U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2020–5015

Prepared in cooperation with the Ohio Water Development Authority

Pilot-Scale Testing of Dairy Manure Treatments to Reduce 

Nutrient Transport from Land Application, Northwest Ohio, 

2015–17
Cover. U.S. Geological Survey employee performing a topographic survey at study site. 

Photograph by Robert Darner, U.S. Geological Survey.
Pilot-Scale Testing of Dairy Manure 

Treatments to Reduce Nutrient Transport 

from Land Application, Northwest 

Ohio, 2015–17

By Donna S. Francy, Amie M.G. Brady, Bethany L. Ash, and W. Robert Midden

Prepared in cooperation with the Ohio Water Development Authority

Scientific Investigations Report 2020–5015

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DAVID BERNHARDT, Secretary

U.S. Geological Survey

James F. Reilly II, Director

U.S. Geological Survey, Reston, Virginia: 2020

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Suggested citation:

Francy, D.S., Brady, A.M.G., Ash, B.L., and Midden, W.R., 2020, Pilot-scale testing of dairy manure treatments 

to reduce nutrient transport from land application, northwest Ohio, 2015–17: U.S. Geological Survey Scientific 

Investigations Report 2020–5015, 31 p., https://doi.org/10.3133/sir20205015.

ISSN 2328-0328 (online)
iii

Acknowledgments

The authors acknowledge assistance from many individuals and agencies in project planning 

and executing this study. Thanks to Matt Davis and his crew at The Ohio State University 

Agricultural Research and Development Center Northwest Agricultural Research Station for 

providing access to the site and their invaluable work in preparing, planting, and harvesting 

the plots. Thanks to Doug Schroeder, Alan Wrasman, and Russ Bales at the Ottawa Water 

Treatment Plant, Ottawa, Ohio, for treating and transporting manure to the field site.

We thank Kevin Elder (Ohio Department of Agriculture) and Kevin King, Norm Fausey, Glen 

Arnold, and Greg LaBarge (The Ohio State University) for providing valuable technical advice on 

agricultural practices and nutrients.

v

Contents

Acknowledgments........................................................................................................................................iii

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................2

Purpose and Scope .......................................................................................................................................2

Methods of Study...........................................................................................................................................2

Site and Equipment Description .........................................................................................................2

Sampling and Sample Processing .....................................................................................................3

Manure Treatment and Data Collection ............................................................................................5

Field Quality Assurance and Quality Control ....................................................................................9

Laboratory Analyses and Associated Laboratory Quality Control .............................................10

Data Management and Calculations of Loads and Flow-Weighted Mean 

Concentrations of Nutrients ................................................................................................10

Quality-Control Measures of Bias and Variability ..................................................................................12

Sampling Events and Concentrations of Nutrients in Surface Runoff and Tile Flow Samples .......12

Dissolved Reactive and Total Phosphorus Concentrations .........................................................13

Nitrate Plus Nitrite and Total Nitrogen Concentrations ...............................................................14

Ammonia Concentrations ..................................................................................................................14

Water Volumes .............................................................................................................................................14

Comparisons of Nutrient Loads and Flow-Weighted Mean Concentrations from Raw 

Manure and Treated Manure Plots .............................................................................................21

Loads.....................................................................................................................................................21

Loads from Surface Runoff and Tile Flow ..............................................................................21

Combined Loads .........................................................................................................................21

Flow-Weighted Mean Concentrations ............................................................................................25

Corn Yields ....................................................................................................................................................25

Summary and Conclusions .........................................................................................................................27

References Cited..........................................................................................................................................28

Appendix 1. Sample Processing Cheat Sheet .....................................................................................30

Appendix 2. Data Tables ..........................................................................................................................31

Figures

1. Map showing location of the study area, northwest Ohio .....................................................3

2. Images showing agricultural test plots separated by grassed berms with 

a central sampling and volume monitoring building; polyvinyl chloride flow 

directors and tipping buckets for measuring volume; and 16 automatic 

samplers to collect water samples for nutrient analyses ......................................................4

3. Diagram showing the numbering system for agricultural test plots and 

automatic samplers in the central building at The Ohio State University 

Agricultural Research and Development Center Northwest Agricultural 

Research Station ..........................................................................................................................5
vi

4. Graphs showing time-series plots of baseline 1, baseline 2, and post-manure 

application events that resulted in substantial surface runoff and (or) tile 

flow, rainfall amounts, and farming activities at The Ohio State University 

Agricultural Research and Development Center Northwest Agricultural 

Research Station, 2015–17 ..........................................................................................................8

5. Box plots showing concentrations of nutrients in samples from surface runoff 

and tile flow from plots with raw manure and treated manure at The Ohio 

State University Agricultural Research and Development Center Northwest 

Agricultural Research Station during baseline 2 and post-manure periods 

in 2016–17.....................................................................................................................................15

6. Box plots showing total volumes of surface runoff and tile flow from plots 

with raw manure and treated manure at the Ohio State University Agricultural 

Research and Development Center Northwest Agricultural Research Station 

in 2016–17.....................................................................................................................................20

7. Graphs showing loads in surface runoff and tile flow from plots with raw 

manure and treated manure at The Ohio State University Agricultural Research 

and Development Center Northwest Agricultural Research Station during nine 

post-manure application rainfall events in 2017 ....................................................................22

8. Step graphs showing by date for combined loads in samples from plots with 

raw manure and treated manure at the Ohio State University Agricultural 

Research and Development Center Northwest Agricultural Research Station 

during nine post-manure application rainfall events in 2017 ..............................................23

9. Graphs showing combined loads in samples from plots with raw manure 

and treated manure at the Ohio State University Agricultural Research and 

Development Center Northwest Agricultural Research Station during nine 

post-manure application rainfall events in 2017 ....................................................................24

10. Box plots showing combined flow-weighted mean concentrations in samples 

from plots with raw manure and treated manure at the Ohio State University 

Agricultural Research and Development Center Northwest Agricultural 

Research Station during nine post-manure application rainfall events in 2017 ..............26

Tables

1. Timeline and sample information from 16 automatic samplers during rainfall 

events that resulted in substantial surface runoff and (or) tile flow and farming 

activities at The Ohio State University Agricultural Research and Development 

Center Northwest Agricultural Research Station, 2015–17 ...................................................6

2. Laboratory method information for nutrients analyzed by the U.S. Geological 

Survey National Water Quality Laboratory and Bowling Green State University 

in surface runoff and tile flow samples from eight test plots at The Ohio 

State University Agricultural Research and Development Center Northwest 

Agricultural Research Station, 2015–17 ..................................................................................11

3. Quality-control field blank, filter blank, and source solution blank data for 

nutrients, 2015–17 .......................................................................................................................13

4. Summary statistics for quality-control split replicates for nutrient 

samples collected and analyzed by Bowling Green State University or the 

U.S. Geological Survey, 2015–17 ..............................................................................................14
vii

5. Total phosphorus applied to 3 raw and 3 treated manure plots and percentages 

of dissolved reactive phosphorus and total phosphorus in combined surface 

runoff and tile flow ......................................................................................................................25

6. Corn yields from Ohio State University Agricultural Research and Development 

Center Northwest Agricultural Research Station test plots, November 2017 ..................25

Conversion Factors

U.S. customary units to International System of Units

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

Volume

gallon (gal) 3.785 liter (L)

Mass

pound, avoirdupois (lb) 0.4536 kilogram (kg)

Area

acre 0.004047 square kilometer (km2)

International System of Units to U.S. customary units

Multiply By To obtain

Length

meter (m) 3.281 foot (ft)

centimeter (cm) 0.3937 inch (in.)

millimeter (mm) 0.03937 inch (in.)

Volume

milliliter (mL) 0.033814 ounce, fluid (fl. oz)

liter (L) 33.81402 ounce, fluid (fl. oz)

Mass

milligram (mg) 0.00003527 ounce, avoirdupois (oz)

gram (g) 0.03527 ounce, avoirdupois (oz)

Concentrations of chemical constituents in water are given in milligrams per liter (mg/L).
viii

Abbreviations

< less than

> greater than

≤ less than or equal to

BGSU Bowling Green State University

GCLAS Graphical Constituent Loading and Analysis System

HAB harmful algal bloom

mgN/L milligrams nitrogen per liter

mgP/L milligrams phosphorus per liter

n number

NWARS Northwest Agricultural Research Station

NWIS National Water Information System

NWQL National Water Quality Laboratory

OARDC Ohio State University Agricultural Research and Development Center

PVC polyvinyl chloride

RPD relative percent difference

USGS U.S. Geological Survey
Pilot-Scale Testing of Dairy Manure Treatments to Reduce 

Nutrient Transport from Land Application, Northwest 

Ohio, 2015–17

By Donna S. Francy, Amie M.G. Brady, Bethany L. Ash, and W. Robert Midden

Abstract

Manure and wastewater from large livestock operations have the potential to negatively affect surface water and 

groundwater, including the eutrophication of surface waters 

and harmful algal blooms. In the Western Lake Erie Basin, 

where there is a high density of animal agriculture, harmful algal blooms have been attributed, in part, to phosphorus 

loading from dairy manure and fertilizer applications. Liquid 

lagoon manure produced by dairy operations typically has low 

nutrient concentrations and high-water content, so transportation costs are high relative to the value of the nutrients when 

applied to fields. Treatment systems are needed to transform 

manure into a dewatered product that is more economical to 

transport greater distances and that slows and (or) reduces the 

release of nutrients in soil, allowing nutrients to remain available for crop growth.

This study was designed to pilot test a treatment solution 

in the Western Lake Erie Basin. The U.S. Geological Survey 

and Bowling Green State University field tested a dewatering treatment process (coagulant/polymer mixture) for dairy 

manure at pilot-scale test plots at The Ohio State University 

Agricultural Research and Development Center Northwest 

Agricultural Research Station. Automatic samplers were 

used to collect samples during 13 baseline and 9 post-manure 

application rainfall events that resulted in substantial surface 

runoff and (or) tile flow from October 2015 through early 

November 2017. Results are reported for three test plots that 

received liquid lagoon manure (raw manure) and three test 

plots that received polymer-treated manure (treated manure).

Nutrient concentrations and flow volumes in surface 

runoff and tile flow were determined in baseline and postmanure application rainfall events. Nutrient concentration 

ranges are reported for 9 baseline and 9 post-manure application events as follows: dissolved reactive phosphorus, 

less than (<) 0.013−2.16 milligrams per liter (mg/L); nitrate 

plus nitrite, filtered, 0.32−77 mg/L; ammonia, filtered, 

<0.05−2.6 mg/L; total phosphorus, <0.01−12.8 mg/L; and 

total nitrogen, 1.49−77.2 mg/L. Volumes are reported for 

6 baseline and 9 post-manure application rainfall events. None 

of the post-manure application runoff volumes were significantly different by plot or by treatment type (raw manure 

versus treated manure).

Because concentrations alone do not reflect the true 

effects of different manure treatments, loads and flowweighted mean concentrations of nutrients during post-manure 

application rainfall events were compared between plots with 

treated manure and those with raw manure. Loads of dissolved 

reactive phosphorus, total phosphorus, nitrate plus nitrite, 

and total nitrogen were calculated using the U.S. Geological 

Survey Graphical Constituent Loading and Analysis System. 

Loads of ammonia were not calculated because many of the 

ammonia concentrations were below the reporting limit.

