Monday, December 14, 2015

The Difference Between Dirt and Soil

Dirt and soil - they mean the same thing, right? Not to a scientist. My graduate school soils teacher had this to say about the topic: "Dirt is dead. Soils are not."

 Soils are actually pretty complex. According to Brady and Weil, in their fine volume The Nature and Properties of Soils:

The four major components of soil are air, water, mineral matter, and organic matter.

What does that mean exactly? Let's break it down.

Air in soil is contained in pore spaces. Different soils have varying amounts of pore space. A well-aerated soil is more likely to grow crops, since it is easier for plants to stretch out their roots. If a soil is highly compacted, nothing is going to grow there. Think of tight packed clay, for example.

Water in soil is pretty easy to visualize. A sandy desert soil, for example, might retain very little water, even after a rain. But a soil higher in organic content, like a loam, will hold more water.

Mineral matter simply refers to the type of bedrock from which the soil was derived. Bedrock is sometimes referred to as a soil's "parent material." A soil that came from granite will have different properties than a soil derived from limestone. (According to this article in Soil Science and Plant Nutrition, red limestone-based soils have higher levels of trace elements than soils derived from other types of bedrock.) 

Organic matter in soil consists of plant or animal residues along with soil-dwelling critters like earthworms. This is probably the biggest difference between dirt and soil, and is the origin of the comment above from my professor: soils are living ecosystems.  

Soils are probably the most underrated of all ecological resources. If you think about it, everything we do depends upon the soil. We rely upon soils to filter the water we drink. We need soils to grow crops for food, lumber for housing, cotton and hemp for clothing. How well a soil compacts - or doesn't - affects our ability to build homes and businesses. In short, we shouldn't treat soil like dirt! 

See what healthy soil looks like

This soil from Illinois is high in organic matter. Photo credit: Natural Resources Conservation Service Soil Health Campaign, via Flickr

Thursday, April 16, 2015

Drive-By Nature

About a week ago, a large fire affected roughly twenty acres of park land near my house. I was out of town during this event, so I drove through the park this morning to see if I could find the impacted land. (I couldn't see it from the road.)

As I was driving - following all of the roads in the park, barely slowing down, never leaving my car - it occurred to me that mainstream American society today often relegates nature to experiences like this. It's as if we want a take-out order of nature, rather than staying for the real experience.

A litany of excuses ran through my mind as I drove:

- I don't have time to stop.
- I'm not wearing the right clothes.
- What if there are ticks?

The sad part is, I like nature. There is no excuse for my behavior other than conditioning and complacency. 

What barriers prevent you from experiencing time outdoors? Are they real barriers or imagined ones?

Wednesday, April 15, 2015

Science Literacy Starts at Home (Science Literacy Series #1)

I think the way we talk about science in this country is flawed. Too often, I hear people speak of science as a subject in school, rather than an integral part of daily life. If we want our children to be literate in science, we need to change the way that we approach the subject.

I once had a discussion with another mother in which I spoke of my love of taking my son to our local nature center.

"Oh," she said. "I don't do that. My husband does the science."

That statement of hers has bothered me ever since. It's not that she doesn't like science - I can appreciate that some people don't. It's that she is modelling the idea that science is somehow separate from the rest of her life - as if science is simply a concept that you can graft on at a later date.

Science needs to be integral to a child's life from the beginning. And by this, I mean that we - as parents - approach teaching our children with science literacy in mind.

1) Ask the what if questions. What if the sky was red instead of blue? What if we dropped this egg from the top of that building? What happens when we microwave marshmallow Easter candy? (Goal: encourage curiosity, thinking outside of the box)

2) Challenge popular thinking. Why does everyone love pop star of the moment? What makes him or her so special? Why should we buy that brand of toothpaste? What is that commercial really trying to sell us? (Goal: critical thinking)

3) Observe your surroundings. What makes this dancer better than the others? Is it the way he moves? The way he uses the space on the dance floor? How he carries himself? (Goal: observation skills, concentration) 

What do you think? How do you encourage science literacy at home?

