Brief Summary of Minutes of Annual Meeting

Minutes of NCERA-180 (Site-Specific Management) Roseville, Minnesota January 9-11, 2008 Host: David J. Mulla The theme of this years meeting was Opportunities in Biofuel Production and Precision Agriculture. In light of that emphasis, members of the Committee spent January 9 touring POET ethanol and Soymor biodiesel plants near Albert Lea, Minnesota. Thursday, January 10, 2008 Dr. David Mulla welcomed the participants and discussed the agenda covering various topics related to using site-specific management to enhance crop quality for biofuel production. Dr. Mulla and Ryan Roggenbuck (University of Minnesota) presented research on Spatial Variation in EONR for crop yield and quality in Southern Minnesota. They covered methods for determining economic optimum nitrogen rates (ENOR) and the relationships between ENOR, crop yield and crop quality. They discussed their observations that spatial variability iin crop quality was often related to variability in soil properties and that managing crop quality using site-specific technologies was likely to result in significant gains in the efficiency of biofuel production. Dr. Kurt Thelen (Michigan State University) presented information on Spatial Variability in Energy Crop Quality Components: Does It Matter?. He showed data indicating the importance of spatial variability in soil properties in determining the amount of oils, sugars, and starch produced by various crops. Clearly, spatial variability in soil properties is an important factor in regulating the amount of energy produced by an acre of land. He then discussed methods for using site-specific management to enhance crop yield and quality. Dr. Newell Kitchen (USDA-ARS, Columbia Mo.) then presented an overview of the emerging technologies for land energy production on marginal soils. While many of these technologies are still years away from fruition there appears to be a good opportunity to use site-specific management practices in conjunction with these technologies to improve energy production. The focus of the sessions then shifted to using site-specific management to improve carbon sequestration and enhancing that aspect of biofuel production. Dr. Brian Wienhold (USDA-ARS, Lincoln, NE) presented research on the effects of crop residues on soil properties in a spatially variable field. Differences in soil texture, nutrient status, and topography were shown to influence the effectiveness of crop residues in improving soil carbon and structure. Dr. David Clay (South Dakota State University) then talked about determining site-specific carbon requirements for spatially variable fields. He detailed site-specific methods for measuring soil carbon. The final presentations of the day covered crop performance at different landscape positions and the role of precision agriculture in the future of biofuels. Dr. Gregg Johnson (University of Minnesota) presented his research on crop yield at different landscape positions. He findings indicate that different crops would be better suited to different landscape positions and that a diversity of biofuel crops is needed to maximize energy production. Dr. Paul Fixen (International Plant Nutrition Institute) then summarized the current research in biofuels and precision agriculture and presented his thoughts on the role that precision agriculture could play in improving the efficiency of energy production from biofuels. Friday, January 11, 2008 K. C. Ting (University of Illinois) gave the Administrators Report. He encourage the participants to highlight the pieces of the NCERA-180 mission that are important. In particular, need to emphasize the education, extension, and research mission with a focus on information exchange. Within 60 days of meeting (March 11) the SAES-442 form must be submitted to the NIMSS online system and that the impact statement must be revised for the mid-term review. He also spoke about funding for specialty crop research and BP grants covering chemical transformations in bioscience and energy solutions from field to processing. Dr. Ronnie Heiniger (North Carolina State University) lead a group discussion on the upcoming plans for the 2009 meeting which will be held in Portsmouth, VA. The focus of that meeting will be on using precision agriculture to mitigate the impact of global climate change. An election was held to select the Chair for the 2010 NCERA-180 meeting. Tim Stombach of the University of Kentucky was unanimously elected, and agreed to hold the 2010 meeting of NCERA-180. Raj Khosla (Colorado State University) discussed the upcoming 2008 International Conference on Precision Agriculture (ICPA). The venue for the conference is being changed to Colorado and will be held at the Hyatt Regency Tech Center in Denver, Co. Over 300 abstracts from 25 countries have been received and are being processed. The conference has been organized by theme areas including traceability, robotics, precision conservation, education, and a possible area to include biofuels. There will be graduate student awards to encourage their participation at the conference. The A to Z portion of the conference will continue with stronger support and speakers. NCERA-180 is assisting in the process of putting on the ICPA by being a strong part of the conference planning committee and will be staffing the conference sessions. Dr. Fran Pierce (Washington State University) finished editing the publication on GIS in Precision Agriculture by CRC Press. This is the first in a series of books on GIS in agriculture. It is envisioned to have 1-2 volumes each year, on topics such as invasive species, IPM, precision conservation, agribusiness, etc. The next volume on GIS applications in agriculture will focus on invasive species with Sharon Clay as the lead author. Fran asked about other topics. The group identified several topics including Conservation Planning, Nutrient Management, Integrated Pest Management, GIS Applications in Agriculture Businesses, and Biofuels. NCERA-180 will provide the leadership with Dr. Pierce in developing these additional books. Dr. Bruce Ericson from Purdue talked about the NCERA-180 taking leadership in developing connections with NRCS to work on guidelines for using EQUIP funds for precision technologies. He suggested that the NRCS program used in Missouri could be used as a model for efforts in this area. The group agreed to develop a team to work on guidelines for equip funds and to make contacts with NRCS to discuss implementing this program. It was suggested that an NRCS representative be at the 2009 meeting to present their side of the story. Dr. Adamchuk (University of Nebraska) presented a demonstration on using GIS to understand the principals of precision farming. The current problem in implementing site-specific management practices lies in the high cost of GIS software that is not adequate for farm situations. He showed how programs presented over the internet could be used to train growers in the use of GIS applications using the software Maniforld 7x Personal and Surface Tools. Currently, the University of Nebraska offers five lessons in GIS Applications in Farming including 1) How to download data, 2) putting boundary data into a project, 3) processing yield data (including the use of yield editor and yield check), 4) visualization of soil data, and 5) prescription map development. The site is located under the University of Nebraska Eric Lund (Veris Tech) talked about two instruments under development the first being the Veris MSP-ph which is a unit that measures pH in real-time. This unit has been improved with a continuing improvement in accuracy. The other unit is the Veris VIS-NIR a Near Infrared (NIR) spectrophotometer that collects data in 8 nm bands from 500-900 nm and from 1100-2200 nm. Light and dark references are collected automatically. NIR is used to estimate soil organic carbon, N, C/N, pH, Ca, Mg, P, K, CEC and moisture. This unit is being used in a USDA stover removal project to measure carbon sequestration and other soil properties. This unit could provide the data needed to quantify the impact of using various management practices on carbon accumulation. William Rudolph (TeeJet Tech) talked about Centerline Guidance Devices and Field Pilot Automatic Steering Systems. He also talked about Swath Manager to turn on and off boom sections depending on whether the area was previously sprayed. TeeJet is developing a controller area network (CAN) based on ISO BUS ISO 11783 open standard to control all these devices. Dr. Newell Kitchen (USDA-ARS, Missouri) talked about Division A-8 Integrated Ag Systems as a venue for symposia and papers on precision agriculture at the annual meetings of the Agronomy Society of America (ASA). Div. A-8. The focus topic is using precision agriculture to balance the impacts of rising demand for food, fiber, and fuel and crop production practices. The Div. A3 session on crop and soil modeling using remote sensing, A4 on sensor technology, A9 on fertilizer maps, S4 on nutrient management, and S6 on water issues in biofuel and plant rooting and soil carbon in the profile are also a possible venues for research from the NCERA-180 group. Dr. Tim Stombaugh (University of Kentucky) talked about the next meeting of ASABE in Providence, RI. Possible sessions included GPS testing and accuracy, tractor guidance performance guidelines and application accuracy. All of these would welcome input from the NCERA-180 group. David Mulla then lead a discussion on future activities of the NCERA-180 group. One key issue was the need for a website to communicate what the group is doing and to provide information about research, extension and outreach projects that the group is involved in. Bruce Ericson from Purdue University will develop a website for the group and host it. There was discussion about a funding source to support Dr. Ericsons efforts and the decision was made to contact CERESS about E-extension funding. This item will be discussed at Portsmouth, VA in 2009. The group asked for more information on the adoption of precision agriculture in the United States and other parts of the world. What is limiting adoption and how can these limitations be overcome so that farmers can benefit from precision technologies? Dr. Ericson presented some information from the SSMC group a Purdue showing the rate of adoption. It was decided that more on-line education information was needed. There will be a short course on spatial variability presented on the extension website at the University of Nebraska in February that could be used as a template for other efforts in education and extension. Dr. David Mulla thanked everyone for coming and officially adjourned the 2008 annual meeting of NCERA-180.

