IRRIGATED CROPPING SYSTEM EFFECTS ON SOIL CARBON AND NITROGEN IN NORTHERN TEXAS.

Authors: Halvorson, Ardell; Reule, Curtis; POOLE, JIM - POOLE CHEM., TEXLINE, TX

Submitted to: Fluid Fertilizer Foundation Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 1/6/2006
Publication Date: 2/12/2006
Citation: Halvorson, A.D., Reule, C.A., Poole, J. 2006. Irrigated cropping system effects on soil carbon and nitrogen in northern texas. Fluid Fertilizer Foundation Symposium Proceedings. 23:126-132. Also CD ROM publication.

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 levels were established in 1999 on separate halves of 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 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 grazed the corn stalks after grain harvest since 2001. 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 1047 lb C/A per year at Dalhart and 1009 lb C/A per year at Texline. Differences in SOC sequestration rates between the N1 and N2 sites have not been observed at either location. The preliminary 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. Data collected to-date 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 levels were established in 1999 on separate halves of 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 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 grazed the corn stalks after grain harvest since 2001. 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 1047 lb C/A per year at Dalhart and 1009 lb C/A per year at Texline. Differences in SOC sequestration rates between the N1 and N2 sites have not been observed at either location. The preliminary 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. Data collected to-date indicate that under irrigated conditions, SOC sequestration is possible while using a RT system and continuous corn production.