Brief Summary of Minutes of Annual Meeting

Individual State Reports IA (Iowa State University) Submitted by Matt Helmers Recent research and extension efforts at Iowa State University relative to drainage design and management practices to improve water quality have centered on nutrient export from tile drainage systems and nutrient management practices to minimize this export of nutrients, specifically nitrate-nitrogen. In addition, work is beginning on evaluating drainage management practices and cropping practices as to their impacts on drainage volume and drainage water quality. One new drainage water management site was installed in 2006. A field day was held as part of this installation on July 12, 2006 near Crawfordsville Iowa (southeast Iowa). Additionally, a field scale (>20 acres) site in central Iowa was identified and monitoring will begin in 2007 at this site. Water quality and subsurface drainage volumes will be monitored from these sites. Work continued on the EPA Targeted Watershed project evaluating drainage water management in north-central Iowa. From detailed topographic analysis of these three drainage districts in north-central Iowa using LIDAR information only about 10% of the area presumed to be tile drained has a slope less than 1% and only about 3% has a slope less than 0.5%. In addition, these relatively flat areas are not in large contiguous areas. Approximately 50-75% of the cropland in these drainage districts is presumed to be tile drained (soils considered somewhat poorly drained and wetter). Extension work has focused on disseminating information relative to drainage water quality and economic design of drainage systems. This has included statewide, regional, and local programming events. In collaboration with colleagues at the University of Minnesota, the IA-MN Drainage Research Forum was held in November 2006 and was attended by approximately 80 stakeholders. Impacts: A drainage management field day was held in conjunction with the installation of a new drainage system at the Southeast Iowa Research and Demonstration Farm in July 2006. This field day was attended by approximately 200 local producers, drainage contractors, and agency personnel. Approximately 1000 farmers and contractors were informed about drainage water management and drainage water quality in 2006 through field days and additional extension presentations and workshops around the state. Based on previous drainage presentations and regional coverage of subsurface drainage bioreactors two local watershed groups in northeast Iowa installed subsurface drainage bioreactors, one in Butler county and one in Buchanan county, with a goal of reducing nitrate concentrations to the downstream receiving water body. IA (National Soil Tilth Lab, Ames) Submitted by Dan Jaynes. To reduce NO3 losses from tile-drained fields, we are comparing the efficacy of several tile and cropping modifications for reducing NO3 in tile drainage versus the nitrate concentration in drainage from a control treatment (CK) consisting of a free-flowing tile installed at 1.2 m below the surface. The modifications being tested include a) denitrification walls (DW) - trenches excavated parallel to the tile and filled with wood chips as an additional carbon source to increase denitrification; b) rye cover crop (CC) - planting rye (Secale cereale L.) after soybean [Glycine max (L.) Merr.] and corn (Zea mays L.) harvest and chemically killing before planting the following spring; c) rotating rye and oat cover crops (CC) - planting oat (Avena sativa L.) after soybean and rye after corn harvest and chemically killing before planting the following spring; and d) using white clover (Trifolium repens L.) as a living mulch under corn and soybean. Each treatment is replicated four times on 30.5 x 42.7 m field plots. We have shown that the RZWQM-DSSAT model can accurately simulate crop yield, water drainage, and nitrate concentrations in drainage for a corn/soybean production field. The calibrated model will be used to look at possible nitrate reductions for drainage water management on this field and for other fields across the Midwest using the model. Drainmod NII will also be evaluated for use with results from this field. A new demonstration/research site has been established on a producers field to examine the efficacy of drainage water management for nitrate removal. Impact: Made invited presentation in December, 2006 to EPA Science Advisory Board Hypoxia Advisory Panel on methods for reducing nitrate contamination of surface waters from corn/soybean fields of the Midwest. Topics covered included drainage water management, in-field tile bioreactors, cover crops, and N management techniques. (Iowa State University) IL (University of Illinois) Submitted by Richard Cooke Flow Measurement in DWM Systems Weir equations to determine flow rates through drainage water management control structures were developed. These discharge equations were based on measured flow rates and water depths in AgriDrain structures ranging in size from 152 mm (6 inches) to 610 mm (24 inches). For each structure, a two-parameter equation for weirs with end contractions was used for low flow rates, and a one-parameter equation at higher flow rates, with the transition occurring at the point of inflection of the two-parameter equation The fitted equations were Q=0.021(L-0.632H)H1.5 for 152 mm structures, Q=0.020(L-1.202H)H1.5 for 203 to 610 mm structures, and Q=0.0172H1.5 above the point of inflection for