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Chemistry

Common Ground

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    Professor Leslie Sherman takes soil samples on a pineapple plantation in Costa Rica.
February 26, 2013
During her sabbatical in Costa Rica, chemistry Professor Leslie Sherman studied how intensive agriculture affects tropical soil, and witnessed one of nature’s most magical events.

It’s a hike from Chestertown, Md., to Guapilis, Costa Rica—about 2,100 miles in fact—and the long, flat fields of Maryland’s Eastern Shore are a world away from the lush landscape and tropical fecundity of Central America. Connection, though, is all about common ground, and Professor Leslie Sherman found plenty of that during her recent sabbatical at EARTH University.

Sherman, Washington College’s W. Alton Jones Associate Professor of Chemistry and director of the Environmental Studies program, is a soil scientist, and much of her work at WC has focused on the native grassland restoration project at the Chester River Field Research Station at Chino Farms. There, she examined how changing the land use from traditional agriculture (corn, soybeans) to native grasses affected soil long-term. Traveling to Costa Rica on a faculty enhancement grant, she studied the same issue, only here the crop was pineapples, and the question focused more closely on a single intense land use over time.

“I’ve always wanted to study a tropical system both because the soils are fascinating and because the agriculture is so different,” Sherman says. She based her work out of EARTH University, which offers students from Latin America, the Caribbean, Africa, and Asia a program in agricultural sciences and natural resources management. Three students from Mozambique, Ecuador, and Bolivia helped Sherman with her with lab and field work.

Pineapples are a major crop, and Sherman was curious how the plants manage to grow so well on highly weathered, nutrient-poor soils, especially considering how densely planted they are—about 75,000 plants per hectare (2.5 acres)—and how intensely they’re managed with pesticides and fertilizers. “In three years you get two whole crops. So it’s incredibly productive. I was interested in how these decades of highly intensive agriculture are impacting the soil quality. It’s still productive, but is anything happening in the long run?”

Sherman studied one plantation, taking samples in plots five to seven years old and plots 25 years old, as well as samples from a bordering pasture, a remnant of a previous land use. She found that the organic matter, which provides structure for the plants, nutrients, and helps keep the soil moist, was not degraded in the cultivated plots, probably because after every planting cycle, the growers chop all the residue plant material and mix it into the soil. “After every crop they did this, and since it was the tropics it gets incorporated very quickly.” However, the older plot showed a build-up of acidity being held in the soil, which in the long run may prove to be a problem.

Sherman also explored some of Costa Rica’s world-famous biological diversity and natural beauty. One of her favorite trips was to Tortuguero National Park, where she witnessed one of nature’s most miraculous and mysterious events, the arribada, or arrival, of female green sea turtles. After traveling thousands of miles through unknown reaches of the sea, for one night they come ashore to the beach where they themselves hatched to lay their eggs in the sand. The spectacle, she says, “was just amazing.”

Much of what she learned will make its way into her classes, from discussions about the tension between conservation of biodiversity and the necessity of agricultural operations, to the potential benefits of ecotourism to help protect endangered species such as sea turtles. Sherman will be writing up her findings during the summer and presenting them at the Soil Science Society of America conference in the fall.

 


Last modified on Feb. 26th, 2013 at 2:28pm by Wendy Clarke.