Dissolved Phosphorus Research Articles

Effect of sediment on concentration of dissolved phosphorus in the Three Gorges Reservoir

Eutrophication and algal bloom has been occurring in the Three Gorges Reservoir ever since the reservoir's impoundment in 2003. The concentration of dissolved phosphorus (DP) is one of the main controlling factors for algal bloom. Fine sediment adsorbs DP thereby affecting the concentration of DP. The effect of the sediment reduction on the DP concentration of the Three Gorges Reservoir is discussed in this paper. Samples were taken from the Yangtze River and its tributaries, i.e. the Minjiang River and the Tuojiang River. The DP concentration of the water samples and the available phosphorus, total phosphorus, and phosphorus-fixing capacity of the sediment samples were analyzed. The amount of phosphorus adsorbed by the sediment was about 3% of the total DP load in the Yangtze River. An experiment was done in the lab simulating the DP concentration, sediment concentration, and turbulence. The results showed that quite a high amount of DP was adsorbed by the sediment. The adsorption capacity of the sediment was 135 mg/kg and the highest rate of adsorption was 29 mg/kg·h. The Xiluodu Dam is located at nearly 1,100 km upstream of the Three Gorges Dam. The Xiloudu Dam will trap sediment and thence reduce the sediment load entering the Three Gorges Reservoir after impoundment in 2013. It is estimated that the sediment reduction due to the Xiluodu Dam may result in an increase of the DP concentration in the Three Gorges Reservoir by 6.8%.

Narrow Grass Hedge Control of Nutrient Loads Following Variable Manure Applications

The effectiveness of a narrow grass hedge in reducing runoff nutrient loads following manure application was examined in this study. Beef cattle manure was applied to 0.75 m wide by 4.0 m long plots established on an Aksarben silty clay loam located in southeast Nebraska. Manure was added at rates required to meet none or the 1, 2, or 4 year nitrogen requirements for corn. Runoff water quality was measured during three 30 min simulated rainfall events. Manure application rate significantly affected dissolved phosphorus (DP) and total phosphorus (TP) loads in runoff on the plots without a grass hedge. However, DP and TP loads were not significantly affected by manure application rate on the plots containing a hedge. The hedge reduced the mean load of DP in runoff from 0.69 to 0.08 kg ha-1 and the load of TP from 1.05 to 0.13 kg ha-1. When averaged across manure application rates, 0.11 kg NO3-N ha-1, 0.02 kg NH4-N ha-1, and 0.49 kg total nitrogen (TN) ha-1 were measured from the plots with a hedge, compared to 0.39 kg NO3-N ha-1, 0.55 kg NH4-N ha-1, and 2.52 kg TN ha-1 from the plots without a hedge. For the plots with a grass hedge, runoff loads of DP and TP where manure was applied were similar to values obtained with no manure application. Each of the runoff water quality parameters was significantly affected by runoff rate. A narrow grass hedge placed on the contour across a hillslope significantly reduced runoff nutrient loads following variable manure applications.

Phosphorus removal from secondary effluents through integrated constructed treatment system

The treatment capacity of an integrated constructed treatment system (CTS) was explored which was designed to reduce phosphorus (P) from secondary effluents. The integrated CTS was combined with vertical-flow constructed wetland, floating bed and sand filter. The vertical wetland was filled from the bottom to the top with gravels, steel slag and peat. Vetiverzizanioides (L.) Nash was selected to grow in the vertical constructed wetland while Coixlacrymajobi L. was grown in floating bed. The results suggested that integrated CTS displayed excellent removal efficiency for chemical oxygen demand (COD), dissolved phosphorus (DP), and total phosphorus (TP). The average COD removal efficiency of the integrated CTS was 90.45% after 40 days of operation, the average DP and TP removal efficiencies of the integrated CTS were 97.43% and 96.40%, respectively. The integrated CTS has good potential in removing COD as well as P from secondary effluents.