all structures, where Q is the flow rate (L/s), L(cm) is the width of the gate, and H(cm) is the flow depth above the gate. Equations were fitted to the observed flow data with rewighted least square fitting procedures, to reduce the effect of outliers. Impact: These equations can be used for the determination of tile flow rates where AgriDrain drainage control structures are installed. Flow and Transport Parameters for Bioreactors A laboratory-scale bioreactor was installed to estimate flow and transport parameters to be used in field-scale systems. The laboratory-scale bioreactor consisted of a 0.25 m (10 inch)PVC pipe (6.1m long) filled with woodchips, with a drainage control structure attached to each end to regulate water flow rates. Center-screened sampling ports for collecting water samples were located at 0.87 m intervals along the PVC pipe. Creek water with nitrate-N concentrations ranging from 3 to 31 mg/L was passed through the bioreactor at several flow rates, and water samples were collected and analyzed for nitrate-N concentration. To determine points of inflexion that reflect the retention time for the resulting breakthrough curves, the observed data were fitted to Logistic functions. A one-dimensional advection-dispersion-reaction model was applied to this study. A Finite Difference procedure and an analytical solution were used to simulate the nitrate-N transport through the bioreactor, and a nonlinear regression approach was used to estimate hydrodynamic dispersion coefficients and first-order decay coefficients of the bioreactor. The estimated hydrodynamic dispersion coefficients were 0.68, 0.58, and 0.34 cm2/sec and the estimated first-order decay coefficients were 0.079, 0.14, and 0.038 hr-1for the three flow rates, respectively. Impact: These results were used in the design and operation of field-scale bioreactors. Three bioreactors were installed at the Illinois Farm Progress Show site with the assistance of members of the Illinois Land Improvement Contractors Association. These systems will be part of the field tour in subsequent shows. IN (Purdue University) Submitted by Jane Frankenberger and Eileen Kladivko Drainage research is continuing at two Purdue Agricultural Centers and three private farms. The long-term study on drain spacing at the Southeast Purdue Agricultural Center (SEPAC) will now transition into a system with more years of corn in the rotation, and the resulting impacts on nitrate losses and crop yields will be determined. Synthesis of data from a companion drainage/agronomic management practices study underscored that practices to improve soil tilth and crop yields (manure, cover crops) are not very effective unless an adequate drainage system exists first. The research study on drainage water management continued at three private farm sites and the Davis Purdue Agricultural Center (DPAC). Site-specific crop yield data have been collected at four sites for two years, and spatial analysis is being used to determine the effect of the practice on crop yields. Data on soil and crop N status during the season are being analyzed. The paired-watershed approach is being used to compare drain flow, nitrate load, and water table measurements from the managed drainage and free drainage field. New flow instrumentation was installed at two of the private farms, due to continuing challenges with flow measurement at those sites. Preliminary data show the electromagnetic velocity-depth sensors to be functioning well. The same three private farm sites are now being continued as part of the demonstration Conservation Innovation Grant regional effort. The Purdue group also led the regional effort to write and produce an extension publication on drainage water management. Nearly 8000 copies have been distributed throughout the region. Impacts: More farmers have become knowledgeable about drainage water management from extension presentations as well as the regional extension publication. Data collected on our project will be used to further educate farmers, drainage contractors, and the public about the water quality benefits of drainage water management and the potential impacts on crop yield. MN (University of Minnesota) Submitted by Gary Sands and Jeff Strock Drainage research continues both at University of Minnesota Research and Outreach Centers (ROC) and on cooperating farms. Numerous faculty at the University of Minnesota and several State agencies are engaged in many projects addressing hydrology, water quality and production impacts of subsurface drainage practices. These projects encompass a multitude of scales, (plot to large watershed), and approaches (field, laboratory and computer modeling). Current research topics include (but are not limited to): shallow and controlled drainage for minimizing nitrate-N losses; pharmaceutical movement and antibiotic resistance in drained soils; ecological approaches to drainage ditch design/management for water quality; impacts of combinations of alternative drainage and other conservation practices; preferential flow theory and modeling, and; modeling soil responses to drainage. Soil and water resource management and drainage research at the University of Minnesota, Southwest Research and Outreach Center (SWROC) is being conducted at multiple scales. This field-based research program focuses on developing integrated soil and water management solutions for crop and livestock producers that combine agronomic, ecological, and engineering approaches in order to