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Title: CROPPING SYSTEM EFFECTS ON SOIL CARON AND NITROGEN

Author
item HALVORSON, ARDELL
item REULE, CURTIS
item POOLE, J - POOLE FARMS, TEXLINE, TX
item FOLLETT, RONALD

Submitted to: Fluid Fertilizer Foundation Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 1/12/2001
Publication Date: 2/18/2001
Citation: Halvorson, A.D., Reule, C.A., Poole, J., Follett, R.F. 2001. Cropping system effects on soil caron and nitrogen. Fluid Fertilizer Foundation Symposium Proceedings. Scottsdale, AZ. 18_116-124.

Interpretive Summary: This research evaluates the influence of soil fertility on soil organic carbon (SOC) sequestration and nitrate-N (NO3-N) leaching potential under irrigated continuous corn production in northwest Texas. Two fertility levels were established on pivot irrigation systems located near Dalhart on a Dallam fine sandy loam soil and Texline, Texas 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 as N1 treatment plus a liquid N and P fertilizer application just prior to fall tillage to aid in corn residue decomposition. Soil samples were collected from the cropped areas plus adjacent native sod areas. Presented are initial corn grain yields, residue biomass, C, and N returned to the soil, and SOC, TSN, and soil NO3-N levels for comparing the native sod and cropped areas. The data presented are initial averages and have not been statistically analyzed. Grain yields have been less than yield goal. Residue biomass and C returned to the soil may be sufficient to build soil C. The preliminary data show that SOC levels at the Dalhart cropped site have been maintained near that of the native sod. In contrast, at the Texline site, SOC levels in the cropped area appear to have increased over that of the native sod areas. Residual soil NO3-N levels were very low for the native sod locations at both sites compared to the cropped areas. Residual soil NO3-N levels in the cropped areas at both sites appeared to be normal following harvest of the 1999 corn crop. Several more cropping seasons will be needed to ascertain whether additional fall fertilizer to the corn residue before tillage will be a benefit to SOC sequestration.

Technical Abstract: This project evaluates the influence of soil fertility on soil organic carbon (SOC) sequestration and nitrate-nitrogen (NO3-N) leaching potential under irrigated continuous corn production. 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 help in decomposition of the corn residues. Soil samples were collected from the cropped areas plus the adjacent native sod areas to oevaluate changes in SOC as a result of conversion from native grass to an irrigated cropping system. Grain yields have been less than yield goal. Residue biomass and C returned to the soil may be sufficient to build soil C at both sites. Results suggest that the SOC level at the Dalhart site has been maintained at the native sod SOC level after about 5 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 four corn crops. Root zone soil NO3-N levels have increased in the cropped area compared to native grass at both sites. The effects of fertility level on SOC sequestration and NO3-N leaching potential will not be assessed at this time since the project was initiated in 1999. Several cropping seasons will be needed to monitor changes caused by fertility level.