Wednesday, July 31, 2019

Varvey Interesting

     I see a book. A 13,000 year old book! Looking at the same scene, most people would see nothing more than a bare, muddy bank. And they'd probably put a little distance between themselves and the nut case babbling on about a book. But look closely. See those thin horizontal layers stair-stepping up the slope. Don't they resemble the pages of a big, open book lying flat on a table?

     These are clay varves. They are another of the many landscape artifacts bequeathed by glaciation. Drumlins, eskers, deltas - those are big topographic features difficult to miss. Varves, on the other hand, lay mostly hidden and it takes some kind of recent excavation to expose them. Even then, they are often visible for just a short time before being cloaked by vegetation...books once again stored in the basement where no one sees or reads them.

     Varves are annual layers of sediment deposited in post-glacial lakes. They occur in light/dark couplets. The lighter layers are rock flour released during the summer melt. They tend to be slightly coarser - silt and fine sand. The thinner, darker layers are clays that settled out in the still waters of winter. Varves vary in thickness depending on the warmth of the year in which they were deposited. They are somewhat similar to tree rings in that respect, building a record of the climate when they were created. Geologists use this fact to construct chronologies of glacial retreat.

Varve core showing winter/summer deposits 
- from North American Glacial Varve Project

Matching varve cores from different sites
- from North American Glacial Varve Project

     Much of the early research on varves was done by Gerard De Geer in Sweden. Indeed, 'varve' comes from the Swedish word for layers. Also in the early years of the last century, Ernst Antevs was using New England varves to document the recession of the ice front. His methods, refined and built upon over time, are still used to date deposits.

De Geer second from left, Antevs on right
- from North American  Glacial Varve Project

     While examining my varved slope I came across odd, rounded inclusions that seem to be the precursors of concretions. They appear to be of the same clay as the varves but slightly harder so that they remain when the surrounding material is eroded away. The concretions added strength comes from being cemented by percolating ground water containing silica, carbonate or iron oxides. There were reddish stains near the ones I saw suggesting iron oxides as the cementing agent. 

     Look for varves (and concretions) in the lowland areas of Washington County. These places were under the waters of Lake Albany and Lake Vermont and that's where the clays and silts settled out. Sometimes road work and ditching will expose them. Streams that have incised into the sediments can also reveal varved banks. 

     My photos come from a spot where the town highway crew had graded a bank that was slumping into the road. It's in a Hudson soil near what would have been the western shore of Lake Albany. The elevation is approximately 185 feet above sea level. I estimate the shale bedrock to be some 25 to 50 feet below the exposed varve and nearby field surfaces are 30 to 40 feet above. There could potentially be as much as 100 feet of varved clay deposits at this location although only about ten feet can be seen.

     Finally, here's one last varve tidbit. When I was a kid my buddies and I used to play on what we called the clay slide. It was a steep bank maybe 25 feet high that dropped into the Snook Kill stream. This was way before the time of water parks and Moms who shuttled their kids from one activity to the next. We were poor, our parents were always working, and we made our own fun out in the wild. I remember hauling buckets of water to the top of the bank. Poured down the slope, this made the clay slick enough for a heart-thumping descent and crazy splash into the water at the bottom. But it wasn't all smooth sliding. More like bumpity, bump, bump all the way down - no doubt because of the varved layers in the clay. Eventually we wore thru the bottoms of so many pairs of cut-off jeans that our mothers made us stop. To this day I think I still have bruises on my butt from the clay slide. But don't panic. There will be no photo documentation of that on this blog. 


     * A great site for more information is the Tufts University North American Glacial Varve Project. Access it here.

Varves from Lake Vermont
- from North American Glacial Varve Project


Saturday, July 20, 2019

Dirt Cheap?

     Standing alongside CO 61, looking at a bare, gullied field, the thought occurs to me: Gabe Brown would not be happy. Brown is the author of the 2018 book Dirt to Soil. He is a farmer and champion of what is called 'Regenerative Agriculture'. I understand that as a production system that builds healthy ecosystems and fertile soils rather than mining and depleting them.

     His book emphasizes five strategies to improve soil health:
     (1) Limit disturbances such as tillage and chemical inputs
     (2) Keep soil covered with living plants or mulch
     (3) Strive for diversity of species
     (4) Manage for living roots year-round
     (5) Integrate animals - everything from worms and pollinators to
           large grazing livestock

     Using these criteria this field outside Shushan would score a big, fat zero. It had been tilled, then planted to a monoculture of corn. And corn is a crop that requires heavy chemical inputs. After harvest for silage the ground lay bare and the only evidence of animals were the deer tracks so ubiquitous in Washington County.

     This is a gravelly silt loam that's obviously prone to erosion. What's harder to see is the lack of soil life that results from this type of management. For half the year the ground lies inert, essentially dead. Then, during the growing season, synthetic fertilizers and sprays do further damage to soil biology. Unfortunately this field is typical of how modern agriculture is done across the country. Gabe Brown and others want to change that.

Web image

     The Dust Bowl era of the 1930's was a wake-up call. How we farmed mattered. Plowing dry-land prairie lead to ecological disaster and social upheaval. Lessons were learned (and perhaps subsequently forgotten). By the 1950's world populations were increasing faster than food supplies and many regions were afflicted with famine. Enter Dr. Norman Borlaug and the Green Revolution. New technologies such as hybrid seed, synthetic fertilizers, pesticides, irrigation and mechanization spread around the world and are credited with saving a billion people from starvation.

