Frequency of Germinable Weed Seeds in Poultry Litters of North Carolina

Purpose

With high input costs in 2022, many farmers are looking for affordable sources of nutrients.  Poultry litter is in high abundance in areas of intense poultry production, such as North Carolina. However, a common concern for farmers is whether poultry litter will carry weed seed onto their farms. With the need to better distribute nutrients throughout these areas, the transport of poultry litter is necessary.    Overcoming the concern about weed seeds is critical to improve these nutrient imbalances. Therefore, a germination study was conducted on 61 random poultry litters collected across North Carolina to determine the presence of viable weed seeds.

What Did We Do?

A series of 61 poultry litters were submitted to NC State University for testing, collected from industry representatives and Extension Agents across the state. Poultry litters were diluted with potting media to allow for germination of any existing weed seeds at a 9:1 (potting media:litter) ratio on a dry weight basis. Germination studies were then conducted using 20 g of the potting media-litter mix, replicated 5 times. Positive controls included potting media alone, and potting media mixed with poultry litter to verify there was no inhibitory effect of the poultry litter on germination. Both positive controls were spiked with one of three weed species at varying rates: 50 mustard, 50 rye, or 30 sicklepod. Additionally, three subsamples (20 g) of 10 of the poultry litters were wet sieved using three sieves with 2.8-, 1.0-, and 0.4-mm mesh sizes and dried at 35 °C. Seeds were counted under a dissecting microscope, and when located, seeds were removed and tested for viability using the imbibed seed crush test as described by Borza et al. (2007).

What Have We Learned?

Germination studies suggest small numbers of viable weed seeds, as only one seed germinated from unspiked samples. However, total weed counts suggest there can be high total seed numbers in the litters, with an average seed content of 1.17 seeds/100-g. Additionally, approximately 15% of the seeds collected were viable.

Future Plans

We intend to continue researching this topic and hope to further understand the impact of stockpiling, litter management, and handling on viable weed seeds in litter sources.

Authors

Stephanie B. Kulesza, Nutrient Management and Animal Waste Specialist, NC State University

Corresponding author email address

Sbkulesz@ncsu.edu

Additional authors

Ramon Leon, Weed Biology and Ecology Specialist, NC State University

Miguel Castillo, Forage Specialist, NC State University

Stephanie Sosinski, Forage Lab Technician, NC State University

 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.

Groundwater Nitrate Variability at the Field Level: How to Unravel the Puzzle

Purpose

Typical groundwater monitoring for nitrate concentrations in single monitoring wells and monitoring- well networks cannot always correctly explain the nitrate distribution in groundwater at the field level. Nitrate can originate from various sources (e.g., chemical fertilizers, manure, etc.) and at various times (e.g., current practice versus legacy nitrate). Nitrate in groundwater can also vary spatially, temporally, and with groundwater flow direction. Figure 1 illustrates some of the causes of spatial and temporal nitrate variations at the field level related to water and dissolved nitrate movement. Figure 2 is one example of how complex geology (e.g., stream meanders) can affect, and complicate, groundwater and nitrate movement.

Figure 1. Factors that can contribute to spatial and temporal variations in nitrate in groundwater at the field level (with permission from the Journal of Nutrient Management).
Figure 2. Common example of a complex hydrogeology that can affect groundwater flow and nitrate concentrations at the field level.

This presentation discusses a case study where we used high resolution and advanced methods to help identify the source(s) of nitrate in groundwater at the field level. These approaches can help in permitting and other issues that center around the reporting of elevated nitrate concentrations in groundwater.

What Did We Do?

This case study involves the “upgradient” monitoring well (MW-D) in a “simple,” sandy, water table aquifer at a commercial dairy. The regulators initially considered the nitrate concentration observed at the upgradient monitoring well, MW-D in Figure 3, which was well below the drinking water criterion of 10 milligrams per liter (mg/L) to be representative of the regional groundwater (background) entering the site. However, the literature indicated the regional groundwater already contained very high nitrate concentrations that originated over many decades of chemical fertilizer applications (“legacy nitrate”). We used both high resolution and advanced approaches to unravel the cause of the anomalous nitrate concentration in groundwater at “upgradient” monitoring well MW-D so we could help negotiate an appropriate and reasonable background nitrate concentration for the dairy’s permit.

Figure 3. Case study – unraveling changes in local groundwater flow directions and nitrate concentrations using continuous groundwater level monitoring.

First, we suspected that MW-D, which is located close to the vegetative treatment area (VTA), was not a representative well for groundwater quality due to large, episodic recharge events caused by ponding on the VTA. To test this hypothesis, we installed three monitoring wells just upgradient from MW-D (MW-A, -B, and -C in Figure 3), equipped all four monitoring wells with water-level data loggers, and used these data to calculate continuous groundwater flow direction changes with time. Monitoring wells MW-A, -B, -C, and –D are screened between 28-38, 28-38, 26-36, and 22-32 feet below ground level, respectively, to monitor the water table. The groundwater elevation data and monthly nitrate monitoring (Figure 3) indicated (1) the water table fluctuated significantly and episodically in response to precipitation and ponding on the VTA, (2) the groundwater flow direction changed significantly when ponding occurred (so what is “upgradient”?), and (3)  the nitrate concentration changed at upgradient monitoring well MW-A from more than 40 mg/L when regional groundwater flowed onto the site to about 2 mg/L when ponding caused an episodic reversal of the groundwater flow direction.

Second, we tested groundwater from selected monitoring wells and ponded water on the VTA for natural isotopes in water molecules (18O and 2H). The water table monitoring wells were screened across the water table with top of screen tops ranging between 22 and 50 feet below ground level, depending on ground elevation. Two of the monitoring wells were deep wells with screen depths of 80 to 85 and 52 to 57 feet below ground level. The 18O and 2H concentrations in precipitation vary with temperature and therefore can vary from storm to storm and season to season. Groundwater acquires a “uniform” 18O and 2H signature which approximates the weighted average of the precipitation over the year(s) and therefore, can be different from that of an individual storm. Figure 4 shows that the 18O and 2H signature of groundwater at the presumptive background well (MW-D) changed from its groundwater signature before the storm to the signature of the ponded water in the VTA, due to a large spring storm that caused flooding on the VTA. The changes in 18O and 2H in groundwater at MW-D are consistent with the rapid groundwater mounding at MW-D. Furthermore, the low nitrate concentration in groundwater at MW-D was consistent with the low nitrate concentration observed in the ponded water on the VTA; the ponded water on the VTA diluted the legacy nitrate from the regional groundwater.

Figure 4. Case study – unraveling changes in groundwater nitrate concentrations due to episodic groundwater mounding using water isotopes.