During the post-manure application period, higher 

nitrogen loads resulted from tile flow than surface runoff. For 

phosphorus, the opposite was true in that higher loads resulted 

from surface runoff than tile flow. Combined loads (surface 

runoff and tile flow) of dissolved reactive phosphorus were 

significantly different between raw manure and treated manure 

plots, but there was no significant difference in combined 

loads of total phosphorus, nitrate plus nitrite, or total nitrogen 

between raw manure and treated manure plots. Flow-weighted 

mean concentrations were calculated for the combined loads 

for the post-manure application rainfall events. Flow-weighted 

mean concentrations of dissolved reactive phosphorus and, 

to a lesser extent, total phosphorus were significantly different between raw manure and treated manure plots. Flowweighted mean concentrations of nitrate plus nitrite and 

total nitrogen were not significantly different between raw 

manure and treated manure plots. The differences in loads and 

flow-weighted mean concentrations between raw manure and 

treated manure plots indicate that dissolved reactive phosphorus was likely retained in the soil and hydrological transport 

was reduced for the plots amended with the treated manure as 

compared to raw manure. Although confirmation field testing needs to be done, these results indicate that the use of 

this coagulant/polymer mixture shows potential in helping to 

reduce flow of dissolved phosphorus from agricultural fields 

with applied manure.
2 Pilot-Scale Testing of Dairy Manure Treatments to Reduce Nutrient Transport from Land Application, Northwest Ohio, 2015–17

Introduction

The livestock industry is continuing a trend towards 

fewer but larger confined operations (U.S. Environmental 

Protection Agency, 2012). Manure and wastewater from large 

livestock operations are a growing concern because of the 

potential to negatively affect water quality. Application of 

animal wastes on fields can cause excess nutrients to permeate soils and move into receiving waters and groundwater 

resources (Burkholder and others, 2007). Liquid, lagoon 

manure produced by dairy operations is typically dilute, the 

nutrient concentration is low, and the water content is high. 

Treatment methods to remove excess water from manure 

and to concentrate nutrients are needed. This will decrease 

the overall manure volume and weight and allow facilities 

to transport the waste greater distances, so nutrients are not 

overapplied on nearby fields. In addition, manure treatment 

that temporarily binds nutrients could reduce the transport 

from agricultural fields into surface water and groundwater 

and allow nutrients to remain available for crop growth.

Treatment systems that transform dairy manure into a 

dewatered product are needed in the Western Lake Erie Basin, 

where there is a high density of animal agriculture. Nutrient 

excesses can cause proliferation of cyanobacteria and harmful algal blooms (HABs), which may produce microcystin 

and other toxins. Concentrations of microcystin above World 

Health Organization guidelines have been observed in the 

Western Lake Erie Basin the last few years and in Ohio 

inland lakes (Ohio Environmental Protection Agency, 2019); 

this has been attributed, in part, to phosphorus loading from 

manure and fertilizer applications (Hoorman and others, 2008; 

Michalak and others, 2013; Ohio Department of Agriculture 

and others, 2013).

One promising technology for treating manure to reduce 

adverse environmental effects is solid-liquid separation 

enhanced with iron and aluminum salts, with or without the 

addition of natural (Garcia and others, 2007) or synthetic 

organic polymers (Chastain and others, 2001; DeBusk and 

others, 2008). Although polymer flocculants have been 

used in the food and municipal waste industries for years to 

enhance solid-liquid separation, the use of this technology 

for managing animal wastes is still new (Timby and others, 

2004). Previous soil column and pilot-field studies in which 

investigators tested polymers for dewatering animal manure 

have been documented in Arkansas (Timby and others, 2004), 

South Carolina (Garcia and others, 2007), and North Carolina 

(Szogi and Vanotti, 2007); however, to our knowledge, this 

type of study has not been done in Ohio. Most of these studies 

were laboratory or feasibility studies, and only a few demonstrated production of a potential fertilizer material.

The U.S. Geological Survey (USGS) and Bowling Green 

State University (BGSU), in cooperation with the Ohio Water 

Development Authority, and in collaboration with The Ohio 

State University Agricultural Research and Development 

Center and the Village of Ottawa, field tested a dewatering 

treatment process for dairy manure. By amending manure with 

a coagulant/polymer mixture, the manure is dewatered yet 

retains nutrient-rich fertilizer in the solid phase. BGSU tested 

different dairy manure dewatering treatments for their abilities 

to slowly release nutrients in laboratory batch and soil column 

studies; these tests were used to identify the best treatment for 

field testing. For this study, data on nutrient concentrations and 

water volumes in surface runoff and tile flow from pilot-scale 

plots that received dairy manure applications were collected. 

The goal of the study was to demonstrate potential improved 

water-quality benefits of a manure dewatering treatment process in a natural field setting.

Purpose and Scope

The purpose of this report is to describe the results 

of pilot-scale testing of dairy manure treatments to reduce 

nutrient transport from land application in northwest Ohio. 

Data were collected during rainfall events that resulted in 

substantial surface runoff and (or) tile flow (hereinafter called 

“events”) from October 2015 through early November 2017. 

These included 4 baseline events used for quality control and 

protocol development (baseline 1), 9 baseline events used for 

determining concentrations and volumes (baseline 2), and 

9 events after manure application (post-manure events). For 

post-manure events, calculated loads and flow-weighted mean 

concentrations of nutrients from plots with polymer-treated 

manure were compared to those with liquid lagoon manure.

Methods of Study

This section describes the methods used for this study 

including those for sample collection and processing, application of the manure treatment, quality control and quality 

assurance purposes, laboratory analysis, and calculation of 

loads and flow-weighted mean concentrations of nutrients. The 

pilot-scale study site and equipment used also are described.

Site and Equipment Description

The pilot-scale field study was done at The Ohio State 

University Agricultural Research and Development Center 

(OARDC) Northwest Agricultural Research Station (NWARS; 

fig. 1). This facility was established in 1974 and consists of 

eight plots, arranged in two blocks of four plots each on either 

side of a sampling and flow monitoring building (Logan and 

others, 1994). Each test plot (30 feet [ft] by 100 ft each) is 

separated from adjacent plots by a grassed berm about 1-meter 

wide and has a heavy plastic barrier around the perimeter to 

a depth of about 1.5 meters (fig. 2A). The surface slope is 

less than (<) 1 percent. Surface runoff drains into a concrete 

gutter, which directs the water into a pipe that transports the 

runoff into the building. Subsurface flow is collected by tile, 
Methods of Study 3

10 centimeters in diameter, located 1 meter deep under the 

center of the plot, draining towards the building at a slope 

of 0.2 percent. Tile flow is transported into the building by a 

separate pipe than surface runoff. Manure was treated at the 

Village of Ottawa Wastewater Treatment Plant. Daily rainfall 

amounts were obtained from the OARDC Weather System 

for the Northwest Station in Custar, Ohio (The Ohio State 

University, 2017).

Each plot transports water through two pipes into the 

monitoring building—one for surface runoff and one for tile 

(subsurface) flow. In the building, each pipe (16 total) is fitted 

with an L-shaped polyvinyl chloride (PVC) flow director that 

empties into a tipping bucket (fig. 2B). The 16 tipping buckets were calibrated through an inlet to the PVC flow director 

and were set to tip when filled with 600‒800 milliliters (mL) 

plus or minus (±) 10 mL, depending on the capacity of the 

bucket. A discharge line from each flow director was attached 

to a refrigerated automatic sampler (fig. 2C). Communicating 

through a modem, a digital I/O port expander (SDM–1O16, 

Campbell Scientific, Inc., Logan, Utah) coordinated the operation of each tipping bucket and automatic sampler. A data 

logger (CR850, Campbell Scientific) contained in a fiberglass 

box recorded the time and number of tips every 5 minutes and 

recorded when sample bottles were filled.

Sampling and Sample Processing

The refrigerated automatic samplers, each with 14 bottles, were numbered from 1 through 16 (fig. 3). Samples were 

collected during rainfall events that resulted in substantial 

surface runoff and (or) tile flow. The volume required before 

the first sample was collected for each event was initially 

set to 30 liters (L) for surface runoff and 15 L for tile flow; 

this could be adjusted based on antecedent field conditions. 

A program was written that adjusted the number of tips 

required for a sample to be collected (after the first sample) 

based on a change in flow rate. For small events, 30- and 15-L 

intervals were usually maintained throughout the event. For 

larger events, larger volume intervals would be collected, 

some as large as 500 L. When a sample was triggered to be 

collected, the line was rinsed first, then each bottle filled to 

!

!

LAKE

ERIE

Village of Ottawa

Waste Water

Treatment Plant

Portage River

GRAND LAKE

ST MARYS

Maumee River

Ohio Agricultural Research

and Development Center,

Northwest Agricultural

Research Station

Blanchard River

Auglaize River

Ottawa

Lima

Defiance

Bowling 

Green

Custar

Fremont

Sandusky

Toledo

Port

Clinton

WOOD

SENECA

ALLEN

HURON

HENRY

HARDIN

PUTNAM

HANCOCK

ERIE

FULTON

RICHLAND

LUCAS

MARION

WYANDOT

DEFIANCE

AUGLAIZE

SANDUSKY

CRAWFORD

PAULDING

WILLIAMS

MERCER

VAN WERT

OTTAWA

MORROW

ASHLAND

KNOX

LORAIN

SHELBY LOGAN UNION

84°40' 84°20' 84°00' 83°40' 83°20' 83°00' 82°40' 82°20'

41°40'

41°20'

41°00'

40°40'

OHIO

Map area Study area

Blanchard River watershed

Portage River watershed

! Study sites

Base from U.S. Geological Survey, variously scaled, 2007 

State Plane projection (feet), Ohio North

Horizontal coordinate information is referenced to the 

North American Datum of 1983 (NAD83)

0 5 10 15 20 25 MILES

0 5 10 15 20 25 KILOMETERS

EXPLANATION

Figure 1. Location of the study area, northwest Ohio.
4 Pilot-Scale Testing of Dairy Manure Treatments to Reduce Nutrient Transport from Land Application, Northwest Ohio, 2015–17

A

B C

Photographs by Robert Darner, U.S. Geological Survey

Figure 2. The, A, agricultural test plots separated by grassed berms with a central sampling and volume 

monitoring building; B, polyvinyl chloride flow directors and tipping buckets for measuring volume; and 

C, 16 automatic samplers to collect water samples for nutrient analyses.

approximately 600 mL. For small events (less than 6 bottles 

were full), all sample bottles with adequate water were processed and analyzed. For larger events, one-third to two-thirds 

of the bottles with water were processed and analyzed; the bottles were selected for processing to provide adequate temporal 

and volume coverage over the event hydrograph.

Bottle contents were processed on site within 72 hours 

of collection for subsequent nutrient analyses. Samples for 

ammonia (filtered), nitrate plus nitrite (filtered), dissolved 

reactive phosphorus, total nitrogen, and total phosphorus 

were processed and preserved as per standard USGS methods 

(Wilde and others, 2004, chap. A5). A 4-layer, 0.45-micron, 

25-millimeter diameter syringe filter (Tisch Scientific, 
Methods of Study 5

Sampler

number

Tile (T) 

or 

surface (S)

Plot 

number

Sampler 

number

Tile (T) 

or 

surface (S)

Plot 

number

01 T 1 16 T 8

02 S 15 S

03 T 2 14 T 7

04 S 13 S

05 S 3 12 S 6

06 T 11 T

07 S 4 10 S 5

08 T 09 T

DOORCENTRAL WALKWAY

Figure 3. The numbering system for agricultural test plots and automatic 

samplers in the central building at The Ohio State University Agricultural 

Research and Development Center Northwest Agricultural Research Station.

GD17034) was used to collect 10–20 mL of sample for filtered 

nutrients. Unfiltered samples for total nutrients (125 mL) were 

preserved with 1.0 mL of 1:7 sulfuric acid. All samples were 

stored on ice immediately after processing and for transport to 

the laboratory.