RESEARCH 1: Improvement in the Efficiency of Nutrient Use: Research by several institutions including the University of Minnesota (UMN), University of Nebraska (UNL), North Dakota State University (NDSU), North Carolina State University (NCSU), University of Missouri (UM), South Dakota State University (SDSU), Purdue (P), University of Arkansas (UArk), University of Florida (UNF), Michigan State University (MSU) and others have resulted in the development of technologies and site-specific techniques for applying fertilizers that have resulted in an improvement in the efficiency of nutrient use. Technologies developed include sensors for measuring crop nutrient status (UNL and UM), high clearance automated applicators (UNL), and algorithms for sensor output (UNL, UM, NCSU, SDSU, UArk) that help determine the amount and location of the application. Techniques developed include delineation of nutrient management zones (NDSU, P), new sampling techniques and technologies (UNL, NCSU, UM, UMN, NDSU), better analysis of sample information (all institutions), and other methods for determining where nutrients are needed and how crop yield responds to these nutrients. The results have been an improvement in the use of site-specific technologies with correlated reductions in nutrient loss. Measured outcomes include a 45% reduction in N use in Nebraska (UNL), increase in farm income of $7,000 to $33,000 using controlled drainage to manage nutrient loss (P, NCSU), increase in use of site-specific management to control N applications (NDSU, NCSU, UMN, UM, UNL)(for example: an increase in North Dakota of 500,000 in 2007), and a measured decline in fertilizer use nationwide largely accompanied by the use of site-specific technologies. 2. Precision Conservation Planning and Identification of Critical Resources Member institutions developed technologies and methods for measuring critical soil properties such as soil carbon, erosion potential, pH, etc. for use in better conservation planning and in developing inventories of soil resources. Examples include 1) research identifying erosion potential by micro-scale landscape features resulting in the identification of field zones with high erosion losses (UMN), 2) soil mapping to improve soil survey information (ND), 3) mapping of total carbon and impact of residue on soil carbon by landscape position (MSU), 4) mapping microbial activity in farm fields (UNL), and 5) hydrological GIS applications (P). These efforts have provided NRCS with important information and guidance in reducing soil erosion, nutrient loss, and enhancing soil carbon sequestration. 3. Development of New Guidance Technologies Member institutions have been leaders in developing guidance technology that has been rapidly and widely adopted by farmers. Studies include examination of visual sensors for guidance (UNL), analysis of guidance patterns, and the development of sensors and standards for guidance systems. More than 60% of the farmers in the US now have automated guidance systems on their equipment with the potential of reducing fertilizer and chemical use by 25% nationwide. 4. NCERA-180 participants are very active in helping to organize or participate in International, National and Regional Conferences on Precision Agriculture. These Conferences reach large numbers of scientists, ag industry professionals and producers, and help disseminate the latest advances in Precision Agriculture, thereby accelerating the adoption of Precision Agriculture. A partial listing of these Conferences over the past three years is given below: Organized the 2006 International Conference on Precision Agriculture in Minneapolis, MN. Conference was attended by 400 scientists and practitioners from 30 countries, and nearly 300 papers were presented on a wide array of Precision Agriculture topics. Organized Precision Agriculture technical sessions for the 2007 International Meeting of the American Society of Agricultural and Biological Engineers in Minneapolis, MN. Technical sessions include roughly 75 papers on soil sensors, automated guidance, remote sensing and GIS and spatial technologies. Organized a special symposium on Precision Agriculture at the 2007 Annual Meeting of the American Society of Agronomy through Division S-8. Approximately 50-60 papers on Precision Agriculture are presented at this Symposium. Organized the Info-Ag Conference