Brix Test A Tomato

Continued from What Is Brix?.

The second reason we may conduct a brix test is more practical and useful in our vegetable gardens.

First, we take our refractometer and measure brix in a leaf or especially a fruit from one of our plants, for example a tomato.

Note that a “fruit” is just the reproductive part of a plant, so botanically-speaking, many foods we call vegetables are fruits, such as tomatoes, pumpkins and avocados. So we test the brix, then foliar feed that tomato plant, wait 30-60 minutes, and measure the brix again.

If the brix meter shows an increase of at least a couple of points relative to a control plant that we also brix test, the tomato liked that fertilizer and we should spray the whole crop. If it stayed the same or even went down, the tomato might not want that fertilizer today.

Even good organic fertilizers are sometimes not wanted by our plants.

This is an advanced technique that takes some practice. It isn’t as useful for organic gardeners with small gardens growing many different kinds of vegetables, with just a few of plants of each variety, because it might not be worth the time to brix test, say, one tomato plant in order to spray the other three.

Or maybe it would. If you’re trying to grow the best tomatoes and you want to get many dozens of tomatoes from each plant, it could be worth it. If you have a huge bed of something like potatoes, go for it.

For many plants, you need 12 brix in all parts of the plant, so if you’re still getting plant predator damage above 12 brix in the fruit, test the leaves. They may be the weak link. Other plants need even higher brix. You also need to make sure you measure from the same place on both the test and control plants.

The way to get brix up long term is through improving the health of your organic soil. Phosphate is especially correlated to brix, so if you get your phosphate availability consistently up, your brix test will move up.

I’m not going to get into the details of using a brix refractometer, as those instructions come with the device, but it’s really simple. Use a pair of pliers or a blender to get a little bit of juice out of the fruit or leaves and place it on the glass plate.

Look through the hole like you would look through a kaleidoscope and you have your brix measurement.

A refractometer can also tell you if you have enough calcium. A blurry line where the upper and lower part of the scale join tells you calcium is sufficient. A sharp line indicates deficiency. Not everyone agrees with this seemingly strange methodology, but I’ve found it to hold true much of the time when compared to a soil test.