Progress 10/01/11 to 01/31/13

Outputs
OUTPUTS: PI is deceased PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
PI is deceased

Publications

• No publications reported this period

Progress 01/01/11 to 12/31/11

Outputs
OUTPUTS: Activities this past year included the analysis of a one-year long set of daily soil temperature data for the purpose of determining an effective thermal diffusivity value for soil at a semi-arid rangeland site near Oracle, Arizona. Observed daily temperature values at the 0.5 m depth were input to the analytic model of Matthias and Warrick to calculate soil temperatures at 1, 3, and 5 meter depths for comparison with observed values at those depths. Calculations were repeated with updated thermal diffusivity values until good was achieved between observed and modeled temperatures. The model includes both deterministic and stochastic components. PARTICIPANTS: This project involves participation of Ms. Sheri Musil of the University of Arizona. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
A soil thermal diffusivity value of 500 centimeters squared per day was found to give good agreement between observed and modeled temperature values at 1, 3, and 5 meters depths at the rangeland site. Root-mean-square deviations between observed and modeled values ranged from 0.13 to 1.35 degrees Celsius at the three depths. This provided another indirect approach for calculating soil thermal diffusivity for a semi-arid site with only limited data input. The results from this approach has led to a manuscript currently in journal review.

Publications

• No publications reported this period

Progress 01/01/10 to 12/31/10

Outputs
OUTPUTS: A dataset with one full year (mid-1983 to mid-1984) of hourly weather and soil temperature values collected to a depth of 5 meters at a semi-arid grassland site north of Tucson, Arizona has been compiled. These data are available upon request for use by other researchers. PARTICIPANTS: This project involves the participation of Dr. Paul Brown and Ms. Sheri Musil of the University of Arizona. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
During this year work was directed toward compiling a dataset of hourly weather and soil temperature values collected in the mid-1980s at a semi-arid grassland research site north of Tucson, Arizona. The data are relatively unique in that soil temperatures were measured to a depth of 5 meters below ground level. These data will be used to evaulate two models (analytical & numerical) for prediction of soil temperatures at relatively deeper depths. The models were developed previously (by Matthias and Warrick) but have not been tested for prediction of temperatures at depths greater than 1 meter.

Publications

• No publications reported this period

Progress 01/01/09 to 12/31/09

Outputs
OUTPUTS: Research on elevated carbon dioxide effects on wheat grain and straw were published in Animal Feed Science and Technology. PARTICIPANTS: This project involves the cooperation and assistance of Drs. Markus Tuller, Marcel Schaap, and Paul Brown of the University of Arizona. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
This project is directed toward modeling evapotranspiration by grass and other selected landscape plants in the arid southwestern U.S. Hourly and daily values of plant water use measured with large weighing lysimeters at the Campus Agricultural Center in Tucson will be compared with modeled values. No significant advances in this work are available to be reported.

Publications

• Porteus, E., J. Hill, A.S. Ball, B.A. Kimball, G.W. Wall, F.J. Adamsen, D.J. Hunsaker, R.L. LaMorte, S.W. Leavitt, T.L. Thompson, A.D. Matthias, T.J. Brooks, and C.F. Morris. 2009. Effects of Free Air Carbon dioxide Enrichment (FACE) on the chemical composition and nutritive value of wheat grain and straw. Animal Feed Science and Technology. 149: 322-332.

Progress 01/01/08 to 12/31/08

Outputs
OUTPUTS: Research on elevated carbon dioxide and irrigation effects on nitrogen gas emissions from irrigated sorghum was completed in 2008. The results from this research were disseminated to the scientific community through a publication in Soil Science Society of America Journal. PARTICIPANTS: The work on evapotranspiration and canopy resistance modeling involves the cooperation of Drs. Markus Tuller, Marcel Schaap, and Paul Brown. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
We learned that elevated carbon dioxide did not significantly impact N gas emissions from soil within an irrigated sorghum crop in Arizona. The policy and management implication of this finding is that future higher concentrations of atmospheric carbon dioxide are unlikely to significantly affect N gas emissions from agricultural systems similar to the irrigated sorghum studied in this research. This project began in 2008 to focus on modeling evapotranspiration and canopy resistances for well irrigated grass and landscape vegetation in the arid southwestern U.S. No significant advances in this work are yet available to be reported.

