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Title: CORN RESPONSE TO NITROGEN FERTILIZATION IN A SOIL WITH HIGH RESIDUAL NITROGEN

Author
item Halvorson, Ardell
item SWHWEISSING, FRANK - CSU, ROCKY FORD, CO
item BARTOLO, MICHAEL - CSU, ROCKY FORD, CO
item Reule, Curtis

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2005
Publication Date: 7/13/2005
Citation: Halvorson, A.D., Swhweissing, F., Bartolo, M., Reule, C.A. 2005. Corn response to nitrogen fertilization in a soil with high residual nitrogen. Agronomy Journal. 97:1222-1229.

Interpretive Summary: A N fertility study was conducted to determine if continuous corn production could reduce the high levels of residual NO3-N present in the soils in the Colorado, Arkansas River Valley where alfalfa, grains, and vegetable crops are produced. Fertilizer N needed to maintain optimum corn yields following alfalfa and vegetables and its impacts on NO3-N leaching potential was also evaluated. Two N sources (urea and a controlled release urea source, Polyon®) and six fertilizer N rates were used. Corn grain yields were not significantly increased by N fertilization the 1st year following watermelon, but increased with increasing residual soil NO3-N levels the 2nd year without additional N fertilization, and increased by N fertilization in the 3rd and 4th years. Nitrogen source did not significantly affect corn grain yields, residual soil N, or nitrogen fertilizer use efficiency (NFUE). Averaged over years, corn grain yields were near maximum with an average N application of 137 kg N ha-1 yr-1. Soil residual NO3-N levels in the fertilized treatments increased with increasing N rate the 1st year, but declined following the 2nd, 3rd, and 4th corn crops. Available soil N declined with each additional corn crop in the check (no N fertilizer) treatment. Average NFUE based on grain N removal over 4-yr was 55 % at the lowest fertilizer N rate and 30 % at the highest N rate. Reducing N fertilizer application rates to corn following vegetable crops would help reduce residual soil NO3-N levels in the root zone and the quantity of NO3-N entering the shallow groundwater and improve NFUE. Producing several crops of continuous corn with minimal N fertilization will reduce residual soil NO3-N levels.

Technical Abstract: High levels of residual NO3-N are present in the soils in the Colorado, Arkansas River Valley where alfalfa (Medicago sativa L.), grains, and vegetable crops are produced. This study evaluated the use of continuous corn (Zea mays L.) to reduce residual N levels in a silty clay soil. Fertilizer N needed to maintain optimum corn yields following alfalfa and vegetables and its impacts on NO3-N leaching potential was also evaluated. Treatments included two N sources (urea and Polyon®) and six fertilizer N rates. Corn grain yields were not significantly increased by N fertilization the 1st year following watermelon, but increased with increasing residual soil NO3-N levels the 2nd year without additional N fertilization, and increased by N fertilization in the 3rd and 4th years. Nitrogen source did not significantly affect corn grain yields, residual soil N, or nitrogen fertilizer use efficiency (NFUE). Averaged over years, corn grain yields were near maximum with an average N application of 137 kg N ha-1 yr-1. Soil residual NO3-N levels in the fertilized treatments increased with increasing N rate the 1st year, but declined following the 2nd, 3rd, and 4th corn crops. Available soil N declined with each additional corn crop in the check (no N fertilizer) treatment. Average NFUE based on grain N removal over 4-yr was 55 % at the lowest fertilizer N rate and 30 % at the highest N rate. Nitrogen application to corn in Arkansas River Valley produced in rotation with vegetable crops and alfalfa may need to be reduced for the first corn crop. Reducing N fertilizer application rates to corn following vegetable crops would help reduce residual soil NO3-N levels in the root zone and the quantity of NO3-N entering the shallow groundwater. Producing several crops of continuous corn with minimal N fertilization will reduce residual soil NO3-N levels.