Finally, we tested nitrate (NO3) ions in the groundwater for their 15N and 18O signatures. Nitrate isotopes have been used to distinguish between nitrate sources, such as chemical fertilizer and manure, for more than 20 years. Figure 5 shows the chemical and manure nitrate source fields based on nitrate isotopes. The groundwater at monitoring wells MW-A through MW-C had both isotopic signatures indicative of chemical fertilizer (legacy nitrate) and elevated nitrate concentrations consistent with those reported for the regional groundwater.

Figure 5. Case study – unraveling the source of legacy nitrate using nitrate isotopes.

What Have We Learned?

For this case study, we needed to demonstrate that the presumptive background monitoring well nitrate was not truly representative of background groundwater nitrate and explain why. Otherwise, the dairy would have been encumbered by an unfairly low background concentration in its permit. Data from typical groundwater monitoring well networks and monitoring plans may not be sufficient for either of these requirements.

High resolution and advanced monitoring approaches, such as using data loggers for continuous water level monitoring and groundwater flow maps and isotopic tracers for sourcing water and nitrate, have been around for decades. Using these approaches to unravel puzzling agricultural problems can be very helpful.

Future Plans

We will continue to use these and other high resolution and advanced investigative techniques, honed in the field of contaminant hydrogeology, to solve agricultural surface water and groundwater issues.

Authors

Michael Sklash, Ph.D., Senior Hydrogeologist, Dragun Corporation, Farmington Hills, MI. Msklash@dragun.com

Additional author

Fatemeh Vakili, Ph.D., Hydrogeologist, Dragun Corporation, Windsor, ON

Additional Information

See Journal of Nutrient Management, 2020 and 2021

 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.

Improving Production and Minimizing Nutrient Loss in Grazing Systems through the Use of Grass-Legume Mixtures

Purpose

Feed costs are typically one of the largest costs of dairy and beef cattle production. Grazing is an option that can greatly reduce the need for, and cost of, hay production.  The addition of legumes into the pasture can reduce the need for additional fertilizer.Unfortunately, grazing can also accelerate nutrient cycling and increase nitrogen (N) leaching.  This study examines the effect of adding birdsfoot trefoil (Lotus corniculatus L.), a legume with condensed tannins (CT), to the grazing system. Condensed tannins are noted for their ability to improve nutrient utilization and shift N excretion from the urine to the feces.  Nutrient cycling under the grass-legume mixtures and grass monocultures were evaluated.  The nitrogen content in urine and feces of cattle grazing forages with, and without CT, was also examined and compared to a traditional total mixed ration (TMR) diet.

What Did We Do?

Four grasses, tall fescue (Schedonorus arundinaceus Schreb.), meadow bromegrass (Bromus biebersteinii Roem. & Schult.), orchardgrass (Dactylis glomerata L.), and perennial ryegrass (Lolium perenne L.) in monocultures, and in binary mixtures with birdsfoot trefoil (Lotus corniculatus L.) were evaluated. The study was conducted at the Utah State University Intermountain Irrigated Pasture facility in Lewiston, Utah.  Jersey dairy heifers (~450 lbs) were used to rotationally graze the paddocks with heifers being moved to a new paddock every seven days for a 35-day rotation cycle. Pastures were irrigated every two weeks.  All pastures were fertilized with Chilean nitrate (25 lbs N/acre) in April.  Grass monocultures also received Feathermeal (31 lbs N/acre) in the late spring/early summer, and an additional dose of Chilean nitrate (25 lbs N/acre) in July.  Body weight, and urine and fecal (grab) samples were collected before each grazing event, and at the end of the grazing season.  Urine samples were analyzed for urea-N on a Lachat FIA analyzer.  Fecal samples were analyzed for total N and total carbon by combustion analysis using an Elementar varioMAX CN elemental analyzer, and ammonia-N on a FIAlab 2500 instrument. Soil samples were collected at the beginning and end of each grazing season, and analyzed for available N (nitrate and ammonia) on a Lachat FIA analyzer.  Soil water (leachate) N was monitored by means of zero-tension lysimeters bi-weekly during the growing season, and as much as possible in the spring and fall.  Leachate samples were analyzed for nitrate-nitrite concentration on a Lachat FIA analyzer. The amount of leachate produced from each lysimeter was measured, and total Leachate N determined. Forage protein levels were determined using NIR. Nutrient cycling in the urine and feces were analyzed and compared to the overall protein levels in the forage.

What Have We Learned?

Average daily gains were greater with the grass-legume mixtures than the monocultures (Figure 1). This is most likely due to the higher protein content of the grass-legume mixtures versus the grass monocultures (data not shown).

Figure 1. Average Daily Gain under grass-legume mixtures versus grass monocultures versus a total mixed ration in a feedlot setting

Both the urea-N concentration in the urine (Figure 2), and the fecal N content (Figure 3) were higher in the grass-legume mixtures than the grass monocultures.  This is most likely the result of being fed a higher protein content diet in the grass-legume mixtures.

Figure 2. Urea-N content in urine when grazing grass-legume mixtures versus grass monocultures versus a total mixed ration in a feedlot setting
Figure 3. Fecal Total N content when grazing grass-legume mixtures versus grass monocultures versus a total mixed ration in a feedlot setting

Although the grass monocultures were not heavily fertilized, and the protein content of the monocultures was lower than that of the grass-legume mixtures, nitrogen leaching observed in the leachate was generally higher under the grass monocultures.

Figure 4. Total NO3 lost in leachate per zero-tension lysimeter per year

Grass-legume mixtures may be able to more effectively capture nitrogen due to the differences in the rooting structure and the microbial populations. The grass-legume mixtures were also better economically.

Future Plans

The forage type explains approximately 40% of the variability. We plan to examine the impact of breed on the rates of gain and nutrient cycling next.

Authors

Rhonda Miller, Ph.D., Agricultural Environmental Quality Extension Specialist, Utah State University

Corresponding author email address

rhonda.miller@usu.edu

Additional authors

Blair Waldron, ARS Forage & Range Research Lab; Clay Isom, Utah State University; Kara Thornton – Kurth, Utah State University; Kerry Rood, Utah State University; Earl Creech, Utah State University; Mike Peel, ARS Forage & Range Research Lab; Jacob Hadfield, Utah State University; Ryan Larson, Utah State University, and Marcus Rose, Bureau Land Management

Additional Information

Hadfield, J., B. Waldron, S. Isom, R. Feuz, R. Larsen, J. Creech, M. Rose, J. Long, M. Peel, R. Miller, K. Rood, A. Young, R. Stott, A. Sweat, and K. Thornton. 2021. The effects of organic grass and grass-birdsfoot trefoil pastures on Jersey heifer development: Heifer growth, performance, and economic impact. J. Dairy Sci. 104(10): 10863-10878. DOI: 10.3168/jds.2020-19524.

