West-central Indiana Research Articles

Compositional dynamics and light regimes in a midwestern old-growth forest preserve1

Forest structure, composition, and understory light patterns were measured at Allee Memorial Woods (AMW) near the forest–prairie ecoregional boundary in west-central Indiana to determine (1) compositional trends over five decades, (2) how different disturbance histories may have affected the dynamics, (3) current understory light regimes and their relationship to sapling densities, and (4) implications for the future of the forest preserve. Permanent sampling grids were re-established during 2011–12 in an uncut stand and two others that were selectively or heavily cut during 1890–1920. All trees > 1 m tall were censused, and those > 7.5 cm in diameter were mapped and measured, to compare structure (density, mean diameter, basal area) and species composition (richness, diversity, similarity) within and across size classes. Photosynthetic photon flux (PPF) was measured in three ways and correlated with sapling densities. Substantial compositional changes occurred in both the uncut and selectively cut stands during 1959–60 to 2011. They have declined in species richness and diversity, especially in smaller size classes, and the relative densities of Acer saccharum L., Fagus grandifolia Ehrh., or both have increased in sapling (1 m tall to 7.5 cm diameter) and mid-sized (7.6–50.7 cm) strata while the overstory (> 50.7 cm) has become more heavily dominated by Quercus spp. and Liriodendron tulipifera L. Light levels under intact canopy are very low in general and sapling densities are correlated with light, especially with longer-term direct PPF measurements at 0.5 m. All three stands show patterns consistent with widespread understory shade tolerance shifts in eastern North America, and the uncut and selectively cut stands have converged in overall size class structure and composition through different pathways related to their disturbance histories. Increased dominance of the overstory by Acer and Fagus, further declines in tree species diversity, and inhibition of regeneration by less shade-tolerant species are predicted for AMW unless there are substantial changes in climate and/or disturbance.

Quantifying Effects of Excess Water Stress at Early Soybean Growth Stages Using Unmanned Aerial Systems

Low-gradient agricultural areas prone to in-field flooding impact crop development and yield potential, resulting in financial losses. Early identification of the potential reduction in yield from excess water stress at the plot scale provides stakeholders with the high-throughput information needed to assess risk and make responsive economic management decisions as well as future investments. The objective of this study is to analyze and evaluate the application of proximal remote sensing from unmanned aerial systems (UAS) to detect excess water stress in soybean and predict the potential reduction in yield due to this excess water stress. A high-throughput data processing pipeline is developed to analyze multispectral images captured at the early development stages (R4–R5) from a low-cost UAS over two radiation use efficiency experiments in West–Central Indiana, USA. Above-ground biomass is estimated remotely to assess the soybean development by considering soybean genotype classes (High Yielding, High Yielding under Drought, Diversity, all classes) and transferring estimated parameters to a replicate experiment. Digital terrain analysis using the Topographic Wetness Index (TWI) is used to objectively compare plots more susceptible to inundation with replicate plots less susceptible to inundation. The results of the study indicate that proximal remote sensing estimates above-ground biomass at the R4–R5 stage using adaptable and transferable methods, with a calculated percent bias between 0.8% and 14% and root mean square error between 72 g/m2 and 77 g/m2 across all genetic classes. The estimated biomass is sensitive to excess water stress with distinguishable differences identified between the R4 and R5 development stages; this translates into a reduction in the percent of expected yield corresponding with observations of in-field flooding and high TWI. This study demonstrates transferable methods to estimate yield loss due to excess water stress at the plot level and increased potential to provide crop status assessments to stakeholders prior to harvest using low-cost UAS and a high-throughput data processing pipeline.

Landscape-wide flight activity by wintering bats predictably follows pulses of warmth in the Midwestern United States