Publications

• Welzmiller, J.T., Matthias, A.D., White, S. and Thompson, T.L. 2008. Elevated carbon dioxide and irrigation effects on soil nitrogen gas exchange in irrigated sorghum. Soil Sci. Soc. Am. J. 72:393-401.

Progress 01/01/07 to 12/31/07

Outputs
OUTPUTS: This project is about the spatial and temporal variability of atmospheric ammonia near land applied biosolids. The two main research tasks include the development and testing of portable samplers for measurement of ambient ammonia in air, and the modeling of ammonia emissions from biosolids incorporated into soils. No significant advances in either task occurred during 2007. Work this past year, however, focused on completion of analysis and interpretation of earlier results from field measurements of nitrogen gas emissions from an irrigated sorghum crop ecosystem. Results from that research will be published in the Soil Science Society of America Journal in early 2008. TARGET AUDIENCES: Municipal wastewater treatment plant operators. Land applicators of biosolids

Impacts
The research addresses the impacts of land-applied biosolids on air quality and odor. This project specifically considers the emissions of ammonia and other N-gas constituents from soils.

Publications

• No publications reported this period

Progress 01/01/06 to 12/31/06

Outputs
The objective of this project is to assess the variability of ammonia in air near land applied biosolids in Arizona. The research involves 1) the development and the testing of field portable samplers for measurement of ambient ammonia concentrations within air near the ground, and 2) the use of measured ammonia concentrations and weather data to model ammonia emissions from biosolids incorporated within alkaline soils. There are no new significant findings to report for 2006. Laboratory work progresses on the assembly and testing of battery operated ambient air ammonia samplers. Work also continues on the assembly of a micrometeorological data acquisition system for use in conjunction with the air samplers. Ammonia collection efficiencies of sulfuric acid traps within samplers will be tested at different air flow rates, temperatures, and ammonia concentrations. Work continues on testing an atmospheric diffusion model for predicting ammonia emissions from from land applied biosolids.

Impacts
This research addresses the effects biosolids upon air quality and odor near land disposal areas in Arizona.

Publications

• Matlaga, J.A. 2006. Ammonia Emissions from Land Applied Biosolids in a Semiarid Region. M.S. Thesis. Dept. of Soil, Water and Environmental Science, Univ. of Arizona. 50 pages.

Progress 01/01/05 to 12/31/05

Outputs
The overall objective of this project is to assess the variability of ammonia in air near land applied biosolids in Arizona. The research involves 1) the development and the testing of field portable samplers for measurement of ammonia concentrations, and 2) the use of measured ammonia concentrations and weather data to model ammonia emissions from land applied biosolids. There are no new findings to report following the revision of the project in 2005. Work continues on the development of the ammonia samplers. Each sampler is a battery powered system that collects ammonia from air bubbled through a 0.05 M sulfuric acid trap. Several units of this collection system have been assembled for laboratory and field testing of collection efficiency and sensitivity to ammonia concentrations. The samplers will be tested at different air flow rates, environmental temperatures, and ammonia concentrations. The influences of other atmospheric constituents, such as particulate matter, on the ability of the samplers to detect low levels of ammonia will also be tested.

Impacts
This research addresses the effects biosolids upon air quality and odor near land disposal areas in Arizona.

