Effectiveness Of Vegetative Filter Strips Research Articles

Risk mitigation measures for pesticide runoff: How effective are they?

One of the most important sources of pesticide pollution of surface waters is runoff and erosion from agricultural fields after rainfall. This study analyses the efficacy of different risk mitigation measures to reduce pesticide runoff and erosion inputs into surface waters from arable land excluding rice fields. Three groups of risk mitigation measures were quantitatively analyzed: vegetative filter strips, micro-dams in row crops and soil conservation measures. Their effectiveness was evaluated based on a meta-analysis of available experimental data using statistical methods such as classification and regression trees, and exploratory data analysis. Results confirmed the effectiveness of vegetative filter strips and micro-dams. Contrary to common assumption, the width of vegetative filter strips alone is not sufficient to predict their effectiveness. The effectiveness of soil conservation measures (especially mulch-tillage) varied widely. This was in part due to the heterogeneity of the available experimental data, probably resulting from the inconsistent implementation and the inadequate definitions of these measures. Both vegetative filter strips and micro-dams are effective and suitable, and can therefore be recommended for quantitative assessment of environmental pesticide exposure in surface waters. However, the processes of infiltration and sedimentation in vegetative filter strips should be simulated with a mechanistic model like Vegetative Filter Strip Modeling System, VFSMOD. The reduction effect of micro-dams can be modelled by reducing the runoff curve number, e.g., in the pesticide root zone model, PRZM. Soil conservation measures are in principle promising, but further well-documented data are needed to determine under which conditions they are effective. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effectiveness of vegetative filter strips for sediment control from steep construction landscapes

Sediment carried off-site by runoff poses a significant water quality threat to receiving water bodies. Best management practices (BMPs) are commonly applied to reduce the impact of runoff on surface water quality. Vegetative filter strips (VFS) are low-cost BMP that often provide significant runoff mitigation in agricultural and urban settings with moderate slopes (<15 %). However, the runoff mitigation effectiveness of VFS under steep, short slopes like those typical of roadway construction is unknown. This study aimed to systematically investigate the efficacy of short (<5 m) and sparse VFS on steep slopes (>15 %). Field experiments were conducted on a steep hillslope (3H:1V, 33.3 %) where three VFS lengths (1.52 m, 3.05 m, and 4.57 m) were monitored during runoff events (10-y, 6-hr) to measure runoff delivery ratio (RDR) and sediment delivery ratio (SDR). The experimental results showed reductions of 60–98 % in runoff and 73–98 % in sediment, confirming the potential efficiency of this BMP in high-sloped conditions like a roadway construction site under certain conditions. The Vegetative Filter Strips Modeling System (VFSMOD) was successfully tested against the observed field values (NSE = 0.98 and 0.89 for RDR and SDR, respectively) and used to explore more scenarios. A wide range of roadway construction settings (VFS size, slope, vegetation density) was investigated with VFSMOD, and two simplified statistical regression equations and nomographs were developed to quantify RDR and SDR based on the simulation results. The proposed equations simplify the complexity of VFS design and can be readily generalized to other locations (rainfall/runoff, soil, vegetation) after reparametrizing coefficients in regression equations based on VFSMOD simulations to obtain new nomographs as a design aid to determine the minimum buffer length for a particular site.

Effects of Shallow Water Table Depth on Vegetative Filter Strips Retarding Transport of Nonpoint Source Pollution in Controlled Flume Experiments

