Fertilizer Dilution Basics
Water-soluble fertilizers are dissolved in water and applied as a liquid feed to plants. Professional growers and hobbyists use ppm (parts per million) to precisely control nutrient concentrations. This is critical for greenhouse production, hydroponics, and fertigation systems.
The most common target is 200 ppm nitrogen for actively growing plants, with lower rates (50-100 ppm) for seedlings and higher rates (300-400 ppm) for heavy feeders during peak growth.
PPM to Grams Formula
Common Application Rates
| Application | N ppm | 20-20-20 per Gallon |
|---|---|---|
| Seedlings / Cuttings | 50 - 75 | 0.5 - 0.7 g |
| General Houseplants | 100 - 150 | 1.0 - 1.4 g |
| Active Growth | 200 | 1.9 g |
| Heavy Feeders | 300 - 400 | 2.8 - 3.8 g |
| Constant Liquid Feed | 100 - 200 | 1.0 - 1.9 g |
Frequently Asked Questions
What does ppm mean in fertilizer?
PPM stands for parts per million. 200 ppm nitrogen means there are 200 mg of nitrogen per liter of solution. This is the standard measurement for liquid fertilizer concentration in commercial horticulture and hydroponics.
How often should I fertilize with liquid feed?
For constant liquid feed (every watering), use 100-200 ppm N. For weekly feeding, use 200-300 ppm N. Always water with plain water between fertilizer applications if you notice salt buildup on the soil surface or pot edges.
Can I use too much fertilizer?
Yes. Over-fertilization causes salt burn, leaf tip browning, wilting, and root damage. Always measure accurately. If you see signs of over-fertilization, flush the soil with plain water (2-3 times the pot volume) to leach out excess salts.