Manure Treatment and Data Collection

The data-collection period was from October 28, 2015, 

through November 9, 2017, and included 22 events in which 

nutrient samples were collected (table 1 and fig. 4). From 

October 2015 through early May 2017, baseline samples were 

collected at the NWARS. The original intention was to identify 

any baseline differences in nutrient concentrations and flow 

conditions between plots as the plots had not been used for 

3 years prior to this study. After the first few events, however, 

it was noted that there were both flow and water-quality differences among the plots. The project team decided to delay 

the application of manure for 1 year to improve the similarity 

of the plots in terms of surface runoff and tile flow. On May 

23, 2016, the plots were tilled, berms redefined, and animal 

burrows were removed. On October 12, 2016, the plots were 

chisel-plowed to break up soil and further restore uniform 

grading. There were no farming activities in 2016. Samples 

were segregated into two baseline periods based on the first 

attempt to redefine the plots. The first baseline period (baseline 1, October 2015‒February 2016) included four events 

that occurred before the plots were first redefined (identified 

as B1.1‒B1.4). Data from baseline 1 were used to collect 

quality-control data and establish sampling and analysis 

protocols. Data from the second baseline period (baseline 2, 

June 2016 through early May 2017) were used to determine 

baseline nutrient concentrations for 9 events (B2.1‒B2.9) 

and baseline volumes for the 6 events that occurred after the 

October 12, 2016, grading (B2.4−B2.9). Baseline volumes 

were approved and reported for all events; however, baseline 

volumes before the grading on October 12, 2016, were not 

used in this report because runoff and flow from the plots were 

not considered to be uniform.

Prior to and during the baseline period, BGSU tested different dairy manure dewatering treatments for their abilities to 

promote separation of solids and liquids, sequester agricultural 

nutrients from water, and slowly release nutrients when mixed 

with soil over time. Extensive laboratory tests under local soil 

conditions using dairy manure indicated that, of the materials 

tested, an aluminum-based coagulant commonly used in drinking water and wastewater applications (Aqua Hawk 1010P, 

Hawkins Water Treatment Group, Roseville, Minnesota) and 

a cationic based flocculant/polymer (Zetag 8816, Hawkins 

Water Treatment Group) performed best by the criteria of (1) 

separating solids and water, (2) reducing the nutrient concentration in the filtrate water, and (3) slowing the release of 

nutrients in soil relative to untreated manure.

On May 9, 2017, liquid manure was obtained from 

a local dairy. Mean nutrient and solid levels in the liquid 

lagoon dairy manure were as follows: dissolved reactive 

phosphorus, 160 milligrams phosphorus per liter (mgP/L); 

ammonia, 970 milligrams nitrogen per liter (mgN/L); nitrate 

plus nitrite, 38 mgN/L; total phosphorus, 320 mgP/L; total 

nitrogen, 1,200 mgN/L; and total solids, 30 mg/L. On May 

9‒17, 2017, 4,000 gallons of liquid manure were treated at the 

Ottawa Wastewater Treatment Plant with Aqua Hawk 1010P 
6 Pilot-Scale Testing of Dairy Manure Treatments to Reduce Nutrient Transport from Land Application, Northwest Ohio, 2015–17

Table 1. Timeline and sample information from 16 automatic samplers during rainfall events that resulted in substantial surface 

runoff and (or) tile flow and farming activities at The Ohio State University Agricultural Research and Development Center Northwest 

Agricultural Research Station, 2015–17.

[B, baseline; BGSU, Bowling Green State University; USGS, U.S. Geological Survey; QC, quality-control; --, no samples were collected; ex, except; NA, not 

applicable; PM, post-manure application]

Event 

number

Event dates 

(month day, year)

Bottles 

filled

Tile flow 

occurred, 

sampler 

number

Surface runoff 

occurred, 

sampler 

number

Runoff type Analyzing agency Data use

Baseline 1

B1.1 October 28‒29, 2015 59 1a, 3 All Surface, 

mainly

BGSU, USGS QC and establish 

protocols

B1.2 November 27‒29, 2015 23 -- All ex 4 Surface BGSU, USGS QC and establish 

protocols

B1.3 December 26, 2015‒

January 4, 2016

151 All All Surface and 

tile

USGS QC and establish 

protocols

B1.4 January 30‒Feb 6, 

2016

93 All All ex 4,12 Tile, mainly BGSU, USGS QC and establish 

protocols

NA May 23, 2016 Plots were tilled and berms redefined

Baseline 2

B2.1 June 22‒23, 2016 51 All ex 16 All ex 10b Surface and 

tile

BGSU Concentrations for 

filtered constituents

B2.2 August 12‒16, 2016 42 Alla All ex 10b Surface BGSU Concentrations

B2.3 September 17‒18, 2016 60 3, 6, 9, 11, 14b All ex 10b Surface, 

mainly

BGSU Concentrations 

except for total 

phosphorus

NA October 12, 2016 Plots were chisel-plowed to break up soil and restore the grading

B2.4 October 20‒21, 2016 38 3, 6a, 9 All ex 4, 10b Surface, 

mainly

BGSU Concentrations and 

volumes

B2.5 January 2‒7, 2017 141 All All Surface and 

tile

BGSU, USGS Concentrations and 

volumes

B2.6 January 10‒15, 2017 195 All All Surface and 

tile

BGSU, USGS Concentrations and 

volumes

B2.7 February 6‒10, 2017 61 All All ex 4b Surface and 

tile

BGSU Concentrations and 

volumes

B2.8 April 3‒16, 2017 120 All All ex 4b Surface and 

tile

BGSU Concentrations and 

volumes

B2.9 May 4‒8, 2017 208 All All ex 4b Surface and 

tile

BGSU, USGS Concentrations and 

volumes

NA May 18, 2017 Manure applied

Post-manure application

PM.1 May 19‒22, 2017 57 All ex 8 All ex 4b Surface and 

tile

BGSU, USGS Post-manure loads

NA May 26, 2017 Plots were tilled to incorporate manure

PM.2 May 26‒27, 2017 15 Alla All ex 4b Surface and 

tile

BGSU Post-manure loads

PM.3 May 28‒29, 2017 15 1, 3, 6, 9, 14a All ex 4b Surface and 

tile

BGSU Post-manure loads

NA June 1, 2017 Plots were planted with corn
Methods of Study 7

Table 1. Timeline and sample information from 16 automatic samplers during rainfall events that resulted in substantial surface 

runoff and (or) tile flow and farming activities at The Ohio State University Agricultural Research and Development Center Northwest 

Agricultural Research Station, 2015–17.—Continued

[B, baseline; BGSU, Bowling Green State University; USGS, U.S. Geological Survey; QC, quality-control; --, no samples were collected; ex, except; NA, not 

applicable; PM, post-manure application]

Event 

number

Event dates 

(month day, year)

Bottles 

filled

Tile flow 

occurred, 

sampler 

number

Surface runoff 

occurred, 

sampler 

number

Runoff type Analyzing 

agency

Data use

Post-manure application—Continued

PM.4 June 13‒14, 2017 137 All All ex 4b Surface and 

tile

BGSU, USGS Post-manure loads

PM.5 June 23‒24, 2017 118 All All ex 4b Surface and 

tile

BGSU, USGS Post-manure loads

PM.6 July 7, 2017 96 All ex 8 All ex 4b Surface, 

mainly

BGSU, USGS Post-manure loads

PM.7 July 10‒11, 2017 210 All All ex 4b Surface and 

tile

BGSU, USGS Post-manure loads

PM.8 August 1‒10, 2017 210 All All ex 4b Surface and 

tile

BGSU, USGS Post-manure loads

PM.9 November 4‒10, 2017 213 All All Surface and 

tile

BGSU, USGS Post-manure loads

NA November 13, 2017 Corn was harvested

aSmall volumes were recorded for this sampler (s) (<10 liters).

bSampler volumes were disparate from other sampler volumes so were suspected to be erroneous.

coagulant and Zetag 8816 polymer and allowed to filter and 

dry on sand beds. Samples of the solid manure cake portion 

left on the sand beds were analyzed for total phosphorus and 

nitrogen. Mean nutrient levels were as follows: total phosphorus, 0.0013 grams of phosphorus per gram of treated solid 

cake; and total nitrogen, 0.0049 grams of nitrogen per gram of 

treated solid cake. On May 18, 2017, manure was applied to 

the surface of the test plots. Calculations were done to ensure 

the amount of total phosphorus in the total volume of liquid 

lagoon manure (raw) and total weight in coagulant-treated 

manure (treated) were consistent. Amounts applied were 

as follows:

• Plots 1 and 2 did not receive manure treatment and 

results were not used in the study after early work to 

establish protocols because of equipment malfunctions 

and (or) atypical runoff or flow volumes;

• Plots 4, 6, and 8 each received 800 gallons (3,000 L) 

of raw manure. This equates to a rate of 11,400 gallons 

per acre. The mean total phosphorus application of 

raw manure per plot was 970,000 milligrams (mg) of 

phosphorus. This amount was chosen to simulate the 

maximum allowable application of liquid manure. The 

maximum amount allowed by Nutrient Management 

Code 590 (U.S. Department of Agriculture, 2013) 

is 910 gallons (3,400 L). Due to the small size of 

the plots and the structure of the manure applicator, 

3,000 L was the amount applied; and

• Plots 3, 5, and 7 each received 1,400 pounds 

(640,000 grams) of treated manure. The mean total 

phosphorus application of treated manure per plot 

was 830,000 mg of phosphorus. The mass of treated 

manure was planned based on laboratory analysis of 

solid, treated manure to match the mass of phosphorus 

being applied on the raw manure plots. However, when 

the solid samples from the actual pilot test were analyzed, they contained lower amounts of phosphorus.

To simulate typical farming practices, the plots were to be 

tilled after manure application to incorporate manure; however, 4 days of rain after manure application (totaling just over 

1 inch) resulted in the plots being too wet for tilling. On May 

26, 2017, the plots dried out and were tilled to incorporate 

the manure, and on June 1, the plots were planted with corn. 

On June 2, the plots were sprayed with pesticides (Corvus; 

Atrazine 4L; 2,4-D Ester lv4; Mad Dog+; and Choice). 

Samples were collected for nine events during the post-manure 

period (PM.1‒PM.9). On November 13, 2017, corn was 

harvested from two rows (103 ft long) down the center of each 
8 Pilot-Scale Testing of Dairy Manure Treatments to Reduce Nutrient Transport from Land Application, Northwest Ohio, 2015–17

11/01/201512/01/201501/01/201602/01/201603/01/201604/01/201605/01/2016

Date

Date

Rainfall, in inches

0

0.5

1.0

1.5

2.0

2.5

3.0

B1.1 B1.2 B1.3 B1.4

Plots tilled and

berm refined

Rainfall

Runoff/flow event

Activity

EXPLANATION

[B, baseline event; PM, post-manure event]

Rainfall data from the Ohio State University (2017)

07/01/201609/01/201611/01/201601/01/201703/01/201705/01/2017

Rainfall, in inches

0

0.5

1.0

1.5

2.0

2.5

3.0

B2.1 B2.2 B2.3 B2.4 B2.5B2.6 B2.7 B2.8 B2.9

Plots were chisel-plowed 

to breakup soil and restore 

the grading 

A

B

Figure 4. Time-series plots of, A, baseline 1, B, baseline 2, and C, post-manure application events that resulted in substantial surface 

runoff and (or) tile flow, rainfall amounts, and farming activities at The Ohio State University Agricultural Research and Development 

Center Northwest Agricultural Research Station, 2015–17.
Methods of Study 9

06/01/2017

07/01/201708/01/2017

09/01/201710/01/201711/01/2017

12/01/2017

01/01/2018

Rainfall, in inches

0

0.5

1.0

1.5

2.0

2.5

3.0

PM.1

PM.2

PM.3 PM.4 PM.5

PM.6

PM.7 PM.8 PM.9

Manure

 applied

Plots 

tilled

Plots

planted

Date

EXPLANATION

[B, baseline event; PM, post-manure event]

C

Rainfall

Runoff/flow event—PM.2–PM.3 and PM.6–PM.7 

were on dates too close to be distinguished

Activity

Rainfall data from the Ohio State University (2017)

Figure 4. Time-series plots of, A, baseline 1, B, baseline 2, and C, post-manure application events that resulted in substantial surface 

runoff and (or) tile flow, rainfall amounts, and farming activities at The Ohio State University Agricultural Research and Development 

Center Northwest Agricultural Research Station, 2015–17—Continued

plot and was used to calculate yield in bushels per acre. The 

corn obtained from harvesting was weighed and measured for 

moisture content.

