Bioenergy crops like switchgrass and miscanthus can improve soil and water quality, provide alternative revenue and grow in areas of fields that have lost productivity. So says Newell Kitchen, a soil scientist with USDA’s Agricultural Research Service and the University of Missouri.
Even when there’s a lack of topsoil, it’s possible to grow a healthy switchgrass crop that will produce 5-7 tons/acre/year, reports Kitchen, who has worked with switchgrass for about five years. Miscanthus can produce 7-15 tons/acre.
Despite this year’s drought, switchgrass is producing 4-6 tons/ acre, he adds. “Compare that to corn grown on adjacent land that only grew 20 to 40 bushels an acre – and actually, in some areas, close to zero yield.”
Switchgrass and miscanthus, being perennials, also develop roots and store carbon below ground during fall. “Carbon being stored below ground has an amazing effect on soil. Some of the carbon will slough off, providing food for soil microbes. When you have a very active microbial pool in the soil, you get a lot of turnover of nutrients. It’s a healthier soil.”
Carbon will also provide structure in the soil, which allows plant roots to readily grow into it as well as let water infiltrate into its profile and store effectively.
That’s especially important in Missouri’s claypan soils, Kitchen says. “They typically have poor soil structure. Structure deteriorated when they were aggressively cultivated, and a perennial plant can help restore that structure quite effectively.”
The crops can also be profitable when used to provide energy, whether that’s being co-fired with coal in a power plant or, potentially, being processed into liquid fuels. “If the markets come into play as we anticipate they will, these soils could be consistent in what they can produce in terms of biomass. That could provide a flow of income for farmers that would diversify their enterprises and make these marginal soils more productive. That’s what I think these crops will demonstrate over time.”