The Economics of Water Only Soils
Note: The photo above is in soil that is over 2 years old.Many people are initially deterred by the cost of Water Only soils and this article is an attempt to look closer at the economics behind this growing method and how it will save you money. I’m going to look at this a few different ways, to address growers of different scale. Whether you have 6 plants or thousands of plants, I believe the numbers add up to considerable savings.
So let’s take a look at the most basic example.
1 plant grown in a 10 gallon container, which would require just under 1.5 cubic ft of soil. Our Water Only Soil sells for $35/bag. That means your entire cost in nutrients and media for that crop is $35. With a more traditional program, you’re spending much less on the media itself, maybe $10-15 but then adding in a bottled nutrient program to supplement the plant’s needs. A typical bottled nutrient program will most likely end up costing you a lot more than $20/plant, but there’s more than just the cost of nutrients. Let’s assume it takes you only 5-10 minutes to measure out the nutrients each feeding, and that you’re feeding 1x/week. That is a time savings of over an hour. However, the real savings comes at the end of your first grow cycle. Since the soil is re-usable and we’ve figured out the best rates and nutrient levels for re-amending, you no longer have the labor and expense of moving the soil in and out of your grow room, and the cost to re-amend the soil is typically under $5 worth of our Nutrient Pack + some high quality compost or castings (around $2-3) + aeration ($1-2 worth). This brings the cost of the next crop to less than what you would pay for a new bag of Fox Farm Ocean Forest or Pro Mix, AND the nutrients are already included. An added benefit of reusing the soil is that the 2nd crop is typically better than the first crop, as the microbes in the soil create soil structure and improve nutrient cycling.
These 4 plants would cost approximately $10 each worth of nutrients to grow in that size container. The second crop in that soil would be $5-7 in cost per plant.
Now let’s say you’re a commercial grower or have a larger setup to where you are buying yards of soil. A yard of the Water Only Soil runs $350/yard or less if you’re buying multiple yards.. That makes the cost of 10 gallons of soil only $20. That’s $20 in both media and nutrients for the entire crop cycle. Re-amending that soil at the end of the cycle will drop down to under $50/yard. These costs drop even further when you scale up to multiple yards as there is typically a price break. The biggest savings in a facility of this size though is the labor and disposal savings on the spent media. How much does it cost you to move the soil in and out of your facility or dispose of the old media responsibly? Not to mention that much of this used media is traditionally high in nitrates and phosphates and contributes to contaminating our groundwater.
Here's a photo from a 502 grower we worked with. They have 4'x4' fabric beds on pallets. Each bed has approximately 1/3 yard of soil. This cost them approximately $115 in media/nutrients per bed the 1st cycle where they yielded 3 lbs/light. Every crop thereafter cost under $30/bed with no loss in yield or quality.
Lastly, there are many growers that will use the soil with their current bottled nutrient program. If you are using only organic amendments, then the soil can be re-used. If you are using synthetic nutrients or mineral salts, then you will want to replace the soil every grow cycle to avoid a buildup of salts. One advantage to Water Only Soils is that you can reduce your bottled nutrient inputs typically by around 75% and should see increased plant health and growth, as well as better terpene expression.
In this photo, these 502 growers are using a combination of mineral salts and our Biochar Soil. They disposed of the soil every cycle but still used it for increased growth and yield over inferior media like coco or Pro Mix.
At first glance these soils may seem more costly, but in reality you will actually save money, reduce your environmental impact, have an organic crop, and save time and labor by switching to this style of growing. Run a test plant in this style of growing and compare for yourself!