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This article in SSSAJ

  1. Vol. 67 No. 5, p. 1533-1543
     
    Received: Aug 15, 2002
    Published: Sept, 2003


    * Corresponding author(s): lsherrod@agsci.colostate.edu
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doi:10.2136/sssaj2003.1533

Cropping Intensity Enhances Soil Organic Carbon and Nitrogen in a No-Till Agroecosystem

  1. L. A. Sherrod *a,
  2. G. A. Petersonb,
  3. D. G. Westfallb and
  4. L. R. Ahujaa
  1. a Great Plains Systems Res. Unit, USDA-ARS, P.O. Box E, Fort Collins, CO 80522
    b Dep. of Soil and Crop Science, Colorado State Univ., Fort Collins, CO 80523

Abstract

Soil organic C (SOC) has decreased under cultivated wheat (Triticum aestivum)-fallow (WF) in the central Great Plains. We evaluated the effect of no-till systems of WF, wheat–corn (Zea Mays)-fallow (WCF), wheat–corn–millet (Panicum miliaceum)-fallow, continuous cropping (CC) without monoculture, and perennial grass (G) on SOC and total N (TN) levels after 12 yr at three eastern Colorado locations. Locations have long-term precipitation averages of 420 mm but increase in potential evapotranspiration (PET) going from north to south. Within each PET location, cropping systems were imposed across a topographic sequence of summit, sideslope, and toeslope. Cropping intensity, slope position, and PET gradient (location) independently impacted SOC and TN to a 5-cm soil depth. Continuous cropping had 35 and 17% more SOC and TN, respectively, than the WF system. Cropping intensity still impacted SOC and TN when summed to 10 cm with CC > than WF. Soil organic C and TN increased 20% in the CC system compared with WF in the 0- to 10-cm depth. The greatest impact was found in the 0- to 2.5-cm layer, and decreased with depth. Soil organic C and TN levels at the high PET site were 50% less than at the low and medium PET sites, and toeslope soils were 30% greater than summit and sideslopes. Annualized stover biomass explained 80% of the variation in SOC and TN in the 0- to 10-cm soil profile. Cropping systems that eliminate summer fallowing are maximizing the amount of SOC and TN sequestered.

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