CHARACTERIZING ACTIVE SOIL ORGANIC MATTER POOLS CONTROLLING SOIL N AVAILABILITY IN MAIZE-BASED CROPPING SYSTEMS (NC218)

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 0213127
• Multistate No.: NC-1032
• Project Start Date: Oct 1, 2006
• Project End Date: Sep 30, 2011
• Program Code: [(N/A)]- (N/A)

Recipient Organization
PURDUE UNIVERSITY
(N/A)
WEST LAFAYETTE,IN 47907

Performing Department
Agronomy

Non Technical Summary
The global challenge of meeting ever-increasing demand for food, fiber and energy from maize-based (Zea mays L.) agro-ecosystems requires the efficient use of fertilizer nitrogen (N) resources. Adequate N supply is required for achieving high maize yields. However, improper N fertilizer use threatens environmental quality and human health at both local and global scales through leaching losses to groundwater, hypoxia, surface water degradation, and greenhouse gas emissions. Fertilizer N also accounts for approximately 50% of the fossil energy input to maize production. With rising energy costs, this has become a major impediment to both the profitability and sustainability of maize-based cropping systems. Since the relationship between crop yield and N uptake is tightly conserved, achieving higher yields to meet demand will require greater crop N uptake. This is most efficiently achieved not by simply increasing fertilizer N inputs, rather by also improving N use efficiency and reducing the amount of reactive N that is released to the environment. This indigenous soil N can be affected by diverse factors. For example, the quantity, quality and timing of carbon inputs to soil influence the formation of new soil organic matter and the storage and release of soil C and N. To elucidate the processes that control the availability and crop uptake of indigenous soil N in maize-based rotations, members of the NC-218 committee will conduct a series of measurements on N forms and dynamics in a range of long-term field experiments and farmers fields that encompass a variety of crop rotations and soil types. A core experimental approach will be utilized across this range of experimental environments to measure gross and net N mineralization and the change in soil N and C storage and release from crop residues. Impacts from the successful completion of the proposed work include a quantitative survey of indigenous N supply under a wide range of edaphic and climatic regions as influenced by cropping system and N management. In addition, we will have obtained a more complete understanding of the consequence of cropping systems on soil C sequestration potential and its link to soil N sequestration, indigenous N supply and fertilizer N use efficiency.

Animal Health Component

(N/A)

Research Effort Categories

Basic

(N/A)

Applied

(N/A)

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
102	0110	1070	100%

Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships;

Subject Of Investigation
0110 - Soil;

Field Of Science
1070 - Ecology;

Keywords

nitrogen use efficiency

water quality

nitrogen cycling

carbon cycling

indegenous n supply

maize

soil organic matter

nitrate leaching

carbon sequestration

Goals / Objectives
Objectives 1. Conduct fundamental work to enhance current understanding of the role of active N and C pools in cropping systems and to predict N mineralization toward more efficient use of N fertilizers. 2. Assess the response of crop N uptake to varying rates of N fertilizer in on-farm trials and explain the responses through the dynamics of the quantities and chemical properties of active fractions of soil C and N, including the light fraction and the mobile humic fraction. 3. Quantify the magnitude and annual variation in the indigenous soil N supply in on-farm trials as influenced by key edaphic properties, climate and cropping system. Outputs 1. Quantitative survey of the size and annual variation in indigenous soil N supply across the major maize producing regions of the North Central region. 2. Quantitative survey of the response of maize yield to external fertilizer N input for several major soil types across the major maize-producing regions of the North Central region. 3. Enhanced understanding of the impact of continuous maize vs maize/soybean rotation on the flux of C and N within active soil C and N pools. 4. Enhanced understanding of the role of cropping systems and external fertilizer N input on the short-term storage and release of soil C and N. 5. Initial database on the contributions of specific amino compounds to either N availability and crop N uptake or to soil N sequestration. 6. An analysis of the annual variation in maize N response to N fertilization in relation to site-specific climate-limited yield potential 7. An analysis of the annual variation in the relative contribution of N supply and climate-induced physiological limitations to maize yield. 8. A comparative analysis of the quantitative difference between apparent fertilizer N use efficiency based on uptake from N exclusion plots and fertilizer use efficiency determined through the isotope dilution technique.

