Dr. Mike Jacobson, professor of forest resources at Penn State University, lead daily tours of the Shrub Willow and Poplar Short-rotation Woody-biomass Crop Bioenergy Research Project at the Russell E. Larson Agricultural Research Center in Rock Springs, PA during Ag Progress Days 2014.
Hosting groups of up to 40 people, Jacobson explained how researchers are taking a close look at different varieties of willow and poplar, with an ultimate goal of finding the ideal crop selection for growing on Pennsylvania’s marginal agricultural land. This could ultimately provide productive cultivation on more than 1 million acres of under-used farmland throughout the Northeast.
Thursday’s tour visited a stand of seven mixed-hybrid willow varieties currently in their second year of growth, which will be harvested in the fall of 2015, as well as a second plot of willow trials and a stand of hybrid poplar.
Jacobson said this five-year project was established as a way to compare the growth and yields of woody materials like willow and poplar as alternatives to corn for ethanol production. Currently, the incentive for farmers to pursue woody material as an ethanol resource has been thwarted by the abundance of natural gas being produced across the U.S. He noted the technology to produce ethanol from woody biomass is available, but the production costs are currently not competitive with those of natural gas.
Jacobson told the group that New York State, along with Cornell University, is further along in their research of these crops as potential fuel renewable resources, having planted more than 1,000 acres of material in recent years. He said their research involving varieties that produces profitable yields in New York State climates, has been successful. Since Penn State’s first planting took place in 2012, the results of his team’s efforts are just now beginning to provide useful data.
“We planted willow cuttings from one-year old, dormant stems that were kept in cold storage until planting time,” he said. “After the first year of growth, the crop is cut close to the ground to invigorate the root systems. The following two years, the plants are allowed to grow with harvest taking place during the winter months following the third year of growth. After that, the crop can be harvested every two to three years depending on the stand.”
Jacobson explained that once the stand has developed a canopy, weed control is minimal. Until then however, weed control is important since weeds can overtake the willow. He said once the stand has matured, it could be productive for up to 20 years with as many as seven harvests. The plants are planted in double-rows, to make management and harvest easier. Each harvest will yield five to seven tons of biomass per acre.
While harvesting “trees” might seem like a significant change from regular crop farming for the crop farmer or livestock producer, it is not. Jacobson noted that CLAAS and New Holland’s self-propelled forage harvesters, those currently used to chop grasses for haylage or corn for silage, can be outfitted with a cutter head designed for cutting willow and poplar up to about five inches in diameter. He said the cutter head is designed specifically for this purpose and that would be the primary difference between harvesting the biomass and haylage or silage.
We then visited a second test area where 24 varieties of willow were being compared in 12 grouped plantings. Jacobson emphasized the height that healthy stands can achieve, saying this was what produced the tonnage of a successful crop. Some varieties did extremely well, while others did not. In the case of one Swedish willow variety, the stands failed entirely. Researchers concluded the weeds along with the attraction of Japanese beetles to this particular variety, made it unsuitable for production in this growing region.
An older stand of hybrid poplar was our final destination. There, we observed how researchers were experimenting with various stands of trees, with some of the poplars planted in alternating rows along with black locust, a nitrogen-fixing tree. It was the hope that the black locust could help replenish the soil’s nitrogen levels to help future poplar stands on that acreage. The idea was that the black locust and the poplars could be harvested for biomass at the same time. While this is still a work in progress, early results indicate the locust, being a much harder wood, makes harvesting much more difficult.
Unfortunately, Jacobson said researchers are finding that the poplar is infected with Septoria canker fungus at the base of the tree. This infection takes place when the tree is cut for the first time to stimulate root development. The open wound allows the fungus to attack the tree, which in turn, affects its re-growth and survival. Work still needs to be done to determine the sustainability of the poplar as a biomass resource.
Jacobson noted in other parts of Pennsylvania, other primary perennials are similarly being considered for biomass production as well. These crops include switchgrass, miscanthus and shrub willow. All of these grow well on marginal land and each offers the benefits that growers desire, such as cold weather tolerance, fast growth, and profitable rates of return economically.