Rose, M., B. Waldron, S. Isom, M. Peel, K. Thornton, R. Miller, K. Rood, J. Hadfield, J. Long, B. Henderson, and J. Creech.  2021. The effects of organic grass and grass-birdsfoot trefoil pastures on Jersey heifer development: Herbage characteristics affecting intake.  J. Dairy Sci. 104(10): 10879-10895. DOI: 10.3168/jds.2020-19563.

Acknowledgements

Funding for this project was provided by OREI, Western SARE, and Utah State University Experiment Station.

 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.

Using COMET Tools to Help Farms Plan for the Future

Purpose

Climate change presents real threats to U.S. agricultural production, forest resources and rural economies. Producers and land managers across the country are experiencing climate impacts on their operations through shifting weather patterns and increasingly frequent and severe storms, floods, drought and wildfire. However, producers and land managers also have an opportunity to help address climate change by mitigating greenhouse gas emissions and sequestering soil carbon.

NRCS Conservation Practice Standards have been used for decades by farmers and ranchers to enhance agricultural lands by reducing soil erosion, improving water quality, creating habitat for wildlife and a number of other benefits. In addition to these benefits, many of these practices may reduce greenhouse gas emissions and sequester carbon in woody biomass and soils. As farms look to the future, USDA’s CarbOn Management Evaluation Tools (COMET) can help estimate climate benefits of adopting certain conservation practices for cropland, pasture, rangeland, livestock operations and energy.

What Did We Do?

COMET-Farm provides a complete analysis for site-specific assessment of greenhouse gas emissions and carbon sequestration. COMET-Farm utilizes peer-reviewed greenhouse gas inventory methods sanctioned by the U.S. Department of Agriculture. Results are provided for carbon dioxide, nitrous oxide, methane and soil carbon. COMET-Planner is a web-based tool designed to provide approximate greenhouse gas mitigation potentials of implementing NRCS conservation practice standards.

The COMET tools were developed through a partnership between USDA NRCS and Colorado State University. There is more than a decade of model development experience reflected in COMET. COMET-Farm uses information on management practices on an operation together with spatially-explicit information on climate and soil conditions from USDA databases (which are provided automatically in the tool) to run a series of models that evaluate sources of greenhouse gas emissions and carbon sequestration. By integrating NRCS SSURGO database and site-specific climate data, locality-specific results are presented to COMET-Farm users. There are several modules nested within the model (i.e., Croplands, Livestock, Agroforestry, Energy), and the model relies on biogeochemical process models, IPCC methodologies, and a number of peer reviewed research results.

What Have We Learned?

Put generally, farmers, ranchers, and others can use COMET to easily estimate farm-scale GHG emissions and to explore the impacts of alternative management strategies on their net emissions. The COMET tools have a variety of additional stakeholders and users, including USDA, state governments, companies, carbon finance groups, non-governmental organization and educational institutions. There are many ways the tools can advance climate smart farming for individual farms, such as: use as part of traditional NRCS conservation planning assistance, evaluation of opportunities for farms to participate in carbon markets, as part of development of a carbon farm plan, or to quantify climate benefits for use in direct consumer marketing of farm products. Additionally, other organizations have advanced climate smart farming principles through the use of COMET, both via private industry and state government programs to incentivize conservation practices based on GHG emission reductions quantified with the tool. For examples of success stories using the COMET tools, see the links under Additional Information.

Future Plans

We look forward to continued use of the COMET tools to advance implementation of climate smart agriculture and forestry practices across the U.S.

Authors

Allison Costa, Air Quality Engineer, United States Department of Agriculture

Corresponding author email address

allison.costa@usda.gov

Additional Information

The COMET tools are available online at:  https://comet-farm.com/ and http://comet-planner.com/.

The COMET help desk, YouTube training videos, a calendar of upcoming training events and other resources can be accessed at http://comet-farm.com/HelpPage.

Example of COMET-Planner use by Ben & Jerry’s: https://www.usda.gov/media/blog/2016/12/21/climate-smart-conservation-partnership-serves-two-scoops-farm-solutions

Example of COMET-Planner use by the California Healthy Soils Program: https://www.theclimategroup.org/our-work/news/californias-healthy-soils-program-interview-dr-amrith-gunasekara

 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.

Reporting 15 year’s of experience in WISE Aeration at manure and wastewater treatment ponds (updated)

Purpose

This presentation offers information about a low-energy high-performance manure and/or wastewater aeration technology.  Referred to as “Widespreading Induced Surface Exchange” (WISE) aeration, its performance is from 4 to 10 times more efficient per watt of energy used compared to traditional bubble blower technology for aeration.  Even though Aeration is well known to provide extensive odor reduction or elimination, its use has not been implemented because of the high energy costs associated with running blowers.  This explains why very little is published about other value offered by aeration.  The presentation discusses WISE aeration, many unexpected benefits, and unstudied results.

This presentation will quickly review the 2019 Waste to Worth presentation previously offered and will then offer additional information learned in the past 3 years, including approximately 20 key points.    For those wanting to visit an actual working site before or after the conference, equipment is installed at a regional composting facility approximately 1 hr away from the Waste to Worth facility, near Wauseon OH.

What Did We Do?

Different manufacturers have created “floating aerators” over the past decades. Some have different issues than others, but all are installed in one of the most hostile environments at any enterprise.  PondLift brand equipment has been installed at various farms, domestic wastewater treatment sites, and composting facilities to bring their ponds into full aerobic treatment, with most sites desiring odor elimination, while also allowing their effluent to be sent to growing crops through irrigation equipment, lowering their effluent handling costs while increasing the value of their effluent since it is often foliar fed, offering as much as 70% yield increase per unit of fertilizer.   The author has been at each site to maintain equipment and learn more of its performance and learn more about results, expected and unexpected.  Among the PondLift equipment installations, there are 3 pond installation sites in Ohio, and another at a dairy farm near Paw Paw MI, easily visited for those who would want to personally visit such sites.  Other sites are further distance from Ohio.

What Have We Learned?