Project Methods
We will use existing long-term experiments including Purdue University's Water Quality Field Station to assess the long-term impact of N fertilization and crop rotation on the status of the mass, C composition, N content, and biochemical nature of the light fraction and MHA. These analyses will be made on composite soil cores taken at four times to a depth of 0-15 and 15-30 cm over an 18-month period. Sampling times will be preplant-year 1, post harvest-year 1, preplant-year 2 and post harvest-year 2. The LF will first be extracted by immersing the soil in a dense (specific weight 1.6 g / cm3) solution of sodium polytungstate. The light fraction (LF) will be recovered from the solution phase through centrifugation, filtering and oven-drying. The heavy fraction that sinks in this solution will then be extracted by sodium hydroxide to recover the MHA fraction. Both fractions will be cleansed of soil and salt contaminants and freeze-dried. Seasonal changes in these quantities will be compared to crop N uptake and effects of field treatments will be established. . Seasonal shifts in contents of specific amino compounds will also be evaluated for the LF and mobile humic acid fraction and compared to corresponding changes in total soil N in order to determine whether (i) these fractions are serving as sensitive indices of subtler changes in total soil N, and (ii) whether the amino contents of the labile fractions constitute significant proportions of the crop N supply. Overall, the relative proportions of the LF and MHA to total soil C and N will be assessed in relation to edaphic site properties and long-term C and N inputs to the cropping system. The relationship of N and C dynamics to final maize yield will be assessed in relation to the crop response to fertilizer rate and total crop N uptake and internal N use efficiency. Maize grain yield, total vegetative production, harvest index and total N uptake in grain and stover will be measured in each plot at the end of the growing season following a strict protocol. This will allow identification of the economic N rate and construction of an N response model at each site. Annual variation in site-specific N response and economic optimum N rate will be due, in part, to annual variation in the internal N use efficiency of the crop (yield/ kg N uptake) as well as variation in the genetic expression of yield potential due to climate and/or variation in indigenous N supply. Total grain and vegetative biomass and N uptake will be used to determine apparent indigenous N supply, internal N use efficiency and apparent fertilizer use efficiency. Annual site-specific yield potential will be determined with the Hybrid-Maize model using site-specific rainfall, solar radiation and rainfall data. The difference between climate limiting yield potential and actual non-N limiting yield provides an index of site specific limitations to yield other than N supply. The relationship of this index to crop N response and internal N use efficiency will be used to determine the contributions of climate and/or physiological limitations to crop N response in relation to N supply.

