Nitrogen Fertilizer Rate Effects on Soil Organic Carbon in Iowa Continuous Corn and Corn-Soybean Systems

Date
2015-01-01
Authors
Helmers, Matthew
Castellano, Michael
Sawyer, John
Poffenbarger, Hanna
Barker, Daniel
Helmers, Matthew
Miguez, Fernando
Sawyer, John
Six, Johan
Barker, Daniel
Castellano, Michael
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Agronomy
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AgronomyAgricultural and Biosystems Engineering
Abstract

Nitrogen fertilizer rate is a key factor affecting soil organic C (SOC) in corn-based cropping systems. The objective of this study was to determine the change in SOC in response to long-term N rates for continuous corn and corn-soybean cropping systems at two sites in Iowa. Soil samples were collected to a depth of 15 cm in 1999 and again in 2014 after 15 years of corn N rate treatments ranging from 0 to 269 kg ha-1. The soil samples were analyzed for total C and N concentrations. For continuous corn at both sites, the average annual change in SOC increased significantly from below 0 Mg ha-1 yr-1 where no N was applied, to an optimum of approximately 0.13 Mg ha-1 yr-1 at N rates between 150 and 200 kg ha-1. For corn-soybean rotations, the average annual change in SOC was generally below 0 Mg ha-1 yr-1 and increased slightly, but not significantly, with increasing N rate. The results indicate that adequately fertilized continuous corn systems have the potential to accrue more SOC than corn-soybean rotations.

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This is a poster from the ASA-CSSA-SSSA Annual Meeting, Minneapolis, MN. 15-18 Nov. 2015. Posted with permission.

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