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United States Department of Agriculture

Agricultural Research Service

Research Project: GLOBAL CHANGE AND BELOWGROUND PROCESSES IN AGRICULTURAL SYSTEMS
2008 Annual Report


1a.Objectives (from AD-416)
Reduce uncertainty regarding: (1) the effects of rising atmospheric carbon dioxide concentration on crop and pasture production; and (2) the role of agronomic ecosystems in the sequestration of atmospheric carbon dioxide as organic carbon in soils, as well as the release of carbon dioxide and other greenhouse gases from soil, as affected by agricultural management practices. Specifically, determine effects of carbon dioxide on belowground processes which affect crop productivity, soil physicochemical/biological properties, carbon/nutrient cycling, and trace gas efflux from soil.


1b.Approach (from AD-416)
Two-year rotational cycles of sorghum and soybean will be maintained under two cropping systems: conventional, using tillage without cover crops; and conservation, using no-till with winter cover crops in rotation (wheat, crimson clover, and sunn hemp). Each cropping system will be grown under current and projected levels of atmospheric carbon dioxide. In addition, a Southeastern pasture system study, using bahiagrass exposed to these carbon dioxide levels, has been initiated. Carbon flux to plants (growth, physiology, and yield) and soil will be determined with supporting data on soil physicochemical properties. Emphasis will be given to measuring soil carbon storage, root development patterns, characterizing the rhizosphere, and trace gas efflux from soil. The relationships of nitrogen to carbon dynamics and to water quality will be examined. Root growth, decomposition, and microbial community structure will be quantified in respect to carbon flow. The effects of carbon dioxide on agronomic systems is a critical, yet neglected, area of research. Integrating data from these studies will help provide a mechanistic understanding of the potential of agronomic systems to mitigated global change via sequestration of atmospheric carbon dioxide in soil.


3.Progress Report
NP204, Component I: Carbon Cycle and Carbon Storage - Cropping Systems and Tillage; Grazinglands, Conservation Reserve Program (CRP) and Buffers. Global change research at the ARS-USDA National Soil Dynamics Laboratory (NSDL) addresses the impacts of elevated carbon dioxide within differing cropping systems (e.g., conservation vs. conventional) as well as under differing pasture management practices (nitrogen) on soil carbon storage. The final (tenth) year of the cropping systems study was completed. Aboveground biomass data have been collected and analyzed; root data are being processed; soil physicochemical properties, including soil carbon are being assessed. Pasture aboveground biomass data have been collected and analyzed; soil cores for root and soil carbon have been collected and are being processed.

NP 204, Component I: Carbon Cycle and Carbon Storage - Organic Carbon Transformations. Our research is seeking to understand factors controlling rate, mass, and timing of carbon dioxide sequestered, fate of carbon within the soil, rate of production and turnover of soil carbon pools, and processes and mechanisms of soil carbon loss. We are also investigating the effects of carbon dioxide on changes in plant structure and subsequent impacts on decomposition (e.g., microbial processes), and soil carbon storage. Soil carbon data from the first four years of the cropping systems study have been published; the remaining six years of data have been collected and are being processed. Soil carbon data have also been collected from the pasture study. Carbon dioxide efflux from both systems continues to be monitored as does carbon flow through soil water.

NP 204, Component II: Trace Gases - Cropping Systems; Rangelands, Pastures and Wetlands. Our research addresses the impacts of elevated carbon dioxide within conservation vs. conventional cropping systems as well as under differing pasture management practices (nitrogen) on trace gas (carbon dioxide, nitrous oxide, and methane) efflux from soil. Trace gases were monitored throughout the final year of the cropping systems study; a publication on the results is in internal review. Trace gases have also been monitored throughout the pasture study; samples are being analyzed and data summarized.

NP204, Component III: Agricultural Ecosystem Impacts - Cropping Systems; Grazinglands (Range and Pastures). Our research involves measurement of plant responses (above and below the ground) in conventional vs. conservation cropping systems and within improved vs. unimproved pastures with increasing atmospheric carbon dioxide and the ability of these systems to assist in mitigation of this rise via soil carbon sequestration. The final year of the cropping systems study was completed. Aboveground biomass data have been collected and analyzed; root data are being processed; soil physicochemical properties, including soil carbon are being assessed. Aboveground pasture biomass data have been collected and analyzed; soil cores for root and soil carbon have been collected and are being processed. Minirhizotron and soil nutrient data continue to be collected and processed.