Abstract During winter hibernation, bats may become active for a variety of reasons. Such winter activity occurs at or near hibernacula, but the degree to which this activity represents long-distance travel across a wider landscape largely is unstudied. We documented patterns in landscape-wide winter activity across a west-central Indiana study site, providing some new insights into winter flight activity. We deployed acoustic recording devices in areas without any known hibernacula, each night from December through March over three consecutive winters. Twilight temperatures (1 h post-sunset) ranged from −23°C to 21°C across three winters. We recorded 4,392 call files and attributed 89% to a phonic group based on characteristic frequencies. Flight activity was recorded at all stations and during all winter months. Nightly activity mainly was a function of the temperature on that night. We recorded low-phonic bats (most likely big brown bats, Eptesicus fuscus) down to −4°C, but most activity occurred when twilight temperatures were > 0°C. Mid-phonic bat activity (most likely eastern red bats, Lasiurus borealis) occurred when temperatures were > 0°C, with most activity occurring when temperatures were > 5°C. Wind speeds > 6 m/s tended to suppress activity. The duration of inactive periods during cold spells had no effect on activity during subsequent warm nights, indicating no increasing drive for activity following long periods of inactivity. Most activity occurred within a few hours of sunset, regardless of temperature. Little pre-sunset activity was recorded in low-phonic bats, but mid-phonic bats sometimes were active in the hour before sunset. Our results suggest widespread and potentially long-distance travel by bats across our study area during warm periods, but the impetus behind this activity remains unclear.

Design and testing of a mechanized tube well installer

To combat water access problems, a mechanized means to install sustainable, driven tube wells was developed. A modified hydraulic post driver was mounted to a Purdue Utility Platform vehicle to provide the impact necessary for a driven tube well installation. The vehicle provided the positioning framework and hydraulic power for the post driver. Low-cost tube wells could potentially provide safe, clean water, increasing hygiene and reducing pathogens typically present in unimproved surface water or artesian sources used throughout the developing world. Five wells were installed at sites across West-Central Indiana, with the deepest well being driven to 7 m. One well was able to produce 13 L/min and remained sanitary after disinfection. This suggests that the well-driver vehicle could install shallow driven tube wells in developing countries.

Improved Load Rating of an Open-Spandrel Reinforced-Concrete Arch Bridge

AbstractAn open-spandrel reinforced-concrete arch bridge in west central Indiana was load posted on the basis of a simplified analytical evaluation. The posting was controlled by the shear-strength...

Do American Golden-Plovers (Pluvialis dominica) Avoid Wind-energy Turbines in Agricultural Fields in Indiana During Spring Migration?

ABSTRACT.— The American Golden-Plover (Pluvialis dominica), a species of conservation concern, uses large agricultural fields during its spring passage through the mid-western United States. In west-central Indiana, large numbers of golden-plovers make a stopover in corn or soybean fields that were harvested the previous fall. Stopovers last for a number of days during which the birds feed and molt into alternate plumage. In recent years, wind energy facilities have been developed in the area with hundreds of wind turbines erected in fields used by the golden-plovers. During spring 2011 and 2012, we investigated patterns of golden-plover behavior at these facilities in Benton County, Indiana at a site where large spring aggregations of plovers have been observed for many years. Our results showed only limited behavioral avoidance of the turbines, and suggested that wind-energy development in this area was not significantly impacting migrant golden-plovers. However, we caution that additional studies could...

Winter ecology of prairie deer mice (Peromyscus maniculatus bairdii) in cultivated habitats: Implications for agricultural ecosystem services

Abstract Prairie deer mice ( Peromyscus maniculatus bairdii ) are permanent residents of row-crop fields in the Midwestern United Sates, and may provide ecosystem services by regulating weed seed and waste grain populations. Seed predation is especially critical in the months of highest seed availability following crop harvest, and is dictated by population density and individual patterns of diet choice. We used a combination of spatial mark-recapture demographic and stable isotope dietary analyses to investigate the ecology of prairie deer mice during this critical over-winter period within corn and soybean agro-ecosystems of west-central Indiana. Winter prairie deer mouse populations were robust in the row-crop habitats we sampled, with densities typically > 13 individuals/ha but variable among trapping grids and throughout winter. Apparent survival of individuals also varied throughout winter (57–79% monthly survival rate), and mean over-winter (December–April) survival of adults was 21%. Winter diets were dominated by waste grain, with corn and soybean contributing 55% and 77% of diet for mice sampled in corn and soybean fields, respectively. Weed seeds contributed less (2–27%) to winter diets. Based on our results and published field metabolic rates, we estimate that prairie deer mice consume 6.3 kg/ha of waste corn and 7.1 kg/ha of waste soybean seeds during the non-growing season. Collectively, our results suggest that prairie deer mice make meaningful contributions to reducing waste-grain populations during winter in post-harvest row-crop fields, during a time of year when most other seed predators are inactive.

