Submitted to: American Chemical Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: April 20, 2000
Publication Date: August 24, 2000
Citation: Halvorson, A.D. 2000. Nitrogen fertilization, tillage, and cropping system influences on soil organic carbon. American Chemical Society Abstracts. Technical Abstract: Conversion of grasslands to cultivated cropland in the Great Plains has resulted in a loss of soil organic matter (SOM). Intensive mechanical tillage has contributed to the release of carbon dioxide to the atmosphere as a result of SOM decomposition. No-till (NT) increases the potential to intensify cropping frequency under dryland conditions and reduce the loss of SOM. More frequent cropping requires N input to maintain economical yields. The effects of N fertilization on crop residue production and its subsequent effects on soil organic C (SOC) in four dryland cropping systems and one irrigated cropping system were evaluated where N had been applied to the same plots from 9 up to 30 years. Crop residue production varied with cropping and tillage system, but increased with increasing N fertilization rate in all systems. The increased amount of crop residue returned to the soil with increasing N rate resulted in increased levels of fSOC in Colorado NT dryland studies. In North Dakota, SOC was not influence by N fertilization or tillage system in a spring wheat-fallow rotation. However, NT resulted in increased SOC levels over that of the minimum-till (MT) and conventional-till (CT) systems in the spring wheat-winter wheat-su er rotation after 12 years. Examination of dryland farming systems in Nebraska also showed increased SOM levels from a NT, intensive cropping system compared to CT, crop-fallow. At an intensively tilled irrigated site in Montana, SOM levels declined from 1953 to 1983, with SOM levels being lowest with the low N rates in 1983 but increasing with increasing N fertilization rate as was observed in the NT dryland systems. The increase in SOC or SOM with N fertilization contributes toward improved soil quality and productivity. AMERICAN CHEMICAL SOCIETY MTG. HANDOUT, Aug. 20-24, 2000.