Soil Testing Results and a Plan

Late last year I talked about my program to improve our garden soil here at Happy Acres. Based on spotty performance in certain areas, I was concerned the soil was losing fertility, and I needed to come up with an action plan before the 2015 growing season. As a first step, I took soil samples and sent them to a lab (Logan Labs) for testing. I wound up getting tests from two garden areas: the main garden and the area I call the kitchen garden.

Let me drop back a bit and say I take a holistic approach to our soil and to gardening in general, and my overall goal is to encourage a healthy soil ecosystem here. I want to feed the soil so the soil can feed the plants, and they can ultimately feed us. Deciding how to go about that task can be complicated though, since every garden presents unique opportunities and challenges. And of course different scientists and garden gurus have different and sometimes conflicting ideas on the subject as well. After gardening for almost 40 years now, I am truly learning as I go along, and there is still much more for me to learn. However, the 2015 gardening season is upon us, so I need to go forward with a plan ASAP.

As I suspected, the soil in both areas tested low in phosphorus and potassium. The pH ranges from 6.4-6.7 which is good for growing most vegetables. The main garden has 4% organic matter and the kitchen garden has 7%. In an area with hot humid summers like ours, organic material disappears quickly, and my goal is to keep the level around 5%, which is in line with Purdue recommendations in their Home Gardeners Guide. So I am doing well in one area and almost there in another. Most of my organic material gets added in spring, as I work in the mulch (straw, paper, leaves) from last year and add new compost for the coming year. The soil test helps me know where to best use my limited supply of compost.

There are ample levels of calcium and magnesium in both areas, but they are low in sulfur and sodium. In the past, our area used to get plenty of sulfur from acid rain, but with stricter environmental controls our rain is less acid now and farmers must often add sulfur. Also, the soil in both areas is low in several of the micronutrients (or trace elements), including zinc, boron, manganese and copper. A little bit of research told me the manganese deficiency is actually pretty common in our area. I am guessing the soil was that way when we got here in 2007, though this is the first time I tested for those elements.

soil amendments and fertilizers

With all that in mind, I surveyed what materials were available locally and which ones I would have to order, and came up with the following action plan. To both garden areas I will be adding bone meal (4-12-0), potassium sulfate (0-0-50), soft rock phosphate (0-3-0), kelp meal (1-0-2), and pelleted chicken manure (5-3-2) plus small amounts of sea salt, borax, manganese sulfate and zinc sulfate. I will mix them up well and add these materials when I prepare each bed for planting. I will still add additional fertilizer to heavy feeding vegetables like broccoli, potatoes, tomatoes and peppers, either adding it at planting time or as side dressing depending on the individual vegetable and its needs.

In the kitchen garden area, I plan on growing potatoes this year in one bed so I will add a bit of elemental sulfur there to lower the pH and use an acid fertilizer (Happy Frog Acid Loving) to side dress the plants. Since the sulfur works slowly, it would have been better to add the sulfur last fall had I known the test results. Potatoes grow best with a ph of 5.0-6.5, so any lowering in pH should help the potatoes. At the same time, I don’t want to lower the pH so much that the next crop I grow there will suffer.

soil amendments ready for garden

It took some calculations to determine how much of each amendment to use, and I used a combination of paper and computer to come up with my plan. First, I referred to the soil tests to determine how much of each element I needed to add per acre. Of course, my garden is nowhere near an acre in size, so then I had to scale everything down. Since an acre is 43560 square feet, and my main garden area is a little over 2000 sqft, I took the value needed per acre and divided by 21. For example, I decided to add nitrogen at the rate of 100 pounds of N per acre. That means I need 4.76 pounds of N for the main garden. For boron the amount was tiny. I needed 2 pounds of B per acre which scales to about .1 pound for my garden. Since borax contains 10% boron, I need to use 1 pound on the garden.

Since many of the amendments contain multiple nutrients, I used a spreadsheet to track all the amounts. I’m going to add 48 pounds of bone meal (two 24 pound bags) to the main garden, and based on the analysis of the brand I’m using that will add 1.92 pounds of nitrogen, 5.76 lbs of phosphorus, 1.2 lbs of sulfur and 5.76 lbs of calcium. The spreadsheet will also document what I actually added this year, and serve as a planning tool for future years. Since the main garden area is divided into 10 equal sized beds, I added a column that shows exactly how much of each material I need to add to the mix for each bed.

spreadsheet for soil amendments

There are several other things I want to try this year, including adding a mycorrhizal inoculant (Mykos) when setting out plants. I’ve been using a soil mix for seed starting (Pro-Mix BX) that has mycorrhizae added, but I’m not sure that is enough to make a difference once plants are set out in the garden. I also want to add liquid kelp to my fish emulsion solution for liquid fertilizing. I’ve used it in the past, and I think what it brings to the mix is important. And I’m adding crab meal to the soil, which is not only a source of nitrogen and phosphorus but the chitin in the shells is a great fungal food. I’m probably going to use a water soluble product like Biomin Booster to add minerals like copper and some of the others in a chelated, bioavailable form.

I’ll share more on this subject throughout the growing season, and I’ll certainly report on results from the garden too. Until the next time, I wish you happy growing from Happy Acres!