Development of a Coupled Water Quality Model

Abstract. . Nonpoint-source (NPS) pollutants, especially from agriculture, continue to be a primary source of waterquality degradation problems. Effective land management decisions at the field scale must be made to minimize nutrient losses that could pollute streams. Existing NPS models often cannot directly estimate the impacts of different land management practices or determine the effectiveness of combined best management practices (BMPs) in a distributed way at the farm scale. In many cases, they rely on application of the Universal Soil Loss Equation (USLE) or its improved versions, which represent fields in a lumped fashion and use empirical rather than process-based modeling methodologies. In this study, a coupled Water Erosion Prediction Project and Water Quality (WEPP-WQ) model was completed, updated, improved, and evaluated for simulation of hydrology, soil erosion, and water quality. The WEPP model is a well-established process-based model that simulates runoff and erosion processes from a hillslope. The water quality components are based on those of the Soil and Water Assessment Tool (SWAT). A single overland flow element (OFE) on a hillslope is used to represent a single soil and land use management. The WEPP-WQ model was tested by comparing simulated values from the coupled model with observed nutrient and sediment concentrations in surface runoff following storm events at experimental sites near Waterloo in northeastern Indiana and at the Throckmorton Purdue Agricultural Center in west central Indiana. Time series evaluation of the WEPP-WQ model was performed with observed nutrient and sediment losses from an experimental plot near Tifton, Georgia. The model performed quite well in simulating nutrient losses for single storm events, with R2 greater than 0.8, Nash-Sutcliffe efficiency (NSE) greater than 0.65, and percent bias (PBIAS) less than 31% for runoff, sediment, nitrate nitrogen, total nitrogen, soluble phosphorus, and total phosphorus losses. In predicting time series nutrient loss, the WEPP-WQ model simulated daily nitrate nitrogen losses adequately, with the ratio of the root mean square error to the standard deviation of measured data (RSR) less than 0.7, NSE greater than 0.55, and PBIAS within the range of ±40%. Comparisons between simulated soluble phosphorus, total phosphorus, and literature results were performed due to the absence of an available observational dataset. The WEPP-WQ model with a single OFE in this study provides a basic but important step for the development of WEPP-WQ models with multiple OFEs that can evaluate the effectiveness of BMPs Keywords: Modeling, Nitrogen, Phosphorus, Soil erosion, Water quality, WEPP.

Measuring Farm Profitability

Farm profitability can be measuring using earnings before interest, taxes, and amortization (EBITA), net farm income, operating profit margin ratio, rate of return on farm assets, and rate of return on farm equity. EBITA, as the name implies, is used to cover interest, taxes, and amortization, which includes depreciation on machinery and buildings. Net farm income is used for family living, to repay debt, and to purchase new and used assets. Though these two measures are extremely important to monitor over time on a particular farm, due to the fact that these measures depend on farm size, it seldom makes sense to compare EBITA and net farm income with other farms. Because they take into account farm size, the profitability measures other than EBITA and net farm income are more useful when making comparisons among farms. The rates of return on assets and equity are extremely useful when comparing farm investments with other investments. However, these two measures are sensitive to how farms asset are valued on the balance sheet. For this reason, the operating profit margin is more conducive for benchmarking profitability among farms. In this article, a case farm in west central Indiana is used to examine operating profit margin benchmarks.

Editor's Note

Editor's Note

Community structure of acorn weevils (Curculio): inferences from multispecies occupancy models

We tested whether community structure of insect seed predators is influenced by spatiotemporal variation in mast availability on host-tree species. Specifically, mast production and acorn weevil (Curculio L., 1758) occupancy were estimated annually from 2006 to 2008 for individual host trees in a sample of 74 northern red oaks (Quercus rubra L.), 100 white oaks (Quercus alba L.), and 81 shagbark hickories (Carya ovata (Mill.) K. Koch) in west-central Indiana, USA. Occupancy and vital rates of nine Curculio species on their primary host-tree species were derived using multispecies, multiseason (MSMS) models within a Bayesian framework, accounting for imperfect detection. Mast production of host trees had a strong positive effect on community-level occupancy and survival of Curculio. Mast production varied considerably between years and generally was spatially autocorrelated only at distances <2 km, which likely reduced interspecific resource competition. Derived estimates of mean weevil species richness per tree and community similarity were highest in 2007 when mast production on all host-tree species was in phase. Generalist species compensated for lower survival rate on secondary hosts with higher colonization rates on these hosts during a year of mast failure in the primary host. We hypothesize that differential suitability of hosts as resources for Curculio created a spatial storage effect that, when coupled with a temporal storage effect induced by prolonged diapause common among Curculio, facilitated species coexistence. Methodologically, increased precision of parameter estimates from MSMS models makes it generally more useful than single-species models in studies of community dynamics.

