Posted: January 9, 2018

Can a dairy farm be profitable while protecting the environment? Penn State's virtual model for dairy farms may have the answer.

The cows may be virtual, but the feed and farm fields used to produce their food are real. It's this authenticity that enables the researchers who run the Sustainable Dairy Cropping Systems Project--situated on a 15-acre experimental farm at the Russell E. Larson Agricultural Research Center at Rock Springs, 10 miles southwest of the University Park campus--to realistically analyze milk profits and environmental impacts under various farming scenarios.

"Crops for dairy production are the biggest use of agricultural land in Pennsylvania, and dairy milk is the top agricultural commodity in terms of dollars sold," says Heather Karsten, associate professor of crop production. But dairy farmers often struggle financially. According to research by the Penn State Extension Dairy Business Management Team, the average dairy farm spends half its income on home-raised and purchased feed.

"We're testing whether it's feasible for dairy farmers in Pennsylvania to grow all of the feed and forage they need using less fertilizer, pesticide, and even tractor fuel, while still remaining profitable," says Karsten.

To test whether new techniques can reduce impacts to the environment and help farmers profit, Karsten and her team, which includes Penn State faculty and staff members, graduate and undergraduate students, and scientists at the USDA Agricultural Research Service, are investigating two innovative farming strategies:

  • manure injection
  • reduced herbicide and insecticide

The team is examining these strategies in "closed-loop" systems; in other words, the farms produce their own feed and forage--such as alfalfa, corn, rye silage, soybeans, sorghum sudangrass, and canola--grown in two six-year rotations. The farmers provide this feed and forage to their cows; the cows produce manure; and the manure fertilizes the crops. This approach minimizes the amount of feed the dairy farmer needs to purchase, as well as utilizes all the manure produced.

Business as Usual

According to Karsten, the need for such a model is great, given the numerous struggles dairy farmers often face. For one, she says, most dairy farmers in Pennsylvania must supplement the corn silage and alfalfa grass forage crops they grow for their cows with costly grain mixes or supplements.

Heather Karsten
Heather Karsten, associate professor of crop production

In turn, the cows produce manure, often much more than the land can handle. "Dairy farms often end up with more manure than cropland to spread it on, which contributes to the challenge of protecting water quality and meeting nutrient management regulations," she says.

In addition, many Pennsylvania farmers--66 percent, according to the last national agricultural statistics survey results--use a no-till strategy, which means they do not plow their land. "No-till conserves soil, protects water quality, and improves soil health; it also reduces fuel and labor needs, but it poses other management challenges," says Karsten. For example, she says, without tillage--the agitation of soil to prepare for a crop to be planted--to return manure to the soil, dairy manure must be broadcast on the soil surface, where it can run off into waterways, and ammonia in the manure can evaporate into the air, returning as precipitation to surface waters.

Another problem with no-till is that farmers have come to rely on herbicides--usually Roundup--to control weeds on their genetically modified Roundup Ready corn and soybean fields instead of tillage to disrupt the weeds in the soil. And the use of Roundup presents its own set of problems. "Crops engineered to withstand Roundup have contributed to weeds evolving resistance to the Roundup formulation," says Karsten.

Roundup isn't the only herbicide used; without tillage to plow their crop residues under at the end of the season, farmers often turn to a variety of herbicides to terminate their crops and make way for the next crop. And herbicides can harm nontarget organisms, such as aquatic organisms and that provide habitat for pollinators and other beneficial species.

In addition to herbicides, farmers commonly use pesticides to protect their crops. For example, they use Bt (Bacillus thuringiensis) corn, which is engineered to produce a protein that is toxic to many insects, but they often still apply insecticides to kill other insect pests.

Reducing Pests

These extra applications of insecticides are unnecessary; John Tooker, associate professor of entomology, is demonstrating why. He and his colleagues are studying the effectiveness of integrated pest management (IPM) practices. IPM uses a variety of techniques to control pests while also minimizing impacts to the environment.

Specifically, Tooker and his students are comparing invertebrate populations in the injected manure, reduced herbicide model to those in the broadcast manure, standard herbicide (conventional) model. "It's pretty clear that most of the pests are in the conventional model," says Tooker. "In the innovative model we see more natural enemy populations and fewer slugs. It's really informed my view of how farming can be done."

Why do the innovative strategies do a better job of maintaining insect enemies and reducing insect pests?

In the conventional model, says Tooker, many farmers, in addition to using Bt crops, also apply an insecticide at or shortly after planting to deal with pests like black cutworm or true armyworm. "They use it as a kind of insurance against pests," he says.

