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Title: TILLAGE, NITROGEN, AND CROPPING SYSTEM EFFECTS ON SOIL CARBON SEQUESTRATION

Author
item Halvorson, Ardell
item Wienhold, Brian
item BLACK, A - USDA-ARS, RET/MANDAN, ND

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/3/2002
Publication Date: 6/1/2002
Citation: Halvorson, A.D., Wienhold, B.J., Black, A.L. 2002. Tillage, nitrogen, and cropping system effects on soil carbon sequestration. Soil Science Society of America Journal. 66(3):906-912.

Interpretive Summary: Soil carbon sequestration can improve soil quality and reduce agriculture's impact on carbon dioxide (CO2)emissions. We examined two long-term (12 yr)dryland cropping systems [spring wheat-fallow (SW-F) and annual crop (spring wheat-winter wheat-sunflower)]in North Dakota to determine the effects of tillage system [conventional-till (CT), minimum-till (MT), no-ti iT)] and N fertilization rate on soil organic carbon (SOC) sequestration. In this study, N fertilization had little impact on SOC sequestration in either cropping system, but did increase the amount of crop residue produce and total residue N returned to the soil. Total crop residue and residue N was greater with annual crop system than with SW-F. As tillage intensity decreased, SOC sequestration increased (NT>MT>CT) in the annual crop system, but not in the SW-F system. The results suggest that continued use of a crop-fallow farming system, even with NT, will result in loss of SOC. Intensifying the cropping rotation and utilizing N farming practices will have a positive impact on SOC sequestration. With NT, an average of 233 kg C ha-1 was sequestered each year in the annual crop system, compared to 25 kg C ha-1 with MT and a loss of 141 kg C ha-1 with CT. Conversion from crop-fallow to more intensive cropping systems utilizing NT will be needed to have a positive impact on reducing CO2 loss from croplands in the northern Great Plains.

Technical Abstract: Soil carbon sequestration can improve soil quality and reduce agriculture's impact on CO2 emissions. The long-term (12 yr) effects of tillage system and N fertilization on soil organic carbon (SOC) sequestration in two dryland cropping systems in North Dakota on a loam soil were evaluated. An annual cropping (AC) rotation [spring wheat (Triticum aestivum L.)-winter wheat (Triticum aestivum L.)-sunflower (Helianthus annuus L.)] and a sprin wheat-fallow (SW-F) rotation were studied. Tillage systems included conventional-till (CT), minimum-till (MT), and no-till (NT). Nitrogen rates were 34, 67, and 101 kg N ha-1 for the AC system and 0, 22, and 45 kg N ha- the SW-F system. Total crop residue returned to the soil was greater with AC than with SW-F. As tillage intensity decreased, SOC sequestration increased (NT>MT>CT) in the AC system but not in the SW-F system. Nitrogen increased crop residue quantity returned to the soil, but generally did not tincrease SOC sequestration in either cropping system. Soil bulk density decreased with increasing tillage intensity in both systems. The results suggest that continued use of a crop-fallow farming system, even with NT, will result in loss of SOC. With NT, an average of 233 kg C ha-1 was sequestered each year in AC system, compared to 25 kg C ha-1 with MT and a loss of 141 kg C ha-1 with CT. Conversion from crop-fallow to more intensive cropping systems utilizing NT will be needed to have a positive impact on reducing CO2 loss from croplands in the northern Great Plains.