guide soil and water resource management decisions that consider all three factors. Collaborative research between the University of Minnesota, USDA-ARS, and Minnesota Department of Agriculture at the Hicks family farm near Tracy, MN was a major focus during 2006. The objective of this project is to evaluate the ecological functions, goods, and services of multifunctional agricultural production systems associated with poorly drained soils. This research includes land in both drained (controlled drainage) and undrained row-crop production as well as undrained natural prairie. Water quality and quantity, crop yield, soil physical and chemical properties, and greenhouse gas emission data are being collected in order to develop hydrologic, carbon, nitrogen, and phosphorus budgets for each of the management systems. A total of 620 producers, agriculture professionals, and local, state and federal employees participated in field days and workshops on topics related to Soil and water resource management and drainage research during 2006. Field research at the University of Minnesota Southern Research and Outreach Center (SROC) in Waseca, MN, is investigating the role of drainage depth and spacing on hydrology and nitrate-nitrogen losses from drained lands. Six years of data beginning in 2001 indicates that shallow drainage can reduce seasonal drainage volumes and nitrate-nitrogen by 18-20 percent over a 6-year period. This research also shows that drain spacing has a similar effect on nitrate-nitrogen losses. When drain spacings designed for a 13 mm/day design drainage rate (intensity) were cut in half (resulting in a 51 mm/d theoretical steady-state drainage intensity), 6-year nitrate-nitrogen loads were reduced by 18 percent. New statistical methods (Meta Analysis) are being examined for their applicability to drainage water quality literature. A traditional statistical tool in the health/medical sciences, the use of Meta analysis in the environmental area is a new field of investigation. Installation of several on-farm controlled drainage research/demonstration sites is being conducted in southern Minnesota. Drainage volumes and nitrate-nitrogen losses will be measured at these sites, in addition to crop yield and soil quality parameters. One literature review was completed in 2006: the impacts of subsurface drainage on aquatic ecosystems. A second literature review, the water quality impacts of water table management systems, is in the final stages of completion. Drainage design workshops continue to be held at two locations in Minnesota annually. The workshops are a collaboration of scientists and extension specialists from Minnesota, Iowa, Wisconsin and North Dakota. University of Minnesota Extension and University of Iowa Extension Service held the seventh annual Drainage Research Forum in Owatonna, Minnesota. The event is typically attended by over 100 university faculty, agency staffs, producers and contractors. Impacts: University of Minnesota research and extension activities continue to serve stakeholders interested in drainage, water quality, and soil/water conservation. The programs serve thousands of stakeholders annually through all facets of delivery. MN (USDA-ARS) Submitted by Tyson Ochsner Participating scientists: John Baker, Tyson Ochsner, Pam Rice, and Rod Venterea In 2006 we collected the second year of data for our first on-farm drainage research site (Stevens Co. #1), and we started work at two additional on-farm sites (Stevens Co. #2 and Redwood Co.) At Stevens Co. #1 we measured nutrient concentrations and loads (N, P, C) in the subsurface drainage systems of two adjacent fields (25 and 60 ha). We also recorded carbon dioxide and nitrous oxide emissions, soil nutrient status, electrical conductivity, plant development, and yield. In October 2006, liquid dairy manure was injected in one field at a rate of ~15,000 gallons per acre. The other received commercial fertilizer. Data collection will continue in 2007 with the aim of documenting the field scale environmental costs and benefits of using manure versus commercial fertilizer. At Stevens Co. #2 we began a double cropping experiment. Two adjacent fields (65 ha each) will be used to test the environmental and economic performance of a corn silage, rye forage annual double crop. Both fields receive liquid dairy manure at equal rates. The drainage system in these fields combines flow from surface inlets and subsurface drains. We installed access points and monitoring equipment for measuring flow and for automated water sampling (N, P, C, sediment). We completed grid sampling for soil nutrients and preliminary electrical conductivity mapping. Background data collection will continue through the 2007 growing season, after which one field will be changed to double cropping. Jeff Strock is the project leader at the Redwood Co. site. We began work at the site in 2006. Two eddy covariance systems were installed for monitoring carbon fluxes and evapotranspiration in adjacent drained and un-drained fields. Chamber based measurements of nitrous oxide fluxes were initiated. Sample collection for pesticide leaching analysis also began. Data collection will continue in 2007 with the ultimate goal to compare greenhouse gas impacts and pesticide transport impacts of free and controlled drainage versus an un-drained field. Impacts: The research at Stevens Co. #1 generated significant interest among area producers leading to the opportunity to begin another project at Stevens