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United States Department of Agriculture

Agricultural Research Service

Title: Irrigated Crop Management Effects on Productivity, Soil Nitrogen, and Soil Carbon

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

Submitted to: Annual Fertilizer Industry Round Table
Publication Type: Proceedings
Publication Acceptance Date: September 1, 2003
Publication Date: January 1, 2003
Citation: Halvorson, A.D., Mosier, A.R., Reule, C.A. 2003. Irrigated crop management effects on productivity, soil nitrogen, and soil carbon. Annual Fertilizer Industry Round Table. CD-ROM/Computer Program.

Interpretive Summary: The influence of N fertility on corn grain yields, residue C inputs to the soil, soil organic carbon (SOC) sequestration, soil nitrate-N (NO3-N) leaching potential, and nitrous oxide (N2O) emissions under irrigated continuous corn production was studied. Two N fertility levels were established in reduced-till (RT), continuous corn production systems utilizing center-pivot irrigation at two Texas sites. The N1 treatment had high yield goal (>250 bu/A). The second N treatment (N2) received the same N rate as N1, plus an application of liquid N fertilizer to the corn residue after harvest and prior to fall tillage to aid residue decomposition. Grain yields and residue C were similar for both N treatments. SOC levels increased linearly with each crop year. Addition of liquid N to corn residue after harvest (N2) has not significantly influenced SOC levels. Root zone soil NO3-N levels have increased in the cropped area compared and have increased more with N2 than N1. At the Colorado site, corn was produced in no-till (NT) and conventional-till (CT) systems at several N fertility levels. Corn grain yields and residue C increased with increasing N rate in both the CT and NT systems. Residual soil NO3-N levels increased with increasing N rate, but were lower in NT than in CT at the highest N rate. Averaged across N rates, no change in SOC was 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 year. Nitrous oxide emissions increased similarly with increasing N rate in both tillage systems. 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 N fertility on corn grain yields, residue C inputs to the soil, soil organic carbon (SOC) sequestration, soil nitrate-N (NO3-N) leaching potential, and nitrous oxide (N2O) emissions under irrigated continuous corn production in two states was studied. Two N fertility levels were established in reduced-till (RT), continuous corn production systems utilizing center-pivot irrigation at two Texas sites. The normal N fertility program (N1) had high yield goal (>250 bu/A). The second N treatment (N2) received the same N rate as N1 plus an application of liquid N fertilizer to the corn residue after harvest and prior to fall tillage to aid residue decomposition. Grain yields and residue C inputs to the soil were similar for both N treatments. SOC levels (1999-2002) increased linearly with each crop year and are now greater than native sod SOC levels. Addition of liquid N to the corn residue after harvest (N2) has not significantly influenced SOC levels. Root zone soil NO3-N levels have increased in the cropped area compared to native grass and have increased more with N2 than N1 treatment. At the Colorado site, corn was produced in no-till (NT) and conventional-till (CT) systems at several N fertility levels. Corn grain yields and residue C increased with increasing N rate in both the CT and NT production systems. Residual soil NO3-N levels increased with increasing N rate, but are lower in NT than in CT 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 without N application in the NT system. At the Colorado site, N2O emissions increased similarly with increasing N rate in both tillage systems. 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.

Last Modified: 10/23/2014