Perfect- plants I need to learn how to grow for Twin Cities yards! These berries or Vacciniums require an unique soil to most areas of the Twin Cities- a soil pH under 5.5, so I needed to order and have shipped in special concoction.
The final combination I selected was 50% coarse sphagnum peat, 25% sand and 25% topsoil. Peat was chosen because of it's low pH but the expense left the volume to be only 50% of the total. Sand was selected to increase drainage and top soil was chosen for nutrition, aeration and to reduce the peat muckiness.
The soil was mixed and the bed was filled by Landcare at the U on May 18th and plants were put in on June 7th by me and one of the team members.
Now before I go any farther in this write-up I'm going to admit that there are several things I did out of order and against the recommendations of very wise blueberry growers and even UMN scientists. My explanation, which may or may not be believable, is the need to make quick decisions based on time and cost of materials = the typical excuses!
So I did things out of order and am now needing to correct the mistakes I made and will be doing so for the next years. I knew this would happen, but one can never fully prepare for these corrections.
The error I'm going to talk about here is with the soil and the pH of the soil concoction, which I THOUGHT was going to be much closer to the low pH we needed. Staring off, the soil analysis for the coarse sphagnum peat is 3.7, sand 7.8 and field soil at 7.3 so I figured the resulting combination would be no more than pH 6.5. What a silly assumption for me to have!
After a couple months, I finally took the time to bring a soil sample into the Soil Testing Laboratory and was a little shocked by the first reading we got back- pH 7.1!!! So much for the hundreds of dollars invested in the peat! Ok, ok...maybe there are other benefits to having peat in blueberry plantings but still, our pH is only a little better than had we just used the field soil! Because of the slight chance an error was made at the laboratory, another soil test will be taken and submitted this year.
But now, it's time for corrections. On the soils test a sulfur recommendation came back that read 5.8 lb per 100 sq. ft in order to bring the pH down. So, the team and I figured out how much that meant for our bed that is 374 sq. ft, which comes to 22 lbs (0.058 lbs per foot x 374 sq ft= ~22 lbs). On August 4th we mixed 22 lbs of elemental sulfur to the top 2-6 inches of the soil using a little garden rake for around the plants and a mini-rototiller in between the plants. Next spring me or a team member will take another soil sample to see if the sulfur has had any affect on lowering the pH.
Soil pH is probably the biggest challenge we'll be having to face with our Vaccinium planting. Of course, that story may change after we see how the plants live with the rabbits and chipmunks during the winter months!