Co. #2. Our conversations with our collaborators at Stevens Co. #2 led them to experiment with including rye in their operation. Over 300 acres were planted in the fall of 2006. These two projects have also created new collaborations with scientists at the Univ. of Minnesota Dep. of Agronomy and the USDA-ARS North Central Soil Conservation Laboratory in Morris, MN. OH (The Ohio State University) Submitted by Barry Allred 1) Activity: Near-surface geophysical methods and an extensive soil sampling program were employed to characterize soil property similarities and differences between test plots at a new controlled drainage research facility in northwest Ohio. Impact: Knowing the soil property similarities and difference between test plots will help with comparing water flow and water quality results between tests plots at this controlled drainage research facility. 2) Activity: A flow rate versus water height relationship for a v-notch weir contained within a hydraulic control structure was developed through extensive field tests. Impact: These field tests prove the feasibility of using v-notch weirs within control structures to accurately measure discharge from agricultural fields with controlled drainage. 3) Activity: Laboratory transient unsaturated horizontal column tests were conducted to evaluate electrostatic processes affecting nitrate mobility in unsaturated soil. Impact: The influences on anion adsorption/exclusion processes affecting nitrate mobility due to factors such as clay mineralogy, moisture conditions, and soil solution ionic were quantified and are useful for predicting nitrate movement through the soil profile. 4) Activity: A field investigation was conducted to determine if ground penetrating radar can be used to evaluate functionality of buried drain lines. Impact: Results of this study indicate that under certain shallow hydrologic conditions, ground penetrating radar can locate isolated obstructions along a drain line that require repair. NC (North Carolina State University) Submitted by Mohamed A. Youssef, R. Wayne Skaggs, and Robert O. Evans A collaborative study has been conducted to test DRAINMOD-N II using a data set from Germany. The data set consists of twelve years of drainage and water quality data, collected from a drained grassland site receiving both mineral N fertilizers and animal waste. The model accurately predicted drain flow but N drainage losses were relatively poorly predicted. Errors in predicting N drainage losses were attributed to the lack of a plant component that considers the effects of climatological conditions and nutrient availability on the growth of perennial grasses. The study has been completed and a manuscript reporting the study results has been submitted for publication. A study, partially supported through a cooperative agreement with the USDA Forest Service, has been started to develop a tree physiology and phenology component for DRAINMOD-N II that can reliably predict tree growth, N uptake, and litter fall. This extension of the model will broaden its scope to include forested lands. Collaborative research, partially supported by a US EPA grant, has been started to test DRAINMOD-N II using several data sets from the Corn Belt States in the US Midwest. The new shell for DRAINMOD 6.0, a major upgrade of the Windows-based DRAINMOD suite of models that incorporates the new nitrogen model DRAINMOD-N II, has been developed by a private software company. A "beta" version of DRAINMOD 6.0 has been released and is being tested before the official release of the model. The development of this version of the model will help increase model popularity among drainage researchers and engineers. The nitrogen component, DRAINMOD-N II, reflects the current understanding of N fate and transport in drained lands. The enhanced interface of DRAINMOD 6.0 makes it easier to use, especially, by non-researchers. NY (Cornell University) Submitted by Larry D. Geohring and Tammo S. Steenhuis Activities - Research activity included cooperating on a project to investigate the nutrient responses in tile drains following liquid dairy manure applications to orchardgrass. Plot treatments include an inorganic fertilizer control, surface applied liquid manure, and surface applied liquid manure followed by an Aerway tillage tool. The liquid manure applications were done during summer after grass harvests. Cooperative work continued on using LEACHM to model the nitrogen responses in tile drains following liquid manure applications. Extension activity included responding to tile drainage discharge water quality violations, whereby the drainage discharge was discolored from preceding manure applications. This resulted in making a presentation and discussions with the Agricultural Environmental Management Certification Subcommittee, a joint committee of the New York State Departments of Agriculture and Markets and Environmental Conservation, which provides training and certification of CNMPs (Comprehensive Nutrient Management Planners); and plans to update and revise the New York State Drainage Guide to include water quality aspects. A training session on Water Quality Concerns from Tile Drain Discharges was subsequently organized and presented at the Northeast Certified Crop Advisors Conference. Impacts: These activities resulted in a greater awareness of the water quality impacts of tile drain discharges, especially with regards to liquid manure applications on soils that may exhibit preferential flow. About 