Submitted to: Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: May 5, 2007
Publication Date: July 15, 2007
Citation: Sainju, U.M. 2007. Carbon and nitrogen storage in dryland soil aggregates as influnced by long-term tillage and cropping system. In: A. Chabbi (ed.) Proc. International Symposium on Organic Matter Dynamics in Agro-Ecosystems. July 16-19, 2007. Poitiers, France. p. 88-89. Technical Abstract: The 21-yr influence of combinations of tillage and cropping systems were determined on soil organic C (SOC) and organic N (SON) contents in whole-soil and aggregates at the 0-20 cm depth in the drylands of Montana, USA. Tillage and cropping systems were no-till with continuous spring wheat (NTCW), spring till with continuous spring wheat (STCW), fall and spring till with continuous spring wheat (FSTCW), fall and spring till with spring wheat-barley (1984-1999) followed by spring wheat-pea (2000-2004) (FSTW-B/P), and spring till with spring wheat-fallow (STW-F). Whole-soil SOC and SON contents were greater in NTCW and STCW than in FSTW-B/P and STW-F at 0-5 cm and greater in NTCW, STCW, and FSTCW than in STW-F at 5-20 cm. Aggregate size distribution was not influenced by treatments at 0-5 cm but aggregate proportion was greater in STW-F than in STCW in 2.00-0.25 mm fraction at 5-20 cm. At 0-5 cm, SOC and SON contents were greater in NTCW and STCW than in FSTW-B/P and STW-F in 4.75-0.25 mm fraction but at 5 to 20 cm, they varied with treatments and aggregate size fractions. Both SOC and SON contents were greater in 2.00-0.25 mm fractions than in other fractions, regardless of treatments. Long-term reduced tillage frequency and increased cropping intensity increased C and N storage in dryland whole-soil and macro-aggregates. Increase in tillage frequency followed by replacement of continuous wheat by wheat-barley/pea reduced C and N storage in whole-soil and aggregates at the surface layer.