The problem is that insecticides kill not only the pesky pests but also the natural insect predators. "It's like telling a general, 'I can kill your enemy, but in doing so I will kill 95 percent of your own troops,'" says Dave McLaughlin, who owns a 525-acre dairy and crop farm in Elliottsburg, Pa.

With Tooker's guidance, McLaughlin implements IPM practices on his farm, including scouting the crops and looking for specific pests. When he finds them, he uses an insecticide that is specific to those species, knocking them back while maintaining the natural insect enemy populations.

Another aspect of IPM is the use of cover crops, which are grown in between the primary income-generating crops. "It minimizes insect pests by confusing them, so they never know what to expect from season to season and year to year," says Tooker. It also provides habitat for beneficial insects, he adds.

McLaughlin is now a firm believer in the value of IPM. "My goal is to maintain and increase my beneficial insects and let nature take its course; you can't do that if you're constantly bombarding the environment with insecticide."

McLaughlin notes that since he first implemented IPM eight years ago, he has only had to use insecticides twice. "I look at the entire farm operation from a 'systems approach'; everything is working together to make the whole system work, and part of that is the IPM and the increase in my beneficials."

Unfortunately, the majority of farmers still are not using IPM. "Too many farmers blindly take the advice of their agronomist or other professionals who don't want to be responsible for farmers losing their crops, so they recommend insurance applications," says McLaughlin.

It's what makes Tooker's efforts on the Sustainable Dairy Cropping Systems Project so valuable. "This study shows that IPM has value; it works," says Tooker. "And more importantly, we've shown that there is more value in IPM than in the preventative practices."

Controlling Weeds

Reducing reliance on another troublesome input--herbicides--is also a goal of the project. "For farmers, weed management is an ongoing battle," says William Curran, professor of weed science, who is leading the effort. Curran and his colleagues are developing strategies to combat weeds while reducing reliance on herbicides, which cost a pretty penny--farmers spend anywhere from $30 to $100 an acre for herbicides used in growing corn and soybeans. "The bottom line--the less we rely on herbicides and the more we can diversify weed control, the better," Curran says.

William Curran
William Curran, professor of weed science

Curran's experiments have examined the use of cultural tactics (changing the environment) and mechanical methods (killing or suppressing weeds through physical disruption) in a no-till production system.

As for cultural methods, the team plants cover crops of cereal rye before soybean, and hairy vetch or red clover before corn. These cover crops grow fast and blanket the ground, inhibiting the growth of weeds by competing for limited resources such as sunlight. They also protect the soil through the fall and winter and can be used as a weed-suppressive mulch after planting the cash crop, Curran notes.

At planting time, researchers employ mechanical tactics by using a roller-crimper to help manage the cover crops and increase weed suppression. The team then uses a technique called "zone herbicide application," in which herbicide is applied at the time of planting in a "band" just over the crop row. The scientists then use a high-residue, inter-row cultivator designed for no-till systems to control the weeds between the crop rows.

"This technique differs from a broadcast herbicide application, which basically covers an entire field," Curran says. "Banding, or zone herbicide application, typically can reduce residual herbicide use by 50 to 75 percent. The high-residue, inter-row cultivator controls the weeds between the crop rows by slicing or cutting the weeds just below the soil surface. The slicing sweeps on the cultivator are designed to travel just below the soil surface to limit the amount of soil disturbance."

Over several planting seasons, the team has compared results of cultural and mechanical controls and banded herbicide use to the more standard practice of relying solely on herbicides. Although the results are sometimes mixed, the banded program reduces corn herbicide use by almost 50 percent and soybean herbicide use by 12 percent. This reduction can be smaller or larger depending on the herbicides selected. The experiment is ongoing, with researchers looking at weed control that involves both banding and cultivating, banding and post emergence herbicide application, and comparing 15-inch- versus 30-inch-wide soybean rows.

"We must reduce reliance on herbicides," Curran says. "Our studies demonstrate that this is achievable, and it's our charge to provide growers with the information and resources they need to make it happen. And when these methods become the norm, benefits will be reaped by growers, consumers, and the environment."

Protecting Water Quality

One of the primary benefits of reducing herbicides--along with pesticides and manure--is the protection of water quality. To protect water quality the team is testing various cover crops--which consists of planting non-revenue-generating crops, such as hairy vetch or red clover, after primary crops are harvested to help keep soil in place and retain and renew soil nutrients--and double cropping--which consists of planting two feed or forage crops back to back in the same growing season.

