As organic gardeners, we pride ourselves on reusing and recycling our soil to promote sustainability as opposed to just discarding it after finishing a run. When growing with salt based nutrients, it’s possible to reuse the soil for another run but many do not choose to opt for this as it requires some extra effort, therefore soil is thrown out after each harvest. With living soil, we have the ability to “re-amend’ or “top dress” our soil as a way to address any deficiencies the soil may have. This can be done by using an all purpose organic fertilizer or sending a sample of your soil to a lab for testing to determine what amendments need to be added.
Sources that we used to gain a greater knowledge of re-amending living soil included Jeremy from Build a Soil, the Intelligent Gardener book and the Ideal Soil 2.0 book. Jeremy from Build a Soil goes in depth on his YouTube channel to discuss organic cultivation of plants, with a focus on cannabis. He had recommended the books we previously mentioned to help gain a better grasp on the math and science that goes into interpreting a soil test. We use a “no-till” method of cultivation, meaning the soil in our living bed is hardly agitated. The farthest we would go in terms of tilling the soil is to take a soil sample or if we were transplanting from a one gallon pot into the bed. When amending the soil, we intend to provide enough nutrients to the top layer so our living ecosystem, including worms and other microbial life, can decompose the nutrients and make them available for plant uptake.
Now, we have just completed our first run using homemade soil. We followed the Build A Soil TAKE ‘N BAKE kit but used ingredients from Black Swallow Living Soils in Canada. Our soil test results after our first cycle were awesome, but there are two aspects that are slightly worrisome. Firstly, our sodium levels are double the target range. Number two, our soil pH has risen by 0.4, clocking in at 7.4pH which can cause locking out of nutrients such as iron, boron, manganese, copper and zinc, making it nearly impossible for the plants to use these minerals. These micronutrients are often overlooked when growing cannabis but they are heavily responsible for plant health.
In this case it took some research to figure out our next steps..
We learned that calcium sulfate is an amendment that can be used to bring down the sodium level in soils. We also learned that to help bring down our soil pH, we can use sulfur. This worked out in our favor as we planned to add gypsum which is “calcium sulfate”. Some other considerations we looked at from our soil test are phosphorus, nitrogen and all micronutrients. For phosphorus, we are adding soft rock phosphate which carries mainly phosphorus and calcium. For nitrogen this time around, we decided not to add anything as we use products such as fish hydrolysate to “spoon feed” nitrogen rather than have the plants working to uptake it. Now, for micronutrients it's tough to keep things fully organic as we tend to resort to sulfates. In this case rather than doing the math and figuring out the exact amount of each element needed, we just picked up a product called ™-7 by BIO-AG. There were other products and amendments we would have liked to add this time around but with the excess of sodium we decided to play it safe. One of the amendments we used when making our soil is likely higher in sodium than the amendments that are used at Build a Soil, hence the discrepancy when we compared soil tests. To err on the side of caution, we added the bare minimum and focused on trying to solve the main issues in the soil.
We are no soil scientists and we really just learned the basics when it comes to amending. As far as the amounts being added into our top dress, they would take some time to explain so, by picking up the books recommended above you can learn a lot about living soils. There's a bit of math and research that has been done and learned by us in the last 6 months in order to understand re-amending. These issues we viewed in our soil test took further research to find out what our next steps were. We feel good about the biology in our soil and our increasing population of red wiggler worms. Adding the bare minimum of amendments keeps us in our comfort zone when it comes to our knowledge with organic living soil. We know that there are plenty of organic growers who reuse their soil without amending it and get amazing results. With our plan of spoon feeding nitrogen, micronutrients and potassium later in flower, we are excited to see what becomes of round 2.
How do you re-amend soil?
If you want to talk about soil testing, message us directly or throw a comment under this post!