Larry C. Brown

Pesticide Transport to Subsurface Tile Drains in Humid Regions of North America

This report reviews and summarizes findings from more than 30 North American studies of pesticide transport into subsurface agricultural drains. Background information about subsurface drainage use and its importance for crop production and environmental protection is also presented. The presence of a subsurface drainage system generally increases the volume of infiltration and consequently decreases the volume of surface runoff water and sediment compared with similar soils where subsurface drainage systems are not installed. Therefore, in general, the presence of subsurface drainage decreases surface runoff losses of sorbed compounds such as pesticides, both because of lower runoff volumes and often also because of lower concentrations in the runoff resulting from the delayed initiation of runoff. Pesticide concentrations and mass losses are usually much lower in subsurface drainage than in surface runoff, often by an order of magnitude. In the medium- and fine-textured soils where subsurface drainage is common, the dominant mechanism for pesticide transport to the drain tiles is most likely preferential flow during rainfall/drainage events occurring soon after pesticide application. Concentrations and mass losses in subsurface drains are highly variable from year to year, depending on weather patterns.

Phosphorus transport in agricultural subsurface drainage: a review.

Phosphorus (P) loss from agricultural fields and watersheds has been an important water quality issue for decades because of the critical role P plays in eutrophication. Historically, most research has focused on P losses by surface runoff and erosion because subsurface P losses were often deemed to be negligible. Perceptions of subsurface P transport, however, have evolved, and considerable work has been conducted to better understand the magnitude and importance of subsurface P transport and to identify practices and treatments that decrease subsurface P loads to surface waters. The objectives of this paper were (i) to critically review research on P transport in subsurface drainage, (ii) to determine factors that control P losses, and (iii) to identify gaps in the current scientific understanding of the role of subsurface drainage in P transport. Factors that affect subsurface P transport are discussed within the framework of intensively drained agricultural settings. These factors include soil characteristics (e.g., preferential flow, P sorption capacity, and redox conditions), drainage design (e.g., tile spacing, tile depth, and the installation of surface inlets), prevailing conditions and management (e.g., soil-test P levels, tillage, cropping system, and the source, rate, placement, and timing of P application), and hydrologic and climatic variables (e.g., baseflow, event flow, and seasonal differences). Structural, treatment, and management approaches to mitigate subsurface P transport-such as practices that disconnect flow pathways between surface soils and tile drains, drainage water management, in-stream or end-of-tile treatments, and ditch design and management-are also discussed. The review concludes by identifying gaps in the current understanding of P transport in subsurface drains and suggesting areas where future research is needed.

Early development of vascular vegetation of constructed wetlands in northwest Ohio receiving agricultural waters

Constructed wetlands are currently being explored for use in reducing non-point source (NPS) pollution. The Wetland Reservoir Subirrigation System (WRSIS) project links water management in agricultural fields, constructed wetlands and water storage reservoirs to enhance crop production and reduce delivery of agrichemicals and sediments to local waterways. Three WRSIS demonstration sites have been developed on prior converted cropland in the Maumee River watershed located in northwest Ohio. Construction of the wetlands was completed in 1996 and they were then allowed to passively revegetate while receiving drainage water from adjacent fields. The primary goal of this study was to characterize the initial development of vegetation, and the availability of propagules within these wetlands. Preliminary vegetation inventories conducted in 1998 identified moderate species richness but low percentage of wetland species. A germination study completed on soils from one location showed additional viable wetland species available in the seed bank. Passive revegetation of these three constructed wetlands associated with WRSIS systems has resulted in good vegetation cover, but it is lacking the desired percentage of wetland species to date. Passive revegetation may prove to be an effective and economical method of revegetating constructed wetlands within agricultural landscapes that have suitable propagule availability.

Bioremediation of nitrate-contaminated shallow soils and waters via water table management techniques: evolution and release of nitrous oxide

