Establishment and Short-term Productivity of Annual and Perennial Bioenergy Crops Across a Landscape Gradient
Bioenergy crops may help achieve multiple energy, economic, and environmental objectives in the US Midwest, but a portfolio of crops must first be developed and tested in comparison to the current standard, maize (Zea mays L.). The nascent, but long-term and ongoing Landscape Biomass Project in Boone County, Iowa, USA examines five cropping systems including continuous maize, a modified maize–soy [Glycine max (L.) Merr.] rotation, nurse cropped maize–switchgrass (Panicum virgatum L.), double-cropped triticale (Triticosecale × Whit.)/sorghum (Sorghum bicolor (L.) Moench), and intercropped triticale–aspen (Crandon [Populus alba × Populus grandidentata]) over an elevation gradient. Here, we report perennial establishment and crop productivity across five landscape positions during the first 4 years (2009–2012) of this experiment. Perennials (switchgrass and aspen) established successfully across the gradient with minimal effect of landscape position. Continuous maize had the highest biomass yields both within and over growing seasons, but they declined over time. In comparison, the diversified and perennial systems had lower, but stable or increasing yields over time, despite extreme weather conditions. Landscape position did not consistently influence biomass yield; its effect depended on year and cropping system. Cropping system productivity was generally consistent across the landscape within a given year with greater variability between years. Findings help explain why landscape is often disregarded in Midwestern crop management: it does not seem to substantially drive crop, and thus economic, performance in the short term. Conversely, related Landscape Biomass studies find landscape influences important ecosystem functions (e.g., soil carbon storage) and should be an integral management consideration.