Publications

• No publications reported this period

Progress 01/01/04 to 12/31/04

Outputs
Land application of biosolids is an increasingly important method for disposal of treated sewage (biosolids), but odors from ammonia and other gases emitted during and after land application may be a source of public concern. Replicated dynamic chamber measurements of ammonia emissions from biosolids applied to samples of soil were performed out of doors during four two-day periods from January to April 2004. Results indicate that mean (and standard deviation) ammonia emissions from biosolids (anaerobically digested, 8 to 10% thickened) incorporated within dry Gila fine sandy loam soil ranged from 1.2 (4.1) to 10.6 (1.0) kg NH3-N/ha/day. These emissions were on average only about 0.3 to 3.0% of the initial ammonium nitrogen within the biosolids. The results indicate that incorporation of biosolids within soil during application results in relatively less odor and negligible loss of ammonia to the atmosphere.

Impacts
This research addresses the effects biosolids upon air quality and odor near land disposal areas in Arizona.

Publications

• No publications reported this period

Progress 01/01/03 to 12/31/03

Outputs
Land application is an important method for disposal of treated sewage (biosolids). Biosolids add nitrogen to soil, however, odors from ammonia and other gases during and after land application may be a source of public concern. Replicated laboratory measurement of ammonia emissions from biosolids were performed during 2003 using a dynamic chamber method. Results indicate that ammonia emissions from biosolids (anaerobically digested, 8 to 10% thickened, from the Ina Road Wastewater Treatment Facility in Tucson) applied to the surface of dry Gila fine sandy loam soil were on average 22% of the initial ammonium nitrogen within the biosolids. Emissions from the surface applied biosolids were below detection limits of the chamber method 48 hours after application. Ammonia emissions from biosolids incorporated within the dry Gila soil were 11% of the initial ammonium N content of the biosolids. Emissions were below detection limits 24 hours after incorporation of the biosolids, which indicate the importance of incorporation as soon as possible following surface application.

Impacts
This research addresses the effects biosolids upon air quality and odor near land disposal areas in Arizona.

Publications

• No publications reported this period

Progress 01/01/02 to 12/31/02

Outputs
Land application is an important method for disposal of treated waste water (biosolids) in the U.S. Biosolids amended to agricultural soils add important plant nutrients, however, odors from ammonia, hydrogen sulfide, and other gases produced during and after land application may be a source of public concern. Review of literature indicates that the rate and total amount of ammonia volatilized from land applied biosolids varies depending upon soil, weather and management related factors. Previous studies indicate that ammonia volatilization is enhanced by high temperatures, high rates of evaporation of water, and high pH of biosolids material. Previous research also indicates that up to 87% of ammoniacal N present within biosolids can be volatilized within several days following application. Work in 2002 focused on literature review and development of methods for measurement of ammonia and hydrogen sulfide concentrations and fluxes in air over biosolids applied to land. A colorimetric based toxic gas monitor was tested in the laboratory for use with a dynamic chamber method for continuous measurement of ammonia and hydrogen sulfide concentrations and fluxes. Field studies comparing the dynamic chamber method with passive diffusive samplers are planned for the summer of 2003.

Impacts
This research is studying the effects of land application of biosolids upon air quality near disposal areas. This research should provide data concerning the fluxes and concentrations of ammonia and hydrogen sulfide gases in air over biosolids applied to agricultural land in Arizona.

Publications

• No publications reported this period

Progress 01/01/01 to 12/31/01

Outputs
Most N2O (and CO2) flux measurements over soil are made using closed chambers. Chambers are relatively inexpensive, small and portable, which often permits multiple flux measurements over small areas of soil. They can, however, markedly change the concentration gradient (which drives the flux) between soil and the air within the chamber. Chambers can also change the thermal environment of the soil. All of these changes can alter biological production and diffusion of the gas from soil to the chamber, which introduces uncertainty in the flux measurement. Current work is addressing the question of how the thermal and radiative properties of chamber materials (e.g. metal, PVC, clear plastic) affect soil and air temperatures, with the intent that chamber design and materials of construction be optimized to minimize impacts. Results are not yet available.