Effluent dissolved organic nitrogen and dissolved phosphorus removal by enhanced coagulation and microfiltration

Plants aiming to achieve very low effluent nutrient levels (<3 mg N/L for N, and <0.1 mg P/L for P) need to consider removal of effluent fractions hitherto not taken into account. Two of these fractions are dissolved organic nitrogen (DON) and dissolved non-reactive phosphorus (DNRP) (mainly composed of organic phosphorus). In this research, enhanced coagulation using alum (at doses commonly employed in tertiary phosphorus removal) followed by microfiltration (using 0.22 μm pore size filters) was investigated for simultaneous effluent DON and dissolved phosphorus (DP) fractions removal. At an approximate dose of 3.2 mg Al(III)/L, corresponding to 1.5 Al(III)/initial DON-N and 3.8 Al(III)/initial DP-P molar ratios, maximum simultaneous removal of DON and DP was achieved (69% for DON and 72% for DP). At this dose, residual DON and DP concentrations were found to be 0.3 mg N/L and 0.25 mg P/L, respectively. Analysis of the trends of removal revealed that the DNRP removal pattern was similar to that commonly reported for dissolved reactive phosphorus. Since this study involved intensive analytical work, a secondary objective was to develop a simple and accurate measurement protocol for determining dissolved N and P species at very low levels in wastewater effluents. The protocol developed in this study, involving simultaneous digestion for DON and DNRP species, was found to be very reliable and accurate based on the results.

Nutrient Transport in Runoff as Affected by Diet, Tillage, and Manure Application Rate

Feedlot operators may increase profitability by including distillers grains in finishing diets. However, the nutrients remaining in the by-product are concentrated by about a factor of three during the distillation process. Manure can be applied to meet single- or multiple-year crop nutrient requirements. The water quality effects of the use of distillers grains in feedlot diets and multiple-year manure application have not been well quantified. The objectives of this study were to (1) compare the runoff water quality effects resulting from the application of manure derived from corn and distillers grain diets, (2) examine the effects of till and no-till conditions on runoff nutrient transport, and (3) compare the water quality impacts of 1-, 2-, and 4-year phosphorus (P) based manure application rates. Simulated rainfall events were applied to 0.75 m wide 2 m long plots soon after manure application. No significant difference in dissolved phosphorus (DP) or total P (TP) load was found between the corn and distillers grain treatments. The runoff load of TP was significantly larger on the no-till plots than on the till plots. The amount of particulate phosphorus (PP), DP, and TP transported in runoff was significantly affected by multi-year application of manure. The TN content of runoff was similar for till and no-till conditions on the plots containing manure obtained from the distillers grain diet. The environmental effects of the use of manure from a distillers grain diet and multiple-year manure application should be considered when developing nutrient management plans.

Shortcut Nitrification and Denitrification of Swine Wastewater in a Sequencing Batch Reactor System

Wastewater generated by confined swine production is characterized by high ammonium nitrogen (NH4 +-N) content, the elimination of which would require significant amounts of air in nitrification and organic carbon, serving as the electron donor, in denitrification. Shortcut nitrification and denitrification (SND) is a novel nitrogen removal process that has drawn researchers' attention lately. In this study, the application of SND in swine wastewater treatment was investigated using two sequencing batch reactors (SBRs) connected in series in order to reduce the needs for energy and carbon dosage. The first SBR produced a nitrite-rich effluent that was fed to the second SBR, where both nitrogen and phosphorus removal were achieved. Three COD/NOx-N ratios (3.6, 4.8, and 6) were selected to test the influence of carbon availability on the total inorganic nitrogen (TIN) reduction and phosphorus removal efficiencies for the second SBR. It was observed that COD/NOx-N ratios of 4.8 and 6 could achieve 97% and 98% TIN removals with effluents containing less than 20 mg L-1 TIN, while the 3.6 ratio resulted in only 84% removal, with a significant amount of nitrate accumulated in the system. The COD/NOx-N ratio had no significant influence on dissolved phosphorus (DP) removal, and the mean value of DP removal was about 52%. Two solid retention times (SRTs) were selected to test the effect of SRT on nitrogen and phosphorus removal. No significant difference in TIN removal was observed under SRT of 16 and 23 days, but DP removal was much better under SRT of 23 days than 16 days (around 67% vs. 38%). In conclusion, the introduction of SND to swine wastewater treatment obtained a satisfactory result for nitrogen removal but not for phosphorus under the current operational settings. Chemical precipitation may have to be used to further reduce phosphorus in the SBR effluent.

