It's also 0.7% of what that facility's flower sells for in a year. If the cheaper fertilizer costs the room a little yield, or a little on price because of grade, the savings disappear and the switch loses money.
The scenarios below are illustrations, not results from a specific facility. Every input is listed so you can check the math or use your own numbers.
The example facility
- 10,000 ft² of flowering canopy, two weeks of veg, a 63-day flower, five harvests a year.
- Water: a flowering plant uses about 2 liters of feed a day, and in my facilities each plant covers about 2 ft². That's 1 liter per square foot per day, or about 18,500 gallons a week for this canopy. Veg runs 10% more plants than flower at about 0.25 liters a day each, or about 2,550 gallons a week for two weeks. A cycle uses 171,600 gallons.
- Both programs fed at 3.0 EC.
- Baseline: Front Row Ag 3-Part, 85 g/ft² (1,874 lb per harvest), selling at $1,000 a pound.
At those volumes, Front Row Ag 3-Part costs $20,738 a cycle and the cheaper program costs $7,362. Over a year that's $103,690 versus $36,809, a difference of $66,881.
Two ways the switch can go
Scenario A: the cheaper fertilizer brings yield down to 75 g/ft². Price holds at $1,000.
Scenario B: yield holds at 85 g/ft², but the flower sells for $950 a pound instead of $1,000 because of grade.
| Per year | Baseline: Front Row Ag 3-Part 85 g/ft² at $1,000/lb | A: Cheaper fertilizer: yield drops to 75 g/ft² at $1,000/lb | B: Cheaper fertilizer: price drops to $950/lb at 85 g/ft² |
|---|---|---|---|
| Flower sold | 9,370 lb | 8,267 lb | 9,370 lb |
| Revenue | $9,369,646 | $8,267,335 | $8,901,164 |
| Fertilizer | $103,690 | $36,809 | $36,809 |
| Revenue minus fertilizer | $9,265,956 | $8,230,526 | $8,864,355 |
| Change from baseline | −$1,035,430 | −$401,601 |
In Scenario A, the switch saves $66,881 on fertilizer and loses $1,102,311 in revenue. The net result is a loss of just over $1 million a year, more than 16 times what it saved.
In Scenario B, nothing changes except a $50 discount per pound. That costs $468,482 a year, about 7 times the savings, for a net loss of $401,601.
How little it takes to cancel the savings
The break-even points are small:
- Yield: the $13,376 saved per harvest equals 13.4 lb of flower at $1,000. That's 0.6 g/ft², a drop from 85 to 84.4.
- Price: spread over 1,874 lb, the savings come to $7.14 a pound. If the flower sells for $993 instead of $1,000, the switch has saved nothing.
Most facilities can't tell 85 g/ft² from 84.4, or $1,000 from $993, between two harvests. Yield and price move by more than that for reasons that have nothing to do with fertilizer. So a switch made on price usually shows up on the invoice as savings, and the loss, if there is one, doesn't show up anywhere.
Why the savings are small and the losses aren't
The savings have a ceiling. The most a switch could ever save is the whole fertilizer bill. In the baseline room, Front Row Ag 3-Part costs $11.07 per pound of flower, 1.1% of what the pound sells for. Even free fertilizer couldn't save more than that. For context, depending on the state it costs roughly $300 to $500 to produce that pound, so fertilizer is a small part of the cost too.
The losses have no ceiling. They scale with the harvest, because the fertilizer affects the harvest. It sets what the plant gets at every stage: the nutrient ratios for veg, stretch and bulking, and whether those ratios hold up as EC changes. It also affects how the feed behaves in the lines. A feed that drifts in pH or drops precipitate can clog emitters and dose plants unevenly, and that shows up as uneven plants and lost weight.
What to do with this
- Put fertilizer on your cost sheet as a share of your wholesale price, not in dollars per gallon. Run it for your own gallons, EC and yield.
- Before you switch, work out your break-even: savings per harvest divided by your wholesale price is the yield you can afford to lose, and savings per harvest divided by pounds harvested is the price you can afford to lose. In this example, both come to 0.7%.
- If you test a different program, run it side by side on the same cultivar and room conditions, change one variable at a time, and compare the rooms on pounds, grade and dollars per square foot per day. That's the only way to see a loss that small before it costs you a year.
