The Main Cropping System Experiment (MCSE) is the signature long-term experiment at KBS LTER. It is comprised of 4 annual crop treatments, 3 perennial crop treatments, and 4 successional communities. Seven treatments (T1-T7) are located at the main site complex as diagrammed in the main site layout map at left. Each treatment is assigned to a 1 ha plot in 1 of 6 replicate blocks.
The annual crops (T1-T4) are corn – soybean – winter wheat rotations. Treatments 1 and 2 receive conventional levels of chemical inputs, with Treatment 1 chisel plowed and Treatment 2 under no-till management. Treatments 3 and 4 are biologically based low chemical input systems with a winter leguminous cover crop; Treatment 3 receives banded herbicide and starter N at planting, and Treatment 4 (certified organic) receives no chemical inputs nor compost or manure. Both T3 and T4 receive additional post-planting cultivation and T4 is rotary-hoed to control weeds.
The perennial systems include continuous alfalfa (Treatment 6) and trees (Treatment 5), the latter planted to a fast growing Populus clone on a 10-year rotation cycle. Treatment 7 is a native successional treatment, abandoned after spring plowing in 1989 and annually burned from 1996. Treatment 8 is a never plowed site, 200 meters (m) south of the others, that serves as an historical control for soil organic matter studies. Individual plots contain subplots established to address specific process level hypotheses (e.g., +/ fertilizer, +/ herbicides, different planting densities). Each plot also contains a permanent set of 5 sampling stations at which most within-plot sampling is performed.
Also included in the MCSE are successional fields abandoned from agriculture in the 1950s (SF), coniferous forest plantings (CF), and mature deciduous forests never cleared for agriculture (DF). These are described in the description of the MCSE Successional and Forest sites.