An in-depth examination of farmers' perceptions of targeting conservation practices.

Watershed managers have largely embraced targeting of agricultural conservation as a way to manage strategically non-point source pollution from agricultural lands. However, while targeting of particular watersheds is not uncommon, targeting farms and fields within a specific watershed has lagged. In this work, we employed a qualitative approach, using farmer interviews in west-central Indiana to better understand their views on targeting. Interviews focused on adoption of conservation practices on farmers' lands and identified their views on targeting, disproportionality, and monetary incentives. Results show consistent support for the targeting approach, despite dramatic differences in farmers' views of land stewardship, in their views about disproportionality of water quality impacts, and in their trust in conservation programming. While the theoretical concept of targeting was palatable to all participants, many raised concerns about its practical implementation, pointing to the need for flexibility when applying targeting solutions and revealing misgivings about the government agencies that perform targeting.

Stopover ecology of American Golden-Plovers (Pluvialis dominica) in Midwestern agricultural fields

ABSTRACT Stopover locations represent critical habitat in the life cycle of migratory birds and the alteration of this habitat can profoundly influence a population. American Golden-Plovers (Pluvialis dominica) migrate though the Midwestern United States each spring, where most natural habitat has been converted to row crop agriculture. We investigated the stopover ecology of the golden-plover in the agricultural matrix of east-central Illinois and west-central Indiana between 2008 and 2012. We found that golden-plovers remained in the region for ∼45 days and individuals spent on average 24 days in the area before departing to the northwest. During a period of peak migration, golden-plovers preferred fields with standing water and, to a lesser extent, soybean fields. Over the 45-day stopover duration, golden-plovers moved extensively (shown by a dynamic occupancy model and area used estimation), with some evidence for tilled fields becoming unoccupied at greater rates than untilled fields. The tendency to...

Are There Too Many Deer in a Large Private Park in West-central Indiana?

Overabundant white-tailed deer (Odocoileus virginianus) can have significant effects on forest understory vegetation, especially in parks where hunting is not permitted. The DePauw Nature Park is a large (210 ha) private park located in west-central Indiana; hunting was prohibited in the park when the park was established in 2003. The park is mostly forest habitat but is surrounded by a rural landscape consisting of a mix of agricultural fields and forest fragments. We assessed the effects of deer on forest understory vegetation in the park using exclosures and control plots and estimated the size of the deer population in the park using infrared digital game cameras. There were almost no changes in forest understory vegetation during the first four years after the exclosures were established. The estimated population size of deer in the park ranged from 46 to 66 deer per km2. Although no observations were made outside park boundaries, we believe that the deer often move in and out of the park, feeding in surrounding fields and returning to the park for shelter. Effects of a large population of deer on forest understory vegetation are mediated by movement of deer in and out of the park as well as hunting pressure outside the park. We conclude that deer are having minimal effects on forest understory vegetation in the park at this time, but we will remain vigilant by continuing to monitor vegetation in the exclosures and control plots during future years.

30년 콩-옥수수 윤작 및 경운처리 장기시험 포장의 토양 온실가스 발생

1. 30년 장기 연용구의 연작 대비 윤작에 의한 옥수수 및 콩의 수량증대는 옥수수보다 콩이 더 컸으며, 연작시 무경운에 따라 수량이 감소되었던 옥수수는 윤작에 의해 수량이 많이 회복되었다. 콩은 연 윤작구 모두 무경운에서도 수량이 감소하지 않았다. 2. 윤작구의 작물재배기간의 이산화탄소 누적발생량은 재배작물 및 처리간 차이가 없었으며, 메탄은 콩의 재배시 plow 경운구에서 생육초기에 증가하였다. 3. 아산화질소의 발생은 옥수수 생육초기 질소시비 후에 질소비료의 무기화 과정에서 발생량이 증가하였는데, 경운방법에 따라 차이가 뚜렷하여 chisel 경운에서 가장 높았고, 무경운에서 가장 낮았다. 4. 콩-옥수수 윤작체계에서 plow 및 chisel 경운에 비해 무경운(no-tillage)의 채택에 따라 작물의 수량 감소없이 콩 재배 시 메탄 <TEX>$0.7kg\;C\;ha^{-1}$</TEX> 및 옥수수 재배 시 아산화질소 <TEX>$2{\sim}4kg\;N\;ha^{-1}$</TEX> 발생량을 감소시킬 수 있었다. Reduction of greenhouse gas (GHG) emissions from upland crop field as well as paddy field is being required, but little information on GHG emissions according to cultivation practices in upland field is available. Soil GHG emissions during the growing season were investigated in the field of three decades rotation and tillage treatments which were consisted of plow, chiesl tillage and no tillage in west central Indiana, USA in 2006. Seasonal cumulative <TEX>$CO_2$</TEX> emissions were not different among treatments. <TEX>$CH_4$</TEX> emission increased a little in plow tillage during early soybean growing season. Most of <TEX>$N_2O$</TEX> emission occurred during early corn growing season after N-fertilizer application from mid June to mid July, and was significantly affected by tillage practices in which seasonal cumulative <TEX>$N_2O$</TEX> emission was significantly higher under chisel tillage. <TEX>$N_2O$</TEX> emission under no-tillage was lower about 64% and 39% than that under chisel tillage and plow tillage, respectively. No-tillage practice with rotation of corn and soybean seems to be promising in point of less GHG emission and less labor for cultivation without grain yield reduction.