Vegetative filter strips (VFSs) have been recommended as the best management practice for reducing runoff nonpoint source (NPS) pollution. The efficiency of VFSs located adjacent to water bodies can vary with shallow water table depths (WTD). A vegetated soil tank containing silt loam soil and Shortleaf Lilyturf vegetation was designed to study the effects of VFSs under shallow WTD (0.08, 0.22, and 0.36 m) on retentions of surface runoff, sediment, phosphorus, and bromide. Experiments were conducted with a simulated rainfall intensity of 28 mm h−1 and inflow rates of 4.02–4.56 L min−1. The results revealed that a deep WTD, low grass spacing, and low slope had high VFS retention efficiencies. The retention efficiencies varied greatly from 35%, 70%, 64%, and 55% at the 0.08-m WTD in the experimental group with high grass spacing (6.69 cm) and low slope (5%) to 96%, 98%, 96%, and 95% at the 0.36-m WTD in the experimental group with low grass spacing (4.18 cm) and low slope (5%) for surface runoff, sediment, phosphorus, and bromide, respectively. A steeper slope (at the same grass spacing) increased the effects of the WTD on VFS performance. For each experimental group, the average surface runoff outflow rate decreased with the WTD, whereas the average subsurface lateral flow rate increased. The transport of phosphorus in the surface runoff almost resembled that of bromide, and the average concentration (C/C0 Ave) of phosphorus and bromide decreased with the WTD. For the subsurface lateral flow, the transport of bromide and phosphorus exhibited typical breakthrough behaviors during each experiment, and both the normalized phosphorus and bromide concentrations in increasing limbs could be described by power equations. The high concentration of pollutants in the subsurface lateral flow may have affected the adjacent water bodies and groundwater. In quantification of the impact of WTD on effectiveness of VFS, we can effectively control the NPS pollutants in a watershed.

A Modeling Approach for Evaluating Watershed-scale Water Quality Benefits of Vegetative Filter Strip - A Case Study in Ontario

Abstract. Vegetative filter strips (VFS) are globally recognized as an effective BMP in reducing non-point source pollution. Maximum effectiveness of a VFS at a watershed-level could be achieved by adequately installing and sizing a VFS along the edge of the field. Existing watershed models have limitations in appropriately representing and modeling VFS at the watershed scale. Therefore, in this research, a new modeling approach consisting of the Agricultural Non-Point Source (AGNPS) model, AGNPS_VFS toolkit, and a regression equation is developed to explore the effectiveness of VFS applied along the edge of fields. AGNPS cells are identified as locations where the edge of the field VFS is to be installed. Further, the approach was tested with a case study. The model was calibrated and validated for a flow and sediment load at the watershed outlet. Thereafter, the modeling approach is used to compute sediment reducing efficiency (SRE) for the edge of the field VFS. Objectives of this study were to test the effectiveness of uniform VFS (5 × 18 m) lengths located at several locations (draining an upstream area of 3, 4, 6 ha, and at spatially variable locations) within a watershed to demonstrate the ability of the developed approach to evaluate effectiveness of VFS application in sediment abatement. Maximum SRE was observed for VFS placed at spatially variable locations; the developed approach reduced nearly 23.03% of sediment yield, while VFS placed along cells draining an upstream area of 3, 4, and 6 ha removed 9.59%, 12.39%, and 5.91% of sediment loads respectively. Keywords: Non-point source pollution, Sediment transport, Vegetative filter strip (VFS), VFSMOD.

Recalibration and cross-validation of pesticide trapping equations for vegetative filter strips (VFS) using additional experimental data

Vegetative filter strips (VFS) are widely used for mitigating pesticide inputs into surface waters via surface runoff and erosion. To simulate the effectiveness of VFS the model VFSMOD is frequently used. While VFSMOD simulates infiltration and sedimentation mechanistically, the reduction of pesticide load in surface runoff by the VFS is calculated with the empirical Sabbagh equation. This multiple regression equation has not been widely accepted by regulatory authorities, because its reliability has not been sufficiently demonstrated yet. A major drawback is the small number of calibration data points (n = 47). To corroborate and improve the predictive capability of the Sabbagh equation, additional experimental VFS data were compiled from the available literature. The enlarged dataset (n = 244) was used to recalibrate the Sabbagh equation, the recently proposed Chen equation and a set of “reduced” Sabbagh equations with fewer independent variables, with ordinary least squares (OLS) regression and to test an alternative, regression-free mass balance approach. The Sabbagh equation fitted the dataset slightly better than the Chen equation (coefficient of determination R2 = 0.82 vs. 0.79). The purely predictive mass balance approach performed slightly worse (Nash-Sutcliffe Efficiency NSE = 0.74), but significantly better than the Sabbagh and Chen equations with their old coefficients. In a k-fold cross validation analysis to assess the predictive capability of the various regression equations, both the full Sabbagh and the reduced Sabbagh equations with two or more variables outperformed the Chen equation. Finally, a maximum-likelihood-based calibration and uncertainty analysis were conducted for the Sabbagh equation using the DREAM_ZS algorithm and two different likelihood functions. The DREAM simulations corroborated the parameter values obtained with OLS regression. The study confirmed the suitability of the Sabbagh equation for regulatory modelling of pesticide trapping in VFS. However, the regression-free mass balance approach turned out to be a viable alternative.