The installations have confirmed that odor elimination is very much possible through low-energy-use WISE aeration, while also preparing the effluent to be used by irrigation equipment for foliar feeding.  Although Odor elimination is valuable, probably the most environmentally valuable result of aeration was the dramatic change in texture of the effluent (in both liquids and solids) so that when applied by traditional means, being “knifed in”, the treated manure was absorbed into the soil much faster than raw manure is absorbed into that soil.  The timeframe is hours instead of days, reducing the potential runoff timeframe significantly, potentially eliminating significant runoff events.  Given this observation at almost every site having WISE aeration, it became obvious that a method for quantifying the phenomena is needed, and this equipment needs to be defined so as to compare aerobically treated effluent to raw manure, preferably in a “side by side” process, while also being able to quantify manure runoff on different soil types, and different slopes of soils.  While the presentation will also offer other phenomena data, the final portion of the presentation defines this equipment and procedures that might be adopted so as to study and quantify runoff, and compare runoff quantities to traditional distribution methods.

And for those who are interested in performing foliar feeding through automated manure nutrient distribution through irrigation equipment, the presentation will expand on several items recently identified, including the stratification that results from WISE Aeration, allowing irrigation without plugging pivot/circle nozzles.  In addition, the presentation includes information about Struvite formation and its harvesting opportunity as well as control methods.

Future Plans

PondLift intends to offer equipment for use in studies focused on any phenomena of interest in manure or liquid waste treatment, as well as commercial use at farms.  The political climate in future years will insist that potential runoff issues be addressed, updating Best Management Practices.  In addition, it is now possible that manure odor be eliminated with a process which is financially feasible for farms.

A short discussion: Automation is valuable at farms.  Bringing WISE Aeration to dairies and other farms which store liquid manure can help automate the manure storage/handling/disposal process.  It is the opinion of the author that the small family dairy farm will continue to survive and thrive, given the advances in feeding/health/genetics at today’s farms, even though such farms offer a small percentage of milk products.

The fact that so many farms have limited potentially useable farm acres at small hilly locations, leads us to focus on improving their automation and reducing equipment and time spent on manure related work.  To this end, work is progressing through PondLift, on a low cost “drop-in-place” sand separator which can easily be placed between the barn and the manure storage pit, allowing operators to remove sand before it gets to storage, which then allows the storage pit to be converted to aerobic treatment, which then allows automated manure nutrient distribution methods to be considered.  Lastly, work continues through an associated enterprise on the SPEWPLI (self-propelled extremely-wide portable linear irrigator) which will be able to attach to a manure pumpers hose at a distant field, and distribute manure nutrients to the crop at the 1,500gpm rate often used by manure pumpers. This is important for farms which are more suited to pumping at high rates to distant fields.

Authors

John Ries, Managing Member PondLift LLC, retired professional engineer

Corresponding author email address

ries@iw.net

Additional Information

PondLift.com

 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.

Perceptions of Agricultural Stakeholders on Manure Use, Benefits, and Barriers

Purpose

Nutrient recycling is fundamental to agricultural systems (Spiegal et al., 2020). Integration of animal and crop production represents an example of the application of a circular economy to manage nitrogen (N), phosphorus (P), and other nutrients (Figure 1) important to crop and livestock production. An integrated system recycles these critical nutrients from animal feed to manure to soils and back to animal feed. Nutrient additions to the farm, like animals, feed, and fertilizer (input arrow), are necessary to offset the nutrients leaving the farm in animal protein products (output arrow), as well as other nutrient losses in the system (Cela et al., 2014). The efficiency of this nutrient recycling process has both environmental and economic sustainability implications.

Figure 1. Recycling of nutrients is critical to an environmentally sound agricultural “circular economy”.

For many regions of the United States, such as the Corn Belt, animal agriculture remains in relatively close proximity to sufficient crop production to allow agronomic recycling of nitrogen and phosphorus (Gollehon et al., 2001, 2016). However, the sources of manure nutrients (livestock and poultry operations) and the consumers of nutrients (cropland) are often managed as independent businesses. In other regions, separation of feed and animal production by distance and business boundaries creates significant challenges for agronomic nutrient recycling (Spiegal et al., 2020).

The willingness of crop farmers to accept manure as part of their fertility program is dependent upon their perceptions of the benefits and challenges associated with using manure. Likewise, behaviors among farmers and agricultural advisors of information-seeking – “purposive acquisition of information from selected information carriers” (Johnson 1996) – must be considered as a precursor to content delivery. Thus, in early 2020, a faculty team from University of Nebraska, University of Minnesota, and Iowa State University collaborated to implement a survey of farmers and their advisors to guide multi-state outreach programming by identifying:
-Challenges that regularly prevent manure’s use in crop production and
-Perceptions of manure’s benefits that may encourage manure transfers from livestock farmers to crop producers.

What Did We Do

A draft survey was tested with three groups (a stakeholder advisory group, the national Livestock and Poultry Environmental Learning Community, and the Nebraska Animal Manure Management team) leading to the final product. The survey was delivered electronically through QualtricsXM survey application tool using a University of Nebraska-Lincoln licensed product. The survey included questions for the participants on the following subjects of interest:
1. Participant’s role in manure decision making.
2. Perceptions and knowledge of manure’s benefits. Participants were asked to rate the degree to which they considered manure to be harmful or beneficial for crop fertility, soil physical characteristics, soil biological characteristics, crop yields, and environmental quality.
3. Perceptions and knowledge of manure’s challenges. Participants were presented with a list of potential barriers which might prevent manure use in crop fertility programs and asked to identify which factors were barriers for their operations, or for their advisees.
4. The types of supporting resources which would be of most value for the participants’ decision making or advising on manure benefits and barriers.

Surveyed Participants
Responses were received from 793 individuals across the U.S. and Canada. The results are heavily weighted towards participants from the Corn Belt and the High Plains regions of the U.S. (44% and 23% of respondents, respectively). Survey participants were 87% male and 13% female. Participants’ experience were reported as 29% with less than 10 years, 22% with 11 to 20 years, and 49% with 21 years or more. Participants self-identified as a crop farmer (13%), animal feeding operation (AFO) (7%), professional advisor for crop fertility or manure management decisions (60%), or some combination of these three roles (20%). Crop farmers indicated that they were an annual user of manure (73%), user of manure within the past 3 years (9%), or user of manure within past 4 to 6 years (9%). Only 10% were not users of manure. Those identifying as advisors suggested that manure management is a primary focus of crop fertility advising (20%), frequent part of crop fertility advising (39%), or an occasional part of a crop fertility advising (36%). Only 4% of advisor responses indicated they did not include manure in their advising.

Figure 1. Region of US and Canada represented by survey participants (N= 793).

A series of five questions were presented to identify real or perceived challenges among respondents that represent potential barriers to using manure in crop fertility programs. Lists of agronomic, economic, neighbor or rural community, regulatory, and logistical challenges were presented based on outcomes of the project team’s advisory group discussions and reviews of previous surveys (Battel and Krueger, 2005; Case et al., 2017; Herrero et al., 2018; Poe et al., 2001). Lastly, respondents were asked to identify the types of supporting resources preferred for information-seeking on manure use in cropping systems.