Development and application of a distributed modeling approach to assess the watershed-scale impact of drainage water management

Drainage water management, also known as controlled drainage, is the practice of using a water table control structure at the end of the subsurface drain pipe to reduce subsurface drainage, and thereby nitrate losses. Methods to quantify the potential effects of drainage water management for entire watersheds are needed to evaluate the impacts of large-scale adoption. A distributed modeling approach was developed to apply the field-scale DRAINMOD model at the watershed scale, and used to assess the impact of drainage water management on nitrate load from an intensively subsurface drained agricultural watershed in west central Indiana. The watershed was divided into 6460 grid cells for which drain spacing, soil parent material, and cropping pattern were estimated, resulting in 600 unique field conditions. The annual edge-of-field nitrate load from each grid cell was estimated as the product of DRAINMOD-predicted drain flow and the average annual nitrate concentration in drain flow, estimated from observations from related drainage sites in northern Indiana. Predicted monthly streamflow was in good agreement with the observed streamflow (Nash–Sutcliffe efficiency of 0.87 and 0.84 during the calibration and validation periods, respectively) and the predicted drain flow matched well with the measured drain flow (77.1cm vs. 77.8cm and 121.3cm vs. 128.4cm). Drainage water management decreased the average annual (1985–2009) predicted drain flow from 11.0 to 5.9cm, and the total nitrate load through subsurface drainage from 236 to 126ton (both about 47% reduction). The percent reduction in nitrate load varied between 40% and 53% for all combinations of drain spacing, soil parent material and cropping patterns, with drain spacing and soil parent material having a greater effect than cropping pattern. The methodology developed in this study showed potential for predicting the watershed-scale effects of subsurface drainage and drainage water management in drained agricultural watersheds.

Forest composition, leaf litter, and songbird communities in oak- vs. maple-dominated forests in the eastern United States

Within the eastern deciduous forest region, forest composition varies, with some areas dominated by a mix of oaks ( Quercus spp.) and other areas dominated by a mix of sugar maple ( Acer saccharum) and other tree species. Prescribed fire is being used on an experimental basis to assess its effectiveness in restoring and maintaining oak-dominated forests. Maple-dominated forests are susceptible to invasion by non-native earthworms, such as Lumbricus terrestris, given the palatability of leaf litter and suitable soil conditions, especially in northern parts of the region. What are the implications of this variation on leaf litter availability and habitat for ground-nesting songbirds? We investigated this question by comparing forest composition, leaf litter, and songbird communities in maple-dominated forests in west-central Indiana and oak-dominated forests, recently burned and unburned, in southeastern Ohio. We also assessed abundance of earthworms and decomposition rates of different types of leaves in the maple-dominated forests in Indiana. Leaf litter and ground-nesting bird species were abundant in unburned oak-dominated forests, but were absent or nearly absent in recently burned oak-dominated forests and in maple-dominated forests. The lack of leaf litter and absence of ground-nesting bird species in maple-dominated forests may be due to the combination of abundant non-native earthworms, alkaline and calcium-rich soils, palatable leaves, and rapid leaf litter decomposition rates. Effects of burning on leaf litter and ground-nesting bird species in oak-dominated forests are probably temporary, as long as prescribed fires are not applied on a frequent or widespread basis. Our study is the first one to show a correlation between forest composition, leaf litter availability, earthworm abundance, and songbird populations. Many researchers are investigating effects of non-native earthworm invasions on ecosystem properties in eastern deciduous forests. We recommend that researchers should also monitor songbird populations to assess whether declines in ground-nesting bird populations are occurring in response to these changes.