Thursday, March 12, 2015

In Praise of Rats

This is Dragon, my son's pet rat.

When we first brought him home from the pet store, we put him in the basement with the hamster and had limited contact with him. I soon noticed that whenever we went downstairs, unlike the hamster, who ignored me and spun on his wheel, the rat would stand up on his hind legs, cock his head to one side, and try to make eye contact. Even my husband, who largely ignores the small animal population at our house, began talking to him. 

I decided that the rat seemed sad and discussed my concern with a rat-loving friend of mine. She told me that pet rats have been described as pocket dogs and need frequent attention to be happy. Social animals, they are often sold in pairs so that they don't get lonely. 

As a result of that discussion, we moved the rat into my boys' bedroom. He seems much happier upstairs. I talk to him daily. He is inquisitive about any activity that surrounds him, and with three kids in the house, there's quite a lot of activity. We started buying him dog toys, soft things that he can shred and tear and sleep on. 

Dragon is a good listener.

And that brings me to the point of this essay: Rats make nice pets. 

Frankly speaking, rats get a bad rap. A recent headline in The Independent screamed, "Bubonic plague-carrying fleas found on New York City rats." What a misleading headline! One would assume that we are headed straight for an epidemic of the plague. The actual article reveals that the rats were found to carry the type of fleas that transmit the disease, not the disease itself.

Another recent article - this one in The Guardian - suggests that giant gerbils, not rats, may have been the source of the Black Death. As reported by the BBC, a team of researchers from Norway "now plans to analyse plague bacteria DNA taken from ancient skeletons across Europe. If the genetic material shows a large amount of variation, it would suggest the team's theory is correct. Different waves of the plague coming from Asia would show more differences than a strain that emerged from a rat reservoir." 

So, the next time that someone tells you that they have a pet rat, try to keep an open mind. You might find that they aren't so bad after all.

Tuesday, March 10, 2015

Is Your Organic Garden Really Organic?

This was the first magazine article that I wrote as a freelance writer, for a natural family website. The site has since changed hands - and many of the articles have been largely rewritten, presumably to evade copyscape - but I managed to find an old copy of my piece and thought I'd post it here for safekeeping.


Is Your Organic Garden Really Organic?
By Julie Bloss Kelsey

You know not to garden near your house, because your home was once painted with lead-based paint. You know not to garden near the road because automobile exhaust used to contain lead. But did you know that former farming practices might have contributed to lead and arsenic contamination in the rest of your soil?

We take for granted that organically grown produce contains lower quantities of harmful pesticides than food grown by conventional means. But organic gardening doesn’t guarantee safe food. Do you know the historic land use of the soil in your garden? Was it ever used for conventional farming? If so, there may be pesticide residues in your soil.

Look back at non-organic farming practices

Arsenic-based pesticides were used by farmers in the United States from the late 1800s until around 1940. After about 1945, U.S. farmers began to use synthetic pesticides, and the use of arsenic-based pesticides declined dramatically. However, in some parts of the country, farmers used arsenic-based pesticides on fruit trees until the mid-1950s and 1960s. Lead arsenate was not banned completely on food crops in the U.S. until 1988.

But problems can develop many years later. In 1997, a routine test conducted by the FDA revealed elevated levels of lead in a package of frozen mixed vegetables. Carrots, grown on old orchard land in the state of Washington, were the source of the lead. At the time the carrots were grown, use of lead arsenate had been banned in that state for over 20 years.

And this wasn’t an isolated incident, as evidenced by the FDA’s Center for Food Safety and Applied Nutrition. As reported on their web site, “In the late 1990s, elevated levels of lead were found in a baby food (chicken and vegetables). The source was traced to carrots grown in fields previously used as apple orchards that had been treated with lead arsenate.”

Reduce your risk

Just because your garden was formerly used for conventional farming does not mean that you should stop gardening. If you follow these simple tips, you will greatly reduce your risk of exposure to any pesticide residues that may remain in your soil.

• Wash your hands after gardening and remove your shoes before coming into the house. Be sure to wipe the feet of pets that have been in the garden with you.