Field Quality Assurance and Quality Control

Quality-assurance and quality-control objectives are to 

(1) ensure that procedures are done consistently with established methods and that data are collected and reported in a 

complete and accurate manner, (2) identify any sampling and 

analytical bias, and (3) quantify the variability of the measurement process.

To address number 1, sampling, processing, and documentation procedures were distributed to all personnel. A 

quality-assurance project plan was written at the start of the 

project, approved by all parties, and updated as needed. To 

provide concise field instructions, a so-called “cheat sheet” 

was distributed to field personnel (appendix 1). To address 

quality-assurance and quality-control objectives 2 and 3, 

sampling crews collected field blanks, filter blanks, source 

solution blanks, and replicates throughout the sampling period. 

Blanks were processed using inorganic-free water provided 

by the USGS. Field blanks were used to determine whether 

contamination was introduced by the entire sampling process, 

including carry over from the intake line, sample bottles, filtering, laboratory bottles, and laboratory procedures. To collect 

a field blank, the intake line was disconnected from the flow 

director and placed in a graduated cylinder containing 500 mL 

of blank water. The 500 mL of blank water was first pumped 

through the sample line to rinse the line and discarded. A 

second aliquot of 500 mL of blank water was then passed 

through the intake line to the automatic sampler and collected 

and analyzed. Filter blanks were 25 mL of inorganic blank 

water filtered through the syringe/filter system and processed 

in the same manner as a regular sample. Source solution 

blanks were prepared by pouring blank water directly into the 

sample bottle or bag at the field site. Sampling crews collected 

replicates by processing and analyzing two subsamples from 

the same 1-L sample bottle for filtered and total nutrients.
10 Pilot-Scale Testing of Dairy Manure Treatments to Reduce Nutrient Transport from Land Application, Northwest Ohio, 2015–17

Laboratory Analyses and Associated Laboratory 

Quality Control

Surface runoff and tile flow samples for nutrient analyses 

(table 2) were transported to the BGSU laboratory by car or 

to the USGS National Water Quality Laboratory (NWQL) 

in Denver, Colorado, by overnight delivery. During most 

baseline 1 events, samples were analyzed by BGSU for total 

and filtered nutrients with some split samples shipped to and 

analyzed by the USGS NWQL to complete the USGS laboratory approval process; for one event in December 2015 

(B1.3), the USGS analyzed all samples due to lack of available BGSU staff. Availability of staff and size of event dictated 

which laboratory analyzed samples during the baseline 2 

and post-manure period. For most baseline 2 and post-manure 

events, BGSU collected and analyzed samples for filtered 

nutrients, and the USGS collected samples to be analyzed by 

the USGS NWQL for total (unfiltered) nutrients.

To quantify the nutrient content of both the raw and 

treated manure that would be applied during the pilot test, 

samples of both types of manure were analyzed by BGSU. 

Raw, liquid lagoon manure was analyzed for both filtered and 

total nutrients. The raw manure was diluted by a factor of 100 

and then syringe filtered for analysis for dissolved reactive 

phosphorus, ammonia, and nitrate plus nitrite (table 2). Raw 

(liquid) and treated (solid) manure samples were digested 

using the alkaline persulfate method and then analyzed for 

total phosphorus and total nitrogen (table 2).

The USGS NWQL has a documented quality management system, is certified by four state agencies, and takes part 

in laboratory proficiency testing and audits (for more information, visit https://nwql.usgs.gov/Public/quality.shtml). BGSU 

participates in the USGS Standard Reference Sample program 

(for more information, visit https://bqs.usgs.gov/srs/), analyzes 

certified wastewater samples with each analytical run, and was 

approved through the USGS laboratory approval process. Data 

were examined to identify outliers including calculating the 

ratios of filtered to total nitrogen or phosphorus. To confirm 

results, reruns were requested for outliers and (or) for filtered 

to total ratios greater than 1.2. Erroneous values were marked 

with a data-quality indicator of “Q” in the USGS database, 

indicating “reviewed and rejected.”

Data Management and Calculations of Loads 

and Flow-Weighted Mean Concentrations of 

Nutrients

Water volume and nutrient concentration data for 

approved periods of record are available through the USGS 

National Water Information System (NWIS) public database, 

NWIS web (U.S. Geological Survey, 2020). USGS 15-digit 

site identification numbers were assigned with the first 13 digits the same (4113050834531) and the last 2 digits specific for 

each tipping bucket/sampler (01–16) (fig. 3). Station names 

for the tipping buckets with associated samplers are “OARDC 

NWARS test plot [1–8] subsurface [OR surface] drainage.” 

Continuous volume data were stored in the USGS NWIS 

database using parameter code 72270 (volume of water, total 

during measurement interval, liters) and are available through 

NWIS web by changing the last two digits for the designated 

sampler number in this link: https://waterdata.usgs.gov/

oh/nwis/uv?site_no=411305083453101. Discrete nutrient 

analyses are stored in the USGS NWIS database for water 

quality samples, available on NWIS web by entering the site 

identification number (https://nwis.waterdata.usgs.gov/oh/

nwis/qwdata).

Results from quality-control samples were examined to 

aid in data interpretations. Concentration and relative percent differences (RPDs) between paired replicates of discrete 

nutrient samples were examined to quantify variability (eq. 1). 

If both replicates had concentrations below detection, RPDs 

were not calculated. RPD was calculated as follows:

 RPD = 

|

_

RA −R

(

R_

A +

2 )

 × 100 (1)

where

RA is the concentration in replicate A, and

RB is the concentration in replicate B.

Detections in the blanks were compared to event flow 

samples. If a flow sample result was less than or equal to (≤) 

two times the detection in the associated blank, a remark code 

“V” for “value affected by contamination” was added to the 

result in the NWIS database for any qualifying samples for the 

event for that constituent.

For post-manure events, nutrient loads were calculated 

using the USGS Graphical Constituent Loading and Analysis 

System (GCLAS; Koltun and others, 2006). For this study, 

GCLAS was used to estimate concentrations for periods 

between measured concentrations during events based on 

the relation between nutrient concentrations and flow. Loads 

of dissolved reactive phosphorus, nitrate plus nitrite, total 

nitrogen, and total phosphorus were estimated for individual 

events. Loads of ammonia were not calculated because more 

than one-half of values for post-manure samples were below 

the reporting limit. GCLAS assigns censored values their 

censoring level when plotting or using the values to compute 

loads (Koltun and others, 2006), so the reporting limit was 

substituted for dissolved reactive phosphorus and total phosphorus concentrations below detection. Event loads calculated 

for events with sample concentrations below the reporting 

limit were reported as less than the total calculated load. 

Flow-weighted mean concentrations were calculated for each 

sampler in each event by dividing the total load by the total 

volume. Flow-weighted mean concentrations were calculated 

per plot for each event by dividing the sum of the total loads 

for both samplers associated with that plot (surface runoff and 

tile flow) by the sum of the volumes for both samplers. By 

substituting the reporting limit for samples with concentrations 
Table 2. Laboratory method information for nutrients analyzed by the U.S. Geological Survey National Water Quality Laboratory and Bowling Green Srunoff and tile flow samples from eight test plots at The Ohio State University Agricultural Research and Development Center Northwest Agricultural R[USGS, U.S. Geological Survey; NWIS, National Water Information System; mg/L, milligram per liter; EPA, U.S. Environmental Protection Agency]

Constituent

NWIS 

parameter 

code

USGS National Water Quality Laboratory Bowling Green State University, Departm

Method and NWIS method code

Reporting 

limit 

(mg/L)

Method and NWIS method code 

Ammonia, filtered, as 

nitrogen

00608 Colorimetry and salicylate-hypochlorate 

(Fishman, 1993), SHC02

0.01 Colorimetry, alkaline phenol and hypochlorite (auto 

EPA–103–A, EPA 350.1 (EPA, 1993), CL015

Nitrate plus nitrite, filtered, as nitrogen 00631 Colorimetry with enzyme reduction- diazolization (Patton and Kryskalla, 

2011), RED01

0.04 Colorimetry, cadmium reduction, EPA–114–A, EPA 

(EPA, 1993), CDR06

Dissolved reactive phosphorus 00671b Colorimetry with phosphomolybdate (Fishman, 1993), PHM01 0.004 Colorimetry, acidic molybdate, EPA–118–A, EPA 3

(EPA, 1993), 00119 

Total nitrogen, unfiltered 62855 Alkaline persulfate digestion (Patton and 

Kryskalla, 2003), AKPO1

0.05 Colorimetry,alkaline persulfate digestion (EPA, 199

and Kryskalla, 2003), AKPO1

Total phosphorus, unfiltered 00665 Colorimetry, EPA 365.1 (EPA, 1993), CL021 0.004 Colorimetry by discrete analyzer, alkaline-persulfat

tion, (EPA, 1993; Patton and Kryskalla, 2003), P

aReporting limit was lower after April 1, 2017.bNWIS parameter code is for dissolved orthophosphate, as phosphorus.
12 Pilot-Scale Testing of Dairy Manure Treatments to Reduce Nutrient Transport from Land Application, Northwest Ohio, 2015–17

below detection, resultant loads and flow-weighted means may 

be biased high. However, the overall effect on the resultant 

total event load or flow-weighted mean is minor.

Because the volume, load, and flow-weighted mean 

concentration data were not normally distributed (based on 

Shapiro-Wilk tests; Helsel and Hirsch, 2002), nonparametric 

statistical tests were used. The Kruskal-Wallis test (Helsel and 

Hirsch, 2002) was used to determine if there were differences 

in median values of volume and flow-weighted mean concentration among the six test plots. If the Kruskal-Wallis test 

determined that at least one median differed from the others, a 

Dunn’s multiple comparison test (which includes a Bonferroni 

adjustment for the pair-wise significance levels; Dunn, 1964) 

on all possible pairs of plots was done to determine differences 

between any of the test plots. The Wilcoxon rank-sum test 

(Helsel and Hirsch, 2002) was used to identify any significant 

differences in median values of volume and flow-weighted 

mean concentration by manure treatment type (values for the 

three treated manure plots were compared to values for the 

three raw manure plots). The Wilcoxon signed-rank test was 

used to identify if the median of differences between paired 

observations equaled zero. Specifically, for each event, loads 

were summed for all plots by manure treatment type, and the 

test was run on the differences per event to determine if one 

treatment type had greater nutrient loads than the other treatment type. For statistical tests, a significance level of α=0.05 

was used.

Quality-Control Measures of Bias and 

Variability

To characterize bias, sampling crews collected 9 field 

blanks, 4 filter blanks, and 3 source solution blanks for 5 nutrient constituents (table 3). There were no detections in any 

of the BGSU-analyzed field blanks. There were detections, 

however, for every constituent in USGS-analyzed field blanks 

because reporting limits were lower than reporting limits for 

BGSU-analyzed samples. There were no detections in the filter 

or source solution blanks analyzed by BGSU or by the USGS.

