These three get compared on forums endlessly: which yields more, which is cheaper, which is "professional". Most of that argument is about brands. The labels tell a shorter and more useful story: all three do the same job, they differ mainly in where the magnesium sits and how heavily they load micronutrients, and the cost gap between dry salts and liquid concentrate is large enough to decide the question on its own once your volume passes a certain point.
Quick glossary: Dry two or three part system - powders you weigh and dissolve yourself (Jack's, Masterblend). Liquid three part system - three bottles of concentrate measured with a cup (Flora Series, sold as TriPart by Terra Aquatica outside the US). Working solution - what ends up in the reservoir after dilution to final strength.
One Job, Three Designs
All three deliver a complete element set while keeping calcium away from sulfate and phosphate in concentrated form. What separates them is where the magnesium lives.
- Jack's 321 - two bags. Magnesium sits inside Part A at 6.3%, and the recipe adds Epsom salt anyway, so the element is counted twice and lands 3.7x over the lettuce reference. Covered in Jack's 321: The Recipe, the Logic, and When It Fails
- Masterblend 4-18-38 - three bags. Magnesium in the blend is 0.50%, near zero, and there is no calcium at all. Both arrive separately and deliberately. Covered in Masterblend 4-18-38 for lettuce
- Flora Series / TriPart - three liquid bottles: Micro, Grow, Bloom. Nothing to weigh, and the ratio shifts by growth stage according to the manufacturer's chart
Dry systems are cheaper and give you full control of the formula. Liquid systems remove a scale accurate to 0.1 g from your kitchen and hold micronutrients in a stable chelated form in an acidic carrier. Everything else is implementation detail.
What the Three Numbers on the Front Do Not Tell You
NPK covers roughly a third of what matters, and the micronutrients that make up the rest diverge far more between these products than the macros do, especially iron and boron against the Cornell CEA lettuce reference.
- Iron: Cornell 0.94 · Jack's 2.85 · Masterblend 2.54
- Manganese: Cornell 0.14 · Jack's 0.48 · Masterblend 1.27
- Boron: Cornell 0.16 · Jack's 0.48 · Masterblend 1.27
- Zinc: Cornell 0.13 · Jack's 0.14 · Masterblend 0.32
Read it as direction, not verdict. Cornell runs a deliberately lean micronutrient program and many working recipes sit above it, particularly on iron. The number that deserves attention is boron, which has the narrowest margin between deficiency and excess of any micronutrient. Masterblend at full strength puts it around eight times the Cornell figure, which is a reason to dilute on leafy crops under low light rather than a reason to avoid the product.
If you build a dry system from generic local salts instead of a branded blend, the failure runs the other way: most general purpose complexes carry far less iron than a hydroponic blend, and you will need a separate chelate. Which form suits your pH is covered in chelates: EDTA, DTPA and EDDHA.
What Each Actually Costs per 100 Liters
Prices move too much to print, so here is the arithmetic instead. Take the dose, scale it to 100 liters, multiply by what you paid.
Dry systems. Jack's 321 at 3.6 g Part A, 1.1 g Epsom and 2.4 g Part B per gallon works out to 188 g of total salt per 100 liters. Masterblend at the forum rate of 2.4 / 2.4 / 1.2 g per gallon comes to 158 g per 100 liters. Divide your bag price by its weight and multiply.
Liquid systems. Terra Aquatica's official chart for the Growing stage calls for TriPart Grow 1.8 mL/L, Micro 1.2 mL/L and Bloom 0.6 mL/L, so 3.6 mL/L in total, or 360 mL of concentrate per 100 liters of working solution. Divide the kit price by its total volume in milliliters and multiply by 360.
Run both and the ratio lands somewhere between six and ten to one in favor of dry salts, depending on pack sizes. What that premium buys is real: no scale, a published chart for every stage, and micronutrients you never have to think about. One fill of a 20 liter reservoir costs UAH 4-5 on Valagro Master and UAH 17-45 on Flora Series, a gap of UAH 12-40 per fill. On a windowsill that is small money. At a couple of metric tons of solution a month the gap reaches UAH 1,200-4,000 and sets your cost of production.
Which One to Pick
Starting out, one or two small reservoirs, no scale: take the liquid three part system. The chart removes a whole category of beginner error, and the money involved is trivial at that volume.
Growing leafy crops at volume, willing to weigh: Masterblend, diluted below the tomato rate. The macros already sit on the lettuce reference; back the whole recipe off and the micronutrients come down with it.
Already running Jack's on fruiting crops and adding a lettuce bench: keep the system, drop the Epsom salt on the lettuce side. Part A alone still supplies 60 mg/L of magnesium.
Three Mistakes That Cost the Most
Choosing a system by the three numbers on the bag. NPK describes a third of the formula. Magnesium, sulfur, calcium and the micronutrients decide as much, and they differ far more between these three than the headline numbers suggest. Compare full labels, not product names.
Switching brands to fix a problem that lives in the water. The common sequence: a recipe underperforms, the grower buys a different fertilizer, nothing changes. If your source water is hard or high in alkalinity, every recipe will behave differently from its calculation. Water analysis first, product choice second, as laid out in water in growing: why everything starts with an analysis.
Treating any published recipe as fixed. Every one of these numbers assumes a water supply, a light level and a crop stage. They are starting points. The working value is found with a meter.
How to Tell the Choice Is Right
Work out your real cost per 100 liters and set it against your volume. If the gap between systems comes to less than the value of the time you spend weighing, take the liquid one and stop thinking about it.
Check that micronutrients are actually covered, especially iron: even green on young leaves, and no interveinal chlorosis while pH sits in range.
And hold EC where the crop wants it rather than where the bag suggests. Terra Aquatica lists 1.3 to 1.8 mS for the Growing stage; Cornell puts lettuce at 1150 to 1250 µS/cm above the source water. Both describe the same thing, and both are settled with a meter rather than a recipe.
If you want to go deeper: Nutrient solution recipes: the logic of building one, not copying one covers building a formula around your own water and crop instead of choosing between someone else's finished kits.