Reach- and Watershed-Scale Associations of Crayfish within an Area of Varying Agricultural Impact in West-Central Indiana

Abstract We studied the associations of crayfish with reach-scale instream habitat and water quality variables and watershed-scale variables of riparian and watershed land cover, runoff, impervious surfaces, and hydrologic soil type in west-central Indiana. Crayfish assemblage was measured by abundance, species richness, and diversity (Shannon's H) at 180 sites. The western portion of the study area, within the Interior River Lowland ecoregion, has been heavily impacted by agriculture, while the eastern portion, within the Interior Plateau ecoregion, is more heavily wooded and less impacted. The ability of variables at each spatial extent to predict crayfish assemblage was assessed using multiple linear regression analysis. Reach-scale models were better predictors of crayfish assemblage than watershed-scale models. A variety of habitat and water quality characteristics, principally instream cover, appeared as important predictors. Forested riparian and watershed land appeared as significant watershed-sca...

The limited role of canopy gaps in the successional dynamics of a mature mixedQuercusforest remnant

Question: Are canopy gap dynamics responsible for driving the structural and compositional changes that have occurred over a 26-year period in a mature Quercus forest remnant? Location: Dobbs Natural Area, an unlogged 3.6-ha forest preserve in west-central Indiana, USA. Methods: We analyzed mapped permanent plot data for a site that illustrates a trend common in Quercus-dominated forests in eastern North America, where recruitment of new stems is dominated by mesophytic, shade-tolerant species such as Acer saccharum, rather than Quercus. We developed a GIS database from stand census measurements taken in 1974 and 2000, employing it to conduct tree-by-tree comparisons that allow direct determination of ingrowth, mortality and survivorship, and to relate the spatial patterns of subcanopy dynamics to canopy gap occurrence. Results: The re-census shows modest changes in canopy composition, but much greater turnover in the subcanopy. Nearly half of all individuals originally present died; much of this mortality resulted from a major decline in subcanopy Ulmus americana. While overall density remained fairly constant, the subcanopy experienced substantial ingrowth of shade-tolerant Acer saccharum, Fagus grandifolia, and Tilia americana. Canopy gaps, although forming at rates in the upper range of regional averages, did not significantly benefit subcanopy populations of Quercus spp. or most other taxa with limited shade tolerance. Conclusions: Canopy gaps play a minor role in driving the recent demographic trends of this stand. The spatial and temporal scales of light availability in gaps do not support regeneration of most shade-intolerant species. Compositional change parallels a historical shift in light regimes.

Detecting subsurface drainage systems and estimating drain spacing in intensively managed agricultural landscapes

Detailed location maps of tile drains in the Midwestern United States are generally not available, as the tile lines in these areas were laid more than 75 years ago. The objective of this study is to map individual tile drains and estimate drain spacing using a combination of GIS-based analysis of land cover, soil and topography data, and analysis of high resolution aerial photographs to within the Hoagland watershed in west-central Indiana. A decision tree classifier model was used to classify the watershed into potentially drained and undrained areas using land cover, soil drainage class, and surface slope data sets. After masking out the potential undrained areas from the aerial image, image processing techniques such as the first-difference horizontal and vertical edge enhance filters, and density slice classification were used to create a detailed tile location map of the watershed. Drain spacings in different parts of the watershed were estimated from the watershed tile line map. The decision tree identified 79% of the watershed as potential tile drained area while the image processing techniques predicted artificial subsurface drainage in approximately 50% of the Hoagland watershed. Drain spacing inferred from classified aerial image vary between 17 and 80 m. Comparison of estimated tile drained areas from aerial image analysis shows a close agreement with estimated tile drained areas from previous studies (50% versus 46% drained area) which were based on GIS analysis and National Resource Inventory survey. Due to lack of sufficient field data, the results from this analysis could not be validated with observed tile line locations. In general, the techniques used for mapping tile lines gave reasonable results and are useful to detect drainage extent from aerial image in large areas. These techniques, however, do not yield precise maps of the systems for individual fields and may not accurately estimate the extent of tile drainage in the presence of crop residue in agricultural fields and/or existence of other spatial features with similar spectral response as tile drains.