50 Fun Facts About Soil

Charles Darwin's last scientific book, in 1881, argued that which animals create the fertile top layer of soil?

Earthworms intrigued Darwin so much that he made an excursion to Stonehenge to see how its monoliths had been buried by their castings. The book sold thousands of copies within weeks.

Which disease, popularly blamed on rusty nails, is caused by bacteria whose spores live in soil and manure?

Tetanus comes from Clostridium tetani, and rust itself is harmless. A dirty nail simply punctures the skin and carries the soil-dwelling spores deep into the wound.

What name did two Australian scientists coin in 1964 for the earthy smell of rain falling on dry soil?

Petrichor joins the Greek word for stone with ichor, the golden fluid said to run in the veins of the Greek gods. Before 1964 the scent was known as argillaceous odor.

Many hydrangeas act as natural soil testers, producing flowers of which color when the ground is acidic?

Blue flowers appear because acidic soil makes aluminum ions available for the shrub to absorb, while alkaline ground turns the same plant pink.

Which Italian landmark began tilting during its 12th-century construction because the ground beneath was too soft?

Tower of Pisa builders had only reached the second floor when it began to sink in 1178. Engineers finally steadied it between 1993 and 2001, trimming the tilt to just under four degrees.

Which waterlogged soil preserved Denmark's Tollund Man so well that his finders in 1950 suspected a recent murder?

Peat builds up where stagnant water starves dead plants of oxygen, and the same acidic bog water tanned the skin of a man who died around 400 BC.

On a bag of NPK fertilizer, the letter K stands for which plant nutrient, known to early chemists as kalium?

Potassium takes its English name from potash, the residue left when wood ashes were soaked in a pot and the water boiled away. The numbers on the bag list nitrogen and phosphorus before it.

Which 1930s disaster followed drought and deep plowing on the Great Plains, raising storms called black blizzards?

Dust Bowl was a name coined by a news editor in April 1935, and its choking clouds traveled as far as New York City and Washington, D.C.

The largest known fungal colony, a honey mushroom spreading under 3.5 square miles of forest, lies in which US state?

Oregon's Malheur National Forest hides the giant, which creeps from tree to tree on black underground cords nicknamed shoestrings. It may weigh as much as 35,000 tons.

Streptomycin, isolated from a New Jersey soil microbe in 1943, became the first antibiotic cure for which disease?

Tuberculosis treatment won lab chief Selman Waksman the 1952 Nobel Prize, although it was his PhD student Albert Schatz who first isolated the drug.

Which Illinois blacksmith built a polished steel plow in 1837 that cut cleanly through sticky prairie soil?

John Deere remembered polishing needles with sand in his father's tailor shop, and reasoned that mirror-smooth steel would shed the earth that clogged older plows.

George Washington Carver urged Southern farmers to revive worn-out soil by rotating in which nitrogen-restoring crop?

Peanuts became Carver's signature crop, and his 1921 testimony to Congress about them made the Tuskegee professor a national name.

Which is the finest of the three soil particle classes, with grains even smaller than those of silt?

Clay turns plastic when wet and hardens when fired, which is why the stickiest ground underfoot is also the raw material of pottery.

Gardeners prize which crumbly soil, a balanced blend of sand, silt and finer particles that drains without drying out?

Loam is about 40 percent sand and 40 percent silt by weight, a mix that holds nutrients and water while letting the excess drain away.

What name is given to ground that stays below freezing for two or more years, as across much of Siberia?

Permafrost lies under about 15 percent of the Northern Hemisphere's exposed land, and the oldest has stayed frozen for around 700,000 years.

The world's soils store roughly three times as much of which element as the entire atmosphere holds?

Carbon held in the world's soils outweighs the carbon in the atmosphere and in every living organism put together.

Which seabird-dropping fertilizer was so prized that an 1856 US law let citizens claim unowned islands holding it?

Guano takes its name from a Quechua word for dung spread on fields, and Spanish colonial records say Inca rulers punished anyone who disturbed the birds with death.

Which soil-free growing method let Berkeley's William Gericke raise tomato vines 25 feet tall in mineral solution?

Hydroponics got its name from Gericke in 1937, after the towering tomatoes in his backyard had already caused a sensation.

Which plant group, including peas, beans and clover, houses bacteria in root nodules that pull nitrogen from the air?

Legumes leave some of that nitrogen behind in the ground for whatever is planted next, which is why farmers have long worked them into crop rotations.

Which dam, finished in 1970, ended the yearly Nile floods that had enriched Egypt's farm soil since ancient times?

Aswan High Dam was built with Soviet help through the 1960s, and it swapped the summer flood and its natural nutrients for year-round irrigation.

Besides soil bacteria, which weather phenomenon converts nitrogen in the air into forms that plants can use?

Lightning forges nitrogen oxides in the air it passes through, doing naturally what fertilizer factories and root-nodule microbes achieve by other means.

Which waterlogged ground, feared in adventure films, is actually too dense for a person to sink in past the waist?

Quicksand is about twice as dense as the human body, so a trapped person floats at around waist height instead of vanishing below the surface.

Centuries of irrigation ruined Sumer's farmland by leaving which substance behind in the soil as the water evaporated?

Salt built up until Sumerian farmers switched from wheat to hardier barley, and even that could not stop harvests and population from collapsing.

Which powder, milled from chalk or similar rock, do farmers spread on fields to correct soil that is too acidic?

Lime works as a base that neutralizes acid in the ground, and the farm-grade powder needs only milling instead of burning in a kiln.

