21 November 2024

9 minute read

By: Global Ag Media

North America

Joshua Faulkner squats in a corn field, scooping out the insides of a hole. He holds a handful of dark grey soil and squeezes it like a sponge. Beside him, a row of yellowed winter rye shakes in the wind.

“It’s a little dry,” Faulkner says. “… But not bad. Everyone is crossing their fingers that we don’t have a repeat of 2023. It really didn’t start raining last year until mid-July.”

He was referring to the statewide flooding in July 10-11, 2023, that devastated feed and vegetable crops and caused about $69,000,000 in agricultural damages. (Despite crossed fingers, flooding occurred on the one-year anniversary.) A 2023 survey conducted by the Vermont Agency of Agriculture, Food & Markets found that nearly 34% of respondents said their most significant losses were to feed crops, with the average suffering $61,000 in losses.

After the 2023 floods, water gauges along three Vermont rivers Faulkner monitors indicated phosphorus levels three times higher than the previous two summers. With leakage from agricultural fields common after heavy rains, could there be alternative ways for dairy farmers to limit nutrient runoff and increase their resilience to extreme weather events?

“Can a dairy farm sequester as much carbon as they emit in their production system? Can a dairy farm be net zero?” asks Faulkner, a research associate professor at the University of Vermont. “In order to [answer] that we have to measure a lot of things.”

That is why Faulkner is gathering soil samples in the middle of a corn field in St. Albans one morning in June. He is part of a team of UVM researchers investigating how to make Vermont’s dairy production more sustainable. They are midway into a six-year study called the Dairy, Soil, and Water Regeneration project administered by the Soil Health Institute, that involves seven universities and spans farms from Vermont, Wisconsin, Texas, Idaho, and California. The idea is to test how methods such as cover cropping, no-till planting, and different fertilizer applications affect water quality, crop yield, economics, and greenhouse gas emissions.

“A lot of the public thinks that greenhouse gas emissions in agriculture are mainly diesel fuel and electricity, and they are not,” Faulkner says. “They come from soil emissions and from manure. So, we are measuring gas emissions from these systems to see if we can determine if this new approach to growing feed and managing soil not only helps with resilience but helps with mitigation at the same time.”

Faulkner pounds a slide hammer into the soil and pulls a long tube of earth from the ground. The sample will be used to test the soil’s bulk density, water holding capacity, and carbon concentration. Higher compaction means less space for air and water and organic matter. It means less healthy soil.

“Low bulk density that is a really good thing,” Faulkner says. “It means the management practices of the farm are working.”

Protecting a valuable resource

In spring, once the trees have leafed out, Vermont’s hillsides seem to glow. The landscape becomes a solid emerald wall, bisected by the occasional dirt road. The Green Mountain State’s lushness is tightly linked to water and, sometimes, we get more than we can handle.

In 2011, nearly every waterway in Vermont flooded during Tropical Storm Irene. Afterwards, UVM Extension launched the Farming and Climate Change Program—the first in the nation of its kind—and tapped Faulkner to lead it. The timing comes as extreme weather events are more common across New England, creating additional risk for farmers, and flooding our rivers and lakes with sediment, phosphorus, and nutrient runoff. These events also carry away topsoil.

“There is no question that soil is the most valuable resource on the farm,” Faulkner says. “If we lose our soils, they take years, in some cases, hundreds of years, to build back. How do we conserve those soils and really maximize [their] health … so that they are sustainable in the long run, but they also maintain productivity for the farm?”

Building soil health can improve resilience from extreme weather events as living roots in the ground hold soil in place, reduce agricultural runoff, and soak up excess moisture. Practices such as reducing tillage and implementing crop rotation provide additional benefits, reducing erosion and adding nutrients back into depleted soil. But how do various fertilization and drainage techniques affect water quality? How does soil health and various management practices impact carbon emission and sequestration?

“It takes a tremendous amount of data to help answer those questions,” Faulkner says. “So that means a lot of time in the field. A lot of sampling work. A lot of runoff water quality measurements.”

The UVM team runs variations of the national experiment on two sites—one in St. Albans, another in Bridport—that collect data such as soil moisture and oxygen levels in 15-minute intervals using sensors that feed results to researchers back in the lab. All of the plots use cover crops and receive fertilizer, but the way fields are tilled differs, as well as how manure is applied.

“On the business-as-usual [approach] it goes on the surface, Faulkner explains. “On the advanced soil health management practice fields, the manure gets injected underground. That way, you avoid runoff, and hopefully you conserve more of the nutrients.”

Differences may emerge across a field managed the same way. Faulkner points to a lower point in the corn field where the corn stalks are a shade or two paler than the dark green plants on higher ground.

“That might be where water ponds,” he says. “The soil might be very different … because there is saturation occurring. So, we are looking at high points and low points across this field.”

