The first in a series of 3 webinars, this presentation introduces the fundamentals of carbon emissions, as well as technologies, practices and market opportunities available to agricultural producers are critical to that transition on the livestock operation. This presentation was originally broadcast on November 18, 2022. Continue reading “Carbon Markets for Livestock Operations: Manure Treatment and Handling”
Worker Safety in Animal Production Systems
There’s more to worker safety than just bumps and bruises. This webinar discusses on-farm injuries related to manure and mortality handling and application as well as potential toxic gas exposures and how to minimize risks of each. This presentation was originally broadcast on October 21, 2022. Continue reading “Worker Safety in Animal Production Systems”
Changes in manure management between CEAP I & II
CEAP uses natural resource and farmer survey data along with physical process modeling to estimate the environmental impacts of conservation practices on cultivated cropland. This presentation was originally broadcast on September 23, 2022. Continue reading “Changes in manure management between CEAP I & II”
Swimming with superbugs: Exploring how antimicrobial resistance moves in our environment
This webinar explores what we know about how AMR moves in our environment and critical needs to improve our understanding of environmental health aspects of the AMR problem. This presentation was originally broadcast on August 19, 2022. Continue reading “Swimming with superbugs: Exploring how antimicrobial resistance moves in our environment”
Manure nutrient trends and creating dynamic “book values” through ManureDB
This webinar highlights ManureDB, a database of manure samples informing “book values”. Having current manure test numbers will assist in more accurate nutrient management planning, manure storage design, manure land application, and serve agricultural modeling purposes. This presentation was originally broadcast on June 17, 2022. Continue reading “Manure nutrient trends and creating dynamic “book values” through ManureDB”
Promoting Manure Composting for Livestock Operations
Purpose
While both raw and composted manure benefit soil health and crop production, there are benefits to creating and land-applying composted manure over raw manure. Product uniformity, volume, weed seed, pathogen and parasite reduction and nutrient stability are just a few of the benefits. However, composting manure in Minnesota and North Dakota have yet to gain popularity.
A group of compost producers, who ultimately became our producer cooperators and partnered with us for workshops, were consulted on the reason composting manure is not more common. One said, “It is lack of understanding and time management that holds most other farmers back from composting manure; they do not know how much composting can help their operation.” Another mentioned, “When I started researching composting for my farm, I took a three-day class in Illinois because there wasn’t anything available in North Dakota or Minnesota. Most farmers are not willing to travel that far. There is a need for composting education programs in the two-state area.”
What Did We Do?
NDSU Extension partnered with the University of Minnesota Extension with the original plan of holding four workshops in two years (two each in ND and MN). When implications from the COVID-19 pandemic ensued, we changed our plans to host an online workshop in 2020 and were able to continue with two in-person workshops in 2021.
The online workshop consisted of 13 videos that were sent to registrants 2 weeks before an online, live discussion was held in August 2020 with the presentation team as well as 3 producer cooperators. One of the videos consisted of on-farm interviews with each of our producer cooperators to show the registrants the ability to manage compost differently with similar results. The videos are still available and have been viewed collectively 1,845 times.
The in-person workshops were held in July and August of 2021. Each workshop covered the same material as the online workshop and all three producer cooperators attended each event. The producer cooperators were responsible for helping attendees with the compost diagnostics activity as well as answering questions during a panel discussion.
What Have We Learned?
Online Workshop
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- 180 people registered for the online workshop and 50 joined the live discussion with presenters and producer cooperators
- 43 responded to the immediate follow-up survey where
- 76% thought the self-paced format was excellent
- 64% thought the amount of material was excellent
- 62% thought the topics covered were excellent
- 15 months after the online workshop, 21 people participated in a follow-up survey and as a result of the workshop, 58% reported they had altered their manure composting practices.
- When asked what manure composting change(s) they made, 58% reported they improved their operations adding,
- “I have more confidence in my ability to compost successfully and have a better understanding of the environmental impacts of composting.”
- “I no longer have to pay someone to haul away our waste”
- “Although not composting on a commercial level, I manage several community gardens where large volumes of biomass are accumulated. After learning additional techniques, my piles were hotter and decomposed more quickly. The key? More moisture!”
Moving the workshop online for the first year allowed us to fully engage our producer cooperators. The online workshop resulted in participant comments such as,
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- “Well organized and executed. Appreciated that videos were individual by topic area, short, and focused. That allowed me to watch what was relevant and fit it into my day more easily.”
- “Really enjoyed the discussion and interaction between the three cooperators. Also appreciated having enough time to flesh out the information, i.e., didn’t try to squeeze it into one hour.”
Though an in-person meeting would have allowed more hands-on experience, the online version reached a broader audience with attendees from 31 states and 3 countries.
