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Concern about [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] contamination of surface waters has prompted the development of agricultural water table management systems to reduce [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] loss in subsurface drainage outflow by subirrigating through the existing subsurface drainage lines during the growing season and controlling off-season outflows. We hypothesized that soil N pools, crop yields, and N uptake in a corn (Zea mays L)-soybean (Glycine max.) rotation differ between subirrigation (water table at 40 cm) with controlled drainage (SI/CD) vs. subsurface drainage (SD) alone on Omulga silt loam (Aeric Fragiaqualfs). Mean microbial biomass N, potentially mineralizable N, dissolved organic N, and ammonia N were not affected by the water table management system. Mean [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] was not affected by the water table management system at 0- to 15-cm and 15- to 30-cm depths, but the 2-yr mean soil [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] concentration at the 30- to 75-cm depth was 46% lower in SI/CD compared with SD. The average corn yield was 19% greater, and the average soybean yield was 64% greater, in SI/CD plots, compared with SD. Corn N uptake was 13% greater and soybean N uptake was 62% greater with SI/CD, compared with SD. The SI/CD water table management system increased plant N uptake and reduced deep-profile [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] concentrations, thereby reducing the amount of [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] potentially available to move via drains to surface waters.

Subsurface drainage, while an important and necessary agricultural production practice in the Midwest, contributes nitrate (NO3-N) and soluble phosphorus (P) to surface waters. Eutrophication (i.e., excessive enrichment of surface water by NO3-N and soluble P) supports harmful algal blooms in receiving waters. The magnitude of NO3-N and soluble P loss in subsurface drainage varies greatly by landscape, weather, and field management factors. This study evaluated both the relative and combined impacts of these factors on observed NO3-N and soluble P concentrations in subsurface drainage water in the Western Lake Erie Basin watershed. Water quality data from multiple drainage outlet sites in northwest Ohio provided evidence that the primary management factors affecting NO3-N and soluble P loss were the amount and time of fertilizer application. Results strongly support following Tri-State fertilizer recommendations and 4R nutrient stewardship principles to reduce the risk of NO3-N and soluble P loss. Results also provided evidence of NO3-N and soluble P transport to subsurface drains via different pathways. Due to differences in NO3-N and soluble P transport through the soil profile (via baseflow and preferential flow, respectively), management approaches taken to reduce one nutrient may exacerbate losses of the other. Further research is needed to address potential changes in field hydrology (and consequently the infield transport of soluble nutrients) from different types of agricultural best management practices (BMPs) and to evaluate optimal stacking of BMPs to achieve reductions in both NO3-N and soluble P loss. Controlled drainage has a high potential for stacking with other BMPs because it is primarily a physical discharge and load reduction practice. [ABSTRACT FROM AUTHOR]

The US Midwest is expected to experience higher intensity rainfall events along with an increased chance of drought during the mid- and late 21st century under projected future climate scenarios. Development of strategies to mitigate the impact of these projected changes on agricultural production and environmental quality is important for ensuring agricultural resiliency to future climate. This study used the DRAINMOD hydrologic model to simulate subsurface drainage discharge at a field site in the headwaters of the Western Lake Erie Basin using future climate patterns projected by 20 general circulation models. Despite projected increases in rainfall, by the late twenty-first century, subsurface discharge was projected to decrease 7% and 11% under representative concentration pathway (RCP) 4.5 and RCP 8.5, respectively. Reductions in subsurface discharge were attributed to increased temperature and evapotranspiration. The performance of controlled drainage was not projected to change on an annual basis throughout the next century. The benefits of controlled drainage systems as an agricultural best management practice were still evident under the projected climate change of the next century. The role of controlled drainage as a means to potentially retain more crop available water in the soil profile could become critically important under future climate conditions. [ABSTRACT FROM AUTHOR]

