BRIX REFRACTOMETER FOR PLANTS.

Brix is an indicator of how much sugar content there is in sap and generally speaking anything over 12% will keep most insects from recognizing any plant as food even if they are full strength beings.   “As a general rule of thumb, 12 or better brix readings confer reasonable plant pest immunity.  This is true for both fruit and leaf readings.”   “You will find pest problems persist until you achieve higher leaf and stalk readings – the target is always 12+.” 

BRIX AND PLANT RESISTANCE TO INSECTS.  

When plants ascend the leaf Brix ladder and reach between 8-11, insects metaphorically “fall off”. This is because at this point in their life cycle they've developed a shield to protect themselves from insect predators; however as a general rule you will find that sucking or chewing insects won't tolerate higher than 10 ~ 11 brix.  

Some examples of these types would be caterpillars who eat leaves directly with enzymes on them while others like grasshoppers feed only when their roots have been ingested causing more damage over time due being high sugar content making things less appetizing/palatable until finally disappearing altogether once reaching 12 brix.   

FROST PROTECTION. 

Plants that have higher brix levels are less prone to frost. This is because high brix plant sap has a lower freezing point than low brix sap. We know that “pure water freezes at 0oC (32oF). However, a 5 brix water-sugar mixture freezes at -3.3oC (26oF); a 10 brix mixture at -5.5oC (22oF); and a 15 brix mixture won’t freeze until it reaches -8oC (17oF).”3  While the freezing points referred to are for sugar water – not exactly the same as sap/plant brix levels – it does give a clear indication of the effect that brix can have on frost susceptibility. 

Crops with a higher sugar content (high Brix) will also have a lower freezing point, with an associated protection against frost damage.  A high Brix reading means higher sugar and mineral content, higher true protein content, a greater specific gravity or density, and a lower nitrate and water content for better storage characteristics.” 

RESISTANCE TO INSECT AND DISEASE ATTACK.

Plants with higher brix readings are more resilient to disease and insect attack.  Dr Callahan, previous entomologist with the University of Florida reports that insects detect various wavelengths in the infrared spectrum.  They relate these different frequencies to food, mates, water etc.  

Plants that are have good mineral balance emit a different frequency to those that have deficiencies. “ Once the quality of a crop surpasses a given level, there will not be an insect problem with it because the crop will not vibrate at a frequency corresponding to the insect’s food.” “As a general rule of thumb, 12 or better brix readings confer reasonable plant pest immunity. This is true for both fruit and leaf readings.”   “You will find pest problems persist until you achieve higher leaf and stalk readings – the target is always 12+.” 

John Kempf, crop nutrition consultant with Advancing Eco Agriculture in the US, has noticed and reported on 4 stages of crop health improvement over time, upon moving from a chemical intensive system to a biological based farming system. 

Kempf says that to have a properly functioning plant, with immunity to diseases and attack from insects, the plant must be able to form complex carbohydrates, lipids and complex proteins.  The four phases he refers to are:  

Phase 1 – Carbohydrate production & resistance to soil pathogens. The first phase is that of complete production of carbohydrates.  At this stage, all the inputs for plant growth and photosynthesis (sunlight, water, air and minerals) are all present and simple sugars or monosaccharides  such as fructose and sucrose are produced by the plant.  More complex polysaccharide sugars such as cellulose, pectin's, lignin and starches (which all store carbohydrates) are produced as this process improves. In Kempf’s experience, if this phase is functioning well, with good photosynthetic activity, the plants will not suffer from soil pathogens and fungi such as fusarium and verticillium. 

Phase 2 – Protein production and resistance to insects. As photosynthesis activity increases, greater amounts of plant sugars are transferred out through the roots, to feed soil microbes, which in turn, make minerals available to the plant.  

These minerals act as coenzymes in the production of complex carbohydrates and especially amino acids which go on to be peptides, which then go on to form proteins.   In the absence of these minerals as coenzymes, the plant is unable to form these complex proteins and the plant has high levels of amino acids (the precursor to protein) in the sap, which insects can readily feed on.  

The simplicity of many insects’ digestive systems means they cannot digest complex proteins, but the amino acids they can.  Kempf refers to resistance against aphids, whitefly and other larval insects at this phase. When synthetic fertilizer's are applied to crops, the plant’s need to feed sugars out through its root system to feed soil microbes for the purpose of seeking minerals is reduced and the need for energy from photosynthesis is also reduced.  

These plant root exudates are what feed the soil microbes, that in turn make some of the little recognized micronutrients available, which are crucial for the coenzymes mentioned above. 