40 people attended the training session. As a result, producers and nutrient management planners are paying more attention to identifying vulnerable tile outlets, and adjusting their manure application methods, rates and timing to reduce risk of manure contaminated tile discharges. Ottawa, (Canada, Agriculture and Agri-Food Canada) Submitted by David R. Lapen and Mark Sunohara. The Watershed Evaluation of Beneficial Management Practices (WEBs) project, led by Agriculture and Agri-Food Canada, currently completed its second field season of data acquisition. The South Nation project focuses on a watershed-scale evaluation of relative environmental and economic effects of drainage water management on water quality. Based on a paired-watershed approach, a total acreage of 730 ha are under evaluation. One watershed is in drainage water management mode with a catchment area of 420 ha. The other watershed is unmanaged in a conventional drainage mode with a catchment area of 310 ha. Field-scale evaluation of drainage water management was based on a paired-field approach. Four paired fields under similar crop management, with one field in free drainage mode and the other in drainage water management mode, were monitored for hydrologic and water quality effects. In 2006, approximately 50 water level control structures were installed, increasing BMP contributing area to 250.6 ha. Infrastructure (auto samplers, flow meters) has been installed in streams and tile outlets for watershed-scale monitoring of water table management practice effects. Tile and stream flow water samples were collected routinely twice weekly and for several storm-driven hydrograph events. Routine monitoring and sample collection were conducted throughout the summer and fall of field and stream hydrological conditions, soil water, groundwater, plant, soil, air samples. WI (University of Wisconsin) Submitted by Sam Kung Hydraulic conductivity is the most critical deterministic parameter that dictates contaminant transport in porous media. Because of preferential pathways, it is difficult to accurately measure hydraulic conductivities of porous media. To compensate for the drawback of using a single averaged hydraulic conductivity to represent the impact of a wide range of flow velocities on contaminant transport through preferential pathways, two types of stochastic conceptualizations have been introduced. Some conceptualized that hydraulic conductivity was stochastic in nature, i.e., this parameter was made of a range of values with certain statistical distribution. Others proposed that porous media were made of multiple domains or stream tubes, each with its own hydraulic conductivity. Nevertheless, after collecting numerous field-scale experimental results, instead of becoming refined and perfected, the applicability of the conventional deterministic approach has been hindered by the lack of methodology to accurately measure hydraulic conductivity and its tremendous spatial variability. Although it is tremendously difficult to handle hydraulic conductivities of porous media, one can very accurately measure chemical mass flux breakthrough patterns. Specifically, mass flux breakthrough patterns measured by the modified tile-drain sampling method and dipole-well sampling method are not only repeatable, but also have very high mass recovery. We found that the tails of mass flux breakthrough patterns measured by these two methods followed certain slopes, depending on how chemicals were introduced into the porous media. These slopes were identical to those under convective transport through cylindrical tubes or planar fractures. Based on this observation, we modified the Transfer Function Model and developed a hybrid approach by using the chemical mass flux breakthrough patterns to derive equivalent pore spectrum of a porous medium. Because the averaged hydraulic conductivity of a porous medium is actually embedded in the equivalent pore spectrum of the porous media, the hybrid approach bypassed the bottlenecks that bogged down the conventional deterministic approached. Impacts: Since Darcy, an averaged hydraulic conductivity has been used to represent the impact of a range of pores on water movement and contaminant transport in porous media. To use an averaged hydraulic conductivity to represent a wide spectrum of preferential pathways is similar to use an averaged intensity to represent a spectrum of electromagnetic waves. We developed a method by using accurately measure chemical mass flux breakthrough patterns to derive the pore spectrum information of preferential pathways.

The committee held its Fourth annual meeting on April 17-19, 2007 in Raleigh, North Carolina in coordination with a DRAINMOD-NII workshop and the ADMSTF (Agricultural Drainage Management Systems Task Force) meeting. The meeting had an international flavor with the attendance of researchers from two Canadian provinces. " Members were educated about drainage management systems through an extensive field tour in North Carolina. This tour of some of the pioneering work in the field, along with visits with folks using the practices, has educated members of the committee and will enable them to do further innovations as they adapt and test the systems in the Midwest. " Many members attended the Drainmod-NII training, which now enables them to use the model for their research sites, and to evaluate the potential impacts of drainage water management on the soils and climatic regions within their states.