What Have We Learned

Perceptions and Knowledge of Manure Benefits. Both private sector advisors and crop farmers shared similar positive impressions of manure’s benefits for crop fertility, yield, and soil characteristics while being less positive regarding their impressions of how manure impacts environmental quality. Crop farmers and private sector advisors recognize the complementary role of manure and fertilizer in a fertility program at 74% and 76% frequency, and at slightly higher rates than all survey responses (71%). The complementary role of manure and fertilizer was also similar across regions (Corn Belt – 70%; High Plains-69%; all other regions – 74%).

Figure 2. Perspectives of manure’s beneficial versus harmful impacts on five crop production and natural resource topics as identified by primary decision makers in crop fertility programs.

The only audience factors that significantly (p<0.05) influenced participant attitudes toward manure benefits were that participants living in the corn belt were less likely to describe manure as beneficial or slightly beneficial for environmental quality (30%, compared to 46% for high plains, and 35% for all other regions). Similarly, we found that private sector advisors were significantly (p<0.05) less likely to describe manure as beneficial to environmental quality (27%, compared with 58%, 53%, and 30% for livestock producers, crop producers, or public sector advisors respectively). No statistical differences were observed for an influence of audience factors on attitudes towards manure benefits to any of the other characteristics of cropping system benefits (crop yield, soil physical properties, soil biological properties, and crop fertility). However, across all audience sectors participants were unlikely to indicate that they thought manure could be beneficial or slightly beneficial for environmental quality (Figure 2). This data suggests that respondents do not associate improved soil physical and biological characteristics with reduced risk for nutrient transport via runoff, erosion, and leaching. Manure and inorganic fertilizer were perceived as complementary to each other by 71% of respondents, while only 17% believed these two products compete.

Figure 2. Proportion of total respondents who described manure as beneficial or slightly beneficial for different categories of cropping system characteristics. (n=793)

Barriers to Manure Use. As with perceptions of benefits of manure use, audience factors had little effect on the perceived barriers to manure use. There was an observed tendency for more advisors to include most factors as barriers to manure use; however, this tendency was only significant (p<0.05) for six potential barriers: compaction, cost of manure transportation, odors, risks posed by manure application to food crops, accessibility of custom applicators, and use of public roads (Table 1). The overall ranking of barriers to manure use can be found in Table 2. Cost of transportation (68%), odor (58%), timeliness of nutrient availability (55%), concerns related to the field conditions for manure application (50%), and access to labor for manure application (48%) were most frequently indicated as barriers for manure use. Interestingly, several of these factors correspond to those where a difference in the level of concern was observed between advisors and producers (Table 1). However, when considering barrier ranking by agronomic role, 4 of the top 5 barriers are similar between farmers and advisors (cost of transportation, odor, timeliness, and labor availability). Farmers rate concerns with weed seeds as a top 5 barrier, while advisors do not, leaving concerns with field conditions for application as the 6th most selected by crop farmers. This similarity of ranking, even where statistical differences exist, indicates that there is agreement on what are the most significant barriers, but some difference in the perceived seriousness or scale of the barrier. In general, crop farmers less frequently indicated factors as barriers to manure use than did advisors.

Table 1: The frequency survey responses identified selected barriers for manure use. Letters indicated statistical differences in how participants with different roles in agronomic decisions perceived barriers of interest at the alpha = 0.05 level.

Comparison by Role in Agronomic Decisions Animal Feeding Operator (n=66) Crop Farmer (n=120) Private Sector Advisor (n=311) Public Sector Advisors (n=196)
Compaction from application 36%a 41%a 59%b 40%a
Cost of manure application 55%a 67%ab 84%bc 85%c
Odors an air quality impairment 44%a 56%ab 75%bc 79%c
Manure application to food crop 15%ab 13%a 20%bc 22%c
Accessibility of custom applicators 20%a 19%ab 40%b 3%ab
Use of or crossing of public roads 15%a 11%a 21%b 13%a

 

Table 2: The frequency all survey responses identified specific factors as barriers for manure use (n=793)

Potential Barrier % Who perceived as a barrier Potential Barrier % Who perceived as a barrier Potential barrier % Who perceived as a barrier
Transport 68% Water Quality 35% $ of Manure 25%
Odor 58% Interference with Reduced Tillage 34% Accessibility 25%
Timeliness 55% Neighbor Concerns 34% Legal Issues 25%
Field Conditions 50% Equipment $ 34% Flies 20%
Labor 48% Regulation $ 32% Interference with Specialty Crops 19%
Low or Inaccessible Nutrients 47% Traffic 31% Risks to Food Crop 15%
Low or Inaccessible Nutrients 47% Traffic 31% Risks to Food Crop 15%
Compaction 44% Planning & Zoning 31% Road Access 14%
Imbalanced Nutrients 44% Harm to Local Infrastructure 28% Foreign Materials 9%
Uniformity 38% Stockpiles 28% Reduced Yield 5%
Setbacks 37% Presence of Applicators 27% Harmful to Soil 3%
Weed Seeds 37% Pollution 27%

Preferred Sources of Educational Materials. Among three broad groups of respondents (farmers, advisors, and educators), all identified their peers as an important source of information. Brief factsheets or news articles are identified by educators as their top resource they would use (81% of educator responses and 65% of advisor responses). Recommended research articles also ranked high among all three groups. At this point in time, social media (short videos, podcasts, and Twitter and Facebook) is a preferred resource for a smaller portion of these audiences (26% or farmers, 15% of advisors, and 47% by educators).

 

Table 3. Most valued resources for agronomic decision making

Resource Type Farmer (n=197) Advisor (n=438) Educator (n=95)
Recommended research articles 49% 53% 55%
Brief fact sheet or news articles summarizing current science 52% 65% 81%
Decision support tool 34% 39% 43%
Short videos or podcasts summarizing current science 20% 12% 36%
Scripted visuals and text for your use on Twitter, Facebook, other 6% 3% 11%
Network of farmers (or advisors or educators) with whom you interact and share experiences 62% 61% 62%
Scripted PowerPoint presentation for use in educational programs 38%

Future Plans

The intent of this survey was to help our project team and others better understand the characteristics of animal manures that are considered beneficial and barriers to future manure use. Recognition of these benefits and hurdles will be critical as the need to transfer manure nutrients from existing animal feeding operations to crop farms, many with limited previous history of using manure, expands. Matching educational and technical services to the perceptions that impede manure transfer will be necessary.