Dr. Norman Borlaug (1914 - 2009) - Web image

     But some saw problems with this type of high input, industrialized style of food production. Various alternative systems include organic, biodynamic, holistic and permaculture. Each has its advocates, books and websites (and detractors).


     You can't really understand a place until you understand its soils. They represent the most recent chapter of geologic history and they influence everything that lives - plants, animals, us. Birds, wildflowers, even rocks each have their loyal tribe of enthusiasts. But soils don't get much loving. When was the last time you saw a naturalist digging a backhoe pit to look at soil horizons? Almost by definition, soils lie underground with only their top exposed and that is usually covered by vegetation. Out of sight, out of mind. But that is unfortunate because the ground beneath our feet is a fascinating part of the ecosystem.

Web image

     The image of a naturalist digging with a backhoe may be farcical but (wouldn't you know it) I'm actually that person. For many years I've used spare time to install drainage tile in my fields.  This is done using a small three point hitch backhoe mounted on a tractor. I dig a two foot wide trench about four feet deep before laying four inch perforated plastic tubing and backfilling. The practice gives excess water a path out of the field while also giving the curious (that would be me) an intimate look at what lies below.
     Not exactly soil science but here are a few observations from my years in the trenches... 
     * Soil formation is initiated when the rocks of the Earth's crust succumb to weathering and are broken down into smaller and smaller sized particles: boulders, cobbles, pebbles, sand, silt, and clay. It can take 500 years for nature to build one inch of soil.

     * Soil is more than just ground-up rocks. Air, water, decayed organic matter (known as humus) and a vast array of living organisms add to the mix.

     * The texture of soils range from fine (clay) to coarse (sand and gravel) while a mix of clay, silt and sand is known as loam.

     * Undisturbed soils have a distinct profile usually marked by three horizons. These develop in part from water leaching thru the soil. The upper layer, rich in organic matter, is called the topsoil (duh). Below that are several layers of subsoil. 

Web image

     * The acidity of soil is an important factor. In the northeast soils tend to be somewhat acid but where limestone is the underlying bedrock they can be more neutral. Farmers add ground limestone to 'sweeten' the soil, counteracting acidity and making their fields more productive.

White clouds of lime being spread

A dusting of lime coats this harvested  field of corn

     * Peat and muck are soil types with high levels of poorly decayed organic matter. They develop in water-logged sites where there is not enough oxygen for active decay.

     * There are several types of humus. Mor humus tends to develop in sandy soils covered with coniferous forest. Mull humus is more often found under deciduous trees. 

     * Classification of soils can get a little confusing. Zonal systems are based on the climate and vegetation where the soil developed. In Washington County the broadest category is the Order and the narrowest is the Series. Inceptisols, Spodosols and Alfisols are examples of Orders, while Hoosic, Hudson and Kingsbury are just three of many Series found here. Across the U.S. 70,000 kinds of soil have been identified. 

Kingsbury and Hudson soils are mapped here

     * It's a zoo down there. In an acre of soil there may be as much as 16,000 pounds of bacteria, viruses, mites, fungi and other soil life. Just a teaspoon of soil can host a billion bacteria, with up to 2,500 different species. Soils become more productive when fungi predominate over bacteria in the microbial community. And while earthworms are generally associated with healthy soils they are actually an invasive species that can harm natural ecosystems.

Creeping menace?

     * Cover crops are a way to protect and enrich the soil between cash crops. An example might be a field of corn that is planted in May and chopped for silage in September. That corn is the year's cash crop. After it is harvested, the field is bare and vulnerable until the following spring when the next cash crop is planted. By seeding a cover crop (such as rye) right after the corn is taken off, the farmer can protect the soil from erosion, absorb leftover nutrients that might otherwise run-off and continue to feed the subsurface microbial community. The following photos are of nearly adjacent fields in the Bald Mountain area of Washington County and were taken at the same time. The first shows a barren field of the previous year's corn stubble. The second photo is of a field that had also been planted to corn but with a subsequent cover crop of rye. 


     I got Dirt to Soil out of the Greenwich Library. In agricultural Washington County it would be great if the book was available in every library. Other individuals involved in the soil health and regenerative agriculture movement include:

     - Allan Savory is an ecologist who developed the concept of Holistic agriculture. He advocates using constantly moving herds of livestock to heal degraded land. His ideas can be found in Holistic Management, Third Edition.

Allan Savory -web image

     - Joel Salatin uses holistic management on his Polyface Farm in Virginia. He's a prolific author and lecturer preaching the gospel of a new agriculture.

Web images

     - Jim Gerrish is a grazing consultant and author based in Idaho and Walt Davis is a rancher/author from the Texas/Oklahoma area. Both are independent thinkers not necessarily on board with the 'green revolution'. 

Jim Gerrish

Walt Davis

     Finally, you can access the online soil survey of Washington County here. Loads of information.

     And the last words come from a time when we had wise leaders:

"A nation that destroys its soil, destroys itself."
- Franklin Roosevelt