1. Allred, B. J., M. R. Ehsani, and D. Saraswat. 2006. Comparison of electromagnetic induction, capacitively-coupled resistivity, and galvanic contact resistivity methods for soil electrical conductivity measurement. Applied Engineering in Agriculture. 22(2):215-230. 2. Bakhsh, A. and R.S. Kanwar. 2006. N-source effects on temporal distribution of NO3-N leaching losses to subsurface drainage water. Water, Air, and Soil Pollution Journal 11270 (6): 1-16. 3. Feyereisen, G.W., G.R. Sands, B.N. Wilson, J.S. Strock, P.M. Porter. 2006. Plant growth component of a simple rye growth model. Trans. ASABE 49: 1569-1578. 4. Feyereisen, G.W., B.N. Wilson, G.R. Sands, J.S. Strock, P.M. Porter. 2006. A probabilistic assessment of the potential for a winter cereal rye cover crop to reduce field nitrate-N loss in southwestern Minnesota. Agron. J. 98: 1416-1426. 5. Gish, T.J. and K.-J. S. Kung. 2007. Procedure for quantifying a solute flux to a shallow perched water table. Geoderma. 138(1-2):57-64. 6. Kalita, P.K.., A Algoazany, J.K. Mitchell, R.A.C. Cooke and M.C. Hirschi. 2006. Agricultuarl chemical transport from a subsurface drained watershed in east-central Illinois, USA. Agriculture, Ecosystem and Environment 115:183-193. 7. Kanwar, R.S. 2006. Effects of cropping systems on NO3-N losses to tile drain systems. Journal of American Water Resources Association 42(6):1493-1502. 8. Kung, K.-J.S., E.J. Kladivko, C.S. Helling, T.J. Gish, T.S. Steenhuis, and D.B. Jaynes. 2006. Quantifying the pore size spectrum of macropore-type preferential pathways under transient flow. Vadose Zone J. 5:978-989. 9. Oquist, KA., J.S. Strock, and D.J. Mulla. 2006. Influence of alternative and conventional management practices on soil physical properties. Invited. Vadose Zone J. 5: 356-364. 10. Reungsang, A., T.B. Moorman, and R.S. Kanwar. 2006. Prediction of atrazine fate in riparian buffer strips soils using the Root Zone Water Quality Model. Journal of Water and Environment Technology 3:209-222. 11. Singh, R., M. J. Helmers, and Z. Qi. 2006. Calibration and validation of DRAINMOD to design subsurface drainage systems for Iowas tile landscapes. Agricultural Water Management. 85: 221-232. 12. Skaggs, R.W., M.A. Youssef, and G.M. Chescheir. 2006. Drainage design coefficients for Eastern United States. Agricultural Water Management 86:40-49. 13. Wang, X., C.T. Mosley, J.R. Frankenberger, and E.J. Kladivko. 2006. Subsurface drain flow and crop yield predictions for different drain spacings using DRAINMOD. Agric. Water Mgmt. 79:113-136. 14. Wang, X., J.R. Frankenberger, and E.J. Kladivko. 2006. Uncertainties in DRAINMOD predictions of subsurface drain flow for an Indiana silt loam using GLUE methodology. Hydrol. Process. 20:3069-3084. 15. Youssef, M.Y., R.W. Skaggs, G.M. Chescheir, and J.W. Gilliam. 2006. Field evaluation of a model for predicting nitrogen losses from drained lands. J. Environ. Qual. 35:2026-2042. Book Chapters: 16. Baker, J. L., M. J. Helmers, and J. M. Laflen. 2006. Water management practices: rain-fed cropland. Chapter 2 in Evaluating the Environmental Benefits of Agricultural Conservation Practices- The Status of our Knowledge. Soil and Water Conservation Society, Ankeny, IA. Extension Publications: 17. Frankenberger, J., Kladivko, E., Sands, G., Jaynes, D.B., Fausey, N.R., Helmers, M., Cooke, R., Strock, J., Nelson, K., Brown, L. 2006. Drainage water management for the Midwest. Purdue Extension, Knowledge to Go. WQ-44. 18. Wortman, C. S., M. Al-Kaisi, M. J. Helmers, J. Sawyer, D. Devlin, C. Barden, P. Scharf, R. Ferguson, W. Kranz, C. Shapiro, R. Spalding, D. Tarkalson, J. Holz, D. Francis, and J. Schepers. 