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Geographical variation in carbon dioxide fluxes from soils in agro‐ecosystems and its implications for life‐cycle assessment
Author(s) -
Koerber Georgia R.,
EdwardsJones Gareth,
Hill Paul W.,
Canals Llorenç Milà i,
Nyeko Philip,
York Elizabeth H.,
Jones Davey L.
Publication year - 2009
Publication title -
journal of applied ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.503
H-Index - 181
eISSN - 1365-2664
pISSN - 0021-8901
DOI - 10.1111/j.1365-2664.2009.01622.x
Subject(s) - environmental science , soil water , context (archaeology) , biomass (ecology) , primary production , carbon cycle , ecosystem , soil respiration , carbon dioxide , soil carbon , agronomy , life cycle assessment , ecology , production (economics) , soil science , biology , paleontology , macroeconomics , economics
Summary1 Exchange of carbon dioxide (CO 2 ) from soils can contribute significantly to the global warming potential (GWP) of agro‐ecosystems. Due to variations in soil type, climatic conditions and land management practices, exchange of CO 2 can differ markedly in different geographical locations. The food industry is developing carbon footprints for their products necessitating integration of CO 2 exchange from soils with other CO 2 emissions along the food chain. It may be advantageous to grow certain crops in different geographical locations to minimize CO 2 emissions from the soil, and this may provide potential to offset other emissions in the food chain, such as transport. 2 Values are derived for the C balance of soils growing horticultural crops in the UK, Spain and Uganda. Net ecosystem production ( NEP ) is firstly calculated from the difference in net primary production ( NPP ) and heterotrophic soil respiration ( R h ). Both NPP and R h were estimated from intensive direct field measurements. Secondly, net biome production ( NBP ) is calculated by subtracting the crop biomass from NEP to give an indication of C balance. The importance of soil exchange is discussed in the light of recent discussions on carbon footprints and within the context of food life‐cycle assessment (LCA). 3 The amount of crop relative to the biomass and the R h prevailing in the different countries were the dominant factors influencing the magnitude of NEP and NBP . The majority of the biomass for lettuce Lactuca sativa and vining peas Pisum sativum , was removed from the field as crop; therefore, NEP and NBP were mainly negative. This was amplified for lettuces grown in Uganda (−16·5 and −17 t C ha −1 year −1 compared to UK and Spain −4·8 to 7·4 and −5·1 to 6·3 t C ha −1 year −1 for NEP and NBP , respectively) where the climate elevated R h . 4 Synthesis and applications. This study demonstrates the importance of soil emissions in the overall life cycle of vegetables. Variability in such emissions suggests that assigning a single value to food carbon footprints may not be adequate, even within a country. Locations with high heterotrophic soil respiration, such as Spain and Uganda (21·9 and 21·6 t C ha −1 year −1 , respectively), could mitigate the negative effects of climate on the C costs of crop production by growth of crops with greater returns of residue to the soil. This would minimize net CO 2 emissions from these agricultural ecosystems.