It was not necessary to qualify any nitrate plus nitrite 

or total nitrogen results, as concentrations in surface runoff 

and tile flow samples were greater than (>) two times the 

concentrations of detections in field blanks. For the other 

constituents, if a surface runoff or tile flow sample result was 

≤ two times the associated field blank concentration during 

that event, the environmental sample result was qualified 

in the database. There were three detections of dissolved 

reactive phosphorus in USGS field blank samples, ranging 

from 0.005 to 0.009 mg/L (table 3); as a result, five USGS 

samples from the B2.6 event were qualified. For ammonia, 

the two detections in USGS samples (0.01 and 0.02 mg/L) 

were considerably less than BGSU reporting limits (<0.29 or 

<0.05 mg/L). Five USGS samples for ammonia in the B1.4 

event and 10 USGS samples in the B2.6 event were qualified. 

Because USGS samples were not used to calculate loads 

of filtered nutrients, blank detections of dissolved reactive 

phosphorus and ammonia did not affect loading calculations. 

That was not the case for total phosphorus. Total phosphorus 

was detected in 6 out of 8 USGS field blanks in concentrations 

ranging from 0.009 to 0.092 mg/L (table 3). These detections 

caused several sample results to be qualified as “V” for “value 

affected by contamination.” These qualified values were examined and used in subsequent data analysis only if the value fit 

with surrounding data points.

To characterize variability, replicate samples were collected. BGSU collected and analyzed 35 or 38 replicates 

per filtered nutrient and the USGS collected and analyzed 

21 replicates for total nutrients (table 4). For BGSU replicate 

pairs, median RPDs for ammonia, nitrate plus nitrite, and 

dissolved reactive phosphorus ranged from 0.0‒1.3 percent. 

Ammonia was only detected in five replicate pairs with a 

maximum RPD of 4.5 percent. For nitrate plus nitrite, RPDs 

were <20 percent for all but two replicate pairs, in which the 

RPDs were 25 percent (18 and 14 mg/L) and 29.8 percent 

(0.690 and 0.511 mg/L). For dissolved reactive phosphorus, 

the highest RPD (65.1 percent) resulted from two low concentrations (0.055 and 0.028 mg/L). For USGS-collected replicate pairs, median RPDs for total phosphorus and nitrogen 

were both 3.8 percent. Only one sample for total phosphorus 

showed a large difference in terms of concentration (2.88 and 

1.52 mg/L) and RPD (61.8 percent). Similarly, only one 

sample for total nitrogen showed a large difference in terms of 

concentration (12.9 and 9.95 mg/L) and RPD (25.8 percent).

Sampling Events and Concentrations 

of Nutrients in Surface Runoff and Tile 

Flow Samples

Rainfall amounts, soil moisture conditions, and time of 

year varied among events. Two events were surface only, four 

were mainly surface, one was mainly tile, and the remainder were various degrees of surface and tile (table 1). The 

mainly tile event (B1.4) occurred in winter when the ground 

was likely frozen so that water may have infiltrated through 

fissures in the subsurface. The surface-only or surface-mainly 

events likely occurred following small amounts of rainfall and 

(or) when the ground was dry due to lack of antecedent rain. 

If all bottles filled, a total of 224 bottles would be collected 

(16 samplers with 14 bottles per sampler). At least 200 bottles 

were collected during 4 events (B2.9, PM.7, PM.8, and PM.9), 

and the fewest number of bottles filled (15) occurred during 

2 small events in May 2017 (PM.2 and PM.3). Equipment 

malfunctions resulted in missing data for sampler 10 during 

B2.1‒B2.4 and for sampler 4 during B2.4−PM.8.

Concentrations of dissolved reactive phosphorus, total 

phosphorus, nitrate plus nitrite, total nitrogen, and ammonia are presented for samples collected for events during 
Sampling Events and Concentrations of Nutrients in Surface Runoff and Tile Flow Samples 13

Table 3. Quality-control field blank, filter blank, and source solution blank data for nutrients, 2015–17.

[B, baseline; BGSU, Bowling Green State University; <, less than; USGS, U.S. Geological Survey; --, not done; NA, not applicable; PM, post-manure application; detections in blanks are bolded and italicized]

Event Collecting/ analyzing agency

Concentration, in milligrams per liter

Dissolved reactive 

phosphorus Ammonia Nitrate plus nitrite Total phosphorus Total nitrogen

Field blanks

B1.1 BGSU <0.013 <0.29 <0.31 <0.013 <0.31

B1.1 USGS <0.004 <0.01 0.115 <0.004 0.16

B1.2 BGSU <0.013 <0.29 <0.31 -- --

B1.2 USGS 0.005 <0.01 0.097 0.012 0.15

B1.4 BGSU <0.013 <0.29 <0.31 -- --

B1.4 USGS 0.007 0.01a 0.100 0.022b 0.016

B2.6 BGSU <0.013 <0.29 <0.31 -- --

B2.6 USGS 0.009a 0.02a <0.04 0.092a 0.39

B2.8 BGSU <0.013 <0.29 <0.31 -- --

B2.9 USGS -- -- -- 0.009 0.08

PM.1 USGS -- -- -- 0.061a <0.05

PM.7 USGS -- -- -- 0.04b 0.126

PM.9 USGS -- -- -- <0.05 <0.25

Filter blanks

B1.4 USGS <0.004 <0.01 <0.04 NA NA

B2.5c BGSU <0.013 <0.29 <0.31 NA NA

B2.8 BGSU <0.013 <0.29 <0.31 NA NA

B2.9 USGS <0.004 <0.01 <0.04 NA NA

Source solution blanks

B2.9 USGS -- -- -- <0.004 <0.05

PM.7 USGS -- -- -- <0.004 <0.05

PM.9 USGS -- -- -- <0.05 <0.25

aSeveral results from this event were qualified because runoff sample results were less than two times the concentration measured in the field blank.

bOne result from this event was qualified because runoff sample result was less than two times the concentration measured in the field blank.

cTwo blanks were collected and analyzed on this date.

baseline 2 and post-manure application periods (fig. 5) for raw 

(orange shading; plots 4, 6, and 8) and treated (gray shading; plots 3, 5, and 7) manure plots. Manure was not applied 

to plots 1 and 2, and they are not included in any subsequent 

data analysis. Flows from plot 1 tile (sampler 1) were substantially higher than those from the other tile samplers (data 

not shown). The sampler for plot 2 surface (sampler 4) often 

failed to trigger and (or) insufficient water was collected. 

Investigators were unable to identify the causes of atypical 

volumes for samplers 1 and 4.

Dissolved Reactive and Total Phosphorus 

Concentrations

Dissolved reactive phosphorus was detected above the 

reporting limit (0.013 mg/L) in all surface runoff samples and 

in 58.6 and 75.2 percent of baseline and post-manure tile flow 

samples, respectively (fig. 5A). In two tile samplers, baseline median concentrations were less than the reporting limit 

(plots 3 and 7). In surface runoff samples, the four highest 

concentrations were from plot 8 (2.05‒2.16 mg/L). In tile flow 

samples, the two highest concentrations were from plots 8 

and 6 (0.489 and 0.343 mg/L, respectively). Concentrations 

of dissolved reactive phosphorus in tile flow samples from 

raw manure plots (plots 4, 6, and 8) post-manure application 

were noticeably higher than those in those same plots during 
14 Pilot-Scale Testing of Dairy Manure Treatments to Reduce Nutrient Transport from Land Application, Northwest Ohio, 2015–17

the baseline period; this difference was not evident for surface 

runoff samples. In addition, concentrations of dissolved reactive phosphorus were generally an order of magnitude higher 

in surface runoff than in tile flow samples.

Total phosphorus was detected above the BGSU reporting limit (0.01 mg/L) in all surface runoff samples, all postmanure tile flow samples, and in 94.9 percent of baseline tile 

flow samples (fig. 5B). The highest median total phosphorus 

concentrations were measured in surface runoff during the 

post-manure period. Concentrations of total phosphorus in 

samples when detected ranged from 0.01 to 12.8 mg/L.

Nitrate Plus Nitrite and Total Nitrogen 

Concentrations

Nitrate plus nitrite was detected above the reporting limit 

(0.31 mg/L) in all samples (fig. 5C). The lowest concentration 

(0.32 mg/L) was measured in three surface runoff samplers 

post-manure application (plots 6, 8, and 7). The five highest 

concentrations (54‒77 mg/L) were measured in tile flow from 

plot 8 (raw manure) post-manure application. Wide ranges of 

nitrate plus nitrite concentrations were measured in baseline surface runoff samples and in post-manure tile and surface runoff 

samples; however, relatively narrow concentration ranges were 

measured in baseline tile flow samples.

Total nitrogen was detected above the reporting limit 

(0.05 mg/L) in all samples (fig. 5D); the lowest concentration 

(1.49 mg/L) was from plot 8 (surface, raw manure) during the 

post-manure application period. The five highest concentrations 

(65.1‒77.2 mg/L) were measured in tile flow from plot 8, the 

same plot where the highest nitrate plus nitrite concentrations 

were found. As was also found for nitrate plus nitrite, wide 

ranges of total nitrogen concentrations were found in postmanure tile and surface runoff samples and in baseline surface 

runoff samples. Relatively narrow concentration ranges of total 

nitrogen were found in baseline tile flow samples.

Ammonia Concentrations

During baseline 2 events, there were two reporting limits 

for ammonia—0.29 mg/L before April 2017 and 0.05 mg/L 

thereafter (table 2; fig. 5E). This change occurred before the last 

two baseline events (B2.8 and B2.9); hence, some of the baseline ammonia data points are below the higher reporting limit. 

Ammonia was detected in 14.2 and 67.0 percent of baseline and 

post-manure surface runoff samples, respectively, due to the 

lower reporting limit of the latter. In tile flow samples, ammonia was not detected in any baseline samples but was detected 

in 19.0 percent of post-manure samples. When ammonia was 

detected, concentrations ranged from 0.05 to 2.6 mg/L.

Water Volumes

Volumes of surface runoff and tile flow in plots 3−8 are 

reported for 6 baseline 2 (B2.4–B2.9) and 9 post-manure events 

(table 2.1) and summarized in boxplots (fig. 6). The highest 

median volumes were found during the baseline period in tile 

samplers because of a large event in May 2017 (B2.9) when the 

ground was saturated (fig. 6). During the post-manure period, 

volumes of surface runoff in plots with raw manure (orange 

background) and treated manure (gray background) were 

similar, with median volumes ranging from 170 to 500 L. For 

tile flow, median volumes ranged from 240 to 940 L with the 

highest median and maximum volumes coming from two of the 

treated manure plots (plots 3 and 5). None of the post-manure 

volumes were significantly different by plot, as determined by 

the Kruskal-Wallis test (p-value=0.46 for tile; p-value=0.95 

for surface) or by manure treatment type, as determined by the 

Wilcoxon rank-sum test (p-value=0.10 for tile; p-value=0.76 

for surface). The volume data from plots 3−8 collected during 

the post-manure period were used to calculate loads and flowweighted mean concentrations of surface runoff and tile flow 

to compare treated manure to raw manure plots.

Table 4. Summary statistics for quality-control split replicates for nutrient samples collected and analyzed by Bowling Green State 

University or the U.S. Geological Survey, 2015–17.