Which French word do winemakers use for the way a vineyard's soil and climate shape the character of its wine?

Terroir comes from terre, the French for land, and the idea underpins the AOC rules that tie a French wine's name to the place it was grown.

What do gardeners call a layer of bark chips, straw or leaves spread over soil to hold moisture and smother weeds?

Mulch also evens out soil temperature through hot days and cold nights, and the organic kinds feed the ground as they slowly break down.

Which building material of the American Southwest is made from sun-dried bricks of earth mixed with straw?

Adobe is simply Spanish for mudbrick, a word that came from Arabic, and the straw is there to help the bricks shrink evenly as they dry.

Which stable, brown-to-black material is left in soil once dead plants and animals have fully decomposed?

Humus is the Latin word for ground, and soil scientists keep it apart from detritus, the name for matter that is still in the middle of rotting.

Terra preta, the fertile dark earth made by ancient Amazonian peoples, owes its black color to which added material?

Charcoal was worked in along with bones, broken pottery and manure, turning the Amazon's naturally poor soil into rich farmland.

A red color in airy, well-drained soil usually signals a buildup of which oxidized metal?

Iron that has built up and oxidized turns well-aerated ground red, whereas a dark brown or black tint usually points to plenty of organic matter.

Which branch of soil science studies how soils form and evolve in nature, rather than how they serve crops?

Pedology comes from the Greek pedon, meaning soil, while its sister field edaphology takes the grower's view of how the ground shapes plant life.

Which fertile black soil of the Ukrainian and Russian steppes also underlies much of Canada's prairie farmland?

Chernozem can be as much as 16 percent decayed organic matter, yet even it needs fertilizer when it is farmed year after year.

What name is given to the partnership in which soil fungi trade water and phosphorus for sugars from plant roots?

Mycorrhiza joins the Greek words for fungus and root, and the fungal partner may also deliver nitrogen and zinc in return for its share of the plant's food.

Which tiny soil animals, such as the lab species C. elegans, may be four-fifths of all individual animals on Earth?

Nematodes often number more than a million in a single square meter of ground, and they turn up at nearly every level of the food web.

Which slow process, working in place through ice, water and living things, breaks solid rock into the grains of soil?

Weathering happens on the spot, which sets it apart from erosion, the carrying away of rock and minerals by wind, water, ice or gravity.

What is the term for rain or irrigation water carrying dissolved plant nutrients down and out of the soil?

Leaching becomes an environmental worry as well as a waste of fertilizer when the washed-out nutrients end up contaminating groundwater.

Which US president warned state governors in 1937 that a nation that destroys its soil destroys itself?

Franklin Roosevelt wrote the line while pressing every state to pass a soil conservation law, pointing to the storms and floods of the previous few years.

Which layer of a soil profile, labeled the B horizon, lies directly beneath the layer at the surface?

Subsoil is built from the same sorts of mineral particles as the layer above it, but it holds a much lower share of organic matter.

Which pale yellow, wind-blown sediment named from German gives its name to a vast plateau in northern China?

Loess is made of silt-sized grains heaped up by the wind, and deposits like it blanket about a tenth of the Earth's land.

Which earthquake hazard makes wet, sandy ground suddenly lose its strength, as it did at Niigata, Japan, in 1964?

Liquefaction turns ordinarily solid ground into something that behaves like a fluid, so buildings standing on it can sink or tip over whole.

Which compound made by soil bacteria gives beetroot its earthy taste and freshly dug ground its smell?

Geosmin is so potent that the human nose can pick it up at just a few parts per trillion, and its Greek name simply means earth smell.

Which deep red tropical soil can be cut into building blocks, a use that inspired its name in 1807?

Laterite comes from the Latin word later, meaning brick, and Khmer builders used it for the temple enclosures of Angkor Wat.

Which soil typical of northern conifer forests has a Russian name recalling the ash-like layer peasants plowed up?

Podzol means under-ash, a nod to the pale, washed-out band lying just below the surface, and the soil mostly forms on quartz-rich sands in wet climates.

Which Russian geologist, often called the father of soil science, made his name with an 1883 study of steppe soils?

Vasily Dokuchaev showed that climate and terrain shape a soil as much as the rock beneath it, and a crater on Mars now carries his name.

Which German chemist, called the father of the fertilizer industry, popularized the law of the minimum for plant growth?

Justus von Liebig taught that a crop grows only as well as its scarcest nutrient allows, however generous the supply of everything else.

Soil scientists record a sample's hue, value and chroma using color charts devised by which American painter?

Albert Munsell worked out his system in the first decade of the 1900s, and the USDA adopted it as the official color standard for soil research in the 1930s.

Which scientist co-wrote the 1928 report Soil Erosion: A National Menace and later headed the Soil Conservation Service?

Hugh Bennett campaigned for years before Congress passed the act of April 1935 that created the agency inside the Department of Agriculture.

Among the five classic factors of soil formation, what term describes the rock or sediment a soil develops from?

Parent material is joined on the list by climate, terrain, living organisms and the sheer number of years a soil has had to develop.

What term describes the water a soil still holds once excess rain has drained away and downward flow has slowed?

Field capacity is also called the drained upper limit, the stage at which the largest pores have emptied and drainage all but stops.

Which tiny soil-dwellers, known to science as Collembola, escape predators using an abdominal organ called a furcula?

Springtails snap the furcula against the ground to fling themselves clear within a few milliseconds, and around 100,000 of them can share one square meter.