• Wash all fruits and vegetables thoroughly before eating them. Ingesting contaminated soil poses a greater human health risk than eating foods grown in contaminated soil.

• Be aware that leafy greens, like lettuce, are the most likely to uptake metals, followed by roots such as carrots. If you are concerned about the soil in your garden, you may wish to grow fruits, such as tomatoes.

• If your land has a known history of conventional agriculture — particularly if it was a cotton field or a fruit orchard — consider importing fresh topsoil from a trusted source for your garden. If you are concerned that the topsoil might erode (for example, your garden is on a slope), you can use an elevated planter.

Above all, don’t let fears of residual soil contamination dampen your enthusiasm for organic gardening. You know more about how your food is grown than most people do. And you can take proactive steps to ensure that your food is as safe as possible.

© Julie Bloss Kelsey

Julie Bloss Kelsey holds a master's degree in environmental management from Duke University, where her master's project was called "The Impact of Historic Pesticide Applications on Former Agricultural Soils."


If you liked this post, check out

Organic gardening is good for native bees.
(Note the discarded antennae on the floor.)

Friday, February 13, 2015

A Naturalist's Thoughts on Invasive Species

Invasive species are defined as exotics that were brought or accidentally introduced to an ecosystem and wreak havoc on it because they have no native predators. Think kudzu in the American South.

A healthy ecosystem has checks and balances to keep each species in line. Visualize a very simple food cycle - let's say trees, white-tailed deer, black bear. Trees sprout and grow but the stand can't get too thick because of deer browsing the seedlings. The deer population is held in check by the bears. And the bears eat the berries on the trees and poop out the seeds, allowing new trees to grow.

Now, this is highly oversimplified, but you can see what I mean about checks and balances. You throw something non-native in the mix and the whole cycle suffers.

But it occurred to me yesterday that native species can become invasive. In reality, the simple food web that I described above doesn't work all that well where I live. Black bears (and other top predators) are rare and the white-tailed deer population has exploded. The understory of the forest here has almost no seedlings because the deer browse everything, leaving no baby trees to replace the ones that are sick or dying. 

In my opinion, white-tailed deer in the mid-Atlantic are an invasive species. Now, the very definition of an invasive species, at this point, implies that a species is non-native. But I would argue that when a native species population explodes out of control with nothing to check it, it's invasive too.

Interesting point of fact: not all exotics are invasive. Some, like the honeybee in the United States, were imported here and the local ecosystem adapted to them - and depend on them - over time.

 Honeybee on lavender
Photo credit: Ryan Wick, via Flickr (cc by 2.0)

Friday, February 6, 2015

A Naturalist's Thoughts on Winter Weather

February in the Mid-Atlantic can bring a wide range of weather - anything from sunny and balmy to freezing cold and snowy. This variability contributes to a wide range of winter precipitation. A wintry mix is a combination of rain, snow, freezing rain, and sleet.

Rain is liquid precipitation. The diameter of the droplets determines whether you have fog, mist, drizzle, light rain, moderate rain, heavy rain, excessive rain, or a cloudburst. Cloudburst droplets, although small at 2.85 mm in diameter, are over 200 times larger than fog droplets. (I wrote a previous post on this topic called How Big Are Raindrops?).

Snow consists of ice particles frozen into complex, six-sided patterns. Non-branching ice crystals - or diamond dust - form in the shapes of needles, columns, or plates.

Little Brother was very little when I took this photo of him playing in the snow.
He was very proud of his snowman!

Freezing Rain occurs when the atmosphere is warm enough for rain, but ground temperatures are 32 degrees F or lower. The rain freezes instantly when it hits the ground, coating everything in a layer of ice. Freezing drizzle is similar, but the individual drops of water are smaller. Freezing fog occurs when ice crystals are suspended in fog.

 I took this picture after an ice storm last winter. The rain froze the instant it hit the tree branches.

Sleet forms when snow melts in the atmosphere and then refreezes before it hits the ground. Sleet does not stick to objects the way freezing rain does.

This article (sans photographs) was first posted at the Audubon Naturalist Society. Come visit Woodend!