Agriculture Reference
In-Depth Information
Plant Testing
There are a couple of methods of directly measuring the health of your plants with in-
struments. Just as with soil, before you get to these more technical tests, it's very important
to simply look at your plants and take some notes.
You can look for insect predators and diseases as indicators of plant sickness. A little
more advanced, you can look for leaf discoloration that indicates certain deficiencies. I
don't use this is my only means of determining deficiencies, because I think it's more com-
plicated than that, but it's useful to compare these indicators with other plant and soil tests.
Here are some examples of visual deficiency indicators.
A calcium deficiency can produce many symptoms, including thick, woody stems and
cell death at the base of the leaves. A nitrogen deficiency often causes the leaves to be a
pale yellow-green color. A sulfur deficiency does this, too. A phosphorus deficiency can
show up as a purplish color on the lower leaves and as overall stunted growth. A potassium
deficiency often shows up as yellowing and cell death around the edges of the leaves, or in
between the veins. A magnesium deficiency often looks like this, too. You can see that it's
not always easy to pinpoint specific deficiencies since they often look the same, but it's a
useful start when you'll be comparing with other tests.
The two main instrument tests for plants are plant brix and plant sap pH. It's also pos-
sible to test the minerals in plant tissue. I don't have any experience with this, so I can't
comment much on it. The tests are becoming more accurate and the good soil consultants
are learning how to do a better job interpreting the data. It used to be they would supple-
ment what was deficient in the plant tissue, but they're learning it's not that easy. They may
find a certain micronutrient is low, for example, but supplementing with that nutrient may
not be the answer.
Brix, however, is one of the most exciting tests in our toolkit. It measures the dissolved
solids in plant juice, which includes sucrose and fructose, vitamins and minerals, protein
and amino acids, and many others. We like to know the brix of our fruits and vegetables for
a couple of reasons.
The first reason is that brix is a rather nice summary of how well we're doing with our
soil management practices. When we balance the soil nutrient ratios, increase organic mat-
ter content, build our soil food web and so on, plants get healthier and brix goes up.
As your brix rises, your food tastes better — I mean way better, and your taste buds
won't lie. Food stores longer and is more nutritious — way longer, and way more nutri-
tious. Very high-brix foods don't rot. Other than tomatoes, most fruits and vegetables will
slowly dehydrate, but stay nutritious and highly edible. They can stay good for years!
Seeds germinate more quickly, and plants get bigger and produce more food. They resist
heat and frost damage and are healthy overall.