Future outreach programming should be designed to:

    • Continue to build general awareness of the agronomic and yield benefits of manure.
    • Focus on assisting AFO managers and advisors with communication of specific messages such as 1) desirable rates/plans to best meet crop N and P needs, 2) field-by-field estimation of manure’s fertilizer replacement value and nutrients contributing the greatest value, and 3) complementary manure and fertilizer recommendations for optimum yields.
    • Focus on connecting improved soil health with improved water quality.
    • Help farmers articulate among themselves and to their rural communities the water quality benefits of organic fertilizers when applied to meet agronomic needs of the crop.
    • Challenges associated with manure that frequently become barriers to manure use should be addressed through research and outreach. Specifically, the authors wish to suggest that four challenges are commonly regarded as significant barriers to manure use and require focus to overcome:
      1. Transportation Costs: Businesses providing manure hauling and land application services will be important when transferring manure to fields more distant from manure sources, and educational experiences addressing the current costs of transporting manure and the comparative economic benefit achieved by individual fields will be important.
      2. Odor: A farmers’ desire to be a good neighbor is counter to their willingness to create odors for their neighbors. Farmer and advisor education and planning for reducing odor risks is critical. Technology options to forecast, assess, and address potential nuisance odors may help alleviate odor concerns resulting from manure application.
      3. Logistical Barriers: Three logistical issues ranking highest include 1) timeliness of manure application; 2) time/labor availability; and 3) field conditions restricting manure application. Business services for transporting and land applying manure as well as manure brokering services can address many logistical challenges. Alternative application time windows, such as side dressing a crop with manure, will also be valuable.
      4. Agronomic Issues: Manure application comes with a history of agronomic concerns such as compaction, poor uniformity, and potential for weed seed and herbicide resistance concerns. Many issues are likely to be regionally and manure source specific, thus the need to adapt agronomic education to local needs. Education and business services that encourage technologies such as precision manure application and related technologies, designer manures, and manure treatment may have value based upon regional needs. A 4Rs strategy (right rate, source, time, and place) for manure, similar to what is being promoted in the fertilizer industry, may be beneficial.

Authors

Amy Millmier Schmidt, Associate Professor, University of Nebraska-Lincoln
aschmidt@unl.edu

Additional Authors

-Mara Zelt, Schmidt Lab Project Director, University of Nebraska-Lincoln;
-Daniel Andersen, Associate Professor, Iowa State University;
-Erin Cortus, Associate Professor, University of Minnesota;
-Richard Koelsch, Emeritus Professor, University of Nebraska-Lincoln;
-Leslie Johnson, University of Nebraska-Lincoln;
-Siok A. Siek, Undergraduate Student, University of Nebraska-Lincoln; and
-Melissa Wilson, Assistant Professor, University of Minnesota

Acknowledgements

Funding for this project was provided by the North Central Region Sustainable Agriculture Research and Education program. Key partners in survey deployment were the American Agronomy Society Certified Crop Advisor Program, the Fertilizer Institute and Manure Manager magazine.

 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.

Nutrient Runoff in a Livestock-Dense Watershed: A Case Study of the Grand Lake St. Marys Watershed

Purpose

Stream Restoration at Mercer County Elks Golf Course, 2019

Grand Lake St. Marys (GLSM), located in Ohio, has experienced harmful algal blooms for decades.  In 2010, a massive algal bloom shut down the Lake for the entire summer season. In 2011, the GLSM watershed was declared “distressed,” requiring a new set of rules imposed upon livestock producers in the watershed. These rules required each farm that produced over 350 tons of solid manure or 100,000 gallons of liquid manure per year to create and maintain a nutrient management plan. There was also a winter manure application ban enacted, which prohibits manure application from December 15 to March 1 of each year. These rules still apply to the watershed today.

What Did We Do?

Coldwater Creek Treatment Wetlands, established 2016 (Photo Summer 2021)

An influx of federal and state funds was poured into the watershed to assist the approximately 135 farms with constructing additional manure storage and other best management practices to improve manure management. Over 130 manure storage structures, 80 feedlot covers, 15 waste treatment systems, 20 leachate collection systems and 5 mortality compost structures were built from 2011 through 2019.

KDS Separator Pilot (Swine Manure Solids), March 2018

Other local efforts to improve water quality in GLSM include the restoration and creation of new wetlands to treat stream flow prior to entering GLSM.  Since 2010, we have more than doubled the acreage of wetlands along the south side of the lake and have seen an incredible diversification of wildlife in the area. Additional best management practices have also been installed, such as stream restoration projects, saturated buffers, tile phosphorus filters, double cropping, cover crops and much more. Mercer County has also expended a considerable amount of effort to research manure nutrient recovery technologies throughout the last six years. Manure nutrient recovery is challenging due to cost; however, many technologies can achieve a 90+% recovery of phosphorus from manure.

What Have We Learned?

Long-term monitoring data is collected on two streams feeding GLSM, Chickasaw Creek (installed in 2008) and Coldwater Creek (installed in 2010). The data from Chickasaw Creek was used to determine the effects of the best management practices installed along with the effects of the winter manure application ban. The data showed a reduction of 10-40% of nitrogen and phosphorus because of these improved practices (Figure 1).

Figure 1.  Nutrient Reduction Trends Pre and Post Distressed Watershed (Pre-Condition 2008-2011; Post-Condition 2012-2016) Jacquemin, etal (2016).

Future Plans

Nutrient management planning is an ongoing effort in the Grand Lake St. Marys watershed and will continue as long as the watershed remains distressed. Research and collaboration continue on manure nutrient recovery and development and adoption of technologies. Monitoring of stream and effectiveness of treatment wetland will also continue to ensure that maintenance and management is conducted appropriately. Additional conservation projects, including wetlands, stream restoration and more are planned in the coming years.

Author

Theresa A. Dirksen, PE, Mercer County, Ohio Agriculture & Natural Resources Director

Additional Information

Jacquemin, Stephen J., Johnson, Laura T., Dirksen, Theresa A., McGlinch, Greg. “Changes in Water Quality of Grand Lake St. Marys Watershed Following Implementation of a Distressed Watershed Rules Package.” Journal of Environmental Quality, January 12, 2018.

Jacquemin, Stephen J., McGlinch, Greg, Dirksen, Theresa, Clayton, Angela. “On the Potential for Saturated Buffers in Northwest Ohio to Remediate Nutrients from Agricultural Runoff.” PeerJ, April 12, 2020.

Link to wetland monitoring data summaries: https://lakeimprovement.com/knowledge-base/

Acknowledgements

Dr. Stephen Jacquemin, Wright State University Lake Campus

Mercer Soil and Water Conservation District

Grand Lake St. Marys Restoration Commission

 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.

