How to Enhance Soil Organic Carbon Sequestration

Authors: Halvorson, Ardell; Reule, Curtis

Submitted to: Fluid Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2007
Publication Date: 3/12/2007
Citation: Halvorson, A.D., Reule, C.A. 2007. How to Enhance Soil Organic Carbon Sequestration. Fluid Journal. Vol. 15, No. 3, Issue #57, pp. 17-19.

Interpretive Summary: Optimizing crop yields and reducing soil erosion can enhance soil organic carbon (SOC) sequestration. The influence of management practices on crop residue C and N inputs to the soil, SOC sequestration, and NO3-N leaching potential under irrigated, continuous crop production in northern Texas was evaluated. Two N management sites were established in 1999 in irrigated fields located near Dalhart (Dallam fine sandy loam soil) and Texline, Texas (Conlen and Dumas clay loam soils) using reduced-till (RT), continuous corn production systems. The N1 site received the normal N fertility program for a corn yield goal of >250 bu/A. The N2 site received the same N fertilizer program plus an additional application of liquid N to the corn residue after harvest to aid residue decomposition. Application of N to the residue at the N2 sites was discontinued in 2002 at Dalhart and 2001 at Texline due to a buildup of residual soil NO3-N. At Dalhart, winter wheat was inserted into the rotation in 2003, with a corn-wheat rotation followed since 2004. At Texline, cattle have heavily grazed the corn stalks after grain harvest since 2003. Grain yields and residue C inputs to the soil have been similar for both sampling sites at both locations. Total soil N (TSN) and SOC levels in the 0-6 inch soil depth have increased linearly with each additional crop year (1999-2004) at both locations, with SOC sequestration rates of about 1000 lb SOC/A per year at Dalhart and Texline. Differences in SOC sequestration rates between the N1 and N2 sites were not observed at either location. The 2005 SOC analysis suggest that the water stress at Dalhart and the cattle grazing corn stalks at Texline may be causing a loss in SOC. Root zone soil NO3-N levels had increased more at the N2 sites than at the N1 sites, but decreased at the N2 sites after N application to the corn residue ceased at both locations. Nitrogen needs to be applied to optimize irrigated crop yields and economic returns, but only the amount needed for optimum yield should be applied to minimize NO3-N leaching potential. Results indicate that under irrigated conditions, SOC sequestration is possible while using a RT system and continuous corn production.

Technical Abstract: Optimizing crop yields and reducing soil erosion can enhance soil organic carbon (SOC) sequestration. The influence of management practices on crop residue C and N inputs to the soil, SOC sequestration, and NO3-N leaching potential under irrigated, continuous crop production in northern Texas was evaluated. Two N management sites were established in 1999 in irrigated fields located near Dalhart (Dallam fine sandy loam soil) and Texline, TX (Conlen and Dumas clay loam soils) using reduced-till (RT), continuous corn production systems. The N1 site received the normal N fertility program for a corn yield goal of >250 bu/A. The N2 site received the same fertilizer program as the N1 site plus an additional application of liquid N to the corn residue after harvest to aid residue decomposition. Application of N to the residue at the N2 sites was discontinued in 2002 at Dalhart and 2001 at Texline due to a buildup of residual soil NO3-N. At Dalhart, winter wheat was inserted into the rotation in 2003, with a corn-wheat rotation followed since 2004. At Texline, cattle have heavily grazed the corn stalks after grain harvest since 2003. Grain yields and residue C inputs to the soil have been similar for both sampling sites at both locations. Total soil N (TSN) and SOC levels in the 0-6 inch soil depth have increased linearly with each additional crop year (1999-2004) at both locations, with SOC sequestration rates of about 1000 lb C/A per year at Dalhart and Texline. Differences in SOC sequestration rates between the N1 and N2 sites have not been observed at either location. The 2005 SOC analysis suggest that the water stress at Dalhart and the cattle grazing corn stalks at Texline may be causing a loss in SOC. Root zone soil NO3-N levels had increased more at the N2 sites than at the N1 sites, but decreased at the N2 sites after N application to the corn residue ceased at both locations. Nitrogen needs to be applied to optimize irrigated crop yields and economic returns, but only the amount needed for optimum yield should be applied to minimize NO3-N leaching potential. Results indicate that under irrigated conditions, SOC sequestration is possible while using a RT system and continuous corn production.