Effectiveness of vegetative filter strips in abating fecal coliform based on modified soil and water assessment tool

Pathogenic bacteria are a serious public health concern. Exposure to these microorganisms can result in illnesses or even death. Therefore, it is important to control pathogenic bacteria sources, transport mechanisms and fate. Best management practices proved to be very effective in the control of non-point source pollution. In this study, the soil and water assessment tool (SWAT) was modified and used to simulate the fecal coliform in Chao River of Miyun Reservoir watershed, China. The model was then used to explore the effectiveness of vegetative filter strips (VFS) in reducing fecal coliform abundance throughout the watershed. The water temperature equation within the SWAT was modified to align the model more closely with the characteristics of the study area and generate a more accurate simulation. The DAFSratio (20, 50, 80, 120 and 150) and DFcon (0.25, 0.4, 0.6 and 0.75) parameters were considered for VFS to see their effects on removal efficiency. The results show that calibration and validation results for fecal coliform and flow can be accepted. Different values for DAFSratio and DFcon have great influence on VFS. Increasing values resulted in a decrease in the removal efficiency of VFS.

Parameter Importance and Uncertainty in Predicting Runoff Pesticide Reduction with Filter Strips

Vegetative filter strips (VFS) are an environmental management tool used to reduce sediment and pesticide transport from surface runoff. Numerical models of VFS such as the Vegetative Filter Strip Modeling System (VFSMOD-W) are capable of predicting runoff, sediment, and pesticide reduction and can be useful tools to understand the effectiveness of VFS and environmental conditions under which they may be ineffective. However, as part of the modeling process, it is critical to identify input factor importance and quantify uncertainty in predicted runoff, sediment, and pesticide reductions. This research used state-of-the-art global sensitivity and uncertainty analysis tools, a screening method (Morris) and a variance-based method (extended Fourier Analysis Sensitivity Test), to evaluate VFSMOD-W under a range of field scenarios. The three VFS studies analyzed were conducted on silty clay loam and silt loam soils under uniform, sheet flow conditions and included atrazine, chlorpyrifos, cyanazine, metolachlor, pendimethalin, and terbuthylazine data. Saturated hydraulic conductivity was the most important input factor for predicting infiltration and runoff, explaining >75% of the total output variance for studies with smaller hydraulic loading rates ( approximately 100-150 mm equivalent depths) and approximately 50% for the higher loading rate ( approximately 280-mm equivalent depth). Important input factors for predicting sedimentation included hydraulic conductivity, average particle size, and the filter's Manning's roughness coefficient. Input factor importance for pesticide trapping was controlled by infiltration and, therefore, hydraulic conductivity. Global uncertainty analyses suggested a wide range of reductions for runoff (95% confidence intervals of 7-93%), sediment (84-100%), and pesticide (43-100%) . Pesticide trapping probability distributions fell between runoff and sediment reduction distributions as a function of the pesticides' sorption. Seemingly equivalent VFS exhibited unique and complex trapping responses dependent on the hydraulic and sediment loading rates, and therefore, process-based modeling of VFS is required.