Progress 10/01/06 to 09/30/11

Outputs
OUTPUTS: This year's efforts focused on the comparative analyses of diverse management effects on long-term patterns (1998-2006) of nitrate, ammonium and phosphate load losses in tile drainage water. We monitored water flow and nutrient concentrations at subsurface drains in lysimeter plots planted to continuous, both phases of corn-soybean rotations, and restored prairie grass. Corn plots were fertilized with preplant or sidedress urea ammonium nitrate (UAN) or liquid swine manure injected in the fall or spring. Nutrient loads were calculated for various time frames (e.g., daily) as the product of flow volume and nutrient concentrations and normalized by drainage lysimeter area (263.5 m2). Annual cumulative flow volume and nutrient load data were calculated by hydrologic year (1October-30 September). Annual values of flow-weighted (FW) nutrient concentrations were back calculated from load and flow volume for each experimental plot. Additionally, a meta-analysis was conducted to provide a comprehensive and quantitative synthesis of soil organic carbon (SOC) changes under biofuel cropping systems. Data from 31 published studies that measured SOC changes under two biofuel candidate crops, switchgrass or miscanthus following conversion of forest, grassland or arable cropping were evaluated. The influences of biofuel species, soil texture, fertilizer and residue management on SOC were evaluated. Results and insights gained from this project were presented at a host of international meetings. Nitrogen dynamics were presented at the Second Annual Argonne Soils Workshop; efficiencies and environmental impacts were presented in 2 symposia and 1 poster session of the 2010 ASA-CSSA-SSSA International Meetings and at the 2011 Water for Food, Sixth Annual Frontiers in Bioenergy and Thirty-first Annual IATUL Conferences. PARTICIPANTS: Purdue University Agronomy Department: S.M. Brouder, PI; J.J. Volenec, collaborator; R. Turco, collaborator; M-J Orr, graduate student; P. Nhamo, post doctoral reasearcher; S. Cunningham, technical assistant; N. De Armond, technical assistant. USDA-ARS National Soil Erosion Laboratory: D.R. Smith, co-PI. NC1032 Regional Research Group, CoPIs International Plant Nutrition Institute: T.S. Murrell, collaborator TARGET AUDIENCES: Scientists through scientific and professional meetings; policy makers through meetings, conferences, and formal visits; Educators through meetings, workshops and informal discussions; Industry groups through meetings and collaborations; students through mentoring and experiential learning. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Restored prairie reduced nitrate loads eightfold compared with fields receiving UAN, yet varying UAN application rates and timings did not affect nitrate loads across all UAN fertilized continuous corn and corn soybean treatments. The nitrate loads from continuous corn with fall manure (33.3 kg N/ha/yr) were substantially higher than for all other cropped fields including continuous corn with spring manure (average 19.8 kg N/ha/yr). With respect to ammonium and phosphate loads, only manured soils recorded high but episodic losses in certain years. Compared with the average of all other treatments, continuous corn with spring manure increased ammonium loads in the spring of 1999 (217 vs. 680 g N ha/yr/), while continuous corn with fall manure raised phosphate loads in the winter of 2005 (23 vs. 441 g P/ha/yr). Our results demonstrate that fall manuring increased nutrient losses insubsurface-drained cropland, and hence this practice should be redesigned for improvement or discouraged. The meta-analysis of 31 published studies found, overall, biofuels cropping resulted in a 4% increase in SOC compared to previous land use systems. The conversion of arable land to biofuel cropping resulted in an 8% increase in SOC whereas there were no significant changes with conversion from grassland and forest. However, the conversion of forests to biofuel cropping tended to reduce SOC by about 1%. The addition of N fertilizers under arable cropping systems resulted in no change in SOC whereas there was an 11% increase in SOC when biofuel crops were grown without the addition of N fertilizers. On the other hand, the conversion of grassland and forest systems to biofuel cropping was not influenced by the addition of N fertilizers. For the studies where N fertilizers were added, there was no change in SOC where less than 100 kg N per ha was added but where more than 100 kg N ha was added there was a 5% increase in SOC. The removal of biofuel biomass resulted in lower SOC than when biomass was not removed. This was more pronounced following conversion of arable cropping systems to biofuel cropping where biomass removal resulted in -0.4% change in SOC whereas there was a 10% increase in SOC where biomass was not removed. Results from this analysis provide important background information on the conditions that will promote SOC sequestration in soil under biofuel cropping systems and thus mitigate carbon dioxide emissions.

