Monday, September 19, 2016

Urban soils

The upcoming Field Day at Downing Park Urban Farm in Newburgh will focus on urban soils and a partnership between the farm and the New York City Urban Soils Institute (USI). The farm is open during the regularly-scheduled Field Day on Saturday, September 24 from 10am-noon and the community is welcome to tour the site and learn about its features and history. Tatiana Morin, Director of the USI, will be on site offering free examination of soil samples brought by residents. Her agency’s goal is to advance the scientific understanding of urban soils and promote conservation and sustainable use.

Downing Park Urban Farm, on the corner of South Street and Carpenter Avenue in Newburgh, was formerly a space for replacement stock used to maintain the gardens of the adjacent Downing Park. The facility was maintained by the City and employed about 30 workers. Until the middle of the century, varieties including irises, tulips, serviceberry, American hazelnut, and coffee trees were grown and stored here. “It was a highly choreographed horticultural operation—and also expensive” said farm manager Marcel Barrick who oversees the site and is involved in its restoration. “Workers would take the bulbs out in fall, winter them up here, and replace them in spring. Trees and shrubs were grown and stored here, too.”

The site of the farm has features that are not uncommon in other urban soils. Some of the elevated sections of the property rest on a hardpan, a hardened and impermeable layer that impedes root growth as well as the movement of water and gasses. Hardpans can be a natural feature but are not desirable on land intended for farming. Barrick explained the hardpan was discovered early in the renovation when after rain storms he noticed water squishing out of the hill along South Street. He said a coal-fueled glass greenhouse sat near the center of the property until it was dismantled. The site has varying levels of coal ash piles, known as slag, from the greenhouse’s furnace. Tests on this site revealed heavy metals such as zinc, lead and arsenic. “It’s an ongoing process,” he said. “The main contamination is at the greenhouse site.” 

In the past, cement sidewalks helped workers move carts around the property but these were removed during renovation, exposing heavily compacted ground. In parts of the hardpan Barrick planted tillage radish, also known as daikon radish, a breed developed to produce a large taproot that penetrates compacted soil. As this variety grows it pushes large thick roots down into ground then dies in winter creating a void, giving the roots of crops planted in later seasons a head start. The large taproot also helps with nutrient retention. The thick roots absorb and retain nutrients that would otherwise be lost when the field is unused in winter.  

At the southwest corner of the farm is a debris pile on a steep slope which Barrick suspects is an old dump site for construction and roadwork projects. He cleaned much of the human-transported material including concrete, asphalt chunks, and construction debris. Glass from the old greenhouse turns up periodically on site. “This is the reality of urban soils and the issues faced by agriculture in modern cities,” said Barrick.

Adjacent to the farm’s demonstration garden is one of two storm water management ponds. A berm system directs water from the road away from the sewer and into the 2’ by 2’ pit. Barrick planted tillage radishes in the pit to experiment with getting water down into the soil.

An unusual element found during renovation is a large smooth rock found underground near the South Street entrance.  It took Barrick weeks to extract the rock with a hydraulic jack and hand tools. It hid only about a foot underneath the soil, but its size and texture make it an unusual find at this site. Barrick also found a round glass fragment during his work.

While urban soils present their own unique issues when it comes to farming and food production, researchers worldwide are discovering what works in terms of remediation and conservation. Barrick encourages residents to take advantage of the free opportunity to meet with the Urban Soils Institute during the Field Day event. The USI is a partnership of Brooklyn College, USDA Natural Resources Conservation Science, and the NYC Soil Water Conservation District. Samples are examined with a handheld XRF spectrometer that supplies energy in x-ray form. Elements will fluoresce in a frequency that indicates lead, cadmium, arsenic or other heavy metals.

“We want people to be confident that their soil is sound and that they can grow healthy vegetables,” said Barrick. “If soil is contaminated, we’ll talk about how to get around these issues.”

Downing Park Urban Farm:

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