Effectiveness of Vegetative Filter Strips in Reducing Pesticide Loading: Quantifying Pesticide Trapping Efficiency

Pesticide trapping efficiency of vegetated filter strips (VFS) is commonly predicted with low success using empirical equations based solely on physical characteristics such as width and slope. The objective of this research was to develop and evaluate an empirical model with a foundation of VFS hydrological, sedimentological, and chemical specific parameters. The literature was reviewed to pool data from five studies with hypothesized significant parameters: pesticide and soil properties, percent reduction in runoff volume (i.e., infiltration) and sedimentation, and filter strip width. The empirical model was constructed using a phase distribution parameter, defined as the ratio of pesticide mass in dissolved form to pesticide mass sorbed to sediment, along with the percent infiltration, percent sedimentation, and the percent clay content (R(2) = 0.86 and standard deviation of differences [STDD] of 7.8%). Filter strip width was not a statistically significant parameter in the empirical model. For low to moderately sorbing pesticides, the phase distribution factor became statistically insignificant; for highly sorbing pesticides, the phase distribution factor became the most statistically significant parameter. For independent model evaluation datasets, the empirical model based on infiltration and sediment reduction, the phase distribution factor, and the percent clay content (STDD of 14.5%) outperformed existing filter strip width equations (STDD of 38.7%). This research proposed a procedure linking a VFS hydrologic simulation model with the proposed empirical trapping efficiency equation. For datasets with sufficient information for the VFS modeling, the linked numerical and empirical models significantly (R(2) = 0.74) improved predictions of pesticide trapping over empirical equations based solely on physical VFS characteristics.

COST EFFECTIVENESS OF VEGETATIVE FILTER STRIPS AND INSTREAM HALF‐LOGS FOR ECOLOGICAL RESTORATION1

ABSTRACT: This paper presents the results of cost effectiveness (CE) analysis of vegetative filter strips (VFS) and instream half‐logs as tools for recovering scores on a fish Index of Biotic Integrity (IBI) in the upper Wabash River watershed (UW) in Indiana. Three assumptions were made about recovery time for IBI scores (5,15, and 30 years) and social discount rates (1, 3, and 5 percent), which were tested for sensitivity of the estimated CE ratios. Effectiveness of VFS was estimated using fish IBIs and riparian forest cover from 49 first‐order to fifth‐order stream reaches. Half‐log structures had been installed for approximately two years in the UW prior to the study and provided a basis for estimates of cost and maintenance. Cost effectiveness ratios for VFS decreased from $387 to $277 per 100 m for a 1 percent increase in IBI scores from first‐to fifth‐order streams with 3 percent discount and 30‐year recovery. This cost weighted by proportion of stream orders was $360. The ratio decreased with decreasing time of recovery and discount rate. Based on installation costs and an assumption of equal recovery rates, half‐logs were two‐thirds to one‐half as cost‐effective as VFS. Half‐logs would be a cost‐effective supplement to VFS in low order streams if they can be proven to recover IBI scores faster than VFS do. This study provides baseline data and a framework for planning and determining the cost of stream restoration.

Effectiveness of vegetative filter strips in attenuating nutrient and sediment runoff from irrigated pastures

Increasing concern about non-point source pollutants released from grazing livestock, a worldwide problem, motivated the present study on the effects of vegetative filter strips (VFS) for controlling pollutants (nutrients, micro-organisms and sediment loading) from grazed, irrigated pastures. Flood-irrigated pastures are an important source of forage for livestock during summer months in California, USA when the surrounding rangelands are dry and dormant. Significant amounts of runoff can be generated from these pastures during irrigation events.Nine plots on an irrigated pasture were assigned randomly to one of three treatments: Control (no VFS), Treatment VFS-1 (8·3×7 m, 0·0058 ha VFS) and Treatment VFS-2 (17·1×7 m, 0·012 ha VFS). In 2000, two grazing events (in April and June/July) occurred during the irrigation season prior to the experiment; further, the experimental plots were grazed between irrigations 2 and 3. Attenuation of runoff loads by VFS treatment was measured during four irrigation events (between 1 August and 3 October 2000) for total suspended solids (TSS), ortho-phosphate (Ortho-P), inorganic phosphate (Inorg-P), total phosphate (Total-P), organic phosphate (Org-P), polyphosphate (Poly-P), total Kjeldahl nitrogen (TKN), NH3, NO3 and presumptive faecal coliforms (FC).On average, approximately 0·43 of the applied water left the plots as runoff. Treatment effects approached significance for TSS and TKN and were significant (P&lt;0·05) for Poly-P and NH3. Irrigation number effects were significant for all but TSS, NO3 and FC. The effects of VFS treatments were not consistent. Treatment VFS-2, although representing the largest buffer strip, did not always produce the lowest pollutant loads in runoff. Slope, relatively high runoff volumes and some channelled flow were probably responsible for the limited effectiveness of VFS in the present study. These results suggest that effectiveness of VFS for reducing sediment and nutrient transport from irrigated pastures may be questionable.