2006. Agricultural nitrogen management and water quality protection in the Midwest. RP189 Heartland Regional Water Coordination Initiative. Iowa State University Extension. Conference Proceeding and Presented Publications: 19. Bakhsh, A. and R.S. Kanwar. 2006. Watershed hydrologic attributes effects on crop yields. In: Proceedings of the International Seminar on Agricultural Engineering: Issues and strategies; held on February 16-18, 2006 at the University of Agriculture, Faisalabad, Pakistan, pp. 101-107. 20. Chun, J. and R. A. Cooke. 2006. Numerical Modeling of Field-scale Subsurface Bioreactors. Innovations in Reducing Nonpoint Source Pollution. Nov. 28-30, Indianapolis, IN. Hanover College. 21. Cooke, R.A. 2006. The Illinois Conservation Drainage Research/Demonstration Program. ASA-CSSA-SSSA Annual Meeting. Nov. 12-16, 2006, Indianapolis, IN. 22. Frankenberger, J., E. Kladivko, G. Sands, D. Jaynes, N. Fausey, M. Helmers, R. Cooke, J. Strock, K. Nelson, and L. Brown. 2006. Drainage Water Management for the Midwest: Questions and Answers About Drainage Water Management for the Midwest. Purdue Extension Publ. WQ-44. http://www.ces.purdue.edu/extmedia/WQ/WQ-44.pdf 23. Frankenberger, J.R., E. Kladivko, R. Adeuya, L. Bowling, B. Carter, S. Brouder, J. Lowenberg-DeBoer, and J. Brown. 2006. Drainage water management impacts on nitrate load, soil quality, and crop yield. Proc. Innovations in Reducing Nonpoint Source Pollution Conf., Nov. 28-30, Indianapolis, Indiana. 24. Helmers, M. J. and R. Singh. 2006. Economic and environmental considerations for drainage design. In Proceedings of the 18th Annual Integrated Crop Management Conference (November 29 and 30, 2006, Iowa State University, Ames, IA), pp. 239-244. 25. Jaynes, Dan, Tom Kaspar, Tom Moorman, and Tim Parkin. 2006. In-Field Bioreactor for Removing Nitrate from Tile Drainage. ASA-CSSA-SSSA Annual Meeting, Indianapolis, IN Nov 12-16, 2006. 26. Kladivko, E.J., and J.R. Frankenberger. 2006. Subsurface drain spacing, cover crop, and fertilizer management effects on nitrate loads to surface waters. Proc. Innovations in Reducing Nonpoint Source Pollution Conf., Nov. 28-30, Indianapolis, Indiana. 27. Kladivko, E.J., F.J. Larney, J.B. Santini, and G.L. Willoughby. 2006. Drainage, tillage, and cover crop effects on soil properties and maize yields. Proc. 17th International Soil Tillage Research Organization (ISTRO) Conf., Aug.28-Sept.1, Kiel, Germany. (published on CD) 28. Qi, Z., M. Helmers, and R. Singh. 2006. Evaluating a drainage model using soil hydraulic parameters derived from various methods. ASAE Meeting Paper No. 062318. St. Joseph, Mich.: ASAE. 29. Rodrique, A., R. A. Cooke and J. Chun. 2006. Effects of Sampling Frequencies in the Evaluation of Nitrate-N Transport from Drainage Related BMPs. Innovations in Reducing Nonpoint Source Pollution. Nov. 28-30, Indianapolis, IN. Hanover College. 30. Singh, R. and M. J. Helmers. 2006. Subsurface drainage and its management in the upper Midwest tile landscape. In Proceedings of the EWRI Congress, ASCE. 31. Thorp, Kelly, Dan Jaynes, and Rob Malone. 2006. Using RZWQM and Drainmod NII to Simulate Drainage Water Management in Iowa. ASA-CSSA-SSSA Annual Meeting, Indianapolis, IN Nov 12-16, 2006. 32. Youssef, M.A. and R.W. Skaggs. 2006. The nitrogen simulation model, DRAINMOD-N II: Field testing and model application for contrasting soil types and climatological conditions. In Proc. 2006 World Environmental and Water Resources Congress. Omaha, NB: EWRI of ASCE.