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Understanding plant sap Brix levels

Brix Test in crop

A refractometer is one of the most straightforward tools available to food producers for assessing plant health. A refractometer measures dissolved solids (mainly sugars), which determines Brix levels in plant sap. Understanding plant sap Brix levels can be a game changer for many farmers, they are an indication of plant sugar production. Healthy plants have high sugar levels and a functioning defence system, making them more resilient to adverse conditions. In this Blog we will explore using Bix levels as a tool to measure plant health.

Key points   

  • Sugar is the end product of photosynthesis
  • Healthy plants have high sugar levels
  • Healthy plants have functioning defense systems
  • A Brix reading measures plant sugar levels

What are you measuring?

A refractometer measures the light refracting (bending) through the dissolved solids (mainly sugars) in the plant sap, it is an effective way to get an idea of nutrient density and is a direct correlation to the amount of sugar the plant is producing.

When testing the Brix of leaf sap you will get a reading between 1 and 20, but what do these results mean?

Leaf Brix 1 – 20 

Refractometer
A Refractometer is used to measure the Brix levels of plants

1-2: These plants are unhealthy and need a supply of nutrients.

3-8: These plants are in with a fighting chance. Once the Brix is above 6, they have increased secondary metabolites and some resilience, eg – less a

ttractive to insects.

8-12: These plants can defend themselves from pests and disease, they are producing more sugars, there is increased water retention due to higher sugars being pumped into the soil, and more secondary metabolites are available for defence.

12-20: A healthy plant!! It is packed full of nutrients and secondary metabolites, with excellent resilience to insects and disease.

Understand your Brix levels
Understanding plant sap Brix levels is key to assessing plant health.

                                                                                           
How to read your Brix results

  • Your goal is to achieve a Brix reading of over 12
  • A fuzzy dividing line is a good sign
    that the plant is accessing the nutrients it needs (Ten Brix Tips)
  • A clean, sharp dividing line can be a signal of free nitrates (How to use a refractometer)

Consistency is the key

In his article The challenges of managing nutrition with Brix readings John Kempf highlights that while measuring Brix is a powerful tool for assessing plant health it does come with challenges. The variability of Brix levels, influenced by time, weather, plant location, and water availability, can make it difficult to rely solely on these readings for managing nutrition.

 

These can be minimised by –

  • Consistency in extracting sap
  • Taking the sample at the same time. Early to mid-afternoon, when photosynthesis is at its peak
  • Consistency with sample location on the plant. Example, it is common for the leaves most closely associated with the fruit to have the lowest Brix
  • Understanding the influence of pending weather events. Brix levels drop before a storm
  • Assessing the hydration of the crop. A dehydrated crop will have a higher concentration of dissolved solids and will produce a higher Brix reading
NutriSoil paid a visit to Victorian farmer Tom Briggs, who stepped us through how easy it is to take a Brix reading.

Using a refractometer to measure the Brix levels of a plant is a useful tool in assessing plant health. Understanding plant sap Brix levels will support you in your crop nutrition decisions.  Using a biological stimulant and plant food like NutriSoil Biological Solution is one step to increase plant photosynthesis and improve the biological health of your soil for future plant health. Biological inputs go hand in hand with good grazing management, plant diversity, reduced soil disturbance, and good ground cover, all of which contribute to improving biological activities in the soil and better plant health.

For further explanation about what your Brix levels mean, see this webinar from Dr Elaine’s Food Web