BRIX TESTING OF PLANTS, THE HOWS AND THE WHYS

December 19, 2019

by Will Winter, DVM

Health, be it for man or beast, comes from consuming full-spectrum, nutrient dense sustenance. That’s just a basic fact of life. The question that comes right after is where can we find it, and how do we know how to determine quality? There are obvious indicators of quality for pastured animals, such as the deep, dark green hue of the forages, and the overall growth and health of the plant. Sick plants are very likely to be plagued by and eventually consumed by insects and disease. Often though it’s impossible to know how nutrient dense the plant is just by looking at it. To make this determination it will require quantifying the levels of density. Sending specimens of plants into the laboratory can be very expensive so its often best to use accurate and inexpensive field test.

That test is called the BRIX TEST, and it involves testing the internal sap from any plant leave, fruit, vegetable or stem. The juice of a plant is the plant kingdom’s equivalent of our blood. If our blood is thin, watery and translucent, that is a very bad sign. Same with plant sap. The Brix test measures the viscosity or thickness of the plant sap, it’s as simple as that.

When evaluating forages for livestock, the part of the plant to measure, is what will be eaten by them, or what will be harvested for storage. In other words, it’s usually the top parts of the growing plants. For testing, we take a handful of leaves, and roll it into a ball about the size of a ping-pong ball. The more it’s softened by vigorous rolling between the palms, the easier it will be to get the juice. During the early parts of summer, or when plants are well-hydrated, a simple garlic press is all that is needed to get a drop of sap. During late summer or in dry times, it’s best to use a stronger tool, in our case, we have welded stainless steel jaws to an American-made vice grips and we clamp the specimen and squeeze. If you don’t get juice at first, roll the specimen back into a ball and keep repeating until the sap is released. It can take four or five tries sometimes.

We then lift the flap of the refractometer and place 2-4 drops of sap on the glass, close the lid then hold it up like a telescope and read a number which will be between 0-32. Unimproved grass or plants will usually measure around 3-4 units, whereas we need at least 12 units to successfully raise animals. It’s possible, with good agronomy, say with foliar feeding or compost tea, to raise the Brix to above 20! The highest we have ever seen was 24! If regenerative grazing techniques, are used, it’s possible to double your Brix in just one year. That is like acquiring another farm of the same size for FREE! This is because you have doubled the nutrient density.

Some people say that the Brix index is measuring the sugar within the sap, which is certainly true, however the picture painted goes much deeper. Sugar is a nutrient which provides the ENERGY we require for production. Energy is also the most common limiting factor to all production. Sugar is also the building block for all the “plant medicines”. These are the so-called “secondary plant metabolites”, mostly polyphenolic compounds that keep the plant strong and healthy (and which will keep us healthy when we eat a plant rich in these nutrients!). Polyphenolic compounds act as antioxidants, antibiotics, vaccines, wormers and immune tonics. Therefore, they prevent the need for additional medicines or crutches to keep animals strong, healthy, growing and disease-free.

The ideal time to test forage plants is just before they are grazed or harvested. Plant nutrients, again based on sugar production, is going to be the absolute highest in the late afternoon. This is the best time to move cattle to new pasture, and the best time to cut hay. This is because the chlorophyll in plants enables them to convert carbon dioxide (CO2) and water into the long-chain hydrocarbon sugar. In the early morning, or on cloudy days, the plants are not making much sugar so that is a low-energy time. At night, when the entire plant is filled with nutrition, it sends the sugar down to the roots where it is stored and where the conversion to plant medicines takes place.

In general, Brix testing does not lie. Brix is used in industry, along with weight to create an algorithm to determine value of fruits, greens and vegetables. There are a few questions that come up though. For example, if your readings are very low, the test itself does not tell you what’s wrong. If your readings are high, say in the 18-20 range then you are on the right track, you are done! Just keep doing what you were doing. For low readings, then it’s time to go to the laboratory to understand the problem. The best place to start is with a soil test. Ideally from an independent laboratory that does deeper tests than the run-of-the-mill NPK-oriented lab. For an even better picture, send in tissue samples for testing. This goes deeper than just soil tests because it shows what the plant is capable of absorbing, not just what is in the soil. If fixing the soil is too costly, especially if you are working with leased or rented ground, one might consider foliar feeding or similar applications.

There are several types of instruments for home or farm use, varying from electronic to manual. Personally, I prefer the manual version because it never needs batteries, almost never needs calibrating (to do so, just put a drop of pure water on the slide and, via the set screw, make sure it reads 0.0 Brix. It just takes a couple of seconds). The refractometer should be of high quality as the cheaper units are not automatic temperature calibrated, and the optics are not always very bright or clear. Don’t forget that the same instrument can go with you to the supermarket or farmer’s market as well as the pasture, where you can test the nutrient-density of all fruits, greens and vegetables.


Order your Refractometer or Sap Extractor from Grass Farmer Supply today!

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