Publications

• Orr, M-J., B. Applegate, S. Brouder, J. Volenec and R.F. Turco. 2010 Nitrogen cycling dynamics in five candidate cellulosic bio-fuel cropping systems. 2nd Annual Argonne Soils Workshop, Chicago IL., 6-8 October.
• Burks, J, J.J. Volenec, and S.M. Brouder. 2010. N cycling dynamics in perennial bioenergy crops. . ASA-CSSA-SSSA International Meetings, Oct. 31 to Nov. 4, 2010. Poster No. 56-14 N. http://a-c-s.confex.com/crops/2010am/webprogram/Paper59353.html.
• Brouder, S.M., and J.J. Volenec. 2010 Environmental impacts of using annual crops for biofuel. ASA-CSSA-SSSA International Meetings, Oct. 31 to Nov. 4, 2010. Presentation No. 250-1. http://a-c-s.confex.com/crops/2010am/webprogram/Paper57723.html.
• Brouder, S.M., and J.J. Volenec. 2010. Grain and dual purpose production: system efficiencies, limitations, and potential. ASA-CSSA-SSSA International Meetings, Oct. 31 to Nov. 4, 2010. Presentation No. 124-2. http://a-c-s.confex.com/crops/ 2010am/webprogram/Paper58277.html.
• Brouder, S.M., P. Woodson, L. Bowling, R. Turco and J. Volenec. 2011. Yield potential, water and N requirements of non-food biofuels. 2011 Water for Food Conference, Lincoln, NE, May 1-4.
• Brouder, S.M., R. Turco, J. Volenec, G. Ejeta, D.R. Smith, L. Bowling, I. Chaubey, B. Gramig. Nitrogen partitioning and utilization in bioenergy cropping systems. 6th Frontiers in Bioenergy Conference & US-Brazil Symposium on Sustainable Bioenergy. West Lafayette, IN, May 15-18 2011.
• Hernandez-Ramirez, G., S.M. Brouder, D.R. Smith, G.E. Van Scoyoc. 2011. Nitrogen partitioning and utilization in corn cropping systems: rotation, N-source, and N timing. European J Agron. 34:190-195.
• Hernandez-Ramirez, G., S.M. Brouder, M.D. Ruark, R.F. Turco. 2011. Nitrate, phosphate, and ammonium loads at subsurface drains in the eastern cornbelt: Agroecosystem and nitrogen management. J. Environ. Qual. DOI: 10.2134/jeq2010.0195.
• Climate Change Position Statement Working Group. 2011. Position Statement on Climate Change. Working Group Rep. ASA, CSSA, and SSSA, Madison, WI, May 11, 2011.

Progress 10/01/09 to 09/30/10

Outputs
OUTPUTS: Research activities in this project year focused on continued monitoring of C/N cycling in all experimental treatments, and analyzing soil C/N cycling dynamics from the experimental site, the Purdue University Water Quality Field Station (WQFS). In addition to the plant N measurements and soil measurement initiated in project Yr1, Yr2 and Yr3 measurements included 1) continuous monitoring of tile drainage water for volume with daily characterization of nitrogen and dissolved organic carbon content, 2) approximately weekly assessment of greenhouse gas emissions, 3) periodic assessment of soil N status including detailed biological assessments such as characterization of the structure of the critical zone bacterial populations, and 5) compositional analysis of biomass and grain at physiological maturity and after the first frost (standing biomass of perennial crops only). Specific objectives related to soil C/N cycling include the assessment or soil quality indicators among a range of cropping systems and the determination of the influence of cropping system on terrestrial N cycling capacity. Laboratory and data analyses of these samples are ongoing. Preliminary results suggest introduction of no-till in the maize with residue removal shows a trend of increasing microbial activity over time. At each sampling throughout the year, the profile of fatty acid methyl ester signature of the native prairie (a control) forms a distinct separate group when compared to the other treatments. Preliminary work on profiling genetic diversity of functional genes related to N transformation found the gene for amoA is absent in prairie soil suggesting a substantial decrease in nitrification capacity compared to the other cropping systems. However, the polymerase chain reaction product for the Archaea version of this gene has been identified and currently is in the process of being characterized using DGGE gels. The ammonia-oxidizer community is relatively stable in cropping systems receiving nitrogen fertilizer. Seasonal variation in relative abundance of these genes with enhancement levels was observed during the summer. The unfertilized prairie, Miscanthus, switchgrass and sorghum exhibited higher diversity of the nitrogenase gene when compared to maize cropping systems. Results from these analyses were reported in formal presentations at the Joint ASA-CSSA-SSSA International Annual Meetings in Pittsburg, PA and in numerous professional meetings and workgroups focused on sustainable food and bionenergy production in the US and in China. Two graduate students were mentored on the project and worked in the areas of soil C/N cycling and modeling of drainage N losses. PARTICIPANTS: Purdue University Agronomy Department: S.M. Brouder, PI; J.J. Volenec, collaborator; R. Turco, collaborator; M-J Orr, graduate student; S. Ale, graduate student; S. Cunningham, technical assistant; N. De Armond, technical assistant. USDA-ARS National Soil Erosion Laboratory: D.R. Smith, co-PI. NC1032 Regional Research Group, CoPIs International Plant Nutrition Institute: T.S. Murrell, collaborator TARGET AUDIENCES: Scientists through scientific and professional meetings; policy makers through meetings, conferences, and formal visits; Educators through meetings, workshops and informal discussions; Industry groups through meetings and collaborations; students through mentoring and experiential learning. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
New knowledge is one key outcome of the research to-date. Large differences in microbial diversity indicate that alternative bioenergy cropping system can alter nutrient cycling as compared to maize-based cropping systems for grain production. Soil C sequestration and nutrient cycling knowledge can lead to improved management strategies and policies that can maintain or enhance productivity with the same or fewer inputs. This has the potential for reducing production costs and improving net farm income.

