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Title: CROPPING INTENSITY ENHANCES SOIL ORGANIC CARBON AND NITROGEN IN A NO-TILL AGROECOSYSTEM

Author
item Sherrod, Lucretia
item PETERSON, G - COLORADO STATE UNIV
item WESTFALL, D - COLORADO STATE UNIV
item Ahuja, Lajpat

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2003
Publication Date: 9/1/2003
Citation: Sherrod, L.A., Peterson, G.A., Westfall, D.G., Ahuja, L.R. 2003. Cropping intensity enhances soil organic carbon and nitrogen in a no-till agroecosystem. Soil Science Society of America Journal. Vol 67, pp 1533-1543.

Interpretive Summary: Implementing no-tillage management practices has allowed a reduction in the frequency of summer fallowing by increasing the cropping intensity. No-tillage management is superior in conservation of precipitation. Increasing water storage efficiency allows for more opportunities to grow crops. It is even possible to successfully intensify the cropping system to continuous cropping without needing summer fallow. As cropping intensity increased so did soil organic C and N. The greatest impact was found in the 0-2.5 cm depth. When depths were summed to 10 cm depth, cropping intensity was still positively impacted by increases in C and N with continuous cropping having 20% more than the WF system

Technical Abstract: Soil organic carbon (SOC) has decreased under cultivated wheat-fallow (WF) in the central Great Plains. We evaluated the effect of no-till systems of WF, wheat (Triticum aestivum)-corn (Zea Mays)-fallow (WCF), wheat-corn-millet (Panicum miliaceum) - fallow, continuous cropping (CC) without mono-culture, and perennial grass (G) on SOC and total N (TN) levels after 12 yrs 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 total N 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 to WF in the 0-10 cm depth. The greatest impact was found in the 0-2.5 cm, 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 total N in the 0-10 cm soil profile. Cropping systems that eliminate summer fallowing are maximizing the amount of SOC and total N sequestered.