on Precision Agriculture for over 500 producers and ag industry professionals during July, 2007 in Springfield, IL. Organized the 2007 Precision Agriculture Data Management, Analysis and Decision Making Workshops in Ohio. Organizing Precision Agriculture technical sessions for the 2008 International Meeting of the American Society of Agricultural and Biological Engineers in Providence, RI. Organizing a special symposium on Precision Agriculture at the 2008 Annual Meeting of the American Society of Agronomy through Division A-8. Collaborated on developing a book series entitled: GIS Applications In Agriculture. First book published in 2007 with the second book due for publication in 2008 EXTENSION 5. Work by NCERA-180 member institutions was critical in the adoption of new technologies and techniques. This is being done through innovative extension programs featuring on-line education courses using state-of-the-art software. Examples of the extension efforts include: 1) The Nebraska Agricultural Technologies Association provides research based information on site-specific crop management, 2) Precision agriculture services survey by Purdue has been instrumental in guiding agribusinesses as they consider adopting precision technologies, Site-Specific user clubs in North Dakota started through extension programming, 3) Currently, the University of Nebraska offers five lessons in GIS Applications in Farming including 1) How to download data, 2) putting boundary data into a project, 3) processing yield data (including the use of yield editor and yield check), 4) visualization of soil data, and 5) prescription map development. The site is located under the University of Nebraska (http://bse.unl.edu/adamchuk/manifold), 6) UArk and NCSU conduct on-farm demonstrations of remote sensing and yield monitors, and 7) all member institutions produce a wide array of extension publications and materials covering all aspects of precision agriculture. EDUCATION 6. All of the NCERA-180 member institutions have developed educational course and training shortcourses to teach site-specific management techniques and technologies to todays farmers and tomorrows generation of agriculturalists. Outcomes in this area include: 1) Arkansas GeoSpatial Newsletter, 2) university courses at all of the major institutions (i.e. AOM 4434 Precision Agriculture (UNF)), and 3) on-line courses (i.e. Spatial Variability in Soils (UNL) http://www. Agronomy.unl.edu/prospective/distanced/agro896-1.html) FUTURE PLANS 7. Future activities of NCERA-180 participants will continue to focus on on five major areas. The first is visioning. NCERA-180 members will meet with agricultural and environmental agency leaders to help identify priority topics for Precision Agriculture research and education. The second is evaluation of Precision Agriculture technologies. NCERA-180 members will form teams to write white papers on emerging technologies used in Precision Agriculture. The third is networking with conservation agencies. NCERA-180 members will work with USDA-NRCS staff to help write 590 Practice Standards for cost-sharing of conservation practices that involve Precision Agriculture (for example, grid sampling for soil nutrients). Fourth is communications and outreach. NCERA-180 members will partner with the ag industry and work to enhance the dissemination of Precision Agriculture research results through extension newsletters, web sites, and training sessions. Fifth is conferences and workshops. NCERA-180 members will continue to be involved in planning and organization of major conferences, symposia and workshops on Precision Agriculture through a variety of Professional Societies and venues. NOTEABLE OUTPUTS Franzen, D.W., 2007. Grid sampling project on two Illinois fields. North Dakota State University. http://www.soilsci.ndsu.nodak.edu/franzen/franzen.html. Pierce, F.W. 2007. GIS Applications in Agriculture. CRC Press. Refer to the publications list for all publications relating to NCERA-180 member activities