Abstract Nitrate (NO 3 –N) commonly accumulates in soils because of fertilizer additions or when crop demand is much less than the rate of NO 3 –N production. Water table management (WTM) has been proposed to stimulate denitrifying bacteria, thus removing the accumulated NO 3 –N by converting it to N 2 O (a greenhouse gas) and N 2 . We studied the emission of N 2 O and N 2 as affected by water table depth. Undisturbed soil columns (30 cm dia by 90 cm long) from three soil series (Blount, somewhat poorly drained Aeric Ochraqualf; Clermont, poorly drained Typic Glossaqualf; and Huntington, well drained Fluventic Hapludoll) were treated with 2.11 g N (as KNO 3 ) applied as a band 10 cm below the surface. Two different WTM schemes were studied: static (WTM1) and dynamic (WTM2). We repeated WTM2 using 15 N and this treatment, applied to the Huntington soil only, was designated WTM3. In general, N 2 O concentrations in a soil column responded to fluctuations in water table depth. Concentrations of N 2 O were usually higher in soils immediately below, as compared to above, the water table. The Clermont columns departed from this general trend. Maintaining the water table at 50 cm depth resulted in N 2 O emission rates (1.8–44 mg N 2 O–N m −2 d −1 ) comparable to those reported for cultivated fields. A water table only 10 cm below the surface caused N 2 O emission rates to increase considerably (60–560 mg N 2 O–N m −2 d −1 ). Four days after imposition of a water table 10 cm below the soil surface, N 2 O comprised 95% of the N gas emitted (i.e. N 2 O mole fraction was 0.95). One week later, however, the N 2 O mole fraction was 0.35 which was significantly ( P ≤0.05) lower than the mole fraction (0.68) measured prior to raising the water table. These results suggest that when using WTM practices, the best option to maintain high NO 3 –N removal rates and to reduce the proportion of N 2 O in the emitted gases is to maintain a high water table for a prolonged period in the most biologically-active portion of the soil profile.

EFFECT OF A WOODY (SALIX NIGRA) AND AN HERBACEOUS (JUNCUS EFFUSUS) MACROPHYTE SPECIES ON METHANE DYNAMICS AND DENITRIFICATION

Wetlands improve water quality through denitrification, but these ecosystems are also an important source of the greenhouse gas, methane. The objective of this research was to determine the effect of two common macrophyte species (Juncus effusus and Salix nigra) on denitrification and on the methane cycle. The research was conducted in a newly constructed wetland on the Columbus campus of The Ohio State University during two growing seasons. In the wetland, some plots were left unplanted, while others were planted with Salix or Juncus species (i.e., 3 treatments; n = 15 per treatment). For each treatment, we quantified concentrations of methane at two depths (15 and 25 cm) in the sediment, emissions of methane from the sediment and through the plants, and denitrification rates. During most of the second growing season, both species had a limited effect on denitrification and methanogenesis. The effects of the plants became evident by the end of the second growing season and during the third growing season. During the third growing season, Salix species enhanced the release of the greenhouse gas methane to the atmosphere, while Juncus limited the emission of methane. In comparison to the unplanted plots, the long-term removal of nitrate by denitrification was favored in the plots planted with Juncus and was not affected by Salix. Our study provides evidence that certain plants (such as Juncus) can be planted in constructed wetlands to favor denitrification, while buffering methane emission.

BIOREMEDIATION OF NITRATE-CONTAMINATED SHALLOW SOILS USING WATER TABLE MANAGEMENT TECHNIQUES: NITRATE REMOVAL EFFICIENCY

Nitrate (NO3 –-N), in excess of plant uptake during crop production, may move below the crop’s rooting zone. In order to protect groundwater quality, water table management (WTM) has been proposed as a way to remove, via stimulation of denitrification, this excess NO3 –-N. We conducted a simulation experiment for 130 days to evaluate the effectiveness of WTM for such purpose. In this experiment, undisturbed soil columns (90 cm long ×30 cm diameter) from three soils were used. The soils were Blount (somewhat poorly drained Aeric Ochraqualf), Clermont (poorly drained Typic Glossaqualf) and Huntington (well-drained Fluventic Hapludoll). A band (< 1 cm thick) of NO3 –-N (2.11 g KNO3-N column–1) treated soil was created 10 cm below the soil surface and removal of that NO3 –-N was attempted using two different WTM schemes: static (WTM1) and dynamic (WTM2). We also repeated WTM2 using 15N to measure N transformations and this treatment, applied to the Huntington soil only, was designated WTM3. Based on denitrification gases (N2, N2O) emitted, from 9 to 14% of the added NO3 –-N was removed from soil columns using WTM1 during the 130 day test period. With WTM2, 24 to 43% of the added NO3 –-N was removed. A comparable NO3 –-N removal estimate (40%) was obtained for the 15N-treated (WTM3) Huntington columns using a mass balance approach. Removal of NO3 –-N was faster when the water table was near the soil surface. Maximum rates of in situ NO3 –-N losses were generally 2 to 7 times lower than soil denitrification potential determined in the laboratory. This experiment shows that NO3 –-N removal from shallow soils and waters can be achieved using WTM techniques. However, the need for long periods of flooding during times when other climatic conditions (e.g., warm temperatures) are conducive to high rates of denitrification may limit successful field application of these WTM techniques for NO3 –-N removal from cropland.

