by Sally Colby
If farmers could adopt new, beneficial practices without oversight by the government, would they?
Dr. Sjoerd Duiker, Penn State agronomist, believes they will. The ‘Without Carrot or Stick’ project was designed to evaluate and promote the use of cover crops after corn silage with an emphasis on small dairy farms. The three-year project was funded through a USDA-NRCS Conservation Innovation Grant. The aim of the project is to stimulate an environmentally beneficial project without any subsidies or enforcement.
“If we have to pay farmers every year for every acre, it costs a lot of money,” said Duiker, referring to traditional incentive programs. “It’s much better if the farmer does it himself and carries it as a production practice. With programs that require enforcement, there’s a cost to have someone checking on the farmer to make sure he’s complying. Farmers are thinking on their own — they can do something that is adaptable to each farm.”
Duiker noted there is also less flexibility for farmers when enforcement is part of the program because factors such as weather and seed prices make it difficult to work on a timeline.
Although the project involves sites on dairy farms throughout Pennsylvania, the results are applicable throughout the northeast. Each farm has demonstration plots with a variety of cover crop mixtures, and the farmer plants a cover crop of their choice surrounding the test plots. The project is also exploring the benefits of applying manure through injection manure rather than broadcasting.
At a recent field day held at one of the 10 plots in the study, Duiker reviewed some of the reasons for using cover crops, including economics. “We call them cover crops, but they can be harvested and used for forage,” he said. “That forage is worth its while. USDA and NRCS look at cover crops as an important practice to absorb nutrients from the soil, especially nitrates, so they aren’t lost through leaching over winter and early spring.”
Cover crops are especially important after corn silage to cover the bare soil surface. Even with no-till, soil may not have adequate cover to protect it from erosion. Most of the phosphorus that is lost to surface water is lost with soil, so cover crops also protect phosphorus loss to streams. Cover crops improve the physical properties of the soil and cover and protect the surface from sealing, which allows more water infiltration.
“Most cover crops we used are mixtures, which is relatively new,” said Duiker. “We try to use cover crops that don’t compete but complement each other. For example, crimson clover with annual ryegrass. The legume fixes its own nitrogen, then the annual ryegrass relies on nutrients from the soil.” Duiker added the protein content of this mixture is good, and if the soil is highly fertile, the ryegrass will be competitive with the crimson clover.
Duiker says another relatively new practice in cover crops is using specific varieties rather than unnamed seed. “We started to realize that if we use a non-stated variety, we might get something that is not adapted to the region,” he said. “For example, I did a lot of work with annual ryegrass, variety non-stated, and there was a lot of winter kill. It needed to be established very early.”
As he dug into each plot, Duiker pointed out how cover crops affect the soil. “We try to keep the soil occupied with roots as much as possible,” he said. “Most roots are in the soil surface, but some go very deep. The roots form nets around the soil particles, which helps with aggregation. The larger roots form channels through the soil, and when the cover crop dries, the channels will be occupied with roots from the next crop.” Duiker referenced work by Dr. Ray Weil (University of Maryland) that showed how root channels were used by soybeans following a cover crop.
Duiker explained that roots produce a lot of exudate, which is an important part of the living soil. “We don’t know how much of the total carbon accumulation of the plant goes into the exudate,” he said, “but I’ve seen some estimates that show that half of the total biomass of the crop could be pushed out of the root system, then the exudate can be used by microbes.”
One of the test plots was planted in crimson clover and triticale. “Triticale has become a popular replacement for rye because it’s easier to manage in spring for forage harvest,” said Duiker. “Triticale has wide leaf blade, and because it’s a wheat/rye cross, it has the advantages of the digestibility wheat and the hardiness of rye.”
In a plot planted in oats and crimson clover, there was significant dead residue on the soil surface. “The oats give us a lot of biomass in the fall that can be harvested for forage,” said Duiker. “When oats are established early in fall after corn silage, they produce more biomass for harvest than rye, triticale, wheat or barley.”
In another plot, the difference between two rye varieties — Huron cereal rye and Aroostook rye — was easy to see. “The Huron looks quite different than the Aroostook,” said Duiker, explaining that the variety was developed in Aroostook County, Maine. “This variety is very cold resistant. We typically get more early growth out of that than out of Huron. For later establishment, Aroostook is probably better than Huron. Huron looks a lot like triticale, with a wide leaf, and it doesn’t grow as aggressively.”
Part of the project includes harvesting a sample of each cover crop and evaluating it for nutrient content and biomass. Values including crude protein, neutral detergent fiber and relative feed value are determined for various cover crop mixtures.
“We believe that we can do this through demonstration plots so farmers can observe and learn about these practices,” said Duiker. “It’s important to emphasize the benefits to farmers themselves — it isn’t only the people downstream who benefit. These practices benefit both.”
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