Numerical modeling is an economical and feasible approach for quantifying the effects of best management practices on dissolved reactive phosphorus (DRP) loadings from agricultural fields. However, tools that simulate both surface and subsurface DRP pathways are limited and have not been robustly evaluated in tile-drained landscapes. The objectives of this study were to test the ability of the Agricultural Policy/Environmental eXtender (APEX), a widely used field-scale model, to simulate surface and tile P loadings over management, hydrologic, biologic, tile, and soil gradients and to better understand the behavior of P delivery at the edge-of-field in tile-drained midwestern landscapes. To do this, a global, variance-based sensitivity analysis was performed, and model outputs were compared with measured P loads obtained from 14 surface and subsurface edge-of-field sites across central and northwestern Ohio. Results of the sensitivity analysis showed that response variables for DRP were highly sensitive to coupled interactions between presumed important parameters, suggesting nonlinearity of DRP delivery at the edge-of-field. Comparison of model results to edge-of-field data showcased the ability of APEX to simulate surface and subsurface runoff and the associated DRP loading at monthly to annual timescales; however, some high DRP concentrations and fluxes were not reflected in the model, suggesting the presence of preferential flow. Results from this study provide new insights into baseline tile DRP loadings that exceed thresholds for algal proliferation. Further, negative feedbacks between surface and subsurface DRP delivery suggest caution is needed when implementing DRP-based best management practices designed for a specific flow pathway. [ABSTRACT FROM AUTHOR]

Subsurface drainage methods and materials technologies were modernized more through innovative research and development between 1960 and 1975 than during the previous 100 years. Original research conducted by ASABE Member agricultural engineers who were employed by the USDA Agricultural Research Service (ARKS) and worked cooperatively with other ARS scientists and technicians plus scientists at The Ohio State University developed the prototype materials and equipment to test the new drainage technology. High-speed installation of plastic subsurface drains with plow- type equipment was made possible and practical in the late 1960s with the adoption of coilable corrugated-wall polyethylene plastic tubing. However, manual control of depth and grade by the operator of the drain plow at speeds of 35 to 50 m/min was not sufficiently accurate or practical. A laser-beam automatic grade-control system was designed and developed to meet the specific requirements of high-speed plow-type draintube installation equipment. The first use of the laser in agriculture was reported to be in the installation of plastic drain tubing with plow and/or trencher equipment. Through cooperative field trial demonstration projects with university extension specialists and industry representatives, the new technology was transferred to industry for final development and marketing. A laser-plane system, rather than the laser-line prototype tested, was developed by the industry cooperators to project a beacon of laser light (a laser plane) over air entire field. Laser-plane technology subsequently applied in precision land grading for surface irrigation vastly improved irrigation efficiency and saved untold millions of acre-feet of irrigation water worldwide. From this agricultural engineering beginning, laser technology expanded rapidly into many engineering agricultural and non-agricultural fields, including surveying, land leveling and grading, construction (highways and buildings), and military tasks. The laser-beam and laser-plane systems are considered the engineering standard method today for alignment and guidance applications. [ABSTRACT FROM AUTHOR]

Techniques are needed to monitor nursery production practices for proper use of water resources and nutrient management. An experimental system to examine water quality, irrigation efficiency and drainage from pot-in-pot nursery container production was established in a commercial nursery. The system mainly consisted of 50 pot-in-pot containers with 50 trees irrigated with micro spray stakes, drainage water measurement devices, container-substrate moisture probes, thermocouples, a weather station, and data loggers. Tests indicated the system was capable to measure irrigation and rainfall inputs, drainage water loss, container substrate moisture content and temperature, leachate of nitrogen, phosphate and potassium in drainage water, and tree growth in pot-in-pot nursery production. The system provided a method to not only monitor the loss of water and nutrients but also continuously monitor the substrate temperature and moisture content during four seasons of a year to evaluate potentials of winter injury or summer heat damage to roots for pot-in-pot nursery production. [ABSTRACT FROM AUTHOR]