Phase 3 – Fat storage and resistance to airborne pathogens. As photosynthetic energy and efficiency increases, plants develop a surplus of energy beyond that needed for basic growth and reproduction. Initially, large quantities of this surplus energy, in the form of sugars, are translocated to the root system, as high as 70% of the total sugar production. 

Later, the plant begins to store this surplus energy in the form of lipids – plant fats – in both vegetative and reproduction tissue.” The phospholipid cell membranes of plants are built from these plant fats.  

The higher the energy and fat levels of the plant, the stronger this membrane becomes and the more able the plant is to resist airborne pathogens.  

Kempf refers to plant resistance to powdery mildew, rusts, scabs and other airborne fungal diseases around this phase.  He stresses the need for a functioning soil microbe community if the plant is to function in this phase. 

Phase 4 – Plant Protectants and Beetle protection. I mentioned in phase 2 that some insects have simplified digestive systems which mean they cannot digest complex proteins.  There are some beetles however that can, and it is not until this final phase is reached in plant growth that John Kempf believes the protection from these will come.   The plant does this by taking the ample lipid levels from phase 3 and produces plant protectant compounds.  These are things such as bioflavonoids, carotenoid's, tannins, terpenoids  and they contain anti-fungal, anti-bacterial properties and digestion inhibiting enzymes. 

It is predominantly the beetle family that have a more developed digestive system and which are the final pest group protected against when plant health reaches this phase 4 – as identified by John Kempf. Experience would tell us that it may take some years of amending soil and farming systems to achieve a phase 4 plant.  

As plants move to a higher phase of health, one would expect this would be reflected in Plant brix levels – but what levels?  John Kempf  informs that they have developed algorithms to predict likely insect or disease susceptibility with a high degree of accuracy, and this is based on the nutrient ratios contained with the leaf sap (a little more complex than brix).  These algorithms haven’t been published yet, but I look forward to learning more from John.  

BRIX LEVELS AND PLANT HEALTH.  

When brix levels are high, plants are stronger and more resistant to cold / frost. The brix readings give us useful information about the plant's ability to fight off disease or future pest infestation. Brix is a term used in horticulture to measure the amount of solids suspended in liquid. Any given liquid contains dissolved sugars, salts, amino acids and proteins. 

Because brix reading remains quite stable throughout plant growth stages (flowering, fruiting or vegetation), brix is an excellent marker for the fertilization needs of plants during flowering (fruiting).   The brix scale ranges from 0-32% with fruits/vegetables generally ranging between 12-18%. A brix level of 4 or 5 would indicate that the plant is suffering from boron deficiency. 

A brix level of 18 would indicate a very healthy and well fed plant.  Larger brix levels allow plants to fight off diseases and pests more easily than those with smaller brix levels. It is easier for plant defenses to absorb small amounts of brix than large amounts.  

The brix levels of leaves and stems must be matched by an adequate brix reading in the sap (juice). If brix levels are high in leaves and stems, but not to par in sap, we can assume that there's stress on either nitrogen or calcium/magnesium.   

FLOWERING.   

Brix readings will also remain high throughout flowering as long as the plant was initially fed well during vegetation. Nutrient ratios should be monitored to prevent brix readings from dropping too low during flowering.   

Brix levels differ basis due to seasonal changes in plant brix from week to week or from day to night (night brix levels are typically about 2 brix lower than daytime brix).  It is not uncommon for brix levels in leaves and stems to be smaller than brix readings in sap. 

Healthy plants will produce more brix when they are stressed because the plant has adapted to stress conditions during vegetation by storing extra sugars in sap, but not in leaves or stems, thus preventing photosynthesis from being inhibited by high brix levels.    

HOW DO WE INCREASE OUR BRIX LEVELS?. 

Rebalancing our soils and increasing microbial activity will help to improve brix levels in plants. 

Any activity that promotes photosynthesis and the natural flow of plant sugars to the root system to feed the soil microbes will likely be a positive for brix levels.   

Soil microbes will help to make micronutrients available – their importance in coenzymes of which we have already mentioned  in cover crops.  

Think of any activities that are supportive of the soil biology.  Chemical intensive systems with high rates of synthetic nitrogen fertilizers will not. It should be noted that the brix level of the plant is just a guide to us.  

It is a reflection of the environment in which the plant is growing – and of the soil particularly.  Using brix levels in conjunction with soil tests and/or other monitoring techniques is suggested.   Multi species cover cropping reports tremendous levels of  health in plant.    

If a foliar application of fertilizer is planned on a crop, measure brix levels and then spray small test plots of the crop with different dosages.  Retest the plots to see which dosage will provide the biggest increase in brix and will therefore be the best choice for crop production. 

Further Khuba Soil conditioner  has provided  links to various video links which provide insight  to  natural sustainable farming. Kindly visit our web site: www.khuba.in