How to Prevent Nutrient Burn During Feeding
Prevent nutrient burn by measuring the electrical conductivity (EC) or parts per million (PPM) of every nutrient solution before it touches the root zone. Start at 25% of the manufacturer's recommended dose. Increase strength only after the plant produces new healthy growth for several days. Always feed to runoff and check the runoff EC to catch salt buildup before leaf tips burn.
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Prerequisites
- Calibrated EC or PPM meter
- Calibrated pH meter
- Base nutrients and any additives
- Clean water
- Container with drainage and a runoff collection tray
Step-by-Step Feeding Procedure
- Calibrate the EC or PPM meter using a fresh calibration solution.
- Mix nutrients into clean water at 25% of the label's recommended strength.
- Measure the EC or PPM of the mixed solution and write down the value.
- Adjust pH to 5.5-6.5 for soil or coco, or 5.5-6.0 for hydroponics.
- Pour the solution over the growing medium until 10-20% of the total volume drains from the bottom.
- Collect the runoff in a clean tray.
- Measure the EC or PPM of the runoff.
- Compare runoff EC to input EC. If runoff is more than 0.6 EC (about 300 PPM on the 500 scale) higher, reduce the next feeding strength by 25%.
- Feed plain pH-adjusted water between nutrient feedings when runoff EC remains high.
- Increase nutrient strength by 10-15% only after the plant shows new growth without burned leaf tips.
- Flush the growing medium with pH-adjusted water at three times the container volume if leaf tips already show burn.
Adjusting Strength Based on Plant Response
Feeding strength is not a fixed number. A clone in early veg may need 400 PPM while a flowering plant in the same room can take 900 PPM. The runoff EC and the leaf tips give you feedback. If runoff EC is stable and leaf tips stay green, hold the current strength. If runoff EC climbs, lower the input strength. If runoff EC drops below the input value, the plant is eating more than you provide, so you can raise strength by 10%.
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Signs You Are Feeding Too Much
- Brown or crisp tips on older leaves
- Dark green leaves with a waxy look
- Leaves that curl downward at the edges
- Slow growth despite adequate light and water
- Runoff EC that keeps rising after each feeding
Why Runoff EC Matters
Runoff EC tells you how much salt remains in the root zone after feeding. A runoff value that is much higher than the input value means the plant is not taking up all the nutrients you supplied. Those leftover salts pull water away from the roots. Over time, the root zone becomes too salty and the plant shows burn. Checking runoff at every feeding gives you a number to act on instead of waiting for visible damage.
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Common Mistakes That Cause Nutrient Burn
- Mixing nutrients at full label strength for young or small plants
- Feeding every watering without a plain water cycle
- Using a meter without a current calibration
- Adding multiple additives that each contain the same macronutrients
- Ignoring runoff EC because the plant looks fine