Forms and Variability of Phosphorus in the Baltic Sea–-A Challenge to Ecosystem Modeling

Knowledge of the partitioning between the dissolved and particulate phases of nutrient elements is a key factor in aquatic ecosystem modeling since partitioning regulates the availability to demand ratio of the nutrient in question. This is seldom taken into account in environmental monitoring programs. In this paper, the occurrence and variability of particulate and dissolved phosphorus were studied in the coastal zone of the Baltic Sea. The particulate fraction (PF) of total phosphorus (TP) concentration in coastal waters from some forty stations along the east coast of Sweden was, on average, 0.33. Dissolved inorganic phosphorus (DIP) was a poor predictor of total dissolved phosphorus (DP) representing only 20%-30% of this fraction. Sensitivity analyses showed that the value of PF had a significant impact on modeled predictions of TP concentration in the water on a Baltic sub-basin scale, whereas an applied coastal model was insensitive to variations in PF. Hence, this study encourages further sampling efforts on the partitioning of phosphorus in the open waters of the Baltic Sea.

Comparative evaluation of phosphorus losses from subsurface and naturally drained agricultural fields in the Pike River watershed of Quebec, Canada

Abstract Phosphorus (P) is the limiting nutrient responsible for the development of algal blooms in freshwater bodies, adversely impacting the water quality of downstream lakes and rivers. Since agriculture is a major non-point source of P in southern Quebec, this study was carried out to investigate P transport under subsurface and naturally drained agricultural fields with two common soil types (clay loam and sandy loam). Monitoring stations were installed at four sites (A, B, C and D) in the Pike River watershed of southern Quebec. Sites A–B had subsurface drainage whereas sites C–D were naturally drained. In addition, sites A–C had clay loam soils whereas sites B–D had sandy loam soils. Analysis of data acquired over two hydrologic years (2004–2006) revealed that site A discharged 1.8 times more water than site B, 4 times more than site C and 3 times more than site D. The presence of subsurface drainage in sandy loam soils had a significant beneficial effect in minimizing surface runoff and total phosphorus (TP) losses from the field, but the contrary was observed in clay loam soils. This was attributed to the finding that P speciation as particulate phosphorus (PP) and dissolved phosphorus (DP) remained relatively independent of the hydrologic transport pathway, and was a strong function of soil texture. While 80% of TP occurred as PP at both clay loam sites, only 20% occurred as PP at both sandy loam sites. Moreover, P transport pathways in artificially drained soils were greatly influenced by the prevailing preferential and macropore flow conditions.

Identifying key environmental factors influencing spatial variation of water quality in upper Shitoukoumen Reservoir Basin in Jilin Province, China

Based on the observed data in monitored drainage areas and GIS spatial analysis tools, watershed basic database of Shitoukoumen Reservoir Basin was built. The multivariate analysis and redundancy analysis (RDA) were used to analyze the spatial and temporal variations of water quality, identify the key environmental factors and their patterns influencing the spatial variation of water quality, and determine the main types and forms of the non-point source (NPS) pollutant export controlled by the key environmental factors. The results show that different patterns of environmental factors lead to great changes in water quality at spatial and seasonal scales. All selected environmental factors explain 64.5% and 68.2% of the spatial variation of water quality over dry season and rainy season, respectively, which shows clear seasonal difference. Over dry season, residential land is the most important environmental factor, which possesses 35.4% of the spatial variation, and drainage area is the second key environmental factor, which possesses 17.0% of spatial variation in the total variance. Over rainy season, slope length and drainage area are the key environmental factors, which possess 29.3% of the spatial variation together. Residential land influences nitrogen export by changing NH4+-N and particulate organic nitrogen (PON) discharge over dry season, and drainage area controls phosphorus export by regulating dissolved phosphorus (DP) drainage over dry season and phosphorus associated particulate (PAP) loss over rainy season, respectively. Although slope length is an important environmental factor, it does not influence NPS pollutant export. It is interesting that soil organic matter, as a minor environmental factor, highly determines phosphorus and nitrogen export by enhancing the DP, PAP and PON loss.

