Title: The greenhouse gas cost of agricultural intensification with groundwater irrigation in a Midwest U.S. row cropping system

Abstract

Abstract Groundwater irrigation of cropland is expanding worldwide with poorly known implications for climate change. This study compares experimental measurements of the net global warming impact of a rainfed versus a groundwater‐irrigated corn (maize)–soybean–wheat, no‐till cropping system in the Midwest US, the region that produces the majority of U.S. corn and soybean. Irrigation significantly increased soil organic carbon (C) storage in the upper 25 cm, but not by enough to make up for the CO ₂ ‐equivalent (CO ₂ e) costs of fossil fuel power, soil emissions of nitrous oxide (N ₂ O), and degassing of supersaturated CO ₂ and N ₂ O from the groundwater. A rainfed reference system had a net mitigating effect of −13.9 (±31) g CO ₂ e m ⁻²  year ⁻¹ , but with irrigation at an average rate for the region, the irrigated system contributed to global warming with net greenhouse gas (GHG) emissions of 27.1 (±32) g CO ₂ e m ⁻²  year ⁻¹ . Compared to the rainfed system, the irrigated system had 45% more GHG emissions and 7% more C sequestration. The irrigation‐associated increase in soil N ₂ O and fossil fuel emissions contributed 18% and 9%, respectively, to the system's total emissionsmore » in an average irrigation year. Groundwater degassing of CO ₂ and N ₂ O are missing components of previous assessments of the GHG cost of groundwater irrigation; together they were 4% of the irrigated system's total emissions. The irrigated system's net impact normalized by crop yield (GHG intensity) was +0.04 (±0.006) kg CO ₂ e kg ⁻¹ yield, close to that of the rainfed system, which was −0.03 (±0.002) kg CO ₂ e kg ⁻¹ yield. Thus, the increased crop yield resulting from irrigation can ameliorate overall GHG emissions if intensification by irrigation prevents land conversion emissions elsewhere, although the expansion of irrigation risks depletion of local water resources.« less

Authors:

McGill, Bonnie M.  ^[1];

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Hamilton, Stephen K. ^[2]; Millar, Neville ^[3]; Robertson, G. Philip ^[4]

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1. W. K. Kellogg Biological Station Michigan State University Hickory Corners Michigan, Department of Integrative Biology Michigan State University East Lansing Michigan
2. W. K. Kellogg Biological Station Michigan State University Hickory Corners Michigan, Department of Integrative Biology Michigan State University East Lansing Michigan, Cary Institute of Ecosystem Studies Millbrook New York, Great Lakes Bioenergy Research Center Michigan State University East Lansing Michigan
3. W. K. Kellogg Biological Station Michigan State University Hickory Corners Michigan, Great Lakes Bioenergy Research Center Michigan State University East Lansing Michigan
4. W. K. Kellogg Biological Station Michigan State University Hickory Corners Michigan, Great Lakes Bioenergy Research Center Michigan State University East Lansing Michigan, Department of Plant, Soil, and Microbial Sciences Michigan State University East Lansing Michigan

Publication Date:

Fri Oct 26 00:00:00 EDT 2018

Research Org.:

Univ. of Wisconsin, Madison, WI (United States); Battelle Memorial Institute, Columbus, OH (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1479506

Alternate Identifier(s):

OSTI ID: 1479507; OSTI ID: 1609258

Grant/Contract Number:  

FC02-07ER64494; AC05-76RL01830

Resource Type:

Published Article

Journal Name:

Global Change Biology

Additional Journal Information:

Journal Name: Global Change Biology Journal Volume: 24 Journal Issue: 12; Journal ID: ISSN 1354-1013

Publisher:

Wiley-Blackwell

Country of Publication:

United Kingdom

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES; Biodiversity & Conservation; Environmental Sciences & Ecology