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Title: NITROGEN AND CROP MANAGEMENT INFLUENCE IRRIGATED CORN YIELDS AND GREENHOUSE GAS EMISSIONS

Author
item Halvorson, Ardell
item Reule, Curtis
item Mosier, Arvin

Submitted to: Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 1/15/2003
Publication Date: 3/1/2004
Citation: Halvorson, A.D., Reule, C.A., Mosier, A.R. 2004. Nitrogen and crop management influence irrigated corn yields and greenhouse gas emissions. Symposium Proceedings. 10:21-27.

Interpretive Summary: We evaluated the effects of tillage system and nitrogen (N) fertility level on corn grain yields, residue carbon (C) returned to the soil, soil organic carbon (SOC) sequestration, nitrate-N leaching potential, and greenhouse gas emissions under an irrigated, continuous corn production system on a Fort Collins clay loam soil. No-till (NT) and conventional-till (CT) systems were studied at several N fertility levels. Data was collected from 1999 through 2002. Corn grain yields and residue C increased with increasing N rate in both the CT and NT production systems. Residual soil NO3-N levels in 2002 increased with increasing N rate in both tillage systems, but were lower in the NT system than in the CT system at the highest N rate. No change in SOC was observed in the CT system from 1999 through 2002, but SOC increased linearly in the NT system with each additional corn crop. Developing trends are for SOC to be greater with N application than where no N fertilizer has been applied in the NT system. Greenhouse gas emissions data in 2002 show nitrous oxide (N2O) emissions increased similarly with increasing N rate in both tillage systems. Carbon dioxide (CO2) emissions were greater with CT than with NT but did not vary with N rate. Methane (CH4) emissions were low and not affected by tillage or N treatment. Therefore, the increase in SOC storage with NT is helping offset N2O emissions from N fertilization needed to optimize crop yields compared with the CT system. Farmers need to apply N to optimize yields and economic returns, but should take care to use only that amount of N fertilizer needed for optimum yield in order to minimize NO3-N leaching potential and N2O emissions in irrigated systems.

Technical Abstract: The influence of tillage system and N fertility on corn grain yields, residue C inputs to the soil, soil organic carbon (SOC) sequestration, NO3-N leaching potential, and greenhouse gas emissions under irrigated continuous corn production was evaluated. Corn was produced on a Fort Collins clay loam using no-till (NT) and conventional-till (CT) systems at several N fertility levels. Soil and plant data have been collected since the spring of 1999. Corn grain yields and residue C have increased with increasing N rate in both the CT and NT production systems. Residual soil NO3-N levels have increased with increasing N rate in both tillage systems, but are lower in the NT system than in the CT system at the highest N rate. Averaged across N rates, no change in SOC has been observed in the CT system with time, but SOC has increased linearly in the NT system with each additional corn crop. SOC has not been significantly increased by N fertilization during the first 4 years, but trends are for SOC to be greater with N application than where no N fertilizer has been applied in the NT system. Several more cropping seasons will be needed to detect significant changes in SOC caused by N fertility management level. Nitrous oxide (N2O) emissions increased similarly with increasing N rate in both tillage systems. Carbon dioxide (CO2) emissions were greater with CT than with NT but did not vary with N rate. Methane (CH4) emissions were low and not affected by tillage or N treatment. Therefore, the increase in SOC storage with NT is helping offset N2O emissions from N fertilization needed to optimize crop yields compared with the CT system. Farmers need to apply N to optimize yields and economic returns, but should take care to use only that amount of N fertilizer needed for optimum yield in order to minimize NO3-N leaching potential and N2O emissions in irrigated systems.