Effectiveness of Vegetative Filter Strips in Removal of Sediments from Overland Flow

Abstract Many forms of natural heritage manifested as streams, rivers, ponds, lakes and wetlands play an integral role in maintaining natural beauty, health and a high quality of life. Agricultural intensification in southern Ontario has contributed to elevated sediments, nutrient and bacteria levels in water bodies. Vegetative filter strips (VFS) are control measures that can partially remove sediments and pollutants adhered to sediments from overland runoff before entering water bodies. The objective of this study was to determine the effect of vegetation type, width of the filter strip, runoff flow rate and inflow sediment characteristics on effectiveness of the VFS in removing pollutants from runoff. The results show that sediment removal efficiency increased from 50 to 98% as the width of the filter increased from 2.5 to 20 m. In addition to the width of the filter strip, grass type and flow rate were also significant factors. This study indicates that the first five (5) metres of a filter strip are critical and effective in removal of suspended sediments. More than 95% of the aggregates larger than 40 µm in diameter were trapped within the first five metres of the filter strip.

Reducing herbicide runoff from agricultural fields with vegetative filter strips: a review

Although the effectiveness of vegetative filter strips (VFS) for reducing herbicide runoff is well documented, a comprehensive review of the literature does not exist. The objectives of this article are to denote the methods developed for evaluating herbicide retention in VFS; ascertain the efficacy of VFS regarding abating herbicide runoff; identify parameters that affect herbicide retention in VFS; review the environmental fate of herbicides retained by VFS; and identify future research needs. The retention of herbicide runoff by VFS has been evaluated in natural rainfall, simulated rainfall, and simulated run-on experiments. Parameters affecting herbicide retention in VFS include width of VFS, area ratio, species established in the VFS, time after establishment of the VFS, antecedent moisture content, nominal herbicide inflow concentration, and herbicide properties. Generally, subsequent transport of herbicides retained by VFS is reduced relative to adjacent cultivated soil because of enhanced sorption and degradation in the former.

Effectiveness of Vegetative Filter Strips for Sediment Removal under Field Conditions

Effectiveness of Vegetative Filter Strips for Sediment Removal under Field Conditions

Overland and near-surface transport of Cryptosporidium parvum from vegetated and nonvegetated surfaces.

Understanding microbial pathogen transport patterns in overland flow is important for developing best management practices for limiting microbial transport to water resources. Knowledge about the effectiveness of vegetative filter strips (VFS) to reduce pathogen transport from livestock confinement areas is limited. In this study, overland and near-surface transport of Cryptosporidium parvum has been investigated. Effects of land slopes, vegetation, and rainfall intensities on oocyst transport were examined using a tilting soil chamber with two compartments, one with bare ground and the other with brome (Bromus inermis Leyss.) vegetation. Three slope conditions (1.5, 3.0, and 4.5%) were used in conjunction with two rainfall intensities (25.4 and 63.5 mm/h) for 44 min using a rainfall simulator. The vegetative surface was very effective in reducing C. parvum in surface runoff. For the 25.4 mm/h rainfall, the total percent recovery of oocysts in overland flow from the VFS varied from 0.6 to 1.7%, while those from the bare ground condition varied from 4.4 to 14.5%. For the 63.5 mm/h rainfall, the recovery percentages of oocysts varied from 0.8 to 27.2% from the VFS, and 5.3 to 59% from bare-ground conditions. For all slopes and rainfall intensities, the total (combining both surface and near-surface) recovery of C. parvum oocysts was considerably less from the vegetated surface than those from the bare-ground conditions. These results indicate that the VFS can be a best management practice for controlling C. parvum in runoff from animal production facilities.