Impacts
Agricultural production of food and fiber impacts upon the atmospheric composition of several important greenhouse gas species, including carbon dioxide and nitrous oxide. The role of managed, agricultural soils in affecting the atmospheric composition of these gases is currently the subject of much scientific interest. In order to help assess this role, chamber methods are needed that accurately measure trace gas fluxes from soil to the atmosphere, and this research is studying how improved accuracy can be achieved through optimized chamber designs and materials of construction.

Publications

• Peralta-Hernandez, A.R. 2001. El Nino Southern Oscillation (ENSO) Effects on Hydro-Ecological Parameters in Central Mexico. Ph.D. Dissertation. University of Arizona Library. 157 pages

Progress 01/01/00 to 12/31/00

Outputs
Closed chambers are commonly used to measure fluxes of trace gases, such as nitrous oxide and carbon dioxide, between soils and the atmosphere. The buildup of trace gas within a chamber can, however, decrease the gas concentration gradient between the soil and the atmosphere, which gradually decreases the flux. A chamber can also modify the soil temperature, which may affect the production of the gas within the soil. Thus, the gas flux into a chamber may markedly differ from the flux that would occur if no chamber were present. A numerical modeling and field study is being done to provide data for optimizing chamber designs and materials of construction that minimize the impacts chambers have upon soil temperatures under a wide range of soil moisture and heat load conditions. Results from this study are not yet available.

Impacts
Agricultural production of food and fiber impacts upon the atmospheric composition of several important greenhouse gas species, including carbon dioxide and nitrous oxide. The role of managed, agricultural soils in affecting the atmospheric composition of these gases is currently the subject of much scientific interest. In order to help assess this role, chamber methods are needed that accurately measure trace gas fluxes from soil to the atmosphere, and this research is studying how improved accuracy can be achieved through optimized chamber designs and materials of construction.

Publications

• Matthias, A.D., Fimbres, A., Sano, E.E. Post, D.F., Accioly, L., Batchily, B.K. and Ferreira, L.G. 2000. Surface roughness effects on soil albedo. Soil Sci. Soc. Am. J. 64:1035-1041.

Progress 01/01/99 to 12/31/99

Outputs
Collaborative work with scientists from the University of Arizona, Arizona State University, and the U.S. Water Conservation Laboratory in Phoenix continued during the second year of a two year free-air CO2 enrichment (FACE) study of sorghum grown under ample and limiting water supplies. This field study was at the Maricopa Agricultural Center. The 1999 sorghum growing season at Maricopa extended from June to November. The FACE treatment plants were grown under atmospheric CO2 concentrations elevated to 200 ppm above current ambient concentrations (370 ppm). Irrigation was by flood application with one-half of the plant population water stressed and one-half well watered. As part of the larger FACE study, fluxes of N2O were measured following irrigations using portable closed chambers deployed over plants and soil. Results from the 1999 support preliminary evidence from the 1998 season that FACE did not markedly increase N2O fluxes under water stress and well-watered conditions.

Impacts
Humans are altering the carbon and nitrogen cycles of terrestrial ecosystems by combustion of fossil fuels, which emits carbon dioxide to the atmosphere. This research is studying how increased atmospheric carbon dioxide may increase the release of nitrous oxide gas to the atmosphere by soil bacteria. Atmospheric concentrations of carbon dioxide and nitrous oxide are increasing and both are important greenhouse gases that help warm the earth.

Publications

• Kimball, B.A., LaMorte, R.L. Pinter, Jr., P.J., Wall, G.W., Hunsaker, D.J., Adamsen, F.J., Leavitt, S.W., Thompson, T.L., Matthias, A.D. and Brooks, T.J. 1999. Free-air CO2 enrichment (FACE) and soil nitrogen effects on energy balance and evapotranspiration of wheat. Water Resources Res. 35:1179-1190.
• Matthias, A.D., Post, D.F., Accioly, L., Fimbres, A., Sano, E.E. and Batchily, A.K. 1999. Measurement of albedos for small areas of soil. Soil Science. 164:293-301.
• Welzmiller, J.T., Thompson, T.L., White, S.A. and Matthias, A.D. 1999. Free-air CO2 enrichment effects on N2O emissions from irrigated sorghum. Agron. Abst., p. 259.