[mg/L, milligram per liter; RPD, relative percent difference; <, less than; %, percent]

Constituent Reporting limit 

(mg/L)

Number 

of sample 

pairs

Number of 

samples with 

at least one 

detection

Range of differences 

(mg/L)

Median RPD Maximum 

RPD

Bowling Green State University

Ammonia nitrogen <0.29, <0.053 35 5 0‒0.013 0.5% 4.5%

Nitrate plus nitrite nitrogen <0.31 38 38 0‒4 0% 29.8%

Dissolved reactive phosphorus <0.013 35 20 0‒0.036 1.3% 65.1%

U.S. Geological Survey

Total phosphorus <0.004 21 21 0‒1.36 3.8% 61.8%

Total nitrogen <0.05 21 21 0‒3.4 3.8% 25.8%
Water Volumes 15

Baseline Post-manure application

Surface Tile

Plot

Dissolved reactive phosphorus, in milligrams per liter (mg/L) as phosphorus

0.001

0.01

0.1

1

(47) (48) (29) (43) (27) (38)

Reporting limit = 0.013 mg/L

0.001

0.01

0.1

1

(28) (34) (29) (34) (36) (30)

ND:

(44) (36) (35) (41) (33) (37)

(28) (30) (34) (48) (45) (37)

4 13 12 18 15 17 21 21 13

4 6 8 3 5 7 4 6 8 3 5 7

Raw Treated Raw Treated

75th percentile

Median

25th percentile

Largest value within 1.5 times

interquartile range above 

75th percentile

Smallest value within 1.5 times

 interquartile range below 

 25th percentile

(47)

ND: 4

Number of samples

Number not detected

Outlier

EXPLANATION

A. Dissolved reactive phosphorus

Interquartile

range

Figure 5. Concentrations of nutrients in samples from surface runoff and tile flow from plots with raw manure and treated manure at 

The Ohio State University Agricultural Research and Development Center Northwest Agricultural Research Station during baseline 2 

and post-manure periods in 2016–17. A, dissolved reactive phosphorus. B, total phosphorus. C, nitrate plus nitrite. D, total nitrogen. 

E, ammonia.
16 Pilot-Scale Testing of Dairy Manure Treatments to Reduce Nutrient Transport from Land Application, Northwest Ohio, 2015–17

0.001

0.01

0.1

1

10

(32) (32) (16) (27) (21) (26)

Reporting limit = 0.01 mg/L

0.001

0.01

0.1

1

10

(21) (25) (20) (24) (25) (23)

ND:

(37) (31) (28) (35) (30) (30)

(25) (25) (26) (41) (38) (30)

Baseline Post-manure application

Plot

Total phosphorus, in milligrams per liter (mg/L) 

Surface Tile

1 5 1

4 6 8 3 5 7 4 6 8 3 5 7

Raw Treated Raw Treated

B. Total phosphorus

75th percentile

Median

25th percentile

Largest value within 1.5 times

interquartile range above 

75th percentile

Smallest value within 1.5 times

 interquartile range below 

 25th percentile

(32)

ND: 1

Number of samples

Number not detected

Outlier

EXPLANATION

Interquartile

range

Figure 5. Concentrations of nutrients in samples from surface runoff and tile flow from plots with raw manure and treated manure at 

The Ohio State University Agricultural Research and Development Center Northwest Agricultural Research Station during baseline 2 

and post-manure periods in 2016–17. A, dissolved reactive phosphorus. B, total phosphorus. C, nitrate plus nitrite. D, total nitrogen. 

E, ammonia.—Continued
Water Volumes 17

Baseline Post-manure application

Nitrate plus nitrite, in milligrams per liter (mg/L) as nitrogen 0.1

1

10

100 (47) (48) (29) (43) (27) (38)

0.1

1

10

100 (28) (34) (29) (34) (36) (30 )

(44) (36) (32) (41) (33) (37)

(28) (30) (31) (48) (45) (33)

Surface Tile

EXPLANATION

Plot

4 6 8 3 5 7 4 6 8 3 5 7

Raw Treated Raw Treated

C. Nitrate plus nitrite

75th percentile

Median

25th percentile

Largest value within 1.5 times

interquartile range above 

75th percentile

Smallest value within 1.5 times

 interquartile range below 

 25th percentile

(47) Number of samples

Outlier

Interquartile

range

Figure 5. Concentrations of nutrients in samples from surface runoff and tile flow from plots with raw manure and treated manure at 

The Ohio State University Agricultural Research and Development Center Northwest Agricultural Research Station during baseline 2 

and post-manure periods in 2016–17. A, dissolved reactive phosphorus. B, total phosphorus. C, nitrate plus nitrite. D, total nitrogen. 

E, ammonia.—Continued
18 Pilot-Scale Testing of Dairy Manure Treatments to Reduce Nutrient Transport from Land Application, Northwest Ohio, 2015–17

Baseline Post-manure application

Total nitrogen, in milligrams per liter (mg/L) as nitrogen

1

10

100 (38) (25) (18) (32) (21) (30)

1

10

100 (21) (29) (20) (26) (27) (23)

(34) (29) (26) (32) (28) (27)

(25) (25) (26) (38) (35) (30)

Surface Tile

Plot

4 6 8 3 5 7 4 6 8 3 5 7

Raw Treated Raw Treated

75th percentile

Median

25th percentile

Largest value within 1.5 times

interquartile range above 

75th percentile

Smallest value within 1.5 times

 interquartile range below 

 25th percentile

(38) Number of samples

Outlier

EXPLANATION

Interquartile

range

D. Total Nitrogen

Figure 5. Concentrations of nutrients in samples from surface runoff and tile flow from plots with raw manure and treated manure at 

The Ohio State University Agricultural Research and Development Center Northwest Agricultural Research Station during baseline 2 

and post-manure periods in 2016–17. A, dissolved reactive phosphorus. B, total phosphorus. C, nitrate plus nitrite. D, total nitrogen. 

E, ammonia.—Continued
Water Volumes 19

Baseline Post-manure application

Ammonia, in milligrams per liter (mg/L) as nitrogen

0.01

0.1

1

(47) (48) (29) (43) (27) (38)

ND: 40 41 25 35 25 33

0.01

0.1

1

(28) (34) (29) (34) (36) (30)

Reporting limit = 0.29 mg/L

ND: 28 34 29 34 36 30

Reporting limit = 0.05 mg/L

(44) (35) (35) (41) (33) (36)

(28) (29) (34) (48) (45) (37)

23 23 18 38 43 34

Tile Surface

Plot

4 6 8 3 5 7 4 6 8 3 5 7

Raw Treated Raw Treated

E. Ammonia

75th percentile

Median

25th percentile

Largest value within 1.5 times

interquartile range above 

75th percentile

Smallest value within 1.5 times

 interquartile range below 

 25th percentile

(47)

ND: 40

Number of samples

Number not detected

Outlier

EXPLANATION

15 9 10 17 10 13

Interquartile

range

[There were two reporting limits (0.29 and 0.05 milligrams per liter) 

for baseline ammonia samples; some detections were below the 

higher reporting limit for baseline surface samples because of a 

change in the reporting limit]

Figure 5. Concentrations of nutrients in samples from surface runoff and tile flow from plots with raw manure and treated manure at 

The Ohio State University Agricultural Research and Development Center Northwest Agricultural Research Station during baseline 2 

and post-manure periods in 2016–17. A, dissolved reactive phosphorus. B, total phosphorus. C, nitrate plus nitrite. D, total nitrogen. 

E, ammonia.—Continued
20 Pilot-Scale Testing of Dairy Manure Treatments to Reduce Nutrient Transport from Land Application, Northwest Ohio, 2015–17

75th percentile

Median and 

 number

25th percentile

Largest value within 1.5 times

interquartile range above 

75th percentile

Smallest value within 1.5 times

 interquartile range below 

 25th percentile

330 Median volume

EXPLANATION

A. Baseline

Surface Tile

Volume, in liters

0

5,000

10,000

15,000

20,000

330

330

530 230 250 260 520

0

5,000

10,000

15,000

20,000

1,900 2,200 2,800

4,100

5,800

4,100

4 6 8 3 5 7

Raw Treated

4 6 8 3 5 7

Raw Treated

Plot

B. Post-manure application

Surface Tile

Plot

Volume, in liters

0

1,000

2,000

3,000

4,000

5,000

500

220 170 350 180 260

0

1,000

2,000

3,000

4,000

5,000

240

670

390

940 710 530

Interquartile

range

Figure 6. Total volumes of surface runoff and tile flow from plots with raw manure and treated manure at the Ohio State University 

Agricultural Research and Development Center Northwest Agricultural Research Station in 2016–17. A, six baseline rainfall events. 

B, nine post-manure application rainfall events.
Comparisons of Nutrient Loads and Flow-Weighted Mean Concentrations from Raw Manure and Treated Manure Plots 21

Comparisons of Nutrient Loads and 

Flow-Weighted Mean Concentrations 

from Raw Manure and Treated Manure 

Plots

Concentrations of nutrients alone do not reflect the true 

effects of different manure treatments. Instead, post-manure 

loads and flow-weighted mean concentrations of dissolved reactive phosphorus, total phosphorus, nitrate plus nitrite, and total 

nitrogen were used to quantify amounts of nutrients that may be 

released from the manure and compare treated manure to raw 

manure plots. Ammonia was not included because of the large 

number of samples below the minimum reporting limit that led 

to incomplete load and flow-weighted mean concentration estimates. Nutrient loading provides information on the quantity of 

nutrients entering a system during a given period; in this case, 

loads were calculated per event. Whereas loads provide data on 

amounts of nutrients per event, flow-weighted mean concentrations provide a measure that normalizes constituent delivery 

values. Flow-weighted mean concentrations were calculated 

to account for differences in flow among the plots during the 

same event and in the same plot for different rain events. For 

example, if two plots had similar constituent loads during a rain 

event but one of the plots had a greater flow volume, the plot 

with greater flow will have more dilution and, therefore, lower 

constituent concentrations than the plot with lower flow volume. 

Therefore, to compare the relative water quality of different 

plots across the entire pilot test period, a flow-weighted mean 

concentration was calculated for each rain event by dividing the 

plot load by the flow volume.

Loads

Loads were computed for four constituents in 12 samplers from 3 raw manure and 3 treated manure plots for each 

of the 9 post-manure events (table 2.2). The nine loads were 

summed for each plot and presented in separate bars for surface runoff and tile flow (fig. 7). Combined loads (surface and 

tile loads added together) are presented in figures 8 and 9.

Loads from Surface Runoff and Tile Flow

Loads of four constituents are shown in bar graphs to 

qualitatively compare contributions between surface runoff and 

tile flow (fig. 7). For dissolved reactive phosphorus and total 

phosphorus, higher loads resulted from surface runoff (black bars) 

than from tile flow (gray bars); this was especially evident in plot 7 

(figs. 7A‒B). In contrast, for nitrate plus nitrite and for total nitrogen, higher loads resulted from tile flow than from surface runoff 

(fig. 7C‒D). This is consistent with the different fate and transport 

mechanisms for phosphorus and nitrogen constituents. Nitrate is 

widely found in groundwater, due to its high solubility, mobility, and easy displacement by water (Follett, 1995a). Phosphorus 

in tile flow is lower than in surface runoff because phosphorus 

is sorbed onto soils from infiltrating water as it moves through 

phosphorus-deficient subsoils (Follett, 1995b).

Combined Loads

Combined loads (surface and tile added together) for nine 

post-manure events are shown in step graphs by date for each 

nutrient constituent (fig. 8). Loads from raw manure plots are 

indicated with solid lines and those from treated manure plots 

are indicated with dotted lines; the nine post-manure events 

are indicated with gray vertical lines. There was a long period 

with little-to-no surface runoff or tile flow from August through 

November 2017, indicated by long horizontal lines between 

PM.8 and PM.9 events. For dissolved reactive phosphorus 

(fig. 8A), combined loads from raw manure plots were consistently higher than those from treated manure plots. Two of the 

raw manure plots (plots 6 and 8) contributed the highest loads of 

nitrate plus nitrite (fig. 8C). In contrast, for total phosphorus and 

total nitrogen, load contributions were similar for raw manure 

and treated manure plots (figs. 8B and 8D). For both dissolved 

reactive phosphorus and total phosphorus, a large proportion 

of the loading came from the later events between July 10 and 

November 9, 2017 (PM.7, 8, and 9). In contrast, for nitrate 

plus nitrite and total nitrogen, the loads increased by more even 

increments than phosphorus throughout the season.