Sediment and phosphorus loss in runoff from an agroforestry catchment, NW Spain

AbstractThis study was conducted to evaluate the factors controlling sediment and phosphorus export in a small agroforestry catchment located in NW Spain. At the catchment outlet discharge was continuously measured and suspended sediment (SS) and total (PT), particulate phosphorus (PP) and dissolved phosphorus (DP) were determined during seven rainfall events occurred in autumn. Sediment and sediment‐associated P export differed significantly between events. Particulate P was a greater portion of P transported in runoff. A large proportion of SS and PP exported from the catchment occurred from a relatively small portion of the catchment and during only two events. Rills and gullies delivered most of the eroded sediment directly to the stream, which contribute to high sediment and phosphorus exportation at the catchment outlet. Strong correlations between P and SS concentrations suggest that erosion processes are important in P fluxes. The highly significant correlation between SS and P concentrations in the stream enables to estimate transported P using SS in the Corbeira catchment. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Dynamic changes of nitrogen and phosphorus losses in ephemeral runoff processes by typical storm events in Sichuan Basin, Southwest China

This study was carried out in the Xujiawan watershed in Sichuan Province, China. The area is characterized by easy weathering of bedrock (sedimentary sandstone and shale) and vulnerability to erosion due to coarse soil texture and weak soil structure. The objective of this study was to understand the dynamics of nitrogen (N) and phosphorus (P) losses during typical storm events. The results showed that runoff generation was sudden and ephemeral, giving rise to flash floods with sharp, narrow hydrographs and short time lags in this type of agricultural ecosystems. The time lag effect of runoff formation depended on soil conditions before storm events. Suspended solids (SS) concentration peaks occurred at the beginning of the storm flow and decreased as rainfall progressed. Meanwhile, SS losses increased at the beginning of runoff flow, then decreased due to flow volume change. Concentrations of NO 3 −-N were four times higher than NH 4 +-N in runoff. NO 3 −-N concentrations first decreased as runoff volume increased until reaching relatively low concentrations, then increased again as runoff volume decreased. Both NH 4 +-N and dissolved phosphorus (DP) in runoff remained at low concentrations with a small magnitude of variation. Suspended particulate nitrogen (SN) was the dominant N form. Losses of NO 3 −-N were higher than NH 4 +-N in the dissolved nitrogen (DN). Suspended particulate nitrogen losses were several times higher than DN in the early period of runoff formation, but the ratio of SN/DN decreased gradually as rainfall progressed, and by the end of the storm event the rate was lower than 1, indicating DN took the main form after the early physical flush. In the early period of storm events, suspended particulate phosphorus (SP)/DP was above 70 and decreased as rainfall progressed, but remained higher than 1, which showed that SP was the main form of P loss. The transport of N, and particularly P, was intimately linked to sediment in the runoff, indicating an obvious soil erosion-associated nutrient transport, especially in relation to P loss.

Nutrient Dynamics during Storm Events in an Agroforestry Catchment

Patterns of phosphorus (P; dissolved and particulate) and nitrate (NO3) delivery were compared between times of base flow and events in a stream draining a small agroforestry catchment in Galicia, northwest Spain. Nutrient concentrations were low during base flow, and only nitrate shows a clear seasonal pattern. In general, particulate phosphorus (PP) was the dominant fraction of the total P. Particulate P concentrations increased significantly during storms, with maximum concentrations occurring on the rising limb of the hydrograph (clockwise hysteresis). The rapid response of PP suggests a near‐stream source of PP during events. The surface runoff is the mainly route to transport PP to the stream, whereas for the dissolved phosphorus (DP) and NO3 the subsurface path is also important.