Publications

• Ale, S., L.C. Bowling, J.R. Frankenberger, S.M. Brouder, E.J. Kladivko. 2010. The influence of climate variability, drain spacing and operational strategy on drainage water management system performance. Vadose Zone J. 9:43-42.
• Brouder, S.M., R.F. Turco, and J.J. Volenec. 2010. Nitrogen use efficiency in bioenergy cropping systems. pp. 27-29. In: Proc. 2nd China-US Workshop on Biotechnology of Bioenergy Plants. Beijing, China. September 19-21.
• Brouder, S.M., J.J. Volenec, R. Turco, D.R. Smith, G. Ejeta. 2009. Ecosystem services of existing and candidate bioenergy cropping systems: Critical research questions. China-U.S. Workshop on Climate-Energy Nexus sponsored by the China-U.S. Joint Research Center for Ecosystem and Environmental Change. Nov. 11-13, Oakridge National Lab, Oakridge, TN.
• Burks, J., J.J. Volenec, and S.M. Brouder. 2010. Nutrient cycling dynamics in perennial bioenergy crops. pp. 24. In: Proc. China-US 2010 Joint Symp. on Energy, Ecosystem, and Environmental Change. Beijing, China. September 22-24.
• Orr, M-J., S. Brouder, J. Volenec, M. Bischoff and R.F. Turco. 2009. Unintended consequences of biofuel feedstock production on carbon and nitrogen cycle dynamics medicated by soil biology. ASA-CSSA-SSSA Annual Meeting. Pittsburgh PA., 1-5 November.
• Volenec, J.J., S.M. Brouder, and R.F. Turco. 2010. Agroecological considerations when growing biomass. pp. 39-40. In: Proc. China-US 2010 Joint Symp. on Energy, Ecosystem, and Environmental Change. Beijing, China. September 22-24.
• Volenec, J.J., S.M. Brouder, R.F. Turco, G. Ejeta, and D. Smith. 2010. Impact of water and nitrogen on biomass production and ecosystem services. pp. 18. In: Proc. Frontiers in Bioenergy, Purdue University, May 24-25.