Crop yield evaluation under controlled drainage in Ohio, United States

Controlled drainage (CD) is an important practice for reducing nutrient loading to surface water bodies across the midwestern United States. There may also be a positive crop yield benefit, which could add an incentive for adoption of this practice. The objective of this multienvironment trial was to assess yield stability and yield performance of CD in northwest Ohio, United States. The trial was a split-plot experiment with environments as whole plots (randomization unit). The main plot factor was crop with three levels: corn (Zea mays L.), popcorn (Zea mays L. var. everta), and soybean (Glycine max [L.] Merr.). The subplot factor was drainage management with two levels: conventional free drainage (FD) and CD. The design of the main plot factor was a completely randomized design. Mixed model analysis showed that CD management produced a statistically greater (p-value = 0.0246) crop yield compared to FD management over 23 site-year environments during 2008 to 2011. Interaction between drainage management and crop was not significant, implying that CD management had the same yield-increasing effect for all crops. The CD management provided 3.3%, 3.1%, and 2.1% greater yield for corn, popcorn and soybean, respectively, relative to the FD management. The stability analysis based on 23 environments suggested that the drainage managements were not different in yield stability, though a larger number of environments are needed to make a more accurate assessment of yield stability. Area of influence analysis indicated that CD can provide more profit than FD for relatively flat fields where the influence of CD extends over the entire field. In conclusion, CD provided crop yield advantage over FD across different environments in northwest Ohio.

Physical Properties of Porous Clay Ceramic-Ware

The focus of this study is on the physical properties of clay ceramic materials compatible for drinking water filtration. A multiparameter lognormal multivariate regression approach is proposed for assessing the combined effects of quantity of compositional constituent of raw materials used in ceramic manufacture on toughness. The approach was validated for two specimen types (T- and S-specimens) derived from a circular base of the frustum shaped, porous clay ceramic ware (PCCW). The PCCW were manufactured from clay and sieved sawdust mixed at distinct volume fractions. The variation of the porosity and density of the PCCW was studied with respect to the amounts of sawdust and clay used in the manufacturing. The research helped to clearly define the roles of clay and sawdust quantities for strength development in both T- and S-specimen. A generalized experimental approach is proposed for estimation of mechanical properties of clay ceramics as a function of the material constituent fractions. A polynomial relationship was developed between the compressive strength and density of the PCCW material. The statistical model expressions developed herein may be used for the prediction of material and mechanical properties of similar materials, including natural and engineered materials.

Measurement Errors in Tipping Bucket Rain Gauges under Different Rainfall Intensities and their implication to Hydrologic Models

Measurements from tipping bucket rain gauges (TBRs) consist of systematic and random errors as an effect of external factors, such as mechanical limitations, wind effects, evaporation losses, and rainfall intensity. Two different models of TBRs, viz. ISCO-674 and TR-525 (Texas Instr., Inc.), being used in Ohios Upper Big Walnut Creek Watershed, were calibrated in the lab to quantify measurement errors at different rainfall intensities. A range of rainfall intensities (12.5 to 230 mm-hr-1) was simulated for each TBR using a pre-calibrated peristaltic pump mechanism. The instantaneous and cumulative values of simulated rainfall were measured at 1-min intervals. Actual and measured rainfall at each intensity was compared. Both TBR measurements showed a significant deviation from the actual rainfall rates with increasing underestimation error at higher intensities (>50.8 mm-hr-1) and slight overestimation at lower intensities (<25.4 mm-hr-1). Model TR-525 showed an earlier and larger deviation (up to 20%) as compared to ISCO-674 (up to 13%) over the range of intensities. These findings are being used to correct precipitation data being collected by both TBRs and test the effect of these corrections on the outputs of hydrologic models, such as SWAT and DRAINMOD.

Simplified residence time prediction models for constructed wetland water recycling systems

Abstract The experimental farmland–channel–wetland systems (FCWS) in Guilin, China have been recently designed based on wetland water recycling systems in Midwest USA. The present article develops a methodology for simplifying the prediction of residence time as a function of the flow rate and physical shape of these contaminant removal systems. A series of two-dimensional simulation studies on surface flow through FCWS wetland of different shapes are performed. Parameters influencing hydraulic characteristics such as empirical values of inlet and outlet flow conditions, and wetland shapes are utilized as inputs to the study. Roughness coefficient was assumed to be constant across the different wetland designs discussed in this article. The mean velocity values within the wetland decreases with increase in ratio of variant inlet widths and wetland inflow rates. The results from the simulation are used as inputs for performing a multivariate multiparameter regression algorithm. This framework models the re...