The site of COBS (Comparison of Biofuels Systems) experiment seeks to identify and develop cropping systems that will profitably produce biofuel feedstock while improving biodiversity and protecting Iowa's soil and water.
Location: Located near Madrid in Boone County, Iowa
Description: The site is arranged in six no-till bioenergy cropping systems. Each of 24 plots is 90 feet by 200 feet.
Background: Starting in 2008, 24 plots that are 61m long x 27m wide, were arranged in a randomized complete block design with four replicates of each cropping system.
Soils: Webster (fine-loamy, mixed, superactive, mesic typic endoaquoll) and Nicollet 9fine-loamy, mixed, superactive, mesic aquic hapludoll). Soil textures to a 30 cm depth are clay loam and sandy clay loam.
Drainage Design: The site is generally flat with less than 1% slopes. Central and border subsurface drains were installed along the long dimension of each experimental plot and instrumented. To ensure hydraulic separation, border drains were installed to prevent lateral flows from the adjacent plots. The center drain of each plot empties into an aluminum culvert where the drained effluent flows from the subsurface drain into a plastic tub.
Treatments: The 24 plots are arranged in a randomized complete block design with four replicates of each cropping system. This experiment compares replicated plots of five cropping alternatives: 1) conventional corn/soybean cash grain system; 2) continuous corn grown for grain and stover, with a winter cover crop; 3) continuous corn grown for grain and stover, without a winter cover crop; 4) a mixture of perennial prairie plants fertilized for high biomass production; and 5) a highly diverse, unfertilized mixture of prairie plants. The latter serves as a benchmark for understanding the functional characteristics of a relatively unmanipulated native community.