Soybean production, worldwide, typically involves full tillage resulting in much less biomass than other crops, leading to decreased soil organic matter and increased soil degradation. The goal of this study was to evaluate the potential benefits of an innovative management system that includes the combinations of no-till, crop rotation, cover crop, and gypsum application on continuous soybean production. The response of soil physical properties, i.e. bulk density and water-stable aggregates, was evaluated across a range of soil types and climatic conditions. Treatments consisted of comparing (1) continuous soybean to a soybean-corn and corn-soybean rotation, (2) cereal rye [Secale cereale (L.)] cover crop to no cover crop, and (3) gypsum surface‐applied at 0, 1.1, and 2.2 Mg ha−1. The study was replicated at four different sites in the United States, including Shorter (AL), Farmland (IN), Hoytville (OH), and Piketon (OH). At the end of the 5-year study, soil bulk density and aggregate stability were determined. Soil bulk density and water-stable aggregates were unaffected by gypsum addition regardless of the location. Including cereal rye as a winter cover increased soil aggregation and bulk density at the Hoytville location only. Rotating the soybeans with corn (compared to continuous soybeans) resulted in soil aggregation and bulk density improvements at all research locations. Results indicated that soybean production that included crop rotation into management system improved soil aggregate stability, whereas cover crop benefits were less effective and amending the soil with gypsum did not significantly affect these soil properties. [ABSTRACT FROM AUTHOR]

Effects of severity of erosion on soil physical properties and corn growth and yield were evaluated on a farm for a Miamian soil in Ohio for 1993 and 1994 seasons. The depth to carbonates, total porosity, and silt content decreased while soil bulk density (rhob), clay content and pH increased with increase in severity of erosion. Corn growth and yield were adversely affected by erosion in 1993, whenprecipitation was lower than normal. Yield reductions in corn grain yield by severe erosion were 29.2% compared to slight erosion, and 32.7% compared to the depositional phase. No clear trend was observed for corn grain yields in 1994, probably due to sufficient rainfall during the grain-fill stage. A regression equation relating corn grain yield (Y) to soil properties in 1993 was Y = 23.9 - 7.11 rhob - 0.163 Clay - 0.919 (R2 = 0.36**), where the yield is in Mg/ha, soil rhob is in Mg/m3, clay is in %, and pH is 1:1 in H2O. [ABSTRACT FROM AUTHOR]

Water quality research and monitoring programs often form the basis from which related legislation is derived. Yet, no standard, protocol, or method is available for guiding the selection of a water quality sampling strategy for runoff from fields and small watersheds. The objective of this study was to develop a methodology that provides guidance in the selection of a water quality sampling strategy for headwater streams (drainage areas less than 2500 ha; 6,177 ac). The developed method is based on the dimensionless unit hydrograph and relationships of measured pollutant concentrations to discharge hydrographs. The methodology was designed for storm events with a specific return interval and a selected acceptable level of error in pollutant load. Nine input parameters (hydraulic length, watershed slope, curve number, drainage area, runoff coefficient, 10-year, one hour precipitation amount, 100-year, one hour precipitation amount, 10 year, 24 hour precipitation amount, and recurrence interval) were used to develop the design hydrograph. Both time- and flow-paced sampling techniques were considered. A global sensitivity analysis of the method indicated that time-paced sampling was primarily sensitive to parameters included in the time of concentration calculation (hydraulic length, watershed slope, and curve number). Flow-paced sampling showed some sensitivity to all nine input parameters. An example application illustrates the utility of the method. Use of the method should facilitate the selection of water quality sampling strategies for field and small watershed scale studies and aid in budgetary planning for sample collection and analysis. The measurements taken based on the recommended sampling strategy will provide more confidence in the pollutant storm load estimates. [ABSTRACT FROM AUTHOR]

Impacts of watershed scale conservation practice adoption on sediment, nutrient, and pesticide losses and adjacent stream biota are not well understood. The objective of this study was to examine the suitability of selected paired watersheds to quantify hydrology, chemical, and ecology effects of conservation practice implementation for channelized and unchannelized watersheds in Upper Big Walnut Creek watershed, Ohio. Channelized watersheds were more similar in watershed characteristics than the unchannelized watersheds. One hydrology, eight water chemistry, and five fish community response variables were measured. Most response variables in both watershed pairs were moderately correlated (r > 0.6), but the minimum percent change required to detect a response difference was greater for the unchannelized watersheds. Detectable temporal trends in the difference between like response variables for the channelized and unchannelized watershed pairs were minimal. These results validate the paired watershed design and suggest that conservation practice induced changes in hydrology, water quality, and fish communities can be quantified. [ABSTRACT FROM AUTHOR]