Progress 01/01/98 to 12/31/98

Outputs
Work was done in collaboration with colleagues from the University of Arizona and the U.S. Water Conservation Laboratory in Phoenix to determine the effects of free-air CO2 enrichment (FACE) on N2O emissions from soil at ample and limiting water supplies within an irrigated sorghum ecosystem. This research is part of a two year (1998 and 1999) FACE experiment at the Maricopa Agricultural Center. The FACE treatment plants were grown under atmospheric CO2 concentrations elevated to approximately 200 ppm above current ambient concentrations (approximately360 ppm). Irrigation was by flood application with one-half of the plant population water stressed and one-half well watered. The sorghum received a seasonal total of about 250 kg N/ha in the forms of dry urea and urea-ammonium nitrate solution. Fluxes of N2O were measured at mid-day on seven days during the 1998 growing season (July to December) using portable closed chambers deployed over plants and soil. Preliminary results indicate no marked effect of FACE on N2O fluxes under water stress and well-watered conditions.

Impacts
(N/A)

Publications

• Matthias, A.D. and Peralta-Hernandez, A.R. 1998. Modeling temperatures in soil under an opaque cylindrical enclosure. Agric. For. Meteorol. 90:27-38.

Progress 01/01/97 to 12/31/97

Outputs
A one-dimensional, finite difference model of soil temperatures beneath an opaque (polyvinyl chloride), cylindrical, closed-chamber was validated using field data. The model was originally developed in 1996 to study how gas flux chambers affect the microclimate of the underlying soil. In 1997 the model was modified to incorporate recent research on the modeling of transient heat flow under plastic mulch-covered soil. The model now uses linear forms of the energy balance equations for the chamber and the soil, including evaporation of water from soil into the chamber. Root mean square deviations between modeled and measured soil surface temperatures were about 1.8 and 1.4 C for dry and wet soils. The model was used to evaluate soil temperature sensitivity to chamber characteristics, including reflectivity, emissivity and size of chamber.

Impacts
(N/A)

Publications

• GUILBAULT, M.R. and MATTHIAS, A.D. 1998. Emissions of N2O from Sonoran Desert and effluent-irrigated grass ecosystems. J. of Arid Environments. 38:87-98.
• WEBER, M.A. 1997. N2O emissions from wheat agro-ecosystems under elevated atmospheric CO2. M.S. Thesis. Dept. of Soil, Water and Environmental Science. University of Arizona.

Progress 01/01/96 to 12/30/96

Outputs
Measurement of trace-gas exchanges between the soil and the atmosphere can be done by deploying a chamber on the soil and determining changes of trace-gas concentration inside the chamber. Although chambers are relatively easy to use, microclimate perturbations due to the chamber may occur resulting in altered trace-gas production, consumption and transport processes within the soil. This project is focussed on measuring and modeling microclimate perturbations under chambers. This past year, a one- dimensional, finite-difference model was developed which simulates soil and chamber temperatures and humidity within open and closed chambers. Model results compared favorably with measurements made in June 1996 using a white-painted, polyvinyl chloride chamber deployed for up to 50 minutes on Gila fine sandy loam soil. The soil surface cooled at an average rate of 0.2 C min-1 when the chamber was deployed on dry soil. On wet soil, the surface warmed at a rate of 0.04 C min-1.

Impacts
(N/A)

Publications

• MATTHIAS, A.D. and PERALTA-HERNAndEZ, A.R. 1996. Effects of a trace-gas chamber on soil environment. Agron. Abst. p. 15.