Evaluation of Agricultural Nutrient Management Technologies at Vermont Natural Ag Products, Middlebury, Vermont

Purpose

The objective of this study was to evaluate nutrient dynamics and operational costs within an existing manure Compost Aeration and Heat Recovery system (CAHR) by Agrilab Technologies, Inc. at the Vermont Natural Ag Products (VNAP) compost facility in Middlebury, Vermont in comparison to conventional windrow manure composting where aeration only occurs via turning.  Constructed in 2016 and 2017, the CAHR has been fully operational since 2018 and has proven effective at reducing VNAP’s expenditures on #2 heating oil, propane, diesel fuel, and labor (Foster et al., 2018).

The basic design of the CAHR system includes compost windrows placed on a paved pad containing a shallow trench oriented longitudinally with the windrow.  The trench contains perforated High Density Poly Ethelene (HDPE) piping bedded in wood chips.  These pipes are connected to solid, insulated HDPE piping which runs to a shipping container outfitted with circulation fans and a heat exchanger.  While the circulation fans are negatively aerating (i.e., pulling vapor from) the compost, warm vapor entering the system transfers heat energy to water piped through the heat exchanger.  Heat recovered from compost windrows has been used to heat the site’s bagging building via radiant floor heating and to dry finished compost prior to the screening and bagging process.  Furthermore, due to elevated oxygen levels provided by positive and negative aeration, CAHR-treated compost has been reported to mature more quickly and require less turning, reducing diesel, labor, and equipment maintenance costs (Foster et al., 2018).

What Did We Do?

Two compost windrows of equivalent feedstock contents and ratios were monitored.  Our control, denoted as “TRAD”, was a conventionally treated windrow that did not receive aeration aside from periodic windrow turning with a Komptech Topturn x53 compost turner.  Our experimental windrow, denoted as “CAHR”, received periodic positive and negative aeration via the CAHR system, as well as aeration through periodic turning.  The initial volumes of the TRAD and CAHR windrows were 480.2 CY and 548.8 CY, respectively.

Compost samples were collected between August 24th, 2021 and December 15th, 2021.  For the first thirteen weeks of the sampling period, samples were taken thrice weekly from both treatments.  At the end of the thirteenth week, on November 19th, VNAP staff deemed the CAHR treatment compost suitable for market and it was pulled for processing.  Sampling continued once weekly for the TRAD treatment for another four weeks, terminating on December 15th, when the TRAD windrow was pulled for processing.  This resulted in a total of 43 samples of TRAD and 39 samples of CAHR composts.

What Have We Learned?

This study evaluated nutrient status, financial cost, and energy cost for a pair of commercial compost windrows in a normal production setting.  From a time and space management standpoint, compost treated with a forced-aeration system was deemed suitable for market in approximately 75% of the time as a conventionally turned windrow; 13 and 17 weeks, respectively.  Analysis of nitrogen species status throughout the study suggests that greater nitrogen losses occurred during conventional treatment than during CAHR treatment, presumably due to higher rates of denitrification and ammonia volatilization.  Data also suggest a lower risk for phosphorus loss through leaching from CAHR-treated compost, as water extractable phosphorus (WEP) concentrations were consistently higher in the conventional treatment.  During the active composting process, it was found that operational costs for CAHR compost were 2.1 times more expensive financially and 5.5 times more energy-intensive than a conventional compost on a per CY basis.  However, the energy and infrastructure cost offsets provided by the CAHR system (as operated at VNAP) could provide a net savings of $4.06/CY finished compost.  In this study, with paired windrows of approximately 12 feet in width, it was shown that a CAHR system produced a comparable compost product, with higher operational input, in less time.

Furthermore, the data suggest that land application of either compost treatment evaluated in this study may reduce phosphorus loss due to leaching versus direct manure application.  For example, WEP concentrations in the finished composts in this study ranged between 0.256 and 0.304 g/kg on a dry weight basis, while WEP concentrations in dairy manures have been found to range between 1.98 and 4.0 g/kg (P. Kleinman et al., 2007; P. J. A. Kleinman et al., 2005).  It is probable that either compost treatment, when applied to agricultural land, would release less phosphorus as WEP during rainfall events than direct manure application, providing water quality benefits.

Future Plans

The Newtrient CIG will continue to evaluate 13 more technologies over the next 2 years to determine their effect on water quality.

Authors

Mark Stoermann, Chief Operating Officer, Newtrient LLC

Corresponding author email address

Mstoerm@newtrient.com

Additional authors

Finn Bondeson, Graduate Student, University of Vermont; Joshua Faulkner, Research Assistant Professor and Farming and Climate Change Program Coordinator, University of Vermont; and Eric Roy, Assistant Professor, Interim Director of Environmental Sciences Program, University of Vermont

Additional Information

Newtrient.com

 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.

Active participation in livestock and poultry sustainability initiatives

Purpose

Whether at the farm, integrator or industry level, sustainability programs have unique goals, metrics and approaches. In many cases, there is no definitive path for meeting long-term goals, but in the ambiguity is opportunity. Meeting sustainability goals will take a community of persons on and off farm willing to support measurements, communication and technology development. This session builds on the Livestock and Poultry Environmental Learning Community’s (LPELC) September 2021 Webinar, Industry Initiatives for Environmental Sustainability – a Role for Everyone.

This Waste to Worth workshop features small and large group discussions to identify modes for active participation in livestock and poultry sustainability initiatives.

What Did We Do?

Industry-led sustainability programs are in various stages of charting a destination for environmental metrics, like greenhouse gas emissions, water quality, water use, etc. However, with respect for the range of individual farm resources, climates and systems, there is no prescriptive path.

As farmers and organizations chart their own sustainability journey, there is a need for on-farm baseline metrics, goal setting, and technology guidance. LPELC’s mission is to provide on-demand access to “the nation’s best science-based resources that is responsive to priority and emerging environmental issues associated with animal agriculture” (LPELC.org). The LPELC is in a strong position to share science and support communication efforts. However, like sustainability journeys, LPELC needs a roadmap.

This workshop will illuminate what resources are currently available, knowledge, technology and communication gaps, and how LPELC members can support on-farm sustainability initiatives. Participants will collectively shape a logic model for a “Community of Support for Producer Engagement in Livestock Industry Environmental Sustainability Initiatives”.

What Have We Learned?

A summary of the workshop results will be shared following the conference.

Future Plans

We intend the workshop results to foster stronger networks and collaborative directions for advancing on-farm sustainability initiatives. We aim for short, medium and long-term outcomes that include stronger understanding of current efforts within the livestock industries and LPELC, along with support mechanisms for decision making and funding opportunities.

