JR Peters Jack’s 21-5-20 is a complete, potentially acidic formula engineered for moderate to high alkalinity water, keeping magnesium and phosphorus soluble for consistent uptake. As a lower-phosphorus alternative to 20-10-20, it supports compact, vigorous growth without excessive P. The balanced profile is perfect for hydroponic systems, soilless mixes, and greenhouse crops where solution stability matters.
This LX formula plays nicely in the tank—mix with 15-5-15, other Jack’s LX blends, and compatible partners like calcium nitrate and magnesium nitrate without diluting micronutrient concentrations. Use it as your stand-alone base or as part of a multi-tank program to fine-tune EC, pH, and growth stage needs. Count on predictable dissolving, clean mixing, and steady performance from vegetative growth through production.
Key features:
Keeps Mg and P soluble in higher-alkalinity water for reliable uptake
Potentially acidic, helping manage solution pH and reduce bicarbonate impact
Lower-P alternative to 20-10-20 for tighter internodes and balanced growth
Tank-mix compatible with 15-5-15, other Jack’s LX formulas, calcium nitrate, and magnesium nitrate
Consistent, clean dissolving for hydroponics, soilless, and greenhouse fertigation