Soil Carbon Dioxide Emission as Influenced by Irrigation, Tillage, Cropping System, and Nitrogen Fertilization

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 (NTBFN), notill malt-barley with 0 kg N ha (NTBON), conventional-till malt barley with 67 or 134 kg N ha (CTBFN), conventional-till malt barley with 0 kg N ha (CTBON), no-till pea (Pisum sativum L.) with 0 kg N ha (NTPON), and undisturbed alfalfa (Medicago sativa L.) and grasses with 0 kg N ha (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.