Progress 01/01/95 to 12/30/95

Outputs
Chambers are commonly used to measure the often small and variable fluxes of trace gases, such as N2O, from soil to the atmosphere. Chambers can, however, markedly perturb soil gas concentrations gradients and microclimates at the soil/atmosphere interface, which may cause significant error in the flux measurement. Both closed and flow-through (dynamic) chambers, when placed on sunlit soil, alter the surface energy balance as well as subsurface temperatures. Shading of soil and modification of turbulent air flow by the chamber may change evaporation rates, soil temperatures, diffusion coefficients and gas production/consumption rates. This project is working toward assessment of microclimate changes resulting from chamber placement over soil. A one- dimensional, finite difference model of energy transfer between soil and chamber is under development. Measurements of microclimate changes within chambers covering soil for 30 minutes at mid-day indicate soil temperature perturbations of > 6 C at 0.01 m depth.

Impacts
(N/A)

Publications

• NO PUBLICATIONS REPORTED THIS PERIOD.

Progress 01/01/94 to 12/30/94

Outputs
Chambers are the method of choice for measurement of nitrogen oxide fluxes from soil within most ecosystems. Chambers are used because they are most suitable for quantifying the often small (and variable) fluxes of N2O and NOx. Chambers do, however, perturb soil gas concentration gradients and microclimates at the soil/atmosphere interface. These perturbations may introduce significant error in the flux measurement. Both closed and flow-through (dynamic) chambers, when placed on sunlit soil, markedly affect the surface energy balance. Shading and modification of turbulent air flow by the chamber may change evaporation rates, soil temperatures, gas diffusion coefficients and gas production/consumption rates. This project is directed toward measuring and modeling chamber effects on soil microclimate, particularly under irrigated, desert conditions. A one-dimensional, finite difference model is being developed to simulate time-dependent energy flow within chambers and soil. This should lead to improved understanding of how chambers influence the flux under study.

Impacts
(N/A)

Publications

• NO PUBLICATIONS REPORTED THIS PERIOD.

Progress 01/01/93 to 12/30/93

Outputs
This project is a continuation of a previous project to study N(subscript 2)O fluxes under field conditions in irrigated and natural conditions. The objectives of this new project are to i) numerically model effects of above ground chambers on thermal and gas diffusion within soil, ii) determine loss rates of N(subscript 2)O from various storage containers, such as syringes, and iii) study the N(subscript 2)O diffusion process from soil to atmosphere using a new, large, weighing lysimeter. Effort is currently focused on the first objective, which involves modifying and combining two existing models for numerically simulating heat and gas diffusion within soil beneath closed and open chambers. For the third objective, use of a new lysimeter facility at the Campus Agricultural Center in Tucson will allow detailed study of seasonal variations of N(subscript 2)O concentrations and fluxes within soil.

Impacts
(N/A)

Publications

• MATTHIAS, A.D., ARTIOLA, J.F., and MUSIL, S.A. 1993. Preliminary measurement of N(subscript 2)O flux over irrigated bermudagrass in a desert environment. 64:29-45.
• GUILBAULT, M.R. 1993. Nitrous oxide emissions from desert soils. M.S. Thesis. University of Arizona Library, p. 89.

Progress 01/01/92 to 12/30/92

Outputs
Field studies have focused on emissions of nitrous oxide (N(2)0) from irrigated turfgrass and natural desert soils. Studies were done in 1991 to evaluate warm season emissions from effluent irrigated turfgrass and natural Sonoran desert near Tucson. Emissions from turfgrass during a 10 week interval exceeded emissions from desert by about one order of magnitude. However, emissions from natural desert (mean of about 0.6 kg N/ha/yr) were found to exceed emissions recently reported in the literature for some other ecosystems including semi-arid shrub and temperate forest. Preliminary studies done in August 1992 on natural and agricultural soils in the Sahel region near Niamey, Niger also indicate N(2)0 emissions comparable to emissions from natural Sonoran desert. In addition a field study was done to measure emissions from a large (128 ha) irrigated bermudagrass (Cynodon dactylon) in Arizona. Measurements were made simultaneously using chamber and micrometeorological (flux-gradient) techniques. Agreement between techniques was relatively good during periods when locally stable surface layer conditions enhanced concentration gradients sufficiently to be measured by gas chromatography. Preliminary results from studies done over irrigated grass and natural desert indicate that emissions from arid and semi-arid regions may be a relatively more important source of atmospheric nitrous oxide than previously believed.

