So you got a soil test…then what? A lot of the information on the reports is clear and easy enough to understand. But when the test report says you need to add (for example) 1 pound of nitrogen per 1,000 square feet, many organic gardeners need a little help. How do I add 1 pound of nitrogen (or other nutrient) per 1,000 sf? What product? And how many pounds?
“How do I add 1 pound of nitrogen per 1,000 square feet?”
Here is one way to answer these questions:
First, figure out how many square feet of soil area you will be amending.
For example, let’s say you have a “GARDEN BED” that is 10 feet wide and 20 feet long. 10 feet x 20 feet = 200 square feet.
Second, determine what your ratio of actual square feet is compared to the baseline of 1,000 square feet. Most soil test reports provide recommendations to amend per 1,000 square feet.
GARDEN BED: 200 sf / 1,000 sf = 0.2 ratio
Third, we multiply that ratio by the number of pounds of nutrient/ingredient the soil test report specified for each 1,000 sf.
For example, let’s say your GARDEN BED soil test report says you need to add 1 pound of nitrogen per 1,000 s.f.. Multiply your square footage ratio of 0.2 times the 1 pound of nitrogen recommendation. In this case, you need 0.2 pounds of nitrogen (1 pound nitrogen times 0.2 = 0.2).
Fourth, (here is where things get a bit more complicated) we divide the needed pounds of nutrient by the percentage of that nutrient in a known ingredient. This gives us the exact number of pounds of each ingredient to add.
For example, 0.2 (pounds of nitrogen you need for your 200 square foot bed) divided by 1 percent (amount of nitrogen in Worm Castings). Then we know that 20 pounds of Worm Castings will provide the needed amount of nitrogen (0.2 / .01 = 20).
In the example above, I chose Worm Castings as the ingredient to supply our nitrogen. But you could use many different products to supply that nitrogen.
In the same case, let’s say you wanted to use Linseed Meal instead of Worm Castings. Linseed Meal has a typical analysis of 6% nitrogen. So, if you wanted to chose that amendment, you would divide 0.2 (pounds of nitrogen you need for your 200 square foot bed) by 6 percent (amount of nitrogen in Linseed Meal). Then you would know that 3.33 pounds of Linseed Meal will provide the needed amount of nitrogen (0.2 / .06 = 3.33).
Hopefully this simplified example scenario helps you understand how to use your soil test reports.
Walt’s Organic Fertilizer Co. offers a service where we will interpret your soil test report for a modest fee and give you a list of amendments to provide the suggested macro and micro nutrients. Contact us for more details on this service.
If you don’t have a soil test report, but want to be smart about fertilizing, you can learn more about maximizing the value of your organic fertilizer here: https://waltsorganic.com/fertilize-your-p-patch/.
Happy gardening!
Walt