KBS LTER Plot MapThe 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 Treatment 3 and Treatment 4 receive additional post-planting cultivation and Treatment 4 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 MCSE treatment plots contain subplots established to address specific process level hypotheses.

  • Since MCSE establishment, Treatments 1 and 2 have contained subplots used to determine long-term effects of weed populations without herbicide applications.
  • Since 2006, Treatments 3 and 4 have contained subplots used to determine how crop yield is influenced by weed populations and nitrogen availability.
  • Since 2011, Treatment 5 has contained subplots used to determine how tree biomass is affected by various nitrogen fertilizer rates and nitrogen fertilizer timing.
  • Since MCSE establishment, Treatment 7 has contained subplots used to determine how succession is influenced by chisel plowing and nitrogen fertilization.
  • Since 1985, Treatment T8 has been shared with the Interactions Experiment.

Each MCSE Main Site 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.

KBS LTER Main Cropping System Experiment: Major management changes

1989: MCSE T5 poplars planted as stem cuttings (Populus × canadensis Moench ‘Eugenei’ ([Populus deltoides × P. nigra], also known as Populus × euramericana ‘Eugenei’)

1993: MCSE rotations in T1 and T2 changed from corn-soybean to corn-soybean-wheat to match T3 and T4 rotations. 1994: MCSE T1 cultivation changed from moldboard plow to chisel plow

1994: MCSE T2 (Replicate 5) was accidentally plowed and is now referred to as T21

1997: Biannual spring burning in MCSE T7 to prevent tree colonization

1999: MCSE T5 poplars harvested in February and allowed to coppice (stem sprout)

2002: Annual spring burning in MCSE T7 to prevent tree colonization

2008: MCSE T5 poplars harvested in January and allowed to go fallow for field season in order to suppress weeds

2009: MCSE T5 poplars replanted as stem cuttings of Populus nigra x P. maximowiczii (‘NM6’) 2009: MCSE T1-T3 soybean varieties changed from conventional to transgenic (glyphosate resistant); T4 variety remains conventional

2009: MCSE T3 soybean weed control changed from mechanical + banded herbicides to broadcast application of glyphosate (same as T1)

2011: MCSE T1-T3 corn varieties changed from conventional to transgenic (glyphosate, European corn borer, and root worm resistant); T4 variety remains conventional

2014 Switched to low pressure injection system for N application.

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