In-person Workshops
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- 31 people attended the in-person workshops in ND and MN, of which 10 participated in a 4-month follow-up survey
- 67% of those who made changes as a result of the workshop stated they started composting manure
- 100% of those who did not make changes were either agency or university Extension/research personnel who reported the workshops impacted them, their work, and/or their relationship with their clients by:
- “Allowing me to be more educated about manure composting so that when producers inquire about composting I am able to give them accurate information.”
- “Using workshop information to inform clients of another manure handling method to consider; composting.”
- 31 people attended the in-person workshops in ND and MN, of which 10 participated in a 4-month follow-up survey
The workshops, both online and in-person, facilitated discussion and mutual learning among experienced and novice composters of livestock manure.
Future Plans
Questions about static composting were asked during both the online and in-person workshops. This practice is not common in North Dakota or Minnesota so there is certainly a future learning and workshop opportunity.
Authors
Mary A. Keena, Extension Specialist, North Dakota State University
Corresponding author email address
Additional authors
Chryseis Modderman, Extension Educator, University of Minnesota; Melissa L. Wilson, Assistant Professor and Extension Specialist, University of Minnesota; William J. Gale, Extension Agent, North Dakota State University
Additional Information
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- Online Composting Workshop Videos YouTube playlist: https://youtube.com/playlist?list=PLnn8HanJ32l6uhwdS9m-G1z8Bq1U0aJzF
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- Two compost-related publications for producers were created for use while at the compost rows:
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- Manure Composting Quick Guide (NM2047)
- Common Manure Composting Problems and Their Solutions (NM2046)
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Acknowledgements
This project was funded by North Central Sustainable Agriculture Research and Education (NC-SARE).
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.
Assessment of physical properties for cover crop and manure applied soils in Idaho’s Magic Valley
Purpose
Idaho ranks in the top 10 in the US for dairy, potato, barley, hay, sugarbeet, corn silage, and dry bean production with the highest producing area being in South Central Idaho. Crop and livestock producers in the Magic Valley depend on affordable access to clean water, healthy and productive soils, and quality grazing land to remain profitable. However, portions of the Middle Snake River, which provides irrigation and drinking water to the Magic Valley, have been impaired by high phosphorous and sediment loading for over two decades (Tetra Tech, 2014). To measure progress in producer efforts for reducing erosion and runoff, appropriate methods need identified. The soils in this region are prone to crusting, have low organic matter, and are high in calcium carbonates making these soils unique to much of the United States. Thus, the overall goal of this project was to identify management practices that enhance soil health physical properties in the Magic Valley.
What Did We Do?
Two study sites were located on the USDA-ARS Northwest Irrigation & Soils Research Laboratory farm in Kimberly, Idaho, and were established in 2013 (Long-Term Manure) and 2016 (Cover Crop). Long-Term Manure was set up as a randomized complete block design with four replicates and eight treatments. The treatments are as follows: annual application of solid dairy manure at rates of (i) 10, (ii) 20, and (iii) 30 ton per acre(dry weight), biennial application of solid dairy manure at rates of (iv) 10, (v) 20, and (vi) 30 ton per acre (dry weight), (vii) application of inorganic fertilizer (applied to match manure N and P rates; Fert), and (viii) no amendments (Control). A commercial crop rotation of wheat-potato-barley-sugarbeet was used at this study site, and sampling occurred under sugarbeet in 2020. All plots were disked immediately after manure application, and all plots were moldboard plowed prior to sugarbeet and potato planting. The Cover Crop study was set up as a split plot design with four replications and tillage as the main experimental factor (strip till vs disk/chisel plow). The four sub-treatments are as follows: (a) no cover crop or dairy manure (Control), (b) cover crop only (CC only), (c) manure only (M only), and (d) cover crop with manure (CC + M). Treatments that did not receive manure received inorganic fertilizer to meet recommended crop needs based on spring soil tests. Inorganic fertilizer was only applied to manure treatments if spring soil tests indicated that additional nutrients were required and the manure did not meet the crop needs. From 2016 to 2021, the field was cropped with continuous silage corn. Triticale was used as a winter forage cover crop and was planted directly after manure application and was harvested within one week of corn planting. Stockpiled dairy manure was applied at a rate of 30 ton per acre (dry weight) in the fall after corn silage harvest and incorporated by disking or left on the surface.
The physical properties accessed for each study in late summer 2020 were soil aggregate stability, runoff rate and rainfall before runoff, bulk density, and compaction. Two methods were used to measure soil aggregate stability: wet sieving and a hybrid method utilizing a Cornell Sprinkle Infiltrometer (CSI). The wet sieving method incorporated four nested stainless steel wire sieves at particle diameters of 5/32, 5/64, 1/64, and 0.002 inch