INFLUENCE OF SOIL FERTILITY LEVEL ON CARBON SEQUESTRATION UNDER IRRIGATED CORN

Authors: Halvorson, Ardell; Reule, Curtis; POOLE, JIM - POOLE FARMS, TEXLINE, TX; Follett, Ronald

Submitted to: Fluid Fertilizer Foundation Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 1/15/2002
Publication Date: 2/17/2002
Citation: Halvorson, A.D., Reule, C.A., Poole, J., Follett, R.F. 2002. Influence of soil fertility level on carbon sequestration under irrigated corn. Fluid Fertilizer Foundation Symposium Proceedings. Scottsdale, AZ. 19:245-252.

Interpretive Summary: The influence of soil fertility on soil organic carbon (SOC) sequestration and nitrate-nitrogen (NO3-N) leaching potential was evaluated under irrigated continuous corn production in northwest Texas. Research has indicated that a soil fertility program that maximizes crop yields may also positively affect SOC levels. Two fertility levels were established on separate halves of pivot irrigation systems located near Dalhart and Texline, Texas. The Dalhart site was on a Dallam fine sandy loam soil and the Texline site on Conlen and Dumas loam soils. The normal fertility program (N1) has a corn yield goal of 250+ bu/a. The higher fertility treatment (N2) received the same fertilizer rates as the N1 treatment plus an additional application of liquid N and P fertilizer to the corn residue just prior to fall tillage to aid the decomposition of corn residues. Soil was collected from the cropped and adjacent native sod areas to evaluate changes in SOC as a result of conversion from native grass to irrigated corn 6 years ago. Results indicate that the SOC level at the Dalhart site has been maintained at the native sod SOC level after 6 years of continuous corn. At the Texline site, SOC in the cropped area appears to have increased above that of the native sod SOC levels after 5 corn crops. Root zone soil NO3-N levels have increased in the cropped area compared to native grass at both sites and has increased more with the N2 management treatment than with N1. Effects of soil fertility level on SOC sequestration was not assessed in this report since insufficient time has lapsed since study initiation to accurately detect changes in SOC. Several more cropping seasons will be needed to monitor changes caused by fertility management level.

Technical Abstract: We evaluated the influence of soil fertility on soil organic carbon (SOC) sequestration and nitrate-nitrogen (NO3-N) leaching potential under irrigated continuous corn production in northwest Texas. Previous research has indicated that a fertility program that maximizes crop yields will also have positive effects on SOC levels. Two fertility levels were established on separate halves of pivot irrigation systems located near Dalhart and Texline, Texas. The Dalhart site was on a Dallam fine sandy loam soil and the Texline site on Conlen and Dumas loam soils. The normal fertility program (N1) has a corn yield goal of 250+ bu/a. The higher fertility treatment (N2) received the same fertilizer rates as the N1 treatment plus an additional application of liquid N and P fertilizer to the corn residue just prior to fall tillage to aid the decomposition of corn residues. Soil was collected from the cropped and adjacent native sod areas to evaluate changes in SOC as a result of recent conversion (6 years) from native gras to irrigated corn. Preliminary results suggest that the SOC level at the Dalhart site has been maintained at the native sod SOC level after about 6 years of continuous corn. At the Texline site, SOC in the cropped area appears to have increased above that of the native sod SOC levels after 5 corn crops. Root zone soil NO3-N levels have increased in the cropped area compared to native grass at both sites and has increased more with the N2 management treatment than with N1. Effects of fertility level on SOC sequestration was not assessed in this report since insufficient time has lapsed since study initiation to accurately detect changes in SOC. Several more cropping seasons will be needed to monitor changes caused by fertility management level.