Soil management practices to mitigate nitrous oxide emissions and inform emission factors in arid irrigated specialty crop system

Authors: ZHU-BARKER, XIA - University Of California, Davis; CARLSON, MARY - Colorado State University; EASTER, MARK - Colorado State University; SWAN, AMY - Colorado State University; THOMPSON, LUCAS - Colorado State University; HORWATH, WILLIAM - University Of California, Davis; PAUSTIAN, KEITH - Colorado State University; Steenwerth, Kerri

Submitted to: Soil Systems
Publication Type: Literature Review
Publication Acceptance Date: 11/21/2019
Publication Date: 11/24/2019
Citation: Zhu-Barker, X., Carlson, M., Easter, M., Swan, A., Thompson, L., Horwath, W.R., Paustian, K., Steenwerth, K.L. 2019. Soil management practices to mitigate nitrous oxide emissions and inform emission factors in arid irrigated specialty crop system. Soil Systems. https://doi.org/10.3390/soilsystems3040076.
DOI: https://doi.org/10.3390/soilsystems3040076

Interpretive Summary: Greenhouse gas (GHG) emissions from California agriculture have been predicted to represent 8% of the state’s total GHG emissions. Although specialty crops compose the majority of the state’s crops in both economic value and land area, the portion of GHG emissions contributed by them is still highly uncertain. Current and emerging land management practices affect the mitigation of those emissions. Herein, we review scientific literature on impacts of agricultural practices in California specialty crop systems on GHG emissions. As such studies from most major specialty crop systems in California are limited, we focus on two annual and two perennial crops with the most data from the state: tomato, lettuce, wine grapes and almond. Nitrous oxide emission factors were developed and compared to IPCC emission factors, and state-wide emissions for these four crops were calculated for specific agricultural management practices. Uncertainties caused by low gas sampling frequency in these studies were identified and discussed. These uncertainties can be remediated by robust and standardized estimates of GHG emissions from changes in agricultural management practices in California specialty crop systems. Promising practices to reduce GHG emissions and meet crop production goals, pertinent gaps in knowledge on this topic and limitations of this approach are discussed.

Technical Abstract: Greenhouse gas (GHG) emissions from California agriculture have been predicted to represent 8% of the state’s total GHG emissions. Although specialty crops compose the majority of the state’s crops in both economic value and land area, the portion of GHG emissions contributed by them is still highly uncertain. Current and emerging land management practices affect the mitigation of those emissions. Herein, we review scientific literature on impacts of agricultural practices in California specialty crop systems on GHG emissions. As such studies from most major specialty crop systems in California are limited, we focus on two annual and two perennial crops with the most data from the state: tomato, lettuce, wine grapes and almond. Nitrous oxide emission factors were developed and compared to IPCC emission factors, and state-wide emissions for these four crops were calculated for specific agricultural management practices. Uncertainties caused by low gas sampling frequency in these studies were identified and discussed. These uncertainties can be remediated by robust and standardized estimates of GHG emissions from changes in agricultural management practices in California specialty crop systems. Promising practices to reduce GHG emissions and meet crop production goals, pertinent gaps in knowledge on this topic and limitations of this approach are discussed.