The mound of soil at Faulkner’s feet looks like clay one could throw on a pottery wheel to make flatware. This is characteristic of the Champlain Valley in Vermont, where clay makes up a significant portion of the soil and can make drainage difficult when heavy rains fall.

“It’s 60 to 70 percent clay in some places,” Faulkner says. “But the farmers here have learned how to work with it for years and years and years. But it is not an easy soil … it goes from like butter to brick within a few days. It is just a very narrow window.”

Testing field emissions

Across the field, Molly Ratliff, a graduate student in the Rubenstein School for the Environment, is zipping a plastic bag filled with nuggets of soil. She is a core part of the UVM team examining emissions—a time intensive effort that involves regular travel to the Bridport site to collect soil samples and measure carbon dioxide, methane, and nitrous oxide readings in real-time. She joined the project in July 2023—just before many of Vermont’s farm fields were inundated with floodwaters. While the experiment sites were not underwater, standing water from heavy rains sat on the fields.

“Especially in Bridport, where there is even heavier clay soils that don’t drain,” she says. “There was standing water for months.”

Ratliff noticed the corn didn’t grow in those locations and flagged unusual emissions readings. Methane gas was coming off the field—the result of oxygen starved microbes in the soil.

“Usually, methane is only produced in environments without oxygen when standing water is on the soil for long periods of time,” she says. “... Just another negative consequence from the flooding.”

Ratliff’s thesis will compare emissions and soil health differences between high and low points of fields. The low spots in the field are usually considered hotspots for gas emissions because there is usually more substrate available—more carbon and nitrogen—and greater soil moisture,” she explains. “But I am curious what happens when these high spots are inundated too—are those also hotspots for gas emissions?

“And how can we translate that to how we manage our field?” she continues. “Maybe grading a field or trying to get rid of low spots is maybe more important than how we manage the manure – or something like that. I’m always trying to relate it back to the practical applications.”

That is the hope of this nationwide study—to determine if and where certain management practices make sense for dairy farmers to adopt. Analyzing emissions over time across several regions will also help researchers uncover if soils on dairy farms are a sink or source of greenhouse gases. Ratliff suspects they will likely find tradeoffs that farmers need to weigh.

“If we find something that is beneficial for gas emissions then maybe it’s not so great for runoff, or for the yield of the corn,” she says. “… Maybe one practice is better for clay soil whereas one practice is better for more loamy soil. Those benefits could be similar for greenhouse gas measurements too.”

One thing she is more certain of is that the emissions from soil will change along with the climate.

“Soil moisture is definitely a driver of greenhouse gas emissions and nitrous oxide emissions. It definitely influences the microbes and the soil temperature,” she says. “And the expected future of climate change—increasing soil moisture, increasing temperature—will both likely impact gas emissions.”

The first rigorous documentation

Ben Tutko hauls a bucket and shovel between rows of corn. He comes after big and small rains to monitor water and runoff at the experiment sites.

“Sometimes we show up and there are no samples,” says Tutko, a water quality research specialist with UVM Extension. “For instance, if it’s dry like this and you get a half inch of rain, I wouldn’t be surprised if there were no runoff samples … but you still need to check.”

In 2023, he visited sites multiple times every week as the rain came and never seemed to turn off.

“It was fast and furious,” Tutko says. “It didn’t stop until maybe April of this year, maybe May.”

He pauses at the feet of Joshua Faulkner who is digging another hole to sample.

“Wettest winter in some parts of new England,” he says, looking up. “It was wet for 10 months. The season started for some farmers with the late frost too, which was really tough for the fruit growers.”

As they work, they reflect on the challenges of farming in changing climate where winters are warming and rain on snow events are more common.

“Runoff can occur any time of the year, it’s not just when it’s actively being farmed,” Tutko explains. “And that is why planting cover crops through the wintertime is important because it keeps that soil in place.”

“Another thing that we are seeing,” Faulkner says, “And there is a good UVM paper on this, is more of the nutrients running off in the winter than used to happen because of the snow melt and the warmup periods in the winter.

“… There is a silver lining in this,” he continues. “The growing season is getting longer, so that is good for farmers in some ways.”

That is, if farmers can manage the uncertainties of weather and water. Because the other side of the climate change coin is drought. Soil samples from the study will indicate their available water holding capacity.

“This is probably a lot more of a critical measurement for the sites in California, for example, versus us where drought happens, it’s not the rule,” Faulkner says scraping the soil. “I think if we can learn how to manage the excess water that we will be okay. … If we can store water, it might be able to buffer those drought periods.”

While they are still a year away from having hard numbers to share, Faulkner is interested in what the study will more broadly reveal about the sustainability of dairy farming.

“This is the first time we’ve taken whole systems look at dairy forage production,” he says. “The other thing is the soil’s ability to sequester carbon. And some people have taken measurements here and there, but this is the first rigorous documentation of that in our dairy systems. And it may be different in Wisconsin than it is here in Vermont and different in California or Texas. We need that local information.”