Combined loads are shown in bar graphs to qualitatively 

and statistically compare contributions between treated manure 

and raw manure plots; summed loads for each group of three 

plots by treatment are included above the bars (fig. 9). For dissolved reactive phosphorus, total phosphorus, and nitrate plus 

nitrite, summed event loads were higher for raw manure than 

treated manure plots; the opposite was found for total nitrogen. 

The RPDs for summed raw minus summed treated loads were 

as follows: dissolved reactive phosphorus, 34 percent; total 

phosphorus, 1.3 percent, nitrate plus nitrite, 7.8 percent; and 

total nitrogen, −6.5 percent.

For statistical analysis, loads from the three plots for 

each manure treatment type were summed for each event. The 

Wilcoxon signed-rank test was used to evaluate the differences 

in summed loads for the nine events. A significant difference 

between the manure treatment types was found for dissolved 

reactive phosphorus (p-value<0.01) but not for total phosphorus (p-value=0.50), nitrate plus nitrite (p-value=0.43), or total 

nitrogen (p-value=0.36). Calculations were done to ensure that 

the significant difference in dissolved reactive phosphorus loads 

between raw manure and treated manure plots was valid, given 

that somewhat disparate amounts of manure were applied to 

the two types of plots (table 5). Though the initial amounts of 

phosphorus applied to the three plots receiving raw manure 

(2,900,000 mg) were higher than those receiving treated manure 

(2,500,000 mg), the percentage of total phosphorus coming off the plots as dissolved reactive phosphorus was higher 

from raw manure plots (0.26 percent) than the percentage that 

came off the treated manure plots (0.22 percent). The opposite, 

however, was found for total phosphorus (table 5).
22 Pilot-Scale Testing of Dairy Manure Treatments to Reduce Nutrient Transport from Land Application, Northwest Ohio, 2015–17

4 6 8 3 5 7

Raw Treated

Plot

4 6 8 3 5 7

Raw Treated

Plot

4 6 8 3 5 7

Raw Treated

Tile

Surface

Plot

4 6 8 3 5 7

Raw Treated

Plot

0

5,000

10,000

15,000

20,000

25,000

Phosphorus, in milligrams

0

500

1,000

1,500

2,000

2,500

Nitrogen, in milligrams

Phosphorus, in milligrams Nitrogen, in milligrams

0

20,000

40,000

60,000

80,000

100,000

120,000

0

25,000

50,000

75,000

100,000

125,000

150,000

175,000

C. Nitrate plus nitrite D. Total nitrogen

A. Dissolved reactive phosphorus B. Total phosphorus

EXPLANATION

Figure 7. Loads in surface runoff and tile flow from plots with raw manure and treated manure at The Ohio State University 

Agricultural Research and Development Center Northwest Agricultural Research Station during nine post-manure application rainfall 

events in 2017. A, dissolved reactive phosphorus; B, total phosphorus; C, nitrate plus nitrite; D, total nitrogen.
Water Volumes 23

06/01/2017 07/01/2017 08/01/2017 09/01/2017

Date Date

10/01/2017 11/01/2017

Treated Raw

Load, in milligrams per event

0

25,000

50,000

75,000

100,000

125,000

150,000

PM.1 PM.4 PM.8 PM.9

06/01/2017 07/01/2017 08/01/2017 09/01/2017 10/01/2017 11/01/2017

0

5,000

10,000

15,000

20,000

25,000

30,000 PM.1 PM.4 PM.8 PM.9

06/01/2017 07/01/2017 08/01/2017 09/01/2017

B. Total phosphorus

D. Total nitrogen

A. Dissolved reactive phosphorus

C. Nitrate plus nitrite

10/01/2017 11/01/2017

Load, in milligrams per event

0

500

1,000

1,500

2,000

2,500

3,000

PM.1 PM.4 PM.8 PM.9

06/01/2017 07/01/2017 08/01/2017 09/01/2017 10/01/2017 11/01/2017

0

50,000

100,000

150,000

200,000

250,000 PM.1 PM.4 PM.8 PM.9

Plot 3

Plot 5

Plot 7

Plot 4

Plot 6

Plot 8

EXPLANATION

[PM, post-manure application rainfall event;

lines between events are for visualization 

only and do not imply that no runoff occurred]

Figure 8. Step graphs by date for combined loads (surface runoff and tile flow) in samples from plots with raw manure and treated 

manure at the Ohio State University Agricultural Research and Development Center Northwest Agricultural Research Station during 

nine post-manure application rainfall events in 2017. A, dissolved reactive phosphorus; B, total phosphorus; C, nitrate plus nitrite: D, total 

nitrogen.
24 Pilot-Scale Testing of Dairy Manure Treatments to Reduce Nutrient Transport from Land Application, Northwest Ohio, 2015–17

A. Dissolved reactive phosphorus

0

500

1,000

1,500

2,000

2,500

3,000

7,600 mg

7,600 mg

5,400 mg

B. Total phosphorus

0

5,000

10,000

15,000

20,000

25,000

30,000

76,000 mg 75,000 mg

C. Nitrate plus nitrite

0

25,000

50,000

75,000

100,000

125,000

150,000

320,000 mg 296,000 mg

D. Total nitrogen

0

50,000

100,000

150,000

200,000

250,000

519,000 mg 554,000 mg

Event

PM.1

PM.2

PM.3

PM.4

PM.5

PM.6

PM.7

PM.8

PM.9

Phosphorus, in milligrams Nitrogen, in milligrams

Phosphorus, in milligrams Nitrogen, in milligrams

4 6 8 3 5 7

Raw Treated

Plot

4 6 8 3 5 7

Raw Treated

Plot

0 4 6 8 3 5 7

Raw Treated

Plot

4 6 8 3 5 7

Raw Treated

Plot

Summed loads, 

in milligrams

EXPLANATION

[mg, milligram; PM, post-manure application rainfall event]

Figure 9. Combined loads (surface runoff and tile flow) in samples from plots with raw manure and treated manure at the Ohio State 

University Agricultural Research and Development Center Northwest Agricultural Research Station during nine post-manure application 

rainfall events (PM.1−PM.9) in 2017. A, dissolved reactive phosphorus; B, total phosphorus; C, nitrate plus nitrite; D, total nitrogen.
Corn Yields 25

Flow-Weighted Mean Concentrations

Flow-weighted mean concentrations for each nutrient 

constituent were computed for surface runoff or tile flow 

(table 2.3) and for combined surface runoff and tile flow 

(table 2.4) for each of the nine post-manure events. Combined 

(surface runoff and tile flow) values for the three raw manure 

plots (orange shading) and three treated manure plots (gray 

shading) are shown in boxplots (fig. 10). The p-values shown 

on the graphs result from Kruskal-Wallis multiple comparison tests for differences in flow-weighted means by plot, and 

Wilcoxon rank-sum tests for differences in flow-weighted 

means by manure treatment (raw versus treated). For examination by plot, flow-weighted means (number [n]=9) for each 

of the six plots were compared; for examination by treatment, flow-weighted means (n=27) for the three raw manure 

plots were compared to flow-weighted means (n=27) for the 

three treated manure plots. Dissolved reactive phosphorus 

was the only constituent where there was a significant difference (p-value<0.0001) in flow-weighted mean concentrations 

by plot. The letters at the top of figure 10A are used to show 

the results of a Dunn’s multiple comparison test for all possible pairs of test plots. Test plots that share the same letter 

have sample populations that are not significantly different 

at the α=0.05 level of significance. Two treated manure plots 

(plots 3 and 5) had significantly lower medians than all three 

of the raw manure plots. Flow-weighted mean concentrations 

of dissolved reactive phosphorus and total phosphorus were 

significantly different (p-value<0.0001 and p-value<0.01, 

respectively) by manure treatment type (figs. 10A and 10B). 

Flow-weighted mean concentrations of nitrate plus nitrite 

(fig. 10C) and total nitrogen (fig. 10D) were not significantly 

different by treatment type.

Corn Yields

After the last event in November 2017, the corn was 

harvested and corn yields from the test plots were calculated. 

Based on the weight of corn obtained from the two rows 

harvested, a yield of bushels per acre was calculated (table 6). 

Mean yields from plots with treated manure was 3 percent 

lower than plots treated with raw manure, and yield from plots 

with no manure was 10 percent lower than plots treated with 

raw manure. Statistical analysis of yield differences was not 

possible because of the small number of data points; however, 3 percent is likely within the range of random variation, 

whereas 10 percent may exceed that random variation.

Table 5. Total phosphorus applied to 3 raw and 3 treated manure plots and percentages of dissolved reactive phosphorus and total 

phosphorus in combined surface runoff and tile flow.

Type of application or load Raw manure Treated manure

Total phosphorus applied to each plot, in milligrams 970,000 830,000

Total phosphorus applied to three plots, in milligrams 2,900,000 2,500,000

Dissolved reactive phosphorus load from three plots, in milligrams of phosphorus 7,600 5,400

Total phosphorus applied that was measured in dissolved reactive phosphorus load from three plots, 

in percent

0.26 0.22

Total phosphorus load from three plots, in milligrams of phosphorus 76,000 75,000

Total phosphorus applied that was measured in total phosphorus load from three plots, in percent 2.60 3.00

Table 6. Corn yields from Ohio State University Agricultural Research and Development Center Northwest Agricultural Research 

Station test plots, November 2017.

Treatment Plot Yield, in bushels per acrea Mean yield

Control/no manure 1 126 132

2 139

Treated manure 3 140 141

5 128

7 156

Raw manure 4 134 145

6 155

8 148

aHarvested corn weight was corrected for moisture content above 15 percent.
26 Pilot-Scale Testing of Dairy Manure Treatments to Reduce Nutrient Transport from Land Application, Northwest Ohio, 2015–17

C B

A. Dissolved reactive phosphorus

Flow-weighted mean, in milligrams phosphorus per liter 

0

0.5

1.0

1.5

2.0

By plot, p<0.0001

By treatment, p<0.0001

B. Total phosphorus

0

2

4

6

8

10 By plot, p=0.09

By treatment, p<0.01

C. Nitrate plus nitrite

Flow-weighted mean, in milligrams nitrogen per liter 

Flow-weighted mean, in milligrams phosphorus per liter Flow-weighted mean, in milligrams nitrogen per liter 

0

10

20

30

40

50 By plot, p=0.84

By treatment, p=0.39

D. Total nitrogen

0

25

50

75 By plot, p=0.80

By treatment, p=0.76

Plot

4 6 8 3 5 7

Raw Treated

Plot

Plot

4 6 8 3 5 7

Raw Treated

Plot

4 6 8 3 5 7

Raw Treated

4 6 8 3 5 7

Raw Treated

A A A B B AB

75th percentile

Median

25th percentile

Largest value within 1.5 times

interquartile range above 

75th percentile

Smallest value within 1.5 times

 interquartile range below 

 25th percentile

Outlier

EXPLANATION

Interquartile

range

p-value results of a Kruskal-Wallis test 

for comparisons by plot and Wilcoxon 

rank-sum test for comparisons by 

manure treatment (raw versus treated) 

are shown on the graphs. Sample 

populations of dissolved reactive 

phosphorus that share the same letter 

symbol are not significantly different at 

the 0.05 level of significance.

