Healthy Soil, Healthy Roots. Healthy Roots, Healthy Leaves.
The above could very well be a parable about the formation of full and self-actualized human beings, but in this case, I am speaking quite literally.
Today we're going to talk about the roots of the tea plant, and in particular their relationship with the soil in which they grow.
Why Tea Roots Matter
We'll get the obvious out of the way. The roots of a plant draw up water and nutrients like nitrogen and phosphorous from the soil, all of which assists any plant in growing. Interestingly enough, though, I just read that moisture in the air is more important to a tea plant than moisture in the soil, as it is ambient humidity that regulates the opening and closing of the stomata of the tea leaves, and this is critical for the plant - but we're getting off topic already.
The really interesting thing about tea roots is that this is where that old amino acid to which I keep referring in post after post (L-Theanine) is produced. Catechins, polyphenols, volatile aromatic compounds...these are all downstream byproducts of the nutrients of the roots, and are produced by the leaves, but it is the roots that use nitrogen to produce savory amino acids that then get shuttled up into the leaves in Spring.
Uh oh, Simon mentioned nitrogen.
That's the other thing I talk about a lot. Nitrogen makes good tea, and in particular, it makes very umami-heavy tea because it is a building block for L-Theanine. But I also have a love/hate relationship with nitrogen because the common practice in Japan in to just dump tons and tons of synthetic nitrogen into the soil, which leads to downstream environmental problems.
What is interesting about this aspect of tea farming is that tea farmers are, ultimately shooting themselves in the foot. This is where soil health comes into play in a big way. Where excessive chemical fertilizers are used, soil health declines. The acidity level of the soil changes, and microbial and fungal biodiversity decreases substantially. Eventually, the capacity of the soil to sustain plant growth on its own is depleted entirely, such that ever-increasing quantities of chemical additives are required.
Even under organic farming conditions this can happen. It's why it was such a revolutionary thing in the middle ages for peasants to develop a rotating field system in which every year one third of their farm was left fallow to recover its health (I'm finally putting my history degree to work in the tea business). That was under medieval farming conditions! Who knows how many years of fallow non-productivity a tea field would have to endure after decades of chemical disruption.
Nature to the rescue!
So, we would seem to have a problem. We want more nitrogen to get into the tea roots to produce more L-Theanine, but, we don't want to destroy the farm for the next generation in doing so.
Nature, however, is pretty cool and farsighted, and has developed some answers to this problem. You see, soil is not just roots, water, and basic elements. It's a whole complex environment, and the fungi and bacteria that live within the soil work together with tea roots to make one another healthier and happier. Consequently, multiple studies have found that greater biodiversity in the soil of tea fields - both in terms of bacteria and fungi - results in higher L-Theanine levels in tea through enhanced Nitrogen uptake.
It would even appear that intercropping with other plants (planting non-tea plants between the rows of tea), contribute to greater soil diversity and, thus to greater flavor.
But here's where things get even more interesting! Soil health doesn't just influence nutrient uptake and L-Theanine production. As I mentioned, these nutrients get converted into other compounds by the tea leaves over time. With this in mind, studies have found that greater soil microbial biodiversity, especially that caused by intercropping, results in teas with higher concentrations of floral and fruity aromas! In particular, bacillus species of bacteria in soil have been positively correlated with higher levels of linalool, jasmone, and geraniol in tea leaves - all highly aromatic and appealing compounds that have been isolated for use in fragrance products for a while now. Finally, symbiotic relationships with fungi on the roots of tea plants can alter metabolic pathways in the plant itself that then influence how molecules get synthesized into different aromatic compounds. (This could all point to another reason why our Wild Yabukita is so special).
This is just insane to me. When you drink tea, you really are drinking an expression of the plant's terroir. You are tasting the result of an endlessly complex interplay between innumerable organisms (google "Indra's Net" if you want to humor me and put my religious studies minor to work in this post too). There's something magical about this, and it's a shame that in the pursuit of ever more L-Theanine we are disrupting this process. Let's stop that. Drink naturally-farmed matcha!
Thanks for reading and happy sipping,
Simon