Progress 10/01/08 to 09/30/09

Outputs
OUTPUTS: Research activities in this project year focused on monitoring C/N cycling in all experimental treatments and analyzing, existing long-term C/N data records from the experimental site, the Purdue University Water Quality Field Station (WQFS). In addition to the plant N measurements and soil measurement initiated in the preceding year, 2nd year measurements were expanded to included 1) continuous monitoring of tile drainage water for volume with daily characterization of nitrogen and dissolved organic carbon content, 2) approximately weekly assessment of greenhouse gas emissions, 3) periodic assessment of soil N status including detailed biological assessments such as characterization of the structure of the critical zone bacterial populations, and 5) compositional analysis of biomass and grain at physiological maturity and after the first frost (standing biomass of perennial crops only). Laboratory and data analyses of these samples are ongoing. Summative analyses of the existing data record focused on greenhouse gas emissions from selected continuous corn and corn-soybean treatments, C loss to surface water as dissolved organic C transported in subsurface tile drains, and soil C and N dynamics as influenced by crop rotation and N management. Drainage volume, N concentration and N load loss data were also used with crop yields in verification simulations of DRAINMOD-N, a mechanistic model designed to identify managements that reduce N load loss via subsurface tile drains. Results from these analyses were reported in formal presentations at the Joint ASA-CSSA-SSSA International Annual Meetings and Geological Society of America Meetings in Houston, TX and at the XVI International Plant Nutrition Colloquium: Plant Nutrition for Sustainable Development and Global Health in Sacramento, CA. Additional presentations were made at other professional venues including the Ecological Society of America Annual meetings and in WQFS tours. Two graduate students were mentored on the project and worked in the areas of soil C/N cycling and modeling of drainage N losses. PARTICIPANTS: Purdue University Agronomy Department: S.M. Brouder, PI; J.J. Volenec, collaborator; R. Turco, collaborator; M-J Orr, graduate student; S. Ale, graduate student; S. Cunningham, technical assistant; N. De Armond, technical assistant. USDA-ARS National Soil Erosion Laboratory: D.R. Smith, co-PI. NC1032 Regional Research Group, CoPIs International Plant Nutrition Institute: T.S. Murrell, collaborator TARGET AUDIENCES: Scientists through scientific and professional meetings; policy makers through meetings, conferences, and formal visits; Educators through meetings, workshops and informal discussions; Industry groups through meetings and collaborations; students through mentoring and experiential learning. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Analysis of existing data to understand the influences of management practice (rotation, and application timing or source of N) on agroecosystem C/N cycling identified strong treatment by environment synergies. For example, treatments significantly influenced seasonal N2O emissions with lowest emission occurring in native prairie (<1 kg/ha) and highest emissions occurring in manure fertilized corn (>8 kg/ha). In laboratory incubations to estimate the magnitude and source (nitrification vs. denitrification) of N2O production, partitioning results were highly variable but suggested that enhanced denitrification occurred after an extreme increase in soil moisture content while a more coupled nitrification-denitrification process drove N2O evolution at more moderate water contents; under anoxic conditions shortly after flooding, manured soils showed higher N2O production than soils receiving inorganic N fertilizer. DRAINMOD-N simulations identified drainage water managements that have the potential to reduce N load losses in tile drainage water. Analysis of yearly dissolved organic carbon losses in tile drainage water found no effect of management practices, and, overall, loss quantities were small (< 10 kg C/ha/yr) when compared to organic C inputs. Analysis of soil C pools found soils under restored native prairies were enriched in total organic C and in several of the soil C fractions when compared to maize-based systems; results showed newly sequestered C was preferentially allocated into particular organic matter supporting use of this fraction as an indicator of management effect on soil C sequestration. At present, a significant barrier to conclusive life cycle analyses comparing C balances of bioenergy crops with that of fossil fuels is the dearth of N2O emission and soil C data for different crop managements and environments; our N2O and soil C sequestration results and ongoing monitoring work are critical to current efforts to improve these life cycle analyses. Ongoing research will further strengthen the existing data record for improved understanding of C/N cycling in agroecosystems.

Publications

• Hernandez-Ramirez, G., S.M. Brouder, D.R. Smith, and G.E. Van Scoyoc. 2009. Carbon and nitrogen dynamics in an eastern corn belt soil: N Source and Rotation. Soil Sci. Soc. Am. J. 73:128-137.
• Hernandez-Ramirez, G., S.M. Brouder, D.R. Smith, and G.E. Van Scoyoc. 2009. Greenhouse gas fluxes in an Eastern Corn Belt soil: Weather, N source and rotation. J. Environ. Qual. 38: 841-854.
• Hernandez-Ramirez, G., S.M. Brouder, D.R. Smith, G.E. Van Scoyoc and Greg Michalski. 2009. Nitrous oxide production in an Eastern Corn Belt soil: Sources and redox range. Soil Sci. Soc. Am. J. 73:1182-1191.
• Ruark, M., S.M. Brouder, and R.F. Turco. 2009. Dissolved organic carbon from tile drained agro-ecosystems. J. Environ. Qual. 38:1205-1215.
• Ale, S., L.C. Bowling, S.M. Brouder, J.R. Frankenberger, M.A. Youssef. 2009. Simulated effect of drainage water management operational strategy on hydrology and crop yield for drummer soil in the Midwestern United States. Agricultural Water Management. 96:653-665.
• Hernandez-Ramirez, G., S.M. Brouder, M. Ruark, R.F. Turco. 2008. Nitrate, ammonium, and phosphate fluxes to subsurface drains in the eastern cornbelt: N source and rotation. Joint ASA-CSSA-SSSA International Annual Meetings and Geological Society of America Mtgs, Houston, TX. Oct. 5-9, 2008.