Recent evidence suggests that turfgrass nutrients in runoff and subsurface flow pose potential risks to surface water quality. Research on water quality associated with turfgrass has generally focused on surface runoff, not subsurface flows. Quantifying the delivery of nutrients, nitrate nitrogen (NO3-N) and dissolved reactive phosphorus, to streams from subsurface drainage features on managed turf sites, and relating the transport to fertility management and season is important for many urban managers, especially those under regulatory scrutiny. NO3-N and dissolved reactive P concentrations from two French drains located on the Morris Williams' Municipal Golf Course in Austin, Texas, were measured over a four-year period (March, 1999 to March, 2003). Time series statistics were used to analyze and relate NO3-N and dissolved reactive P concentrations to weather and management. A weak statistical relationship (r² = 0.55) was detected between discharge and NO3-N concentration at one of the two drains. The relationship between discharge and dissolved reactive P concentration was not significant. Median NO3-N concentrations from the two drains were 1.27 mg L-1 and 0.32 mg L-1 NO3-N loading from the drains was 2.7 kg ha-1 (2.4 lb ac-1). The NO3-N concentrations and load from the turf area were approximately 10 percent of those values reported for typical row crop agriculture. Median dissolved reactive P concentrations were o.11 mg L-1 and 0.09 mg L-1 while dissolved reactive P loading was 0.46 kg ha-1. Significant (α = 0.05) seasonal tendencies were found with respect to NO3-N and dissolved reactive P. A strong correlation was evident between the timing of peak NO3-N losses and nitrogen application; and between the timing of peak NO3-N losses and air temperature. There was a similar correlation between the timing of peak dissolved reactive P losses and phosphorus application. Our results suggest NO3-N transport in subsurface drainage from this golf course is not a water quality issue. However, our findings suggest significant dissolved reactive P transport through the drains and a need for an integrated (turf, nutrients, and water) management plan that includes consideration of subsurface drainage fluxes. [ABSTRACT FROM AUTHOR]

Within-event variability in rainfall intensity may affect pesticide leaching rates in soil, but most laboratory studies of pesticide leaching use a rainfall simulator operating at constant rainfall intensity, or cover the soil with ponded water. This is especially true in experiments where macropores are present--macroporous soils present experimental complexities enough without the added complexity of variable rainfall intensity. One way to get around this difficulty is to use a suitable pesticide transport model, calibrate it to describe accurately a fixed-intensity experiment, and then explore the affects of within-event rainfall intensity variation on pesticide leaching through macropores. We used the Root Zone Water Quality Model (RZWQM) to investigate the effect of variable rainfall intensity on alachlor and atrazine transport through macropores. Data were used from an experiment in which atrazine and alachlor were surface-applied to 30 x 30 x 30 cm undisturbed blocks of two macroporous silt loam soils from glacial till regions. One hour later the blocks were subjected to 30-mm simulated rain with constant intensity for 0.5 h. Percolate was collected and analyzed from 64 square cells at the base of the blocks. RZWQM was calibrated to describe accurately the atrazine and alachlor leaching data, and then a median Mid-west variable-intensity storm, in which the initial intensity was high, was simulated. The variable-intensity storm more than quadrupled alachlor losses and almost doubled atrazine losses in one soil over the constant-intensity storm of the same total depth. Also rainfall intensity may affect percolate-producing macroporosity and consequently pesticide transport through macropores. For example, under variable rainfall intensity RZWQM predicted the alachlor concentration to be 2.7 microg ml(-1) with an effective macroporosity of 2.2 E(-4) cm(3) cm(-3) and 1.4 microg ml(-1) with an effective macroporosity of 4.6 E(-4) cm(3) cm(-3). Percolate-producing macroporosity and herbicide leaching under different rainfall intensity patterns, however, are not well understood. Clearly, further investigation of rainfall intensity variation on pesticide leaching through macropores is needed.