Including Source-Specific Phosphorus Mobility in a Nonpoint Source Pollution Model for Agricultural Watersheds

Most widely used nonpoint source models associate pollutant loads almost exclusively with land use via pollutant export coefficients and some kind of runoff coefficient. Not surprisingly, the range of management options suggested by such models’ simulations are largely linked to changes in land use. This problem is addressed by developing models of dissolved phosphorus (DP) mobility for specific agricultural sources: manure, fertilizers, soil/plant complexes, and impervious surfaces and those associated with baseflow P loads. These models are coupled with a spatially distributed hydrologic model, the variable source loading function model. The model was applied to a small (164ha), upstate New York watershed and tested against 1996–2000 stream flow and DP data. The source-specific model required no direct calibration of parameters compared to eight parameters needed in a similar export coefficient type model. Both models predicted stream DP loads well but the source-specific model provided additional insights into, for example, how much DP in the stream was derived from accumulated soil P as opposed to direct leaching from manure. This type of information is necessary to develop and assess a full range of options for best management practices, especially those that involve nonstatic activities such as manure spreading.

Nutrient and Bacterial Transport in Runoff from Soil and Pond Ash Amended Feedlot Surfaces

The addition of pond ash (fly ash that has been placed in evaporative ponds and subsequently dewatered) to feedlot surfaces provides a healthier environment for livestock and economic advantages for the feedlot operator. However, the water quality effects of pond ash amended surfaces are not well understood. The objectives of this field investigation were to: (1) compare feedlot soil properties, and nutrient and bacterial transport in runoff, from pond ash amended surfaces and soil surfaces; (2) compare the effects of unconsolidated surface materials (USM) (loose manure pack) and consolidated subsurface materials (CSM) (compacted manure and underlying layers) on nutrient and bacterial transport in runoff; and (3) determine if the measured water quality parameters are correlated to soil properties. Simulated rainfall events were applied to 0.75 m wide 2 m long plots with different surface materials and surface conditions. Measurements of calcium, magnesium, sulfur, and pH were found to be significantly greater on the pond ash amended surfaces. In comparison, the soil surfaces contained significantly greater amounts of Bray 1-P. The runoff load of NH4-N was significantly greater on the pond ash amended surfaces, while the total phosphorus (TP) load was significantly greater on the soil surfaces. The NO3-N and total nitrogen (TN) loads in runoff were significantly greater on the feedlot surfaces containing CSM. Concentrations of E. coli in runoff were similar on the pond ash amended surfaces and soil surfaces. The dissolved phosphorus (DP), particulate phosphorus (PP), and TP load of runoff were all significantly correlated to Bray 1-P measurements.

Managing Biosolids Runoff Phosphorus Using Buffer Strips Enhanced with Drinking Water Treatment Residuals

Vegetated buffers strips typically have limited ability to reduce delivery of dissolved phosphorus (DP) from agricultural fields to surface waters. A field study was conducted to evaluate the ability of buffer strips enhanced with drinking water treatment residuals (WTRs) to control runoff P losses from surface-applied biosolids characterized by high water-extractable P (4 g kg(-)(1)). Simulated rainfall (62.4 mm h(-1)) was applied to grassed plots (3 m x 10.7 m including a 2.67 m downslope buffer) surface-amended with biosolids at 102 kg P ha(-1) until 30 min of runoff was collected. With buffer strips top-dressed with WTR (20 Mg ha(-1)), runoff total P (TP = 2.5 mg L(-1)) and total DP (TDP = 1.9 mg L(-1)) were not statistically lower (alpha = 0.05) compared to plots with unamended grass buffers (TP = 2.7 mg L(-1); TDP = 2.6 mg L(-1)). Although the applied WTR had excess capacity (Langmuir P maxima of 25 g P kg(-1)) to sorb all runoff P, kinetic experiments suggest that sheet flow travel time across the buffers ( approximately 30 s) was insufficient for significant P reduction. Effective interception of dissolved P in runoff water by WTR-enhanced buffer strips requires rapid P sorption kinetics and hydrologic flow behavior ensuring sufficient runoff residence time and WTR contact in the buffer. Substantial phosphate-adsorbent contact opportunity may be more easily achieved by incorporating WTRs into P-enriched soils or blending WTRs with applied P sources.

