Soil carbon sequestration and greenhouse gas fluxes in the eastern Corn Belt
Abstract
The relative impact of different crop production systems on global warming is not completely documented. This study was conducted to enhance the current understanding of carbon sequestration and greenhouse gas sources/production/fluxes in the Corn Belt as affected by N source and crop rotation. Soil surface fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) were measured by static-chamber, soil organic matter (SOM) fractions to a soil depth of 15 cm were determined by physical (particulate organic matter, POM) and chemical (non-hydrolyzable C, NHC) fractionations, as well as dry matter (DM), and N accumulation and/or partitioning were assessed by harvest index (HI) during two consecutive growing seasons. Agricultural systems evaluated were continuous corn with either spring or fall liquid swine manure (CCSM and CCFM, respectively), continuous corn and corn phase of corn-soybean rotation with urea-ammonium nitrate (CCUAN and CSUAN, respectively), soybean phase of corn-soybean rotation (SC) and restored prairie grass (PG) grown in Drummer and Raub soil series. In addition, soil N2O production as influenced by redox potential as well as source-partitioning (nitrification vs. denitrification) by 15N-labeling were assessed in aerobic and anaerobic incubations, respectively, evaluating CCUAN and CCFM. Among corn treatments, CO2 and N2O contributed 86 and 14%, respectively, to global warming potential. Seasonal CO2 emissions did not differ among treatments, but N2O emissions were sharply impacted by treatment (Grouping of treatments: CCSM 8.2a, CCUAN 6.4ab, CSUAN 4.9bc, CCFM 3.3cd, SC 1.0de, PG 0.2e kg N2O – N ha -1) as they were driven by pulse emissions following N fertilizer inputs coinciding with major rainfall events. Both greater N2O production with increasing soil water content in manured soils and the source-partitioning results suggested that denitrification was the predominant pathway. Redox potential range for N2O production occurred at moderate reducing conditions (420 to 575 mV) and was not affected by N source. Partitioning of DM and N into corn grain was slightly enhanced (3-4%) by UAN and corn-soybean rotation, respectively. As an N management system, CCFM appears to mitigate global warming because it enhanced soil C, POM-C and NHC concentrations as well as mitigated N2O emissions at the soil surface. However, CCFM had the lowest productivity (9 Mg DM grain ha-1 yr -1). Timing of N application had a large impact on global warming mitigation in agricultural soils.
Degree
Ph.D.
Advisors
Brouder, Purdue University.
Subject Area
Agronomy|Biogeochemistry|Soil sciences
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