Tasting soil to determine its quality is an old practice spanning centuries and continents. I did not know this until a few weeks ago, when I started a garden and, for the first time in my life, found myself directly concerned with dirt.
Our first garden is a large rectangular raised bed shaded by a maple. Before it was ours, it was someone else’s. On April 28, it was assigned to my husband, Paul, and me by the garden czar of the Charles River Community Garden in Boston.
Even the smallest vegetable garden’s success depends on its soil. Soil is no single, boring constant, but a great, diverse, maddening spectrum of possibilities — and potential problems. Beware, for not all soils are best suited for your aspiring asparagus.
The Moorish medieval agriculturalist Ibn al-Awwam, author of the “Book of Agriculture,’’ published in Arabic in the 12th century, notes that “The first precept of agronomy . . . is to know the land and to know how to distinguish between what is of good quality and what is of inferior quality. The person who does not possess these notions . . . deserves . . . to be called an ignoramus.’’
Ibn al-Awwam suggests several ways of classifying soils. He considers touch and sight our most reliable senses for this task, but he also mentions smell and taste. To taste a soil the 12th-century way, first you must dig a trench. Then gather some of that deep earth into a glass vessel and cover with rainwater. Mix. After the soil settles, taste the water. If it tastes good, the land will be good as well.
French written records of a similar practice go back as far as 1583, and soil tasting persists in many places across France today. In deep East Texas, my own grandfather and great-grandfather tasted their soils.
I was determined not to be called an ignoramus. I too would eyeball, touch, smell, and taste my soil.
“Taste can tell you a bunch of things,’’ Justin Richardson, an assistant professor in the geosciences at UMass Amherst and a longtime member of the Soil Science Society of America, enthusiastically told me by phone.
Richardson reports that he has tasted “a good amount of soil — on purpose and on accident.’’
Ensure your garden is free of contaminants like lead, he said, and then start your taste test with a small amount of soil.
“A little pinch to start,’’ he counseled. “You’re not trying to eat a meal.’’
I asked whether there are any circumstances in which he would not taste a soil.
“I definitely don’t want to taste soggy soil,’’ he said. “That’s where you get interesting microbes living there. So, unfortunately, soils are home to terrible things like brain-eating amoebas.’’ He laughed heartily.
“Soil in and of itself is not dangerous,’’ he added. “There are things that could be dangerous in certain soils, but generally soils are actually pretty healthy.’’
Several ingestion-free soil-testing techniques do exist today, including many inexpensive home kits. Scientific soil analysis in this country was already popular and widely available a century ago. “It pays to test soil at home,’’ a typical advertisement promised in a 1918 edition of the New York Sun. “This man saved $49.20 on 10 acres by testing his soil at home!’’
The switch to industrial farming in America and around the world led to a move away from understanding the land through our senses. Since the early 20th century, commercial agriculture has wanted, and needed, numbers.
“Your tongue can’t taste and get a number,’’ Richardson said.
This is confirmed by Claude Bourguignon, a preeminent soil microbiologist who, along with his wife, Lydia, runs a soil-testing laboratory, the Laboratoire d’Analyses Microbiologiques des Sols, north of Dijon, France. The Washington Post recently called the Bourguignons the “world’s most famous ‘soil doctors.’ ’’
“The machine gives a number,’’ Claude Bourguignon tells me in French, “but the machine is not very sensitive. Our sense of smell is much, much more sensitive than any machine. Our sense of sight is more sensitive than any machine.’’
Even in France, the sensory knowledge of the land — a kind of earthly memory beyond the written archive — has “dramatically’’ disappeared since World War II and the industrialization of agriculture, he said.
“We have ceased to be in relation with the earth. We have become barbarians who destroy the soils.’’
My husband and I scheduled our sensory encounter with the land for a cool Sunday morning in May.
I chose the middle of the plot with the idea — a pure, but soothing fiction — that this spot would be the cleanest in the garden, and dug a shallow hole with my hands.
It was about 10:30. Rain threatened. There we were, Paul and I, beaming in the garden — unable to stop that contagious, sheepish grin characteristic of terrified, excited fools.
We stood embarrassed before the land. I tried piously, and unsuccessfully, to stop smiling. I wondered whether Adam and Eve had grinned like two idiots, also, when they’d tasted the forbidden thing in their garden. Of course, we knew we were misbehaving.
The top layer of earth was light gray and slightly dull, like some seashore pebble after it leaves the surf, dries, fades, and disappoints. Just beneath the surface, though, the earth was dark and cool. I crushed some between my fingers. The soil was nothing like sand — it could be broken down further into something else. It wasn’t really one thing, but many things: different browns and blacks, flecked with shiny whites.
“Smell and taste go hand in hand,’’ Richardson had reminded me.
Our sample smelled only of moist earth, and I took this as a good sign.
“Chemically farmed soils stink,’’ Bourguignon had warned. “Living soils have a very nice forestial odor.’’
I put a three-finger pinch on my tongue.
The first shock was how that puny sample completely filled my mouth. Every single grain of earth seemed to swell instantly to 20 times in size. All of a sudden my mouth was full of giant rocks. Millions of those formerly harmless, beautiful, tiny specks now felt very sharp. My new powers were frightening. A mouthful of texture is oppressive. It was too much information. I needed to silence the million new voices in my mouth. We rinsed with water and spat.
“That was cool,’’ Paul, a scientist, said. “I could feel parts of it dissolve and parts of it not dissolve.’’
“Taste-wise —’’ he said, “it kind of tastes like nothing. The flavor of it is nothing.’’
Our dirt was not sour or salty (either would have been a bad omen for a garden), but nor was it sweet or otherwise delicious.
“ ‘Tastes like dirt’ is a lie,’’ Paul concluded. “Dirt tastes like no food.’’
Hours later, a kind of dull mustiness lingered; my molars fit together a little differently; and I was a little disappointed.
Our dirt tastes like nothing, I mused. It tells no story.
But even as this thought crossed my mind I was struck by how similar it was to the way the first Europeans had written off America. This land is a wilderness. It has no history. They could not have been more wrong.
Soil speaks, I just don’t yet know its language.
Gene Tempest is a writer and historian who lives in Cambridge. Send comments to [email protected]. Subscribe to the Globe’s free real estate newsletter — our weekly digest on buying, selling, and design — at pages.email.bostonglobe.com/AddressSignUp. Follow us on Facebook, Instagram, and Twitter @globehomes.