Spatio-temporal dynamics of nutrients in the upper Han River basin, China

The upper Han River basin with an area of approximately 95,000 km 2, is the water source area of the Middle Route of China's South to North Water Transfer Project. Thus, water quality in the basin's river network is of great importance. Nutrients including dissolved inorganic nitrogen (DIN), NO 3 −-N, NH 4 +-N, and dissolved phosphorus (DP) were analyzed in 41 sites during the period of 2005–2006. Cluster analysis (CA), analysis of variance (ANOVA) and general linear models (GLM) were performed to explore their spatio-temporal variations in the basin. The results revealed that the DIN, NO 3 −-N and NH 4 +-N increased over the 2 year study period, and their concentrations in the wet season was higher than those in the dry season. The seasonal variation in nitrogen was strongly associated with seasonal pattern of precipitation and there was a negative relationship between DP concentration and river flow. Cluster analysis indicated high nutrient contents in the urban and agricultural production areas. The research will help articulate water resource management strategy for the interbasin water transfer project.

Eficacia de franjas filtrantes para la reducción de nutrientes en escorrentía de pasturas enmendadas con efluentes de vaquerías.

Se realizó un experimento para probar la hipótesis de que las franjas vegetativas filtrantes son efectivas en reducir las concentraciones de nutrientes y sedimentos en la escorrentía que se genera de pasturas enmendadas con cieno de estiércol vacuno. El experimento se realizó siguiendo prácticas recomendadas en dos predios de una finca dedicada a la ganadería de leche en San Sebastián, Puerto Rico. La escorrentía que se generaba luego de cada evento de precipitación se canalizaba a un aparato para recoger escorrentía localizado a 0,10, y 20 m dentro de una franja vegetativa filtrante. Las muestras se analizaron para sedimentos suspendidos (SS), nitrógeno total Kjeldahl (TKN), fósforo disuelto (DP) y fósforo total (TP). Las concentraciones de SS en escorrentía entrando a la franja filtrante fueron muy bajas, lo cual es indicativo de que las pérdidas de SS de suelos bajo pasturas con buena cobertura vegetativa no afectan significativamente la calidad del agua. En eventos de escorrentía que ocurrieron 10 días luego de la aplicación del cieno de estiércol se observaron concentraciones elevadas de TP y TKN. Estos resultados indican que el agricultor debe evitar aplicar el estiércol cuando se esperan eventos de precipitación significativa ya que la escorrentía que se genera causaría pérdidas excesivas de nutrientes si no hubiese una franja filtrante. En ambos predios evaluados, las concentraciones de DP en la escorrentía se redujeron con la franja filtrante de 20 m, mientras que las concentraciones de TP se redujeron solamente del predio con mayores concentraciones en escorrentía (Toronjo). Se registró una reducción de 27% en las concentraciones de TKN del predio con la franja de 20 m, pero la reducción no fue estadísticamente significativa. Aunque la implementación de franjas filtrantes de 20 m son efectivas para reducir las concentraciones de nutrientes en la escorrentía de predios enmendados con cieno de estiércol vacuno, la implementación de otras prácticas de manejo son necesarias para reducir las pérdidas de nutrientes a unos niveles que no amenacen la integridad de las aguas receptoras.

Dairy Milking Wastewater Treatment Using a Lab-Scale Sequencing Batch Reactor (SBR)