Authors

Erin Cortus, Associate Professor and Extension Engineer, University of Minnesota

Corresponding author email address

ecortus@umn.edu

Additional authors

Marguerite Tan, Director of Environmental Programs, National Pork Board; Hema Prado, Director of Sustainability, American Egg Board; Michelle Rossman, Vice President – Environmental Stewardship, Dairy Management Inc.

Additional Information

Webinar – Industry Initiatives for Environmental Sustainability – a Role for Everyone https://lpelc.org/industry-initiatives-for-environmental-sustainability-a-role-for-everyone/#more-33017

US Pork Industry Sustainability Goals https://www.porkcares.org/pork-industry-sustainability-goals-and-metrics/

US Roundtable for Sustainable Poultry https://www.us-rspe.org/

US Dairy Net Zero Initiative https://www.usdairy.com/getmedia/89d4ec9b-0944-4c1d-90d2-15e85ec75622/game-changer-net-zero-initiative.pdf?ext=.pdf

 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.

Impact of Sludge on Nutrient Concentration in Anaerobic Swine Lagoon Supernatant

Purpose

The most common waste management practice on hog farms in Eastern North Carolina are anaerobic lagoons. Lagoons contain three zones: [1] sludge storage zone at the bottom, [2] treatment zone for incoming manure in near the middle, and [3] a liquid (supernatant) storage zone at the top. The supernatant is land applied throughout the year as a nutrient source for growing crops on farms while the middle (treatment) zone is required to remain full to ensure effective treatment.

Considering the risk that hurricanes pose to North Carolina and the hog sector (particularly during late summer months), close lagoon management is critical to avoid risk of overflow or breach. Currently, regulations allow swine growers to lower the effluent level in their lagoons by applying part of the treatment zone effluent. Conditional to this allowance, however, is that the treatment zone contains at least 4-feet of depth that is sludge-free. This condition aims to ensure applied effluent is safe for application.

While this condition is helpful to reducing the risk of applying higher concentration of phosphorus, zinc, and copper to crops, many producers do not meet this condition due to excessive sludge buildup and would not be able to lower the lagoon level which poses a significant risk during intense rainfall events.

This study aims to quantify the impact of the sludge-free depth in the lagoon on the quality of supernatant during the drawdown period. Findings will help with precision nutrient application from swine manure and allow for further drawdown during necessary storm events.

What Did We Do

This study used a dataset representing 27 swine operations in Eastern North Carolina between 2016-2021. The dataset includes:
1. Monthly effluent/waste sampling analysis,
2. Annual sludge surveys, as well as
3. Lagoon level readings.

This dataset was analyzed using statistical methods to quantify the impact of seasonality (time of year), farm type (sow, finisher, or farrowing), and sludge level on nutrient concentration in the effluent.

Most growers use depth, in inches, to report volumes applied or available for storage. However, when comparing lagoons with different designs, this can be a challenge. As such, we developed two parameters to facilitate cross-farm, cross-lagoon comparisons. The first is “freeboard ratio” (FBR), which refers to the relative “fullness” of the storage zone in the lagoon. FBR value between 0 and 1 indicates the lagoon is currently within the storage volume (between start and stop pumps), values greater than 1 indicate the lagoon is in drawdown, and negative values indicate the lagoon level exceeded the storage volume and is currently in the rainfall/storm storage zone and must be lowered promptly. The equation used to calculate FBR is as follows:

TBR= LFB-Lstart , variables defined in Figure 2.
Lstop-Lstart

The second variable is “sludge level ratio” (SLR), which refers to the relative treatment volume available compared to the 50% treatment volume required. SLR values greater than 1 indicate that more than 50% of the treatment volume is sludge-free in the lagoon and therefore drawdown can proceed, and no sludge removal is necessary. SLR values less than 1 indicate that less than 50% of the treatment volume is available and drawdown might not be feasible. The equation used to calculate SLR is as follows:

SLR= Lsludge-Lstop , variables defined in Figure 2.
L0.5. Trt-Lstop
Figure 2. Anaerobic lagoon zones used to calculate study parameters FBR and SLR

What Have We Learned

In analyzing the dataset we observed that only 2% of the samples were collected while the lagoon level exceeded storage level (above the start-pump level). This suggests the majority of studied operations were successful in managing effluent despite the wet years observed between 2016 and 2021. By comparison, 22% of the samples were collected while the lagoon was at a draw-down state (the entire storage volume is empty and the treatment zone is partially emptied).

Additionally, 38% of the samples collected were associated with lagoons that needed sludge removal (SLR < 1). These results are summarized in Table 1, with 12% of samples collected from lagoons in drawdown (FBR > 1) and in need of sludge removal (SLR < 1). This latter group of samples represent the primary concern for lagoon drawdown.

 

Table 1. Summary of FBR and SLR Interactions
Lagoon Sample Class Sludge Level Ratio (SLR)
No Removal Removal Due
Freeboard Ratio (FBR) Above stop-pump 40% 26%
In drawdown 22% 12%

The season was a significant predictor of the lagoon level (p < 0.001), with the late irrigation season (July – Sept) showing the least effluent volume in the lagoon. On average, 91% of the storage volume was unoccupied. This compares to the winter months (Oct – Feb) and the early irrigation season (Mar – June) with 81 and 69% of the storage volume empty, respectively.

For all seasons the mean ratio of N : P2O5 : K2O in the supernatant is 4 : 1 : 8.2. There was less variability for N and K content with the lagoon level than for P, Zn, and Cu. This can be attributed to the N and K being primarily in soluble forms in the lagoon supernatant compared to P2O5, Zn and Cu which are mostly bound to solids.

The analysis showed a greater variability in Zn, Cu, and P levels with changes in solid concentration in the supernatant as well as the amount of suspended solids as a result of wind or active lagoon agitation/sludge removal.

Overall, the results showed lagoon drawdown and existing sludge reserves to have a combined effect on nutrient concentrations in the supernatant, particularly for phosphorus.

Future Plans

This study will inform ongoing research to predict temporal variability in nutrient content in the lagoon due to weather, operational decisions, and time of year. Near term, these observations will help guide application rates to ensure P levels meet crop demands particularly during late-season drawdown without significantly increasing soil P levels. In addition, this work will be part of a larger study to predict the performance of anaerobic treatment lagoons under future climate conditions.

Authors

Presenting Author:
Carly Graves, Graduate Research Assistant, North Carolina State University

Corresponding Author:
Dr. Mahmoud Sharara, Assistant Professor & Waste Management Extension Specialist, North Carolina State University
msharar@ncsu.edu

Acknowledgements

Thank you to Smithfield Foods, Inc. for funding this research and providing datasets of sludge surveys.

Videos, Slideshows and Other Media

https://content.ces.ncsu.edu/sludge-sampling-in-anaerobic-treatment-swine-lagoons

 

The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.