PESTICIDE TRANSPORT WITH SURFACE RUNOFF AND SUBSURFACE DRAINAGE THROUGH A VEGETATIVE FILTER STRIP

Vegetative filter strips (VFS) have become an established best management practice during the last 25 years. This study examined the effectiveness of VFS of brome grass in central Iowa for reducing the mass transport of sediment and pesticides (atrazine, acetochlor, and chlorpyrifos) with surface runoff under natural rainfall conditions. Measurements of pesticide concentrations in water from a single subsurface drain under the plots were also made. Overall results showed that many factors affect pesticide transport, such as rainfall timing and intensity, hydrology, source–to–VFS area ratios, and the adsorption properties of pesticides in VFS inflow. Two primary mechanisms (inflow water infiltration and sediment deposition) had a significant effect on pesticide passage through VFS. Sediment deposition increased with decreased flow volume and velocity, and was considerably higher for the 15:1 area–ratio plots than for the 45:1 plots; this in turn aided in the reduction of transport of pesticides adsorbed to sediment. Reductions in atrazine and acetochlor transport were primarily controlled by the infiltration efficiency of the VFS, as they are moderately adsorbed, and the major portion of these pesticides moved in solution in the surface runoff water phase. Chlorpyrifos was highly adsorbed to the sediment, making sediment deposition in the VFS equally, if not more, important than infiltration for mass removal. The herbicides (atrazine and acetochlor) had low to moderate adsorption characteristics and moved primarily in the runoff water phase. Data collected for the subsurface drainage from the tile line showed that there were measurable concentrations of the moderately adsorbed herbicides in the tile flow at the time surface runoff was taking place; however, concentrations of the more strongly adsorbed chlorpyrifos were below detection. The statistical difference was most prominent in the event with the smallest runoff volume. This showed that at lower flow rates, VFS can effectively reduce runoff, sediment, and pesticide transport from cropland.

Design, Construction, and Operation of Tilted Beds to Simulate Agricultural Runoff in Vegetative Filter Strips

This paper describes the design, construction, and operation of tilted beds to investigate the effectiveness of vegetative filter strips (VFS) in removing agricultural chemicals from runoff water. The beds are designed to catch surface runoff, leachate, and subsurface lateral flow. Switchgrass was established on beds filled with Cullen clay loam or Emporia sandy loam. Switchgrass establi shed on Cullen clay loam beds reduced surface runoff by 60% and by 11% in sandy loam containing switchgrass compared to respective bare soils. Infiltration was 64, 26, 17, and 8% for clay loam with switchgrass, clay loam without switchgrass, sandy loam with switchgrass, and sandy loam without switchgrass, respectively.

Effectiveness of Vegetative Filter Strips in Controlling Losses of Surface-applied Poultry Litter Constituents

Vegetative filter strips (VFS) have been shown to have high potential for reducing nonpoint source pollution from cultivated agricultural source areas, but information from uncultivated source areas amended with poultry litter is limited. Simulated rainfall was used in analyzing effects of VFS length (0, 3.1, 6.1, 9.2, 15.2, and 21.4 m) on quality of runoff from fescue (Festuca arundinacea Schreb.) plots (1.5 24.4 m) amended with poultry litter (5 Mg/ha). The VFS reduced mass transport of ammonia-nitrogen (NH3-N), total Kjeldahl nitrogen (TKN), ortho-phosphorus (PO4-P), total phosphorus (TP), chemical oxygen demand (COD), and total suspended solids (TSS). Mass transport of TKN, NH3-N, TP, and PO4-P were reduced by averages of 39, 47, 40, and 39%, respectively, by 3.1 m VFS and by 81, 98, 91, and 90%, respectively, by 21.4 m VFS. Effectiveness of VFS in terms of mass transport reduction was unchanged, however, beyond 3.1 m length for TSS and COD and averaged 35 and 51%, respectively. The VFS were ineffective in removing nitrate-nitrogen from the incoming runoff. Removal of litter constituents was described very well (r2 = 0.70 to 0.94) by a first-order relationship between constituent removal and VFS length.

