In the July-August Bay Journal, Past is Prologue examined the development of the hoe and its impact on agriculture, particularly in the Chesapeake watershed. This month, it examines some of the impacts that agriculture has had the region, especially in Pennsylvania.

Pennsylvania’s Lancaster County—partly because it was south of the great continental glaciers’ scouring effect—has wonderful, deep agricultural soils. They were a magnet for settlers from the Chesapeake, particularly the followers of William Penn after 1683, who migrated to the hinterlands to clear and farm these deep soils.

Yet some reports indicate that erosion stripped all of the topsoil in some areas within a quarter century: In 1753, “Our runs (streams) dry up apace, several which formerly would turn a fulling mill, are now scarce sufficient for the use of a farm.” Another records: “Creeks mentioned by Mr. Penn to be navigable, are no longer so.”

Agriculture spread in successive waves across the land as some of the earlier settlers migrated deeper into Pennsylvania.

Pennsylvania’s loss of soil and the environmental integrity of its streams had causes beyond agriculture. These included the timbering of the state’s vast woodlands. By the Civil War, most of the remaining forests were cut to make charcoal. In Lancaster County, this was used to sinter limestone to make lime to condition the soil.

Coal mining, which released highly acidic waters to surface streams, also denuded forests: In the 1890s alone, 140,000 acres were cut annually to supply the wooden props used to support walls and roofs in mine tunnels.

But from the first, most of the cleared land went into agriculture, feeding as well as supporting the trade of a new nation.

Pennsylvania’s farmers had less success than their neighbors with tobacco and after a series of collapses in the lucrative European and British tobacco markets, they and farmers throughout the Chesapeake region considered other strategies.

One answer was grain crops, notably wheat. Even Thomas Jefferson pointed out that wheat was easier to produce than tobacco and worth more in the final analysis. (See Past is Prologue, July-August 2004.)

During the Napoleonic Wars in the early 19th century, the British fleet carried on a massive blockade of France’s Atlantic ports. Hundreds of ships loaded with U.S. grain went elsewhere or risked capture and confiscation. The market became wildly overpriced under such conditions. Meanwhile, plantations in South America and the Caribbean were relying on food imports to feed their massive labor populations devoted to cash crops like sugar and rum.U.S. agriculture prospered under these conditions.

To keep up with demand, magazines from that period featured articles touting more aggressive farming techniques. Farmers began to apply animal manure or South American and Pacific guano—bird droppings mined from massive seabird colonies—on fields (See Past is Prologue, October 2002). They were also liming their cropland with “marl,” nutrient-rich fossil materials mined for this purpose.

All of these techniques presaged the subsequent use of massive amounts of chemically synthesized fertilizers (See Past is Prologue, December 2002).

The nutrient loads from these practices and erosion from heavy plow-based tillage across the watershed were massive.

On a journey this April in Pennsylvania’s Lancaster County, I stopped near Octoraro Creek, which discharges into the Susquehanna. A fine forest canopy rose above me. Because of the steep terrain, it seemed unlikely that this was ever logged. The stream, busy from spring rains maintained a low roar, furthering the illusion that this place was unspoiled. But upon inspecting the stream channel higher up, one could see that outside the riffles over rocky substrate, broad fans of sediment had been deposited in the stream’s slower portions.

This is Pennsylvania’s forest floor and farmland being borne downstream toward the Chesapeake via the Susquehanna, which carries almost half of the freshwater discharged into the Chesapeake Bay.

Since its construction in the 1920s, Conowingo Dam has trapped about 70 percent of sediments that would have otherwise been deposited downstream. But Conowingo will begin releasing its loads, especially when its storage capacity for sediment is exceeded, which the U.S. Geological Survey predicts will take place in about 15 years.

It already happens when major storm systems roar turbulently through the Conowingo pool upstream of the dam.

The only way to prevent future loads from entering the upper Chesapeake, is to stop them at their sources farther upstream.

Above the Conowingo Dam, each in a series of dams stretching toward the Susquehanna’s source on Lake Oswego, NY, stores sediment. Many are at or near saturation for sediment storage. The cascade could be prodigious.

My journey continued across the sunlit farmland of Lancaster, rolling fields in various states of tillage or sprouting crops which stretched to the horizon. It is an iconic U.S. rural landscape, among the nation’s most productive agricultural regions, but it has produced a lot of sediment.

Dr. Bob Walter, who is on the faculty at Franklin and Marshall College in Lancaster, offered an in-depth look at the generation of sediment through Lancaster County’s history.

The area was settled in the 1600s, and serious cultivation was under way by 1720. By the mid-18th century, grains production exceeded local needs and was being exported.

A former Franklin and Marshall professor, the late John Moss, estimated that about half of Lancaster’s original 16 inches of topsoil has been lost to erosion. The county’s streams deliver more sediment per acre than any other part of the Susquehanna drainage, with the exception of strip mining sites in the northcentral Pennsylvania. The total Lancaster County load already represents millions of tons of topsoil lost.

Eventually, grain was being grown on 80 percent of the county’s land area. This was before the development of a long-distance road system, making local grist mills a necessity.

Research by Walter and his colleague Dorothy Merritt, also of Franklin and Marshall, has inventoried the grist, fulling, saw and other water-powered mills constructed in Lancaster County over nearly three centuries, including 500 erected by the mid-1800s, including at least one grist mill still in business (See “Rohrer’s an extraordinary run-of-the-mill experience, Bay Journal, September 2004).

Walters calculated that on average, there was one mill for every two miles of stream length. He took me to a former mill on the West Branch of the Little Conestoga River. Pointing upstream, he noted that there were 10 mills—one for every kilometer.

We walked with the former owner of the mill, which has since been refurbished as a home. Stonework rose 10 feet above us as we walked along the channel. It was the mill race, which conducted water from a dam to the mill wheel. On both sides of the stream were remnants of a dam that was breached long ago when the pond above filled with sediment and no longer stored enough water to make the mill work.

The stream thereafter engaged in a process called down cutting—sawing its way through a wall of sediment that records at least 300 years of Lancaster’s history.

Downstream, mud and silt banks stretch away down a bend, tracking the course of this sediment on its way toward the Chesapeake with each successive storm.

Walters, with gestures of his arm, offered a tour through time: “There at the bottom, you see the stones over which this stream used to flow. Look at the fine peaty material formed over that.” After a discussion, we conclude such features could have been beaver dams. “This layer dates with carbon-14 to about 1690.”

This dam was erected in 1730, and would have held back a substantial pond. “Look there,” Bob said, indicating leafy debris, just a little higher in the cross section, which he said sometimes had wood in it. “That material dates from about 1760.” Is this the clearance of forest from the surroundings as agriculture advanced?

A few yards above this rising is a clean-cut wall of sediment nearly 20 feet high, with layer upon layer of distinguishable sediments. It is unclear whether these represent annual cycles, or major storm events or some blend of the two. These are leaves in a book about the history of this watershed, which require only a reader with the requisite skills.

About 60 percent of Lancaster County is still agricultural land, and there are large communities of Amish and Mennonite farmers still cultivating and harvesting using 19th century technology. They are self-sustaining, live off the electrical grid, and do not accept government assistance.

This also means that conventional media appeals for modern ideas about fertilizer use, and the effects of nitrogen, phosphorus and sediment on downstream communities do not reach them as effectively.

Even the farmers outside these communities who do get these messages are not necessarily putting best management and nutrient management practices into use.

With 300 years of sediments still in the riverbeds and banks, moving onward incrementally and in high flow episodes. I don’t see the muddying of our waters decreasing in my lifetime.