4.Accomplishments
1. Determined the response of invasive plants important to the southeastern U.S. to elevated atmospheric carbon dioxide.

Invasive weeds can impact biodiversity and cost billions of dollars each year in control and lost productivity. Understanding how the rising level of carbon dioxide may alter establishment, spread, and control of invasive weeds will be crucial to future management strategies. Purple (Cyperus rotundus) and yellow (C. esculentus) nutsedge and Chinese privet (Ligustrum sinense) had more biomass when grown under elevated carbon dioxide, suggesting that these invasive weeds will present agricultural producers with even greater problems as atmospheric carbon dioxide continues to rise.

This accomplishment addresses Global Change National Program (NP204), Agricultural Ecosystem Impacts, Problem Area 4. Pests.

2. Analyzed nutrient composition of crop tissue grown under elevated atmospheric carbon dioxide and no-tillage management.

The quantity and quality of plant tissue may impact feed quality and nutrient cycling in a future, high CO2 world. The findings of this research showed that high CO2 increased nutrient content (e.g., N, P, K), especially in grain. This increase was greater for soybean (Glycine max) than for sorghum (Sorghum bicolor). Crop residues (stover and roots), which become nutrient inputs to the soil, showed similar increases in nutrient content but were more variable than grain. Predictions of nutrient outputs under future, high CO2 conditions will be more reliable than those associated with nutrient inputs to the soil from crop residues.

This accomplishment addresses Global Change National Program (NP204), Agricultural Ecosystem Impacts, Problem Area 2. Cropping Systems.

3. Determined the impact of elevated atmospheric carbon dioxide on soil carbon dynamics.

Increasing atmospheric CO2 has led to concerns about changes in the global environment and, in particular, how increased crop growth may impact the buildup of soil organic matter. Two years of free-air CO2 enrichment led to more soil carbon storage in a sorghum production system regardless of irrigation regime. Increased biomass production, from growth in high CO2, suggests more carbon input to soil which can improve soil quality as well as help mitigate the rise in atmospheric carbon dioxide.

This accomplishment addresses Global Change National Program (NP204), Carbon Cycle and Carbon Storage, Problem Area 8. Interactions of Carbon and Nitrogen Cycles.


5.Significant Activities that Support Special Target Populations
We have recently initiated investigations into alternative crops (sweet potato, cassava, and kudzu) which small farmers might grow, with little input, for ethanol production.


6.Technology Transfer

Number of Non-Peer Reviewed Presentations and Proceedings8
Number of Newspaper Articles and Other Presentations for Non-Science Audiences3
Number of Other Technology Transfer3

Review Publications
Prior, S.A., Runion, G.B., Rogers Jr, H.H., Torbert III, H.A. 2008. Effects of atmospheric CO2 enrichment on crop nutrient dynamics under no-till conditions. Journal of Plant Nutrition. 31(4):758-773.

Prior, S.A., Torbert III, H.A., Runion, G.B., Rogers Jr, H.H., Kimball, B.A. 2008. Free-air CO2 enrichment of sorghum: Soil carbon and nitrogen dynamics. 37:753-758.

Rogers Jr, H.H., Runion, G.B., Prior, S.A., Price, A.J., Torbert III, H.A., Gjerstad, D.H. 2008. Effects of elevated atmospheric CO2 on invasive plants: Comparison of purple and yellow nutsedge (Cyperus rotundus L. and C. esculentus L.). Journal of Environmental Quality. 37:395-400.

Smith, K.E., Runion, G.B., Prior, S.A., Price, A.J., Rogers Jr, H.H., Torbert III, H.A. 2008. Chinese privet (Ligustrum sinenese) in an elevated CO2 environment. Botany Research Journal. 1:43-48.

Kang, H., Shannon, D.A., Prior, S.A., Arriaga, F.J. 2008. Hedgerow pruning effects on light interception, water relations and yield in alley cropped maize. Journal of Sustainable Agriculture. 31(4):115-137.

Kornecki, T.S., Prior, S.A., Runion, G.B., Rogers Jr, H.H., Erbach, D.C. 2008. A hydraulic core extraction-cutting device for soil-root studies. Communications in Soil Science and Plant Analysis. 39:1080-1089.

Last Modified: 11/28/2014
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