Effectiveness of Vegetative Filter Strips in Retaining Surface-applied Swine Manure Constituents

Simulated rainfall was used to evaluate the effectiveness of vegetative filter strips (VFS) of varying lengths (0, 3, 6, 9, 15, and 21 m) in reducing sediment and nutrient losses from plots treated with liquid swine manure at 200 kg N/ha. Mass transport of ammonia nitrogen (NH3-N), total Kjeldahl nitrogen (TKN), ortho-phosphorus (PO4-P), total phosphorus (TP), and total suspended solids (TSS) was reduced significantly (p < 0.05) by fescue (Festuca arundinacea Schreb.) VFS. The 3 and 21 m VFS removed 65 and 87% of incoming TKN, 71 and 99% of incoming NH3-N, 65 and 94% of incoming PO4-P, and 67 and 92% of the incoming TP, respectively. Effectiveness of VFS, however, did not increase significantly beyond 3 m for TSS and chemical oxygen demand and averaged 61 and 50%, respectively. Mass transport of TKN, NH3-N, PO4-P, and TP was minimized at the 9 m VFS length. The VFS did not significantly reduce nitrate nitrogen and fecal coliform from the incoming runoff. First-order kinetics described the removal of manure constituents.

Water-quality benefits of having cattle manure deposited away from streams

A series of runoff and infiltration studies with bovine feces placed 0.0, 0.61, 1.37, or 2.13 m from a collection point were used to assess effectiveness of vegetative filter strips. Effectiveness was evaluated on the ability of the separation distance to reduce the number of fecal coliform (FC) bacteria being transported from the manure to the edge of the plots. Bacterial transport was evaluated under conditions of variable distance, soil permeability, and rainfall intensity. The FC bacteria yields were 40–115 million at the edge of the manure pile. This is only 17% of the FC in the manure. FC concentrations and yields were further reduced as the separation increased. The analysis of data did not indicate significant differences of bacteria transport in relation to rainfall intensities of 5 cm/h versus 10 cm/h at the 0.61, 1.37, or 2.13 m distances.

Vegetative Filter Strips for Agricultural Nonpoint Source Pollution Control

ABSTRACT Arainfall simulator was used to evaluate the effective-ness of vegetative filter strips (VFS) for the removal of sediment, nitrogen (N), and phosphorus (P) from cropland runoff. Simulated rainfall was applied to nine experimental field plots on an eroded Groseclose silt loam soil (clayey, mixed, mesic Typic Hapludalt) with a 5.5 by 18.3 m bare cropland source area and either a 0, 4.6, or 9.1 m VFS located at the lower end of each plot. Fertilizers were applied to the plots at rates of 222 kg/ha of liquid N and 112 kg/ha of P2O5 and K2O. Water samples were collected from the base of each plot and analyzed for sediment and nutrient content. One set of plots was constructed to encourage concentrated rather than shallow uniform flow. The 9.1 and 4.6 m VFS with shallow uniform flow removed an average of 84 and 70% of the incoming suspended solids, 79 and 61% of the incoming P, and 73 and 54% of the incoming N, respectively. Soluble nutrients in the filter effluent were sometimes greater than the incoming soluble nutrient load, presumably due to lower removal efficiencies for soluble nutrients and the release of nutrients previously trapped in the filters. Concentrations of soluble inorganic N and P in filter strip effluent were sufficient to cause eutrophic plant growth in aquatic ecosystems. Observation of existing VFS showed that on-farm VFS were not likely to be as effective as experimental VFS because of problems with flow concentrations.