Figure 10. Combined flow-weighted mean concentrations (surface runoff and tile flow) in samples from plots with raw manure and 

treated manure at the Ohio State University Agricultural Research and Development Center Northwest Agricultural Research Station 

during nine post-manure application rainfall events (PM.1−PM.9) in 2017. A, dissolved reactive phosphorus; B, total phosphorus; 

C, nitrate plus nitrite; D, total nitrogen.
Summary and Conclusions 27

Summary and Conclusions

Nutrient excesses from large livestock operations are a 

growing concern because of the potential to cause eutrophication of surface waters from runoff and permeate soils to reach 

groundwater resources. In the Western Lake Erie Basin where 

there is a high density of animal agriculture, phosphorus 

loading to Lake Erie from dairy manure and fertilizer applications is a likely contributor to harmful algal blooms (HABs). 

One option to help alleviate nutrient loads is to treat manure 

to reduce the water content and slow and (or) reduce the 

release of nutrients when applied to soils. Manure treatment 

may enable more economical transport to fields for application and slow the transport of nutrients to surface water and 

groundwater. A promising technology, tested during this study, 

is solids-liquid separation enhanced with iron and aluminum 

salts with the addition of organic polymers.

A pilot-scale field study at The Ohio State University 

Agricultural Research and Development Center Northwest 

Agricultural Research Station was done to estimate the 

performance of treated manure (coagulant/polymer mixture) 

relative to liquid lagoon (raw) manure in a natural field setting. Samples were collected and analyzed for concentrations 

of nitrogen and phosphorus constituents that resulted from 

surface runoff and tile flow from pilot-scale test plots. Tipping 

buckets and refrigerated automatic samplers contained in 

a central building were used for collection of volume and 

water-quality data. Treated manure was applied to three plots 

and raw manure to another three plots. Data were collected 

during rainfall events that resulted in substantial surface 

runoff and (or) tile flow—13 baseline events and 9 events 

after manure application (post-manure events). The first four 

baseline events (baseline 1) were used to establish protocols 

and collect initial quality-control samples. Samples from the 

next 9 baseline events (baseline 2) and 9 post-manure events 

were used to report nutrient concentrations from the 6 plots; 

samples from 6 baseline and all post-manure events were used 

to report flow volumes. Loads and flow-weighted mean concentrations were calculated and used to compare surface runoff 

and tile flow from three treated manure to three raw manure 

test plots during the nine post-manure events.

Samples were retrieved from the automatic samplers and 

analyzed for dissolved reactive phosphorus, total phosphorus, 

nitrate plus nitrite, total nitrogen, and ammonia. To characterize bias and variability, quality-control samples were collected 

and analyzed throughout the sampling period. Concentrations 

for baseline 2 and post-manure events were as follows: 

Dissolved reactive phosphorus, less than (<) 0.013 to 2.16 milligrams per liter (mg/L); total phosphorus <0.01 to 12.8 mg/L; 

nitrate plus nitrite, 0.32 to 77 mg/L; total nitrogen, 1.49 to 

77 mg/L; and ammonia, <0.05 to 2.6 mg/L.

Water volumes in surface runoff and tile flow were 

reported from six baseline 2 and nine post-manure events. 

There were no significant differences in volumes of surface 

runoff or tile flow by plot or by manure treatment type for 

the nine post-manure events. Baseline 2 volumes were not 

used for statistical tests. The volumes measured during the 

post-manure period were used to calculate loads and flowweighted mean concentrations of dissolved reactive phosphorus, nitrate plus nitrite, total phosphorus, and total nitrogen; 

these were used to compare flow from treated manure plots 

to flow from raw manure plots. Ammonia was not included 

because of the large number of samples below the minimum 

reporting limit.

For nitrogen during the post-manure period, higher loads 

resulted from tile than surface runoff. For phosphorus, the 

opposite was true in that higher loads resulted from surface 

runoff than tile flow. This is consistent with a different fate and 

transport mechanism for phosphorus and nitrogen constituents. 

Combined loads (surface and tile) were used in subsequent 

data analysis. In terms of timing of combined loads, a large 

proportion of the phosphorus loading came from the last three 

events. For nitrogen, however, the loads increased by more 

even increments than phosphorus throughout the season. 

Combined loads of dissolved reactive phosphorus were significantly different by manure treatment type; loads were higher 

for the raw manure treated plots than for the treated manure 

plots. Combined loads of total phosphorus, nitrate plus nitrite, 

or total nitrogen were not significantly different by manure 

treatment type.

Combined (surface runoff and tile flow) flow-weighted 

mean concentrations were also examined. Combined flowweighted mean concentrations of dissolved reactive phosphorus were significantly different by plot and by manure 

treatment type. Flow-weighted mean concentrations of total 

phosphorus were significantly different by treatment type 

but not by plot. Flow-weighted mean concentrations of total 

nitrogen and nitrate plus nitrite were not significantly different 

by plot or by treatment type.

The purpose of treating the liquid dairy manure with a 

coagulant and cationic polymer was to dewater the manure 

and sequester nutrients in a solid matrix that retained more 

nutrients in soil, better matching the rate of assimilation by 

crops. In theory, this would reduce the amount of free nutrients in the soil, which is susceptible to hydrological transport. Degradation of the matrix in the soil releases nutrients 

throughout the growing season instead of it all being available at the time of application. Differences in loads and 

flow-weighted mean concentrations between raw manure and 

treated manure plots indicate that dissolved reactive phosphorus was likely retained in the soil and hydrological transport 

was reduced for the plots amended with the treated manure 

as compared to raw manure. HABs in the Western Lake Erie 

Basin are promoted more by dissolved phosphorus than total 

phosphorus so reduction in dissolved phosphorus transport 

may be more effective for reducing the risk of HAB formation. In addition, corn yields from plots with treated and raw 

manure were in a similar range. The use of this coagulant/

polymer mixture, therefore, shows promise in helping to 

reduce dissolved forms of phosphorus loading into waters 

of the Western Lake Erie Basin and thus reducing the risk 

of HABs. Additional field tests are needed to reproduce and 
28 Pilot-Scale Testing of Dairy Manure Treatments to Reduce Nutrient Transport from Land Application, Northwest Ohio, 2015–17

confirm these results and to investigate the transportation cost 

savings that the treatment provides; these studies are in progress. Future studies could focus on scaling-up testing from the 

pilot to the full-scale field level.

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A.A., 2007, Solid-liquid separation of dairy manure with 

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and Islam, K.R., 2008, Agricultural impacts on lake and 

stream water quality in Grand Lake St. Marys, Western 

Ohio: Water, Air, and Soil Pollution, v. 193, no. 1–4, 

p. 309–322.

Koltun, G.F., Eberle, M., Gray, J.R., and Glysson, G.D., 

2006, User’s manual for the Graphical Constituent Loading 

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Techniques and Methods, book 4, chap. C1, 51 p.

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30 Pilot-Scale Testing of Dairy Manure Treatments to Reduce Nutrient Transport from Land Application, Northwest Ohio, 2015–17

Appendix 1. Sample Processing Cheat Sheet

This document was used in the field and served as 

concise step-by-step instructions for collecting and processing samples from 16 automatic samplers at The Ohio State 

University Agricultural Research and Development Center 

Northwest Agricultural Research Station, 2015–17. Samples 

are processed within 72 hours of automatic sampler collection.

1. Label bags and USGS sample bottles. Label a set of 

Whirl-pak bags for filtered nutrients and 125-mL clear 

polyethylene bottles for total nutrients with the sampler 

number and the order in the sampler (i.e. sampler 2, 

bottle 7 would be “2-7”).

2. Rinse bottles 2X with deionized water (DIW). The 

labeled USGS bottles, if not pre-rinsed, are rinsed 2 

times with DIW.

3. Total nutrients. Shake the 1-L bottle. Pour a small 

amount of sample into the WCA bottle to rinse the 

bottle. Shake the 1-L bottle again and fill the WCA 

bottle to the shoulder. Acidity with 1 mL 4.5 N H2SO4

and place the acid sticker on the WCA bottle. Chill the 

WCA bottle.

4. Filtered nutrients. Process the filtered sample. Remove 

20 mL using a syringe, insert a filter into the Luer-lock, 

and filter the sample into a Whirl-pak bag.

5. OPTIONAL USGS. Filtered nutrient analysis by the 

USGS is done for QC purposes or at the request of 

BGSU. Use a 125-mL brown polyethylene bottle that 

has been rinsed 2X with DIW. Using a syringe, remove 

approximately 20 mL from the 1-L bottle to rinse the 

syringe; discard the rinse. Remove a second 20-mL 

aliquot and insert a filter into the Luer-lock. Filter 5-10 

mL through the filter into the brown bottle, rinse the 

bottle with this small amount of water, and discard the 

rinse water. Resume filtering and immediately chill the 

brown bottle. You need to provide at least 10–20 mL in 

the brown bottle.

6. Save water for pH and spC. From each sampler

composite the water from two of the Isco bottles into a 

500-mL bottle (staggered, for example bottles #1 and #7 

OR #5 and #11). Measure the pH and specific conductance of each within 24 hours of sample collection.

7. Discard the water from the rest of the bottles.

8. USGS paperwork (next working day is OK). Write in 

the sample collection date/time and your initials on the 

pre-printed label. Some labels need the last two digits of 

the site ID. Fill out an Analytical Service Request (ASR) 

form. To a pre-printed surface or tile ASR, enter

a The last two digits of the Station ID

b Begin Date and Begin Time

c To the Station Name, enter the plot #; to the Field 

ID, enter the Sampler #

d Collected by, phone number, and date Shipped

e Specific conductance and pH values (measure and 

write this on the field form also).

Make a copy of the ASR to include with the samples. 

Ship the samples by overnight mail on ice within 72-hours of 

collection.

National Water Quality Laboratory, Building 95, Entrance 

E3, Denver Federal Center, Denver, CO 80225-0046 Phone: 

303-236-3707.
Appendix 2. Data Tables 31

Appendix 2. Data Tables

Total volume, nutrient loads, and flow-weighted mean 

concentrations of nutrients for 12 samplers (6 plots) during 

9 post-manure (PM) rainfall events that resulted in substantial 

surface runoff and (or) tile flow at the Ohio State University 

Agricultural Research and Development Center Northwest 

Agricultural Research Station, 2015‒17, are provided in 

this appendix (tables 2.1–2.4, available for download at 

https://doi.org/10.3133/sir20205015).

Table 2.1. Total volume, in liters, for 12 samplers during 6 baseline 2 and 9 post-manure application rainfall events that resulted in 

substantial surface runoff or tile flow at the Ohio State University Agricultural Research and Development Center Northwest Agricultural 

Research Station, 2015–17.

Table 2.4. Flow-weighted mean concentrations of nutrients, in milligrams per liter, for 6 plots during 9 post-manure application rainfall 

events that resulted in substantial surface runoff and tile flow (combined) at the Ohio State University Agricultural Research and 

Development Center Northwest Agricultural Research Station, 2017.

Table 2.2. Nutrient loads, in milligrams, for 12 samplers during 9 post-manure application rainfall events that resulted in substantial 

surface runoff or tile flow at the Ohio State University Agricultural Research and Development Center Northwest Agricultural Research 

Station, 2017.

Table 2.3. Flow-weighted mean concentrations of nutrients, in milligrams per liter, for 12 samplers during 9 post-manure application 

rainfall events that resulted in substantial surface runoff or tile flow at the Ohio State University Agricultural Research and Development 

Center Northwest Agricultural Research Station, 2017.
For more information about this publication, contact:

Director, Ohio-Kentucky-Indiana Water Science Center

U.S. Geological Survey

6460 Busch Boulevard Suite 100

Columbus, OH 43229–1737

614–430–7700

For additional information, visit:

https://www.usgs.gov/centers/oki-water

Publishing support provided by the Madison and Rolla Publishing 

Service Centers

Francy and others—Pilot-Scale Testing of Dairy Manure Treatments to Reduce Nutrient Transport from Land Application, Northwest Ohio, 2015–17—SIR 2020–5015

ISSN 2328-0328 (online)

https://doi.org/10.3133/sir20205015