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Soil Ecosystems: Maintaining Critical Microbial Life

earthworm soil life.tifSoil ecosystems aren’t always the first things people notice when they are in nature.

When asked to describe a forest or a meadow, most people would probably begin with the plants, the species diversity or the color of the foliage. They probably wouldn’t pay much attention to the soil ecosystems and the critical microbial life. But a new Yale-led study shows the importance of earthworms, beetles and other tiny creatures to the structure of grasslands and the valuable soil ecosystem services they provide.

During a 3-year study, researchers found that removing these small animals from the soil of a replicated Scottish sheep meadow altered the plant species that grew in the ecosystem, reduced overall productivity and produced plants that were less responsive to common agricultural management, such as fertilization.

The results reflect the long-term ecological impacts of land use changes, such as the conversion of forests to agricultural land, researchers say.

“We know these soil animals are important controls on processes which cause nutrients and carbon to cycle in ecosystems, but there was little evidence that human-induced loss of these animals has effects at the level of the whole ecosystem on services such as agricultural yield,” said Mark Bradford, lead author of the study published in the Proceedings of the National Academy of Sciences.

This article appears in the December 2014 issue of Acres U.S.A.

Soil Ecosystems: Nutrient Additions

New research from Iowa State University shows that agricultural inputs such as nitrogen and phosphorus alter soil microbial communities and soil ecosystems. Adding nitrogen and phosphorus fertilizers, commonly used as fertilizers, to the soil shifts the natural communities of fungi, bacteria and microscopic organisms called archaea that live in the soil, said Kirsten Hofmockel, associate professor.

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Hofmockel and other scientists associated with the Nutrient Network, a global group of scientists, revealed that microbial community responses to fertilizer inputs were globally consistent and reflected plan responses to the inputs. Many soil microbes perform helpful functions in the native ecosystems and altering those microbial communities may have negative environmental consequences, Hofmockel said. The researchers found nutrient additions favored fast-growing bacteria and decreased the abundance of fungi that share a symbiotic relationships with grassland plants.

This encapsulation of the research is from the December 2015 issue of Acres U.S.A.

Soil Ecosystems: Synthetic Nitrogen Lingers for Decades

Nitrogen fertilizer applied to crops lingers in the soil ecosystems and leaks out as nitrate for decades towards groundwater — “much longer than previously thought,” scientists in France and at the University of Calgary say in a new study.

Thirty years after synthetic nitrogen (N) fertilizer had been applied to crops in 1982, about 15 percent of the fertilizer N still remained in soil organic matter, the scientists found.

After three decades, approximately 10 percent of the fertilizer N had seeped through the soil ecosystem toward the groundwater and will continue to leak in low amounts for at least another 50 years.

The findings show that losses of fertilizer N toward the groundwater occur at low rates but over many decades, says Bernhard Mayer, U of C professor of geochemistry and head of the Applied Geochemistry Group.

That means it could take longer than previously thought to reduce nitrate contamination in groundwater, including in aquifers that supply drinking water in North America and elsewhere, he says.

“There’s a lot of fertilizer nitrogen that has accumulated in agricultural soils over the last few decades which will continue to leak as nitrate towards groundwater,” Mayer says.

Canada and the United States regulate the amount of nitrate allowed in drinking water. In the 1980s, surveys by the U.S. Environmental Protection Agency and the U.S. Geological Survey showed that nitrate contamination had probably impacted more public and domestic water supply wells in the United States than any other contaminant.

The study, “Long-term fate of nitrate fertilizer in agricultural soils,” was published in the Proceedings of the National Academy of Sciences.

This summary appears in the December 2013 issue of Acres U.S.A.

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