The BuildASoil Way Complete Supplemental Feeding Calculator
Want the simple printable version instead of the Calculator? Download the printable chart (PDF) or view it as an image.
Enter your garden size and we'll calculate the complete weekly feed chart, topdressing schedule, and shopping list for the entire BuildASoil Way supplemental program.
Feed strength
Step 1: Garden size
Step 2: Veg length
Includes 1 week seedling or clone, plus the remaining weeks of veg dosing
Step 3: Product variants
Quillaja / surfactant
Veg-stage FPE (Veg + Pre-Bloom + Bloom Stretch)
Flower-stage FPE (Pre-Bloom + Bloom + Full Bloom)
Step 4: Rootwise dosing
Root zone rate is the published Rootwise rate measured against the top 6 inches of your soil, applied at the base of each plant after you water. It is the cheapest way to run it and it matches the dose chart on the product pages. Dose the full watering mixes it into every gallon you water instead, which lands around ten times the published rate. More biology is not harmful and plenty of growers run it that way on purpose, so pick whichever you want: the first is the value play, the second is going hard.
Getting Rootwise where it actually works
Water and feed first. The root zone pass is not a watering. Doing it into already-moist soil means the dose stays near the surface roots instead of running straight through to the bottom of the pot.
Mix it into about 1 cup of water per plant. Four plants is a quart. Sixteen plants is a gallon. That is all the water you need, and it is the same ratio the dose chart on the product pages is built on: five gallons of solution is sized for eighty plants, not for four.
Stir it, and keep stirring while you pour. Then pour slowly in a ring at the base of each plant, from the stem out a few inches. Mix only what you will use that day.
Why the full-watering option needs roughly ten times as much. Mycorrhizae have to physically reach a root to form the relationship. They do not travel far on their own. A propagule that lands eight inches out in bulk soil may never meet a root at all.
Put the dose in a cup of water at the base of the plant and almost all of it lands in the few inches of soil where the feeder roots are. Put that same dose in your full watering and it spreads through the whole container, most of which is soil with no root in it. Same product, same cost, far fewer successful introductions. That is the entire reason the two options differ by so much: you are not buying more biology, you are buying enough of it that a diluted application still finds roots.
Step 5: Optional extras for bigger plants
Water + grow summary Full strength
Total sq ft
128
Gal per bed / wk
6.4
Gal per watering
25.6
Total water (run)
358
Total run length
14 wk
Based on 0.2 gallons per sq ft, one watering per week
Weekly schedule
Weekly feed chart
Mix this amount of each product into the gallons of water shown for that week
Topdressing schedule
Apply directly to the soil surface (not mixed in water). All topdressing rates are calculated per square foot of soil surface.
