Barreca Vineyards

Barreca Vineyards

From Vine to Wine since 1986

How Sweet It Is

How Sweet It Is

The quest for evidence-based information is ongoing.  So are the efforts to dismiss it. As Yuval Noah Harari pointed out, science is based on the admission of ignorance.  With science, as soon as you think you know something new, other scientists are going to poke holes in your ideas and try the same things to see if they work all of the time.  It is an uncomfortable way to proceed. But it has given us all the major changes of the last 200 years.

So scientific methods are now taught in school.  I was given the chance to see how that works while volunteering to be a science fair judge at Curlew School near the end of March. (Full disclosure, my daughter, April, teaches science in Curlew and pretty-much volunteered me and many other friends.)  Each student displayed their project on little countertop cardboard kiosks.

Vice Grip grass crusher, scissors, PH meter and refractometer

The theories ranged from “younger kids are kinder” to soda pop taste tests.  The project that struck me as the most contemporary was one questioning where the most bacteria accumulated on common surfaces around the school.  The hypothesis was that keyboards would surpass bleacher seating, doorknobs and other sites.  After a lot of testing and culturing of cultures, doorknobs turned out to be the most unsanitary.  The variables were the different surfaces. The procedure was to swipe each surface in the morning and start a culture from the swab, then to do that again in the afternoon. After counting the density of microbes in the cultures, the conclusion was that doorknobs were actually the most unsanitary. 

Almost every experiment had a secondary conclusion that the methods and materials could have been improved to show more accurate results.  Therein lies another annoying characteristic of science, it consistently confounds the desire for simple solutions.  That tendency has confronted me with many annoying results. 

For instance, a key measurement of soil health is SOM, soil organic matter.  With an increase of 5% to 10% in SOM on earth’s cultivated ground, enough carbon could be sequestered in the soil to offset thousands of years of plowing up roots and burning fossil fuels. SOM is also a strong indicator of microbial life and healthy soil which produces stronger, more abundant and nutritious food.  Win. Win. Win! Right?  Just measure SOM on a broad scale and you have an index of the health of the soil, a little like measuring CO2 to get a simple measure of climate change.  Not so fast on both counts.

Turns out that the SOM variable is very variable from Spring through Fall as an indication of plants taking up nutrients to grow and releasing them again when they die. Percentages vary from one soil type to another reflecting different crops.  As a broad indicator it is very good.  Getting to that bigger picture takes a lot of study.  Often that work involves Citizen Science, annual bird counts or referendums on the most interesting objects in the universe. (Google VV 689 and the Galaxy Zoo Project.)  Thousand of citizen scientists contribute observations and opinions, a few scientists crunch the numbers and pick a result.

Meanwhile, down on the farm, how can we tell what is going on?  We still have theories, variables and procedures.  But our tests, conclusions and decisions just become management.  Actually there is some common ground.  Case in point: brix.  Brix is a measure of liquid density, usually an indication of sugar content.  Just as light bends when it enters water because water is denser than air, light bends more in liquids denser than water and you can measure that on a simple instrument called a refractometer.

As a winemaker, I measure brix regularly during harvest season to see when sugars are high enough in grape juice to ferment completely into a finished wine.  Plant scientists have begun using brix for a wide spectrum of reasons.

Within a given species of plant, the crop with the higher refractive index will have a higher sugar content, a higher mineral content, a higher protein content and a greater density. This adds up to sweeter-tasting, more nutritious food with a lower nitrate and water content and better storage characteristics. (https://johnkempf.com/tag/sap-analysis/ – which I highly recommend)

To measure brix in a crop, you need a drop or two of liquid sap to put on your refractometer.  With leafy crops like grass, that is not so easy.  I needed a tool that is essentially a pair of vise grips with a spoon lip makeover.  With a little experimentation and a few adjustments, I had some grass juice to put on the refractometer.  It’s sticky and very green.  My first sample came in at 8° brix, which is a good, but not a great number.  Again the variables are critical.  Brix is lower in the morning. Sugars are stored in roots at night and used up a little by morning.  They climb during the day.  Hay cut in the afternoon is generally sweeter and healthier than that cut in the morning – except if it rains, which happens regularly. To track progress you need a series of measurements at a consistent time of day under consistent weather conditions.

It turns out that brix as a one-size-fits-all plant health indicator is (like SOM) just too simple.  A more critical variable is PH and PH is a slippery slope.  It is measured on a logarithmic scale with each degree being 10x the degree below it.  So 9° PH indicate 100x the alkalinity of the neutral 7° and 5° PH are 100x more acidic than 7° PH.  The sweet spot  (so to speak) is 6.4° PH.  My grass was 6.0°. 

As PH gets more alkaline, the risk of insect damage goes up.  As PH gets more acidic, the risk of disease damage goes up.  As brix goes up, a plant’s resources to fight insect damage increase.  These are immediate test results than you can use to manage your crops in real time without waiting weeks for soil and other lab tests.  The common ground is that you can do the tests for your own crops and the professional scientists can advise you what the results mean and what to do about them on the internet.

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