How to use Brix as a grower’s decision tool
1. What is Brix and why it matters
Brix is a measure of dissolved solids—mainly sugars—in plant sap. It reflects the plant’s photosynthetic performance and nutrient balance.
High Brix values generally indicate:
- Efficient photosynthesis
- Strong root activity
- Good nutrient uptake and transport
- Higher resistance to pests and stress
In short: Brix tells you how well your crop is functioning at that moment.
2. What you need
To get started:
- A handheld refractometer (digital or optical)
- A sap extractor or garlic press
- Distilled water and tissue for cleaning
- A notebook or digital log to record your readings
Optional:
- A temperature-compensated refractometer for more accurate results
- A Brix reference card for your specific crop
3. How to take a Brix measurement
- Select a representative leaf – choose a fully developed, healthy leaf from the middel of the plant.
- Extract the sap – crush the leaf in the press and collect a drop of sap.
- Place a drop on the refractometer lens and close the cover plate.
- Read the brix value – this is expressed in °Bx (degrees Bx).
- Same can be done for roots. Wash excess of dirt and tap dry with paper.
- Extract the root-sap.
- Read the value of the root-Brix.
Use the form below as a first indicator to check if your plant is in balance
4. When and how to measure
For consistent insights:
- Always compare similar leaves and plant positions.
- Use the same plant for root- and leaf-brix
- Repeat in critical phases like fruit set or rapid growth
5. What to do when the Brix is off?
Need help lifting your brix? PQS can guide your next step.
Information related to sampling and testing for Brix
The Brix value (°Bx), a measure of soluble sugars in plant sap, can serve as an indirect indicator of plant resistance. Here’s how this can be used practically and biologically to predict disease resistance and pest pressure.
Brix Monitoring Schedule – Example Strawberry Cultivation
| When to Measure | What to Measure | How to Measure | Why |
| Once a week at a fixed time (e.g., Wednesdays 10:00 AM) | Leaf sap Brix (youngest fully developed middle leaf) | Use a refractometer, extract sap using a garlic press or rubber hammer or any other device to mash up plants | Baseline monitoring of photosynthesis and plant energy status |
| Before and 24 hours after fungicide application | Brix in leaf + (optional) root sap | Leaf: same as above Root: crush fresh crown/root tissue for juice | Check plant stress response to fungicide |
| After stress events (heatwave, cold shock, heavy rain) | Leaf Brix | Same method | Detect breakdowns in plant balance that can trigger root rot |
| At early signs of disease (wilting, leaf spots, slow growth) | Compare Brix in healthy vs. affected plants | Sample plants in the same area for contrast | Identify plants with increased vulnerability or early infection |
| Before and 3 days after biostimulant or salicylic acid treatments | Leaf Brix | Same method | Evaluate the effect of resilience-enhancing treatments |
| At harvest (optional) | Fruit Brix | Use handheld refractometer on fruit juice | Indirect indicator of plant health & fruit quality |
Practical Tips:
- Always measure at the same time of day, ideally between 10:00 and 14:00 when light conditions are stable.
- Use clean tools and fresh samples for accuracy.
- Record growing conditions: date, weather, treatment, irrigation, plant phase, etc.