Optical Refractometer, pasture brix levels

Yes, it's official, I've gone off the deep end now. Some people who are close to me, names with held to protect the innocent, have been aware of this situation for quite some time.

If you remember I am interested in mob grazing and was recently reading some articles which mentioned pasture forage brix levels. Huh??

Well, apparently brix is the sugar content, and a handheld device called an optical refractometer can measure the sugar content, or brix, of things like honey, grapes, corn, garden produce, and even grass. For example, vinyards will measure brix levels of grapes to determine the proper harvest time.

So, some grass farmers have started to measure the brix levels in their pastures and are reporting very interesting findings. If a pasture is well managed one can achieve brix levels above 10%, even above 20%. Animals perform very well on high brix forage, and a high brix pasture is very healthy. Interestingly, destructive insects such as grass hoppers will leave high brix pastures alone.

I went to Amazon.com and ordered myself a 0-32% optical refractometer so I too could measure brix levels. I paid about $60. An optical refractometer is an interesting device. One collects a few drops of liquid from a sample and puts the liquid on the surface of a prism and then closes a transparent plate which spreads the liquid out in an even film across the surface of the prism. One then holds the device up so that sunlight passes through the sample and looks into an eyepiece and reads the brix level of the sample directly on a scale.

How it works: sunlight passes through the liquid sample and bends, or refracts, just like light bends when it enters a pool of water. If the sugar content of the sample is low then the light is not bent very much. A high sugar content causes the light to bend more. The bent light is collected in the prism and directed to a scale where one can directly read the brix level.

There are a few gotcha's. The readings are temperature sensitive, so the reading must stabilize or one must use a temperature corrected refractometer. Brix levels in grass change during the day, they are lowest early in the morning and highest later in the afternoon on a sunny day. Sunshine, and photosynthesis, cause sugar levels to increase in the plant. So, if you are making hay you might want to cut your hay crop later in the day.

The device measures refraction, but refraction is influenced by minerals and other solids in the sample besides sugar. Many pastures and fields today have been mined of essential minerals so it is good to have brix readings, as well as soil samples.

I measured brix levels in my pasture and had readings in the 3% - 5% range (in doing so I destroyed our flimsy garlic press, which I employed to squeeze juice out of balls of pasture grass, I now need to find a sturdy unit). These are fairly low brix levels. Mob grazing and certain other management practices (such as raw milk applications) are said to be able to increase pasture brix levels above 10% and even above 20%. To be continued.