Project title:
Carbon sequestration in dryland and irrigated agroecosystems: Quantification at different scales for improved prediction (UN-L Carbon Sequestration Program)
S. Verma, K. Cassman, T. Arkebauer, A. Dobermann, A. Gitelson, K. Hubbard, J. Knops, D. Walters
Duration: 2000-present
Funding: U.S.
Department of Energy, U.S. Department of Energy - Nebraska EPSCoR
Contact:
Shashi
Verma
University
of Nebraska-Lincoln
School
of Natural Resource Sciences
Lincoln,
68583-0728
(phone:
402-472-6702)
Web
site:
UNL
Carbon Sequestration Program
The Carbon Sequestration Program is a focused interdisciplinary research program to improve our understanding of biophysical controls on soil carbon (C) sequestration and to apply this knowledge towards development of improved methods to predict annual C sequestration. Recent studies have highlighted the potential of agroecosystems to offset a significant amount of anthropogenic C emission through soil C sequestration; therefore, our research focuses on C balance measurements within the context of the major agroecosystems of the north-central USA. Nebraska is uniquely situated for this research because of its location at the intersection of major continental climate zones with both rainfed and irrigated cropping systems. Our over-arching hypothesis is two-fold: (1) through the use of innovative management practices, that increase plant primary production and minimize adverse environmental effects, the major agroecosystems in the north-central USA will substantially increase present rates of C sequestration and (2) by improving our understanding of biophysical controls on annual C balance we can predict the effects of various management practices on C sequestration in these agroecosystems.
Our central hypothesis is that the potential for C sequestration and high productivity in agricultural systems is greatest in intensive continuous maize and maize-soybean systems, for which Nebraska is one of the most representative states in the country. Unlike neighboring states, however, irrigated maize-based systems also are prevalent because the climate in much of Nebraska is too dry to achieve adequate maize yields and the state has bountiful ground and surface water resources. Because crop water relations and nitrogen supply are among the primary determinants of crop productivity and C balance, the study of maize-based systems in Nebraska allows a wide extrapolation domain, which makes the location ideally suited for the proposed research program.
The overall long-term goal of the program is to investigate the C sequestration potential of major rainfed and irrigated agroecosystems in the north-central USA using an ecosystem-level research approach, and the role of C sequestration in mitigating increases in atmospheric CO2 concentrations. We intend to better understand the biophysical controls on C sequestration and to apply this knowledge towards development of land management technologies to increase C sequestration and to predict how land managers might benefit from increased C sequestration by enhancing revenues and/or incomes. Specific objectives of the proposed effort include:
· Quantify the amount of C sequestered at the landscape level, employing eddy covariance flux systems year-round, in major rainfed and irrigated crop production systems that provide a wide range of primary productivity.
· Quantify and explain the interannual variability of C sequestered in these ecosystems by detailed direct measurements of C dynamics in relation to biophysical controlling factors at different spatial scales.
· Develop improved analytical methods, including remote sensing-based methods, for linking ecosystem level measurements of C balance with those based on mass balance at the plant and soil level.
· Develop cost-effective procedures for predicting annual C sequestration and changes in soil C stocks at the scale of a single production field by comparing methodologies based on four approaches: (a) eddy covariance measurements of whole-field C flux, (b) destructive sampling and soil C measurements, (c) use of existing ecosystem C models with input data for soil properties and crop biomass production, and (d) destructive sampling in combination with information about spatial variability in yields, crop residue inputs and soil properties that govern C cycling.
· Quantify the intrinsic "C costs" of crop management practices (e.g., N fertilizer, irrigation, grain drying) to obtain estimates of net C sequestration. Identify management practices that maximize the net C sequestration in these agroecosystems.
· Design mechanisms including markets, or mixtures of market and other elemental forms of organizations and mechanisms that hold the greatest potential in enhancing C sequestration.
We are investigating C sequestration within three major agroecosystems, each represented by a large production field (1/4 section) at Mead, NE:
Site 1: Irrigated continuous maize system
Site 2: Irrigated maize-soybean rotation
Site 3: Rainfed maize-soybean rotation
Our effort
includes: (a) quantifying annual amounts of C sequestered and the associated
interannual variability, at the landscape level, employing eddy covariance flux
systems year-round, (b) quantifying soil C changes using georeferenced soil
samples, (c) developing reliable, cost-effective procedures for predicting
annual C sequestration and changes in soil C stocks at the scale of a single
production field using detailed crop yield mapping, (d) identify sensitive
predictors of intra- and inter-annual C flux based on measurements taken at the
soil-plant level and from remotely sensed data on biophysical properties of
plant canopies and soil conditions and (e) ensure science-based incentive
mechanisms can be created to achieve C sequestration goals while ensuring
benefits exceed costs. To achieve this effort, we will make detailed
measurements of plant photosynthesis and respiration, and soil C respiration
and examine the interannual variability in C sequestration in terms of
biophysical and physiological controlling factors. We will also quantify
"C costs" of applied energy-dependent inputs (e.g., N fertilizer,
irrigation, grain drying), and changes in N2O and CH4
emissions and integrate these results into net C sequestration values. In
the second phase of this project, we plan to refine our management strategies
to further increase C sequestration and productivity and decrease greenhouse
gas fluxes associated with N fertilizer use.
Key
results:
Publications: