Earthworms are not indigenous to the Northern woodlands. The last ice age meant extinction for earthworm species anywhere where the glaciers reached. Earthworms only returned to the northern parts of North America with the early settlers. Now there are 17 species that we know of in Vermont. Some effects of earthworms on ecosystems have been documented. Yet, there still is much to be learned about their modification of forest soil physical, chemical and biological processes. Furthermore, it seems that much needs to be learned about the way that some of the more invasive earthworms adapt to new environments. Ryan Melnichuk (PhD student, Class of 2014) is currently working on soil chemical changes and greenhouse gas emissions caused by earthworms. Meghan Knowles (Class of 2014, MS student with Don Ross) is investigating the distribution of carbon in forest soils with and without earthworms. Funding of her study is provided by the Northastern States Research Collaborative (http://nsrcforest.org/)
A side-line of this research is looking into how horticultural ecosystems are affected by earthworms, particularly by
Amynthas species. In Vermont, Amynthas agrestis are found in forests, home gardens, nurseries etc. Some damage to plant material, such as Lady Slippers, may be caused by Amynthas. What causes the loss of plants is not clear. There are no obvious clues in any of the nutrient analyses of the soils from the Lady Slipper beds. Speculatively, the modification of soil structure into Amynthas‘ hallmark aggregates may disrupt the roots and their mycorrhizal associations.
Presently, Vermont organic farmers are still permitted to use Chilean nitrate to boost plant nutrition during the early growing season. Chilean nitrate may soon be decertified as an organic amendment in Vermont, as it has in other states already (http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELPRDC5088619). It mainly comprises sodium nitrate. Nitrate is nitrate is nitrate whether it comes from the chemical factory or the Atacama desert. With an analysis of 16-0-0 and most of the nitrogen in nitrate form Chilean nitrate is very susceptible to leaching and denitrification.
Peter Austin (MS student, Class of 2014) is studying fast acting organic replacements for Chilean nitrate. The study is funded by Northeast SARE (http://www.nesare.org/Grants). Rachel Schattman of Bella Farm is our farming partner. Compost is provided by Highfields Center of Composting (http://www.highfieldscomposting.org/) in Wolcott Vermont and Wormpower (http://www.wormpower.net/) of Avon , NY. Thanks to their enthusiastic support for the project.
Pasture Compaction and Rejuvenation Research
In rotational grazing cows remain in small paddocks for only a short period of time before they are moved on to the next one. This gives pastures a longer time to recover between grazings. This benefit is offset by high stocking rates that can result in soil compaction. Many hoofs make for compacted soils. The objective of a CIG and SARE funded research project was to observe how keyline plowing, a subsurface tillage method, and tillage radishes (Daikon) may mitigate effects of compaction. In both cases deep macropores are created that would cut through compacted layers and improve infiltration.
Effect of Flooding on Soil Fertility
Climate change may bring about greater flooding frequencies on some of the best farmland in Vermont. The impetus for this research was the prolonged spring flood of 2011 that put farmland under water for weeks as well as the flooding that was caused by tropical storm Irene in 2011. A similar spring flood occurred this year (2013). Lindsey Ruhl (MS student) obtained two SARE grants to measure fertility in flood prone fields as a function of micro-topography and evaluate cover crops as ways to manage flood damage.