QUANTITATIVE AND QUALITATIVE ASSESSMENT OF SOIL ORGANIC CARBON IN NATIVE
AND CROPLAND SODLS IN CALIFORNIA
Principal Investigator:
Laosheng Wu
Associate Professor and CE Water Management Specialist
Department of Environmental Sciences, UC-Riverside
Co-Principal Investigator:
Andrew C. Chang
Professor
Department of Environmental Sciences, UC-Riverside
Collaborating Investigators:
Blake McCullough-Sanden, Farm Advisor, UCCE, Kern County.
Khalid Bali, Farm Advisor, UCCE, Desert Agricultural Research and Extension Center.
Duration of the Project: 2 years
Soil organic carbon (SOC) helps to stabilize soil aggregates, increases water-holding
capacity, promotes soil fertility, and sequesters atmospheric carbon dioxide
(CO2) to mitigate greenhouse gas emissions against their effects
on global warming. Organic matter in soils originates from various sources,
has complex chemical structures and decomposes at different rates. In general,
it is conceptualized to consist of one pool that has a rapid turnover rate
and another pool with a slower turnover rate. Limited information suggests
that carbon storage and turnover rates of SOC are different in native and
irrigated cropland soils, and such differences are related to the properties
of soil organic matter (SOM) and degree of soil aggregation. No such information,
however, is available with respect to California soils. Hence, a study of
SOM associated with different size fractions of soil aggregates should improve
our understanding of SOC storage and dynamics in California soils. The overall
objective of the proposed research is to determine the difference in carbon
storage and dynamics associated with bulk soil and with various size fractions
of aggregates in native soils and in soils managed under different cropping
systems in California. Paired native and irrigated cropland soils will be
collected from sites in the San Joaquin and Imperial Valleys where records
of cropping history are available. Total soil organic carbon (SOC), labile
carbon (LC), light fraction of OC (LF), and natural abundance of d13C will
be determined on bulk soil samples and on aggregates of various size fractions.
Experimental data from virgin and systems under various cropping regimes will
be evaluated in terms of their sustainability and possibility as a tool to
predict the soils' capacity to store and sequester carbon.
Soil organic matter plays a key role in sustaining agricultural production
so that it can supply nutritious foods, useful fibers, and natural resource
products in adequate amounts at low cost without adverse effects on the physical
environment or consumer. The SOC storage and turnover rate is the determinant
factor influencing soil structure and carbon sequestration in soil. Knowledge
gained from this study will help to ensure a physical environment of high
quality by enabling the growers to manage and enjoy their natural resource
endowments more wisely.