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Managing Brix-levels in crops: The myths and facts

Sucrose production in plants is one of the most fundamental steps of photosynthesis and a readily available source of energy for plant growth, maintenance and vitality. During the early 1800`s, Adolf Brix developed a quick method and scale, using refractometry, to measure sucrose levels for the wine and fermentation industries. His method is still being used today where the refractive index of 10 g pure sucrose in 100 ml water at 20º Celsius, expressed as degrees Brix or Sucrose serves as primary reference. With the Brix scale, sucrose per volume at 20° Celsius is therefore measured in contrast with other scales such as degrees Plato and degrees Baume, where density of the sample come into play. Plant Brix (sucrose) can be measured with a hand-held refractometer (Figure 1a), or preferably with a bench-type refractometer (Figure 1b) which compensates for temperature – something the hand-held instruments cannot do.

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Figure 1a: A typical hand-held refractometer and crusher used for field measurements; and

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Figure 1b: An Omnia Chemtech bench refractometer setup with temperature correction and OmniSap® presses

Interestingly, when searching the web for practical uses of Brix in the production of crops, you get lost in an ocean of myths around Brix where "organic certified", "the new way agriculture", "we want organic food", "nutrient dense crops" and "fix my soil" are some of the key phrases upheld by the so-called “Brix Movement”. They thrive on the notion of the mineral depletion of food over the last 50 years as published by the Ministries of Agriculture, Fisheries and Foods and Royal Society of Chemistry, UK. In addition to this, claims that high Brix crops have less pest pressure are common. The movement also focuses on the questionable Albrecht system advocating the importance of only certain nutrients and their connection to Brix.

In a review article by Syrovy and Prasad (2010) using literature and personal interviews, the concept of using Brix alone as an indicator of pest pressure came the spotlight. It was concluded that Brix alone could not explain insect and pest pressure, but that the influence and combination of various nutrients and total plant vitality carried more weight.

Therefore, to fully understand the scope and importance of sucrose in plants (as expressed in Brix units), one needs to look at the basic and uncluttered process of photosynthesis where carbon dioxide is converted into three hydrolised carbon sugars and converted to sucrose and starch in the leaves of all higher plants by means of the Calvin cycle.

The importance of sucrose in plants can be summarised as follows:

  1. Sucrose is the primary product of photosynthesis (with fructose and glucose being the intermediate and short life predecessors of sucrose).
  2. Sucrose is utilised as a source of energy for plants during the day, whereas stored sucrose (starch) is used for plant respiration during the night to restore the plant's carbon balance.
  3. Sucrose provides the carbon skeletons for all plant compounds which are necessary for growth (biomass) and maintenance.
  4. Sucrose is transported to all plant parts and is the primary transport of sugars within plants.
  5. Sucrose, combined with nutrients from the roots, is converted to amino acids, proteins and enzymes via the tricarboxylic acid (TCA) (Krebbs Cycle) which governs all plant processes.

Therefore, to optimise crop production and yield and minimise risk for the grower, Omnia has combined the science of plant sap analysis (which dates back to the 1930`s) with sucrose (Brix) measurement as an indicator of plant vitality and growth. By looking at the Brix count as well as the OmniSap® analysis, a much clearer picture of the general condition of the plants can be compiled. This will especially be of value in the identification of crop problems.

Omnia is an advocate of sound scientific principles and research, separating myth and fact. As such, we are always on the lookout for new technologies to assist our clients in opstimising yield and reducing risk.

By Willem Jonker (Specialist agronomist)