Climate Change's Effects on Kentucky Horse Pastures

Climate Change's Effects on Kentucky Horse Pastures

McCulley and her team use infrared radiant heaters to warm the air to study how climate change could affect Kentucky pastures' composition and what those changes could mean for forage quality.

Photo: Danny Walls

Rebecca McCulley, PhD, a grassland ecologist and researcher in the University of Kentucky College of Agriculture's Department of Plant and Soil Sciences, is studying how climate change could affect Kentucky pastures' composition and what those changes could mean for forage quality.

McCulley's Experiment

McCulley and her team use infrared radiant heaters to warm the air to study how climate change could affect Kentucky pastures' composition and what those changes could mean for forage quality.

McCulley's study--which she began in 2008--examines how predicted increase in temperatures, changes in rainfall amounts, and a lengthened growing season might impact pastures.

"We are looking at a higher carbon dioxide world," she said. "There is uncertainty, but it will get warmer. An altered climate will affect what horses and cattle eat. We just don't know how the changes will unfold."

A few years into her study, McCulley is able to predict that forage quality won't take much of a hit.

"At this stage, a warm and wet Kentucky will be weedier, and it will have a lot of crabgrass," McCulley said. "But tall fescue and Kentucky bluegrass will still be around. Crabgrass will be more prominent in the future pastures of Kentucky; the real test will be to see if animals respond by eating it."

The project, which is based on pasture representative of a typical Central Kentucky landscape, contains common hay field species: tall fescue, Kentucky bluegrass, red clover, white clover, bermudagrass, crabgrass, and other common weed species. McCulley said her team has neither applied fertilizers, nor have they done any reseeding. Johnsongrass has been removed by hand. The grasses and legumes were planted in 2008, whereas crabgrass and other weedy species were recruited from the seed bank or grew naturally. The project encompasses 20 plots, each receiving one of four different treatments:

  • Ambient conditions;
  • Added heat;
  • Added precipitation; or 
  • Added heat and precipitation. 

For the added precipitation treatment, rain and runoff from an equine barn at the Maine Chance Equine Campus is applied to mimic natural weather patterns, only intensified--researchers apply 30% more precipitation during rainfall events than the long-term historical growing season amount. They use infrared radiant heaters to warm the air, and added heat and precipitation plots 3ºC (5.4ºF) above ambient temperatures.

McCulley and her team used traditional metrics to test the forage. They gathered "grab samples," which are randomly collected grasses and weeds--whatever is growing in the plot--or enough to fill a large paper bag. The remaining grass is then cut and removed to simulate haying.

The team has measured forage quantity and quality each year in June, July, and September since 2009.

"There are small shifts in forage quality, but overall the significant changes are in plant species composition," she said. "We are finding that forage quality is okay. Annual crabgrass has become dominant in the added heat treatments. The added heat plots tend to be weedier, with pretty big weeds."

With another two years left in the study, McCulley said that a nitrogen application is possible.

"We're trying to strike a balance between experimental constraints and the real world management scenarios," McCulley said.

Karin Pekarchik is an editorial officer in UK's Agricultural Communications Services.


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