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United States Department of Agriculture

Agricultural Research Service

Title: Soil Carbon Dioxide Emission As Influenced by Irrigation, Tillage, Cropping System, and Nitrogen Fertilization

Authors
item Sainju, Upendra
item Jabro, Jalal "jay"
item Stevens, William

Submitted to: Proceedings of the Workshop on Agricultural Air Quality: State of the Science
Publication Type: Proceedings
Publication Acceptance Date: March 31, 2006
Publication Date: June 5, 2006
Repository URL: http://handle.nal.usda.gov/10113/15511
Citation: Sainju, U.M., Jabro, J.D., Stevens, W.B. 2006. Soil carbon dioxide emission as influenced by irrigation, tillage, cropping system, and nitrogen fertilization. Workshop on Agricultural Air Quality. pp. 1086-1098.

Interpretive Summary: Global warming due to increased concentration of greenhouse gases, such as carbon dioxide (CO2), in the atmosphere is a major concern. Agricultural practices contribute about 25% of total anthropogenic emissions. Soil can act as both source and sink of atmospheric CO2. The CO2 fixed in plant biomass through photosynthesis can be stored in the soil as organic C by converting plant residue into soil organic matter after the residue is returned to the soil. On the other hand, management practices, such as tillage, can increase CO2 emission from the soil by disrupting soil aggregates, increasing aeration, incorporating plant residue, and oxidizing soil organic C. Respiration by plant roots and soil microflora and fauna also contribute a major portion of CO2 emission from the soil. The CO2 emission from the soil to the atmosphere is the primary mechanism of C loss from the soil and provides an early indication of C sequestration in the soil when changes in soil organic C due to management practices are not detectable within a short period. An experiment was set up in Nesson Valley in western North Dakota in 2005 to examine the effects of irrigation, tillage, crop rotation, and nitrogen fertilization on soil CO2 emission. Irrigation increased CO2 flux by 27% compared with non-irrigation by increasing soil water content during dry periods. Similarly, tillage increased CO2 flux by 58% compared with non-tillage by increasing soil temperature. The CO2 flux was 1.5 to 2.5-fold greater in tilled than in non-tilled treatments following heavy rain or irrigation. Crop rotation and nitrogen fertilization had limited to no effects on CO2 flux. The CO2 flux in undisturbed alfalfa and grasses treatment was similar to that in no-tilled crops. Tillage followed by heavy rain or irrigation during the crop growing season drastically increased CO2 flux in the coarse-textured soil previously managed under Conservation Reserve Program (CRP) planting for more than 20 yr.

Technical Abstract: Soil and crop management practices can influence CO2 emission from crop and grasslands and therefore on global warming. We examined the effects of two irrigation systems (irrigated vs. non-irrigated) and six management practices [no-till malt barley (Hordeum vulgaris L.) with 67 or 134 kg N ha-1 (NTBFN), no-till malt-barley with 0 kg N ha-1 (NTBON), conventional-till malt barley with 67 or 134 kg N ha-1 (CTBFN), conventional-till malt barley with 0 kg N ha-1 (CTBON), no-till pea (Pisum sativum L.) with 0 kg N ha-1 (NTPON), and undisturbed alfalfa (Medicago sativa L.) and grasses with 0 kg N ha-1 (UAGON)] on soil surface CO2 flux and soil temperature and water content at the 0 to 15 cm depth. Weekly CO2 flux, soil temperature, and soil water content were monitored during the crop growing season from May to November 2005 in Lihen sandy loam (sandy, mixed, frigid, Entic Haplustolls) in western North Dakota. Irrigation increased CO2 flux by 27% compared with non-irrigation by increasing soil water content during dry periods. Similarly, tillage increased CO2 flux by 58% compared with non-tillage by increasing soil temperature. The CO2 flux was 1.5 to 2.5-fold greater in tilled than in non-tilled treatments following heavy rain or irrigation. Nitrogen fertilization increased CO2 flux compared with no N fertilization in 2 out of 17 measurements while cropping system did not influence CO2 flux. The CO2 flux in undisturbed alfalfa and grasses was similar to that in no-tilled crops. The CO2 flux was linearly related with soil temperature and daily average air temperature at the time of CO2 measurement. Tillage followed by heavy rain or irrigation during the crop growing season drastically increased CO2 flux in the coarse-textured soil previously managed under Conservation Reserve Program (CRP) planting for more than 20 yr.

Last Modified: 7/28/2014
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