Adamchuk, V.I. and P.T. Christenson. 2007. An instrumented blade system for mapping soil mechanical resistance represented as a second-order polynomial. Soil Tillage and Research 95(1): 76-83. Adamchuk, V.I., E.D. Lund, T.M. Reed, and R.B. Ferguson 2007. Evaluation of on-the-go technology for soil pH mapping. J. Prec. Ag. 8:139-149 Adamchuk, V.I., D.B. Marx, A.T. Kerby, A.L. Samal, L.K. Soh, R.B. Ferguson, and C.S. Wortmann. 2007. Guided soil sampling for enhanced analysis of georeferenced sensor-based data. In: U. Demsar, ed. Proceedings of the Ninth International Conference on Geocomputation 2007 Conference, Maynooth, Ireland, 3-5 September 2007. National University of Ireland. Adamchuk, V.I., R.M. Hoy, G.E. Meyer, and M.F. Kocher. 2007. GPS-based auto-guidance test program development. In: Precision Agriculture: Papers from the Sixth European Conference on Precision Agriculture, Skiathos, Greece, 3-6 June 2007, 425-432. J. Stafford, ed. Wageningen, The Netherlands: Wageningen Academic Publishers. Bajwa, S. G., and E. D. Vories. 2007. Spatial analysis of cotton canopy response to irrigation in a moderately humid area. Irrigation Science 25(4): 429-441. Bajwa, S. G., and M. Mozaffari. 2007. Effect of N treatments on vegetative index of cotton canopy  A spatial regression approach. Transactions of the ASABE 50(5):1883-1892. Balasundram, S.K., D. J. Mulla and P. C. Robert. 2007. Spatial data calibration for site-specific phosphorus management. International Journal of Agricultural Research 2:888-899. Bogrekci, I., and W. S. Lee. 2007. Comparison of ultraviolet, visible, and near infrared sensing for soil phosphorus. Biosystems Engineering 96(2): 293-299. Boomsma, C.R., and T.J. Vyn. 2007. Plant-to-Plant Uniformity is Essential for Optimum Yield in No-Till Continuous Corn. Purdue Extension AY-329-W. Bullock, David, and J. Lowenberg-DeBoer, Using Spatial Analysis to Study the Values of Variable Rate Technology and Information, Journal of Agricultural Economics, 58:3 (2007), p. 517-535. Chinchuluun, R., W. S. Lee, and R. Ehsani. 2007. Citrus yield mapping system on a canopy shake and catch harvester. ASABE Paper No. 073050. St. Joseph, Mich.: ASABE. Cohen, M. J., R. Mylavarapu, I. Bogrekci, W. S. Lee, and M. W. Clark. 2007. Reflectance Spectroscopy for Routine Agronomic Soil Analyses. Soil Science 172(6): 469-485. Cugati, S.A., W.M. Miller, J.K. Schueller, A.W. Schumann, S. Buchanon, and H.K. Hostler. 2007. Benchmarking of dynamic performance of two commercial variable-rate controllers and components. Transactions of the ASABE. 50(3):795-802. Ferguson, R.B., T. Kyaw, V.I. Adamchuk, D.D. Tarkalson, and D.L. McCallister. 2007. Site-specific management of pH-induced iron chlorosis of maize. In: J. Stafford (ed). Precision Agriculture: Proceedings of the 6th European Conference on Precision Agriculture, Siakthos, Greece, 3-6 June 2007. pp 151-156. Wageningen Academic Publishers. Griffin, T.W., Craig Dobbins and J. Lowenberg-DeBoer, Spatial analysis of On-farm Experiments and Subsequent Farm Management Decision Making: A Case Study, Selected Paper, American Agricultural Economics Association Annual Meeting, Portland, OR., USA, July, 2007 (http://agecon.lib.umn.edu/cgi-bin/pdf_view.pl?paperid=26241&ftype=.pdf). Grigera, M.S., R.A. Drijber, K.M. Eskridge, and B.J. Wienhold. 2006. Soil microbial biomass relationships with organic matter fractions in a Nebraska corn field mapped using apparent electrical conductivity. Soil Science Society of America Journal 70:1480-1488. Grigera, M.S., R.A. Drijber, and B.J. Wienhold. 2007. Redistribution of crop residues during row cultivation creates a biologically enhanced environment for soil microorganisms. Soil and Tillage Research 94:550-554. Grigera, M.S., R.A. Drijber, and B.J. Wienhold. 2007. Increased abundance of arbuscular mycorrhizal fungi in soil coincides with the reproductive stages of maize. Soil Biology and Biochemistry 39:1401-1409. Grigera, M.S., Drijber, R.A., Shores-Morrow, R.H., and Wienhold, B.J. 2007. Distribution of Arbuscular Mycorrhizal Biomarker C16:1cis11 Among Neutral-, Glygo-, and Phospho-Lipids Extracted from Soil During the Reproductive Growth of Corn. Soil Biol. Biochem. 39:1589-1596. Hager, B.R., S. Brantley, J. Bloxham, R. Eisner, A. Goetz, C.J. Johannsen, J. Kirchner, W. Rose, H. Shah, D. Smit, H. Zebker and M. Zuber. 