No one worked the soil on our farm for five years. The front four acres were used to grow soybeans, when we bought the land they were covered in overgrown brush.
The soil looked gray, lifeless, dead.
When I decided to start growing organic vegetables there, I knew that I’ll need to add some supplement to it.
But the world of organic soil supplements can be a little intimidating. In the beginning, I was completely overwhelmed with all the options and a bit lost as to what to choose.
Let me share with you the results of my research…
Why Should I Add Organic Supplements to My Soil?
My first question was why. Why should I bother with soil supplements? Why should I spend all this money? Is it really necessary?
The crew at Espoma put this wonderful video together, I couldn’t explain it better…
- Nitrogen (N) – For plant growth.
- Phosphorus (P) – For root development and flowering.
- Potassium (K) – To make plants hardier and disease resistant.
What’s My Soil Missing?
Obviously, you can’t just look at your soil and see that there is not enough phosphorus in it. You’ll need the help of a lab.
Thankfully, you can collect soil samples and send them to the lab through your county’s cooperative extension (it’s a free service in most counties).
Make sure to take different samples for different areas in the garden and label them. Blueberries need acidic soil for good growth while vegetables need somewhat neutral pH for better growth. You should take one soil sample for the blueberry patch and another for the vegetable patch since you will probably need to amend them differently.
It takes two to three weeks until you get a report from the lab. Make sure to send it early to give yourself enough time to prepare your garden for planting since it’s better to add the supplements before planting than after.
Above is an example of the report the extension will email you (you can click the image to view it a bit larger).
Now let’s see what is going on with my precious soil here. First, make sure this is your report, it’s not going to do you any good reading your neighbor’s soil report.
You can also see on the right side in the middle it says “Soil ID: VEG.” I sent two samples and named one VEG for the vegetable patch and BERRY for where I wanted to plant blueberries. Make sure you know which area of your garden you are looking at.
Soil test results for vegetable garden area:
pH – My soil pH is 6.5 which is good since optimum soil pH for most vegetables is between 5.8 and 6.5. This means that I don’t need to add lime to my soil. Adding lime will make it more alkaline which is not very good for most veggies.
Phosphorus – 35, or in other words way too low. The optimum here is between 50-70. So I will have to add Phosphorus.
Potassium – 72. Slightly higher than the optimum at 50-70. I do not need to add Potassium.
As you can see, the test does not measure nitrogen (N) levels. The reason is that nitrogen levels are very unstable in soils. What they recommend is to add nitrogen anyway if you can.
Choosing Organic Soil Supplements:
After much reading and research, I chose to purchase Espoma supplements.They are organic, safe to use around pets and kids, made in the US, and they are actual rock, not liquid so they will release into the soil over time.
I will repeat the soil test next year, but from what I’ve read it sounds like I will have to add those every few years (4 or so), which makes it a good investment.
Gypsum – since my soil pH is 6.5 I shouldn’t use lime as a soil conditioner. Lime will increase my pH further, making my soil alkaline which is not great for vegetables.
So instead of lime, I chose gypsum. It is meant to improve the soil structure, just like lime, but it doesn’t affect the pH levels in the soil. It is also great for breaking clay soil, helping your soil to become softer and easier for the plants to grow on.
Rock Phosphate – since my Phosphorus level is super low, I needed some rock phosphate. Remember, phosphorus helps plants develop strong and healthy roots. Strong and healthy roots mean better support for your plants and ease in finding and absorbing water and other nutrients from the soil.
Greensand – this is another soil conditioner which has many many minerals in it like potassium and trace elements from natural marine deposits. It helps grow healthy and strong plants.
How to Apply Organic Soil Supplements?
Gypsum, Greensand and Rock Phosphorus need to be applied at time of planting.
Gypsum – 1 lb = 1 3/4 cups. Apply 6 lb per 30 sq ft. Mix into top 6 inches of soil.
Rock Phosphate – 1 lb = 2 cups. Apply 5 lb per 100 sq ft. Spread on top of the soil.
Greensand – 1 lb = 1 1/3 cups. Apply 5 lb per 100 sq ft. (10 lb per 100 sq ft for medium application and 30 lb per 100 sq ft for heavy application). Spread on top of the soil.
Here is an example of two beds in our farm. They are 30” wide and 30′ long with a 20” walkway in between.
The Process –
- Clean the bed of old plants, weeds, and rocks.
- Till (if it’s a new bed or if the soil is too compacted).
- Apply gypsum and compost.
- Till or mix (with a rake) the top 6 inches of the soil.
- Apply rock phosphate and greensand.
- Sow your seeds.
How Much to Apply?
This is a great time to use your child’s young, fresh mind. If you don’t have a child handy, borrow the neighbor’s. If the neighbor doesn’t have a child, you’ll have to figure this out yourself. Just try not to curse yourself too hard for day dreaming during math class in 6th grade. We all had much more important things to do in 6th grade than math!
Anyway, 30” are 2.6 feet. 2.6 feet times 30 feet = 78 square feet.
Gypsum – (1 lb = 1 3/4 cups. Apply 6 lb per 30 sq ft). Let’s convert from lb to cups. Since every 1 lb of gypsum = 1 3/4 cups, 6 lb of gypsum = 10.5 cups (1.75 x 6). So now I know that I need to apply 10.5 cups per 30 sq ft. But each of my beds is 78 sq ft. So let’s divide 78 to 30 = 2.6, now we can multiply 2.6 x 10.5 = 27.3. I need to apply 27.3 cups of gypsum per bed.
Rock Phosphate – (1 lb = 2 cups. Apply 5 lb per 100 sq ft). Again, let’s convert 5 lb to cups. 1 lb of phosphate = 2 cups, so 5 lb = 10 cups (5 x 2). So we need to apply 10 cups per 100 sq ft. Let’s divide 78 to 100 = 0.78 x 10 cups = 7.8 cups. Let’s round up and say I need to apply 8 cups of phosphate per bed.
Greensand – (1 lb = 1 1/3 cups. Apply 5 lb per 100 sq ft for light application). Again, converting lb to cups first. 1 lb of greensand = 1.33 cups, so 5 lb = 6.65 cups (5 x 1.33). This means we need 6.65 cups per 100 sq ft. Let’s divide 78 to 100 =0.78 x 6.65 cups = 5.19. Let’s round down and say that I need to apply 5 cups of greensand per bed.
I am no math teacher, but I hope you understand the calculation (if I made any mistakes, please let me know).
Espoma’s products are safe around kids and pets, approved for organic gardening and are pure products. They will help you grow healthy plants with fewer pest problems.
I presented only three of their products here, but they have many more. Their line of products covers anything from seed starting to lawns, tomato plant feeding, supplements for flowers and many more. You can find more information on the Espoma website, and you can find their products for sale on Amazon.