"We have a graduate student looking at water quality impacts from double-cropped silage rye versus rye cover crops, and another graduate student who is working with case-study commercial farms to see how they are making double cropping of winter rye after corn silage work in their favor," says Karsten. "Double cropping reduces dairy forage production costs and provides an additional crop to make use of excess manure, so it can essentially help 'pay' farmers to protect water quality."

Another avenue to protect water quality the team is testing is a manure-injection system. A manure injector, Karsten explains, has a big round coulter, or metal blade, that cuts a slit in the soil. The liquid manure goes through a tube and into that slit, and then press wheels come behind to close the slit. "Over the first seven years of our project, we've found that manure injection reduces the need to purchase off-farm inorganic nitrogen fertilizer by 33 percent and protects water compared to broadcasting manure on the soil surface," says Karsten.

The researchers measure the contaminants that run off the field through the use of lysimeters, catchment systems installed in the soil that measure the water and nutrients, such as nitrogen and phosphorus, that leach into the groundwater and that run off into surface water. The researchers also measure the nutrients that are lost to the atmosphere--ammonia gas and nitrous oxide.

Karsten explains that manure injection significantly reduces ammonia and phosphorus runoff losses; but if the soil becomes saturated with precipitation soon after manure is injected, nitrous oxide emissions become higher than from surface-applied manure. "The amount of nitrogen lost as nitrous oxide is relatively small compared to the ammonia loss and the total manure nitrogen applied, but since nitrous oxide is a potent greenhouse gas, this is a disadvantage of manure injection," says Karsten. "Since manure injection significantly reduces the need for additional inorganic fertilizer nitrogen, a life-cycle analysis of greenhouse gases is needed to fully assess the greenhouse gas footprint of manure injection."

A Virtual Dairy Herd

How do these various farming tactics affect milk production and a farmer's bottom line? Those questions are answered through the use of a virtual dairy herd--65 milking cows, 10 dry cows, and some 60 to 65 heifers--managed and analyzed by Virginia Ishler, extension dairy specialist.

Virginia Ishler
Virginia Ishler, extension dairy specialist

"This project is unique in that we're studying the whole farm system," says Ishler. "Typically a lot of research is just on the crop side or just on the animal side. This project takes into account the total yields that are produced on the plot, the rations available for the herd, the shrink that comes through feeding and storage losses, the milk production, the current milk prices, and the farmer's profits."

In a computer model, Ishler fills "silos" with the feed harvested on the research farm. "My rations are very similar to what producers are really dealing with from year to year because the research farm goes through the same droughts and other weather conditions as any other farm," she says. The model then calculates the amount of milk produced by the cows. She compares her results to that of the Penn State dairy herd, which is fed a very similar ration.

Ishler explains that the modeling results have helped the team fine-tune the crops they grow. "Over the years, we've changed the crop rotations somewhat so now we're feeding a heavier corn-silage-based ration, along with small grain silage and sorghum sudan silage, to better meet the needs of the cows and to lower the cost of production," she says. For example, at one point the hay crop forage tested extremely high in protein. "It was too much protein for our heifers," says Ishler. "Incorporating sorghum sudan, which is lower in protein, into the crop rotation better suited our young stock, and using small grain silage has also helped reduce the amount of protein we were feeding through the forages."

And the Winner Is...

According to Ishler, results of the model, along with various financial analyses she runs, so far suggest that the injected manure, reduced herbicide model performs equivalently to the broadcast manure, standard herbicide (conventional) model. "This means protecting the environment is possible without losing money," she says.

The next step is to demonstrate to dairy producers that they can shift their farming practices in a sustainable direction without losing profits. With that goal in mind the researchers are working with a few case-study farms to promote the injected manure, winter annual double crops, and cover cropping practices. In doing so, they are further documenting the benefits of these strategies. Additionally, they are developing extension programs and educational materials to encourage even more farmers to adopt the sustainable strategies.

Dean Patches, a dairy and broiler-hen farmer in Lebanon County, has already benefited from the knowledge obtained through the team's research. He has implemented some of the strategies, including IPM, and is watching closely to see what else is proved to work. He says he's particularly interested in the injected manure experiments.

"There is a great history of extension work and research at Penn State to identify practices that help farmers reduce their production costs; conserve their land, soil, and nutrients; and reduce their reliance on off-farm inputs," says Karsten. "You often hear that there are all these costs associated with protecting the environment, but we're helping farmers identify strategies that can reduce their production costs, protect the environment, and improve the long-term productivity of their farms."

-- Sara LaJeunesse