NITROGEN FERTILIZATION OF IRRIGATED CORN FOLLOWING ALFALFA AND WATERMELON AT AVRC (ARKANSAS VALLEY RESEARCH CENTER). (WILL BE PUBLISHED AS A COLORADO STATE UNIVERSITY AG. EXPERIMENT STATION TECHNICAL REPORT)

Authors: Halvorson, Ardell; SCHWEISSING, FRANK - CSU/ARK. VAL. RES. CNTR.; Reule, Curtis

Submitted to: Experiment Station Bulletins
Publication Type: Experiment Station
Publication Acceptance Date: 3/25/2003
Publication Date: 10/15/2003
Citation: Halvorson, Ardell, Schweissing, Frank, Reule, Curtis. 2003. Nitrogen fertilization of irrigated corn following alfalfa and watermelon at AVRC. Colorado Agric. Exp. Sta. Technical report TR03-8, Colorado State University. p. 13-18.

Interpretive Summary: High levels of residual NO3-N are present in the soil profile of fields cropped to vegetables, alfalfa, and grain crops in the Arkansas Valley of Colorado. The groundwater in this area also contains high levels of NO3-N. This study evaluated the effects of N fertilizer rate and N source (urea and Polyon®) on corn yields for 3 years following 5 years of alfalfa and one year of watermelon production. Corn grain yields were not increased by N fertilization in 2000, but were increased by increasing residual soil N levels in 2001, and by N fertilization in 2002. Nitrogen source did not significantly effect corn yields in 2000 and 2001, but Polyon® had slightly higher yields than urea in 2002. When averaged over 3 years, corn grain yields were near maximum with the application of 75 lb N/a per year. Silage yields generally increased with increasing N rate each of the years. Soil residual NO3-N levels were increased with increasing N fertilizer rate in 2000. Residual soil N levels declined following the 2001 corn crop which was not fertilized with additional N. The 3 year average N fertilizer use efficiency was 64% at the lowest fertilizer N rate and less than 40% at the higher N rates. Thus, N fertilizer application to corn in Arkansas River Valley produced in rotation with vegetable crops and alfalfa may need to be reduced to prevent NO3-N contamination of groundwater in this area. Based on this study, it appears that a minimal amount (50 to 75 lb N/a) of N fertilizer may be needed to maintain high grain and silage corn yields in the Valley in rotation with vegetable crops and alfalfa. Fertilizer N appears to be moving out of the root zone with downward movement of irrigation water.

Technical Abstract: High levels of residual NO3-N are present in the soil profile of fields cropped to vegetables, alfalfa, and grain crops in the Arkansas Valley of Colorado. The groundwater in this area also contains high levels of NO3-N. This study evaluated the effects of N fertilizer rate and N source (urea and Polyon®) on corn yields for 3 years following 5 years of alfalfa and one year of watermelon production. Corn grain yields were not increased by N fertilization in 2000, but were increased by increasing residual soil N levels in 2001, and by N fertilization in 2002. Nitrogen source did not significantly effect corn yields in 2000 and 2001, but Polyon® had slightly higher yields than urea in 2002. When averaged over 3 years, corn grain yields were near maximum with the application of 75 lb N/a per year. Silage yields generally increased with increasing N rate each of the years. Soil residual NO3-N levels were increased with increasing N fertilizer rate in 2000. Residual soil N levels declined following the 2001 corn crop which was not fertilized with additional N. The 3 year average N fertilizer use efficiency was 64% at the lowest fertilizer N rate and less than 40% at the higher N rates. Thus, N fertilizer application to corn in Arkansas River Valley produced in rotation with vegetable crops and alfalfa may need to be reduced to prevent NO3-N contamination of groundwater in this area. Based on this study, it appears that a minimal amount (50 to 75 lb N/a) of N fertilizer may be needed to maintain high grain and silage corn yields in the Valley in rotation with vegetable crops and alfalfa. Fertilizer N appears to be moving out of the root zone with downward movement of irrigation water.