Jacks vs MasterBlend: which hydroponic nutrient is better? In the Jacks vs MasterBlend comparison, both are three-part dry programs mixed with calcium nitrate and Epsom salt, and both can grow lettuce, herbs and tomatoes well. Jack’s 3-2-1 uses 3.6 g of 5-12-26 Part A, 2.4 g calcium nitrate and 1.1 g Epsom salt per gallon. MasterBlend uses 2.4 g of 4-18-38, 2.4 g calcium nitrate and 1.5 g Epsom salt per gallon.
Key takeaway: An Ask Extension expert advises home growers to mix dry hydroponic salts by EC or ppm with an inexpensive meter rather than by volume, and to keep each part separate until dissolved. That advice matters more than the brand. The real Jacks vs MasterBlend differences are the base formula, magnesium content and mixing rates, as printed on each label.
| Item | Jack’s 3-2-1 | MasterBlend 4-18-38 | Source |
|---|---|---|---|
| Base formula | 5-12-26 Part A | 4-18-38 | Product labels |
| Base per gallon | 3.6 g | 2.4 g | Jack’s / MasterBlend |
| Calcium nitrate per gallon | 2.4 g | 2.4 g | Jack’s / MasterBlend |
| Epsom salt per gallon | 1.1 g | 1.5 g | Jack’s / MasterBlend |
| Magnesium in base | 6.3% | 0.50% (bulk label) | Product labels |
| Mixing order | Base, Epsom, calcium nitrate | Base, Epsom, calcium nitrate | Both labels |
What Is the Main Difference in Jacks vs MasterBlend?
The base fertilizer. Jack’s 3-2-1 is built on a 5-12-26 Part A, which the JR Peters label lists with 6.3% magnesium, 8.5% sulfur and chelated micronutrients. MasterBlend’s 4-18-38 Tomato Formula has more phosphate and potash per pound, but its bulk label lists only 0.50% magnesium, so MasterBlend relies more on added Epsom salt.
- Jack’s Part A: 5-12-26 with high built-in magnesium.
- MasterBlend: 4-18-38 with higher phosphate and potash.
- Both: calcium comes from separate calcium nitrate.
For full charts, see our Jack’s 3-2-1 feed chart and MasterBlend 4-18-38 recipe.
How Do You Mix Jack’s 3-2-1?
Jack’s Nutrients says the name comes from the grams per gallon: 3.6 g Part A, 2.4 g Part B (calcium nitrate) and 1.1 g Epsom salt. The order is very important. Dissolve the 5-12-26 first, then the Epsom salt, then the calcium nitrate. The label says this gives about 150 ppm nitrogen and 116 ppm calcium in the final solution.
- Dissolve 3.6 g Part A per gallon (3.8 L).
- Add 1.1 g Epsom salt and dissolve fully.
- Add 2.4 g calcium nitrate last.
- Check EC and pH before use.
How Do You Mix MasterBlend 4-18-38?
MasterBlend’s mixing chart lists 2.4 g of 4-18-38, 1.5 g magnesium sulfate and 2.4 g calcium nitrate per gallon (3.8 L). For larger batches, it lists about 8 oz (227 g) of 4-18-38, 5 oz (142 g) of Epsom salt and 8 oz (227 g) of calcium nitrate per 100 gallons (379 L). The order is the same: base, Epsom salt, then calcium nitrate last. MasterBlend also says to use half rates until seedlings are well established.
- Dissolve 2.4 g 4-18-38 per gallon.
- Add 1.5 g Epsom salt and dissolve.
- Add 2.4 g calcium nitrate last.
- Use half rate for young seedlings.
Why Must Calcium Nitrate Go In Last in Jacks vs MasterBlend?
To avoid precipitation. Both labels put calcium nitrate last, after the base and Epsom salt are fully dissolved. The Ask Extension expert warns that mixing the products together may cause precipitation, which you want to avoid. Never combine dry parts in one jar or mix concentrated stock solutions together in either Jacks vs MasterBlend program.
Our guide to nutrient mixing order shows how to prevent cloudy solution.
Which Is Better for Lettuce and Herbs in Jacks vs MasterBlend?
Both work when mixed to the right strength. The University of Kentucky lettuce guide gives an example recipe near 1.5 mS/cm EC and a pH of 5.5 to 6.0. The Ask Extension expert suggests keeping leafy crops under about 400 ppm on a home meter and at pH 5.5 to 6.5. Mix either program at a lower rate for greens, then adjust by EC.
- Lettuce: aim for moderate EC and pH 5.5 to 6.0.
- Herbs: similar to lettuce; avoid overfeeding.
- Seedlings: start at half strength.
Which Is Better for Tomatoes and Peppers in Jacks vs MasterBlend?
Both programs are designed for fruiting crops. MasterBlend markets its 4-18-38 as a tomato formula for tomatoes, peppers and leafy greens, and Jack’s describes 3-2-1 as a blend for almost any controlled environment crop. For fruiting crops, the bigger factors are EC, light and consistent calcium supply rather than the brand. Check EC weekly as plants grow.
Does Jacks vs MasterBlend Supply Enough Magnesium?
Yes, at label rates. The Jack’s Part A label lists 6.3% magnesium, so much of the magnesium in Jack’s 3-2-1 comes from the base itself, with 1.1 g Epsom salt on top. MasterBlend’s bulk label lists 0.50% magnesium, so nearly all of its magnesium comes from the 1.5 g of Epsom salt per gallon. When switching in a Jacks vs MasterBlend test, use each brand’s own Epsom salt rate rather than carrying the old dose over.
- Jack’s: magnesium built into Part A plus a small Epsom dose.
- MasterBlend: magnesium mostly from added Epsom salt.
How Should You Choose Between Jacks vs MasterBlend?
Pick by availability, price per gallon and magnesium needs. Jack’s builds magnesium into Part A, so it uses less Epsom salt. MasterBlend uses less base per gallon. The University of Kentucky notes that a two-part method, calcium nitrate plus a complete fertilizer, is a simpler alternative to custom recipes, and both brands follow that idea. Buy a scale and an EC meter either way.
FAQ About Jacks vs MasterBlend
Is Jacks vs MasterBlend a big difference in results?
Usually small; mixing accuracy and EC control matter more.
Can I mix Jack’s and MasterBlend together?
Neither label covers that; follow one label’s recipe.
Do both need calcium nitrate?
Yes; both labels add calcium nitrate as a separate part.
Which uses more Epsom salt?
MasterBlend lists 1.5 g per gallon; Jack’s lists 1.1 g.
Should I measure by teaspoons?
An Ask Extension expert recommends measuring by ppm with an EC meter.
Which has more magnesium in Jacks vs MasterBlend?
Jack’s Part A lists 6.3% magnesium; MasterBlend lists 0.50%.
What pH should I use?
About 5.5 to 6.5, per the Ask Extension expert.
Sources
- Jack’s Nutrients (JR Peters) — Jack’s 321 Technical Bulletin
- Jack’s Nutrients (JR Peters) — 5-12-26 Part A and 15-0-0 Part B Labels
- Masterblend International — 4-18-38 Tomato Formula
- Ask Extension — Hydroponic Using a Master Blend Mix
- University of Kentucky Center for Crop Diversification — Hydroponic Lettuce
- Photo credits (Wikimedia Commons, edited with titles): NPK 19-19-19 Fertilizer (1) by Suyash Dwivedi (CC BY-SA 4.0); Nutrient film technique hydroponics by Oregon State University (CC BY-SA 2.0)