Impacts
(N/A)

Publications

• MATTHIAS, A.D., ARTIOLA, J.F. and MUSIL, S.A. 1991. Measurement of nitrous oxide flux over a large irrigated turf field. Agron. Abst. p. 21.
• GUILBAULT, M.R. and MATTHIAS, A.D. 1992. Nitrous oxide emissions from effluent-irrigated turfgrass soils. Agron. Abst. p. 41.
• GUILBAULT, M.R. and MATTHIAS, A.D. 1992. Nitrous oxide emissions from effluent-irrigated and unmanaged desert soils. Southwestern and Rocky Mountain Div., Am. Assoc. Adv. Sci. (Abstract).

Progress 01/01/91 to 12/30/91

Outputs
Nitrous oxide (N(subscript 2)O) is a radiatively active greenhouse gas in the Earth's atmosphere, and is also an important precursor involved in stratospheric ozone chemistry. It is believed to be produced mainly by biogenic processes of denitrification and nitrification in terrestrial soil-plant systems. Measurements indicate the atmospheric concentration is steadily increasing due to an imbalance between production and destruction of the gas. The cause of the imbalance is not known, but could be related to increased worldwide use of nitrogen fertilizer and irrigation. Our research this past year focused on measurement of N(subscript 2)O emissions from irrigated turfgrass and undisturbed desert soils. Chamber an micrometeorological profile methods were used to measure flux from a large (1600 by 800 m) turfgrass field near Casa Grande, AZ. The two methods gave relatively good agreement during periods when fluxes were large and atmospheric conditions were stable. During periods with low fluxes and/or unstable conditions, the micrometeorological method tended to give higher estimates of flux. A one year study was begun in June 1991 to monitor N(subscript 2)O flux from 3 desert sites and 3 effluent irrigated golf course sites near Tucson. During a ten-week period of the summer, mean fluxes from the desert and golf course sites were about 0.6 and 12.9 kg N ha(superscript -1) yr(superscript -1), respectively.

Impacts
(N/A)

Publications

• MATTHIAS, A.D., ARTIOLA, J.F., and MUSIL, S.A. 1991. Measurement of nitrous oxide flux over a large irrigated turf field. Agron. Abst. p. 21.
• DUGAS, W. A., FRITSCHEN, L.J., GAY, L.W., HELD, A.R., MATTHIAS, A.D., REICOSKY, D.C., STEDUTO, P. and STEINER, J.L. 1991. Bowen ratio, eddy correlation and portable chamber measurements of sensible and latent heat flux over irrigated sprin.

Progress 01/01/90 to 12/30/90

Outputs
This new project is focusing on measurements of nitrous oxide emissions from irrigated and fertilized field soils. These measurements are needed in order to evaluate the effects of various irrigation and fertilizer management practices on the biological and chemical processes producing nitrous oxide in soil and releasing it to the earth's atmosphere. Both chamber and micrometeorological techniques are proposed for use in various aspects of this project. Several metal chambers were constructed for use on turfgrass and cotton beginning in early 1991. Both techniques will require precise determination of nitrous oxide mixing ratios in air samples brought to the laboratory in gas-tight syringes and Tedlar bags. An existing Varian 3400 gas chromatograph with an electron capture detector is being modified with a new sample valve and a new Porapak Q column for use in quantifying nitrous oxide at or above ambient levels..

Impacts
(N/A)

Publications

• NO PUBLICATIONS REPORTED THIS PERIOD.