2007. Solid-Earth Hazards, Natural Resources, and Dynamics, Earth Science Systems, Chapter 8, In Andres, R.A., B. Moore III, et al. (Editors), Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond, pp 217-255, National Research Council, National Academy Press, Washington, DC. Hemmat, A., V.I. Adamchuk, and P. Jasa. 2007. On-the-go soil strength sensing using an instrumented disc coulter. In: Proceedings of the International Agricultural Engineering Conference (IAEC-2007), Bangkok, Thailand, 3-6 December, 2007. Pathumthani, Thailand: Asian Association for Agricultural Engineering (CD publication, 8 pages). Huang, X., S. Senthilkumar, A. Kravchenko, K. Thelen, and J. Qi. 2007. Total carbon mapping in glacial till soils using Near Infrared Spectroscopy, Landsat Imagery, and topographical information. Geoderma 141:34-42. Kane, K. E., and W. S. Lee. 2007. Multispectral imaging for in-field green citrus identification. ASABE Paper No. 073025. St. Joseph, Mich.: ASABE. Lambert, D.M., J. Lowenberg-DeBoer, and G. Malzer, Managing Phosphorous Soil Dynamics over Space and Time, Agricultural Economics 37 (2007), p. 43-53. Lee, K.H., M. R. Ehsani, and J.K. Schueller. 2007. Forward Movement Synchronization of Two Vehicles in Parallel Using A Laser Scanner. Journal of the Applied Engineering in Agriculture. 23(6): 827-834. Miao, Y., D. J. Mulla, G. W. Randall, J. A. Vetsch and R. Vintila. 2007a. Predicting chlorophyll meter readings with aerial hyperspectral remote sensing for in-season site-specific nitrogen management of corn. pp. 635-641. In: J. V. Stafford (ed.), Precision Agriculture 07. Wageningen Acad. Publ. The Netherlands. Miao, Y., D. J. Mulla, J. A. Hernandez, M. Wiebers and P. C. Robert. 2007b. Potential impact of precision nitrogen management on corn yield, protein content and test weight. SSSAJ 71:1490-1499. Nistor, Adela and J. Lowenberg-DeBoer, Drainage Water Management Impact on Farm Profitability, Journal of Soil and Water Conservation, Nov./Dec. 2007, 62:6, p. 443-446. Okamoto, H., W. S. Lee, and K. E. Kane. 2007. Hyperspectral imaging for green citrus fruit detection. 6th European Conference in Precision Agriculture and 2nd European Conference on Precision Livestock Farming, June 3-6, 2007, Skiathos, Greece. Pantaleoni, E., B.A. Engel and C.J. Johannsen. 2007. Identifying Agricultural Flood Damage Using Landsat Imagery. Journal of Precision Agriculture, Vol. 8:27-36. Robertson, G. P., L. W. Burger Jr., C. L. Kling, R. Lowrance and D. J. Mulla. 2007. New approaches to environmental management research at landscape and watershed scales. pp. 27-50. In: (M. Schnepf and C. Cox, eds.), Managing Agricultural Landscapes for Environmental Quality. Soil and Water Conservation Society. Ankeny, IA. Schueller, J.K. 2007. Intelligente Landtechnik in den USA. Forschung für intelligente Landtechnik. (Festveranstaltung zur Emeritierung von Prof. Dr. Dr. habil. Hermann Auernhammer.) VDI-Seminare am Wissenschaftszentrum. Technischen Universität München. Munich. July 19. Sripada, R.P., D.C. Farrer, R. Weisz, R.W. Heiniger, and J.G. White. Aerial color infrared photography to optimize in-season nitrogen fertilizer recommendations in winter wheat. Agron. J. 99:1424-1435. Smith, D.R., P.R. Owens, A.B. Leytem and E.A. Warnemuende. 2007. Nutrient losses from manure and fertilizer app lications as impacted by time to first runoff event. Environmental Pollution.147:131-137. Solari, F., J. Shanahan, R. Ferguson, J. Schepers and A.A. Gitelson. 2007. Active sensor reflectance measurements of corn nitrogen status and yield potential. Agron. J. (in-press). Urcola, Hernan, J. Lowenberg-DeBoer, A Stochastic Dominance Method for Incorporating Yield Monitor Data into the Hybrid and Variety Decisions of Argentinean Farmers, Computers and Electronics in Agriculture, 58:1 (Aug., 2007), p. 4-12. Varvel, G.E., W.W. Wilhelm, J.F. Shanahan, and J.S. Schepers. 2007. An algorithm for corn nitrogen recommendations using a chlorophyll meter based sufficiency index Agron. J. 99:701-706. Varvel, G.E., W.W. Wilhelm, J.F. Shanahan, and J.S. Schepers. 2007. Nitrogen fertilizer applications for corn based N sufficiency index calculations. Agron. J. 99: 701-706. Weisz. R., R.P. Sripada, R.W. Heiniger, J.G. White, and D.C. Farrer. 2007 In-season tissue testing to optimize soft red winter wheat nitrogen fertilizer rates: Influence of biomass. Agron. J. 99:511-520. Williams, J.D., C.R. Crozier, J.G. White, R.W. Heiniger, R.P. Sripada, and D.A. Crouse. 2007. Illinois soil nitrogen test predicts southeastern U.S. corn economic optimum nitrogen rates. Soil Sci. Soc. Am. J. 71: 735-744. Whipker, Linda and Jay Akridge. A Midwestern Precision Update. CropLife. June 2007, pp 10-14. Whipker, Linda and Jay Akridge. Biofuels: Future Challenges and Opportunities. CropLife. June 2007, pp 16-18.