Sometimes I find it hard to understand the aggressive funding in the US towards dedicated bioenergy crops – crops like switchgrass and miscanthus that proponents argue can be grown on degraded land (land that we wouldn’t be able to grow other crops) with little or no fertilizer or water.
This recent study is one example, but I’m sure there is more evidence out there or soon to be published that really questions the validity of this approach.
They found that growing switchgrass and reed canary grass on low yielding land, not surprisingly, also had low yields for switchgrass and canary grass biomass. Interestingly, they found little or no impact of fertilizer on yields. In their discussion they point out that this maybe due to the type of soil. They also discuss that water may be a limiting factor, but they did not do rigorous measurements of the water levels and they didn’t have a well watered control plot, so it is unclear if this is the cause of the low yield.
Of course, this is 2 locations over 3 years so hard to extrapolate to other locations and conditions, but it certainly indicates that our dream of high yielding energy crops on degraded lands will take more effort, especially in identifying and breeding varieties that are able to grow well with little water and fertilizer.
Shield, I., Barraclough, T., Riche, A., & Yates, N. (2012). The yield response of the energy crops switchgrass and reed canary grass to fertiliser applications when grown on a low productivity sandy soil Biomass and Bioenergy, 42, 86-96 DOI: 10.1016/j.biombioe.2012.03.017