Use of a sequencing batch reactor (SBR) to treat dairy milking wastewater was investigated in this project. Characterization work showed that the milking wastewater properties varied a great deal with the milk content in the wastewater, possibly due to bulk milk wastage. Average biochemical oxygen demand (BOD) and soluble chemical oxygen demand (COD) levels of the milking wastewater were 1608 and 1010 mg L-1, respectively. Most of the phosphorus was soluble, and almost all the suspended solids were volatile. Good linear relationships among BOD, soluble COD, and total COD were observed for the milking wastewater used. The SBR was operated in fixed 8 h cycles, each consisting of 1 h anaerobic, 3 h aerobic, 2 h anoxic, 1 h aerobic, 50 min settle, 10 min decant, and idle with an HRT of 5.3 days and an SRT of 40 days. In organic loading tests, it was found that the optimal loading rate for the SBR studied was around 0.125 kg COD kg-1 MLSS d-1 (MLSS = mixed liquor suspended solids), at which a COD removal efficiency greater than 99% and an effluent with COD and BOD concentrations less than 55 and 25 mg L-1, respectively, was obtained. The average removal efficiencies for total Kjeldahl nitrogen (TKN), ammonium nitrogen (NH4+-N), total phosphorus (TP), dissolved phosphorus (DP), total solids (TS), and total suspended solids (TSS) were 96.7%, 92.4%, 95.9%, 94.0%, 78.5%, and 96.6%, respectively. The reactor sludge settleability was good, with a sludge volume index (SVI) always under 100 mL g-1 during all the test periods.

Spatial Variations in Nutrient and Microbial Transport from Feedlot Surfaces

Nutrient and microbial transport by runoff may vary at different locations within a beef cattle feedlot. If the areas making the largest contributions to nutrient and microbial transport can be identified, it may be possible to institute site-specific management practices to reduce runoff nutrient and microbial transport. The objectives of this study were to: (1) measure selected feedlot soil properties and nutrient and microbial transport in runoff from various feedlot locations, (2) compare the effects of unconsolidated surface materials (USM) (loose manure pack) and consolidated subsurface materials (CSM) (compacted manure and underlying layers) on nutrient and microbial transport, and (3) determine if nutrient and microbial transport in runoff are correlated to selected feedlot soil characteristics. Simulated rainfall events were applied to 0.75 m wide by 2 m long plots. No significant differences (P < 0.05) in feedlot soil characteristics or nutrient transport in runoff were found between USM and CSM. However, concentrations of E. coli were significantly greater in the USM than the CSM. Pen location was found to significantly influence feedlot soil measurements of Bray-1 P, calcium, chloride, copper, electrical conductivity (EC), loss on ignition, organic N, phosphorus, potassium, sodium, sulfur, total N (TN), water-soluble P, and zinc. Runoff measurements of dissolved phosphorus (DP), EC, and NH4-N were significantly influenced by pen location and were correlated to selected feedlot soil characteristics. Thus, it may be possible to estimate DP, EC, and NH4-N in runoff from selected feedlot soil parameters.

Narrow Grass Hedge Effects on Nutrient Transport Following Compost Application

The placement of stiff-stemmed grass hedges on the contour along a hillslope has been shown to decrease nutrient transport in runoff. This study was conducted to measure the effectiveness of a narrow grass hedge in reducing runoff nutrient transport from plots with a range of soil nutrient values. Composted beef cattle manure was applied at dry weights of 0, 68, 105, 142, and 178 Mg ha-1 to a silty clay loam soil and then incorporated by disking. Soil samples were collected 243 days later for analysis of water-soluble phosphorus (WSP), Bray and Kurtz No. 1 phosphorus (Bray-1 P), NO3-N, and NH4-N. Three 30 min simulated rainfall events, separated by 24 h intervals, were then applied. The transport of dissolved phosphorus (DP), total P (TP), NO3-N, NH4-N, total nitrogen (TN), runoff, and soil erosion were measured from 0.75 m wide 4.0 m long plots. Compost application rate significantly affected soil measurements of WSP, Bray-1 P, and NO3-N content. The transport of DP, TP, NO3-N, NH4-N, TN, runoff, and soil erosion was reduced significantly on the plots with a grass hedge. Mean runoff rates on the hedge and no-hedge treatments were 17 and 29 mm, and erosion rates were 0.12 and 1.46 Mg ha-1, respectively. Compost application rate significantly affected the transport of DP, TP, and NO3-N in runoff. The experimental results indicate that stiff-stemmed grass hedges, planted at selected downslope intervals, can significantly reduce the transport of nutrients in runoff from areas with a range of soil nutrient values.