Progress 10/01/07 to 09/30/08

Outputs
OUTPUTS: Research on this project was initiated during the 2008 growing season. The experimental site is an existing, long-term field laboratory, the Purdue University Water Quality Field Station. The treatments used in this experiment include: 1) continuous corn fertilized preplant according to university recommendations and fall tillage for residue and soil management, 2) continuous corn fertilized preplant according to university recommendations with fall residue removal and no-tillage soil management, 3) continuous corn fertilized with liquid swine manure in either the fall or the spring (separate plots for fall and spring applications) and fall tillage for residue and soil management, 4) corn-soybean rotation with corn fertilized preplant according to university recommendations and fall tillage for residue and soil management, 5) corn-soybean rotation with corn fertilized by sidedressing at a rate lower than the university recommendation and fall tillage for residue and soil management, and 6) an unfertilized prairie dominated by big bluestem as a control. Baseline soil samples include previously archived samples collected at 15 cm increments to below 1 m. In season crop nitrogen status was assessed at the start of the reproductive phase by measuring earleaf greenness with a SPAD or "chlorophyll" meter; earleaves were subsequently collected and analysis of leaf total nitrogen content is on-going. Whole plant samples were collected at physiological maturity (blacklayering) and partitioned into grain and stover. Samples were weighed, dried and ground and are awaiting laboratory analysis. Post-harvest soils samples were collected and analysis is ongoing. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Crop scientists PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
The relationship of nitrogen and carbon dynamics in the plant-soil system to final crop yield will be assessed with the goal of characterizing system nitrogen use efficiency. Analysis of plant and soil carbon and nitrogen content and composition measurements will be combined with measurements of nitrogen leached through the soil profile and soil nitrous oxide emissions for a partial mass balance comparison of system level carbon and nitrogen cycling. These results will be combined with the results from other study sites in the NC1032 study network to determine the contributions of climate and soil productivity potential to realized crop nitrogen response in relation to soil nitrogen supply.

Publications

• Brouder, S.M. and J.J. Volenec. 2008. Impact of climate change on crop nutrient and water use efficiencies. Physiologia Plantarum. 133:705-724.
• Brouder, S.M., R. Turco, and J.J. Volenec. 2007. What we know about the influence of best management practices on nitrogen and dissolved organic carbon losses from agricultural fields in the Eastern Cornbelt. N2007, 4th International N Conference, Costa do Sauipe, Bahia, Brazil, Oct. 1-5, 2007.
• Carter, B., S.M. Brouder, and E. Kladivko. 2007. Effect of Controlled Drainage on Corn and Soybean Yields and Corn Crop N Balance. Presentation 308-3. ASA-CSSA-SSSA International Meetings, Nov. 4 to 9, 2007. New Orleans, LA. http://a-c-s.confex.com/crops/2007am/techprogram/P33745.HTM
• Hernandez-Ramirez, G. S.M. Brouder, D. Smith, G.E. Van Scoyoc, T. Filley, and G. Michalski. 2007. Nitrous oxide production in an Eastern Cornbelt soil: Sources and redox range. Presentation 96-7. ASA-CSSA-SSSA International Meetings, Nov. 4 to 9, 2007. New Orleans, LA. http://a-c-s.confex.com/crops/2007am/techprogram/P32723.HTM.