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

Abstract

Management practices can influence soil CO 2 emission and C content in cropland, which can effect global warming. We examined the effects of combinations of irrigation, tillage, cropping systems, and N fertilization on soil CO 2 flux, temperature, water, and C content at the 0‐ to 20‐cm depth from May to November 2005 at two sites in the northern Great Plains. Treatments were two irrigation systems (irrigated vs. non‐irrigated) and six management practices that contained tilled and no‐tilled malt barley (Hordeum vulgaris L.) with 0 to 134 kg N ha−1, no‐tilled pea (Pisum sativum L.), and a conservation reserve program (CRP) planting applied in Lihen sandy loam (sandy, mixed, frigid, Entic Haplustolls) in western North Dakota. In eastern Montana, treatments were no‐tilled malt barley with 78 kg N ha−1, no‐tilled rye (Secale cereale L.), no‐tilled Austrian winter pea, no‐tilled fallow, and tilled fallow applied in dryland Williams loam (fine‐loamy, mixed Typic Argiborolls). Irrigation increased CO 2 flux by 13% compared with non‐irrigation by increasing soil water content in North Dakota. Tillage increased CO 2 flux by 62 to 118% compared with no‐tillage at both places. The flux was 1.5‐ to 2.5‐fold greater with tilled than with non‐tilled treatments following heavy rain or irrigation in North Dakota and 1.5‐ to 2.0‐fold greater with crops than with fallow following substantial rain in Montana. Nitrogen fertilization increased CO 2 flux by 14% compared with no N fertilization in North Dakota and cropping increased the flux by 79% compared with fallow in no‐till and 0 kg N ha−1 in Montana. The CO 2 flux in undisturbed CRP was similar to that in no‐tilled crops. Although soil C content was not altered, management practices influenced CO 2 flux within a short period due to changes in soil temperature, water, and nutrient contents. Regardless of irrigation, CO 2 flux can be reduced from croplands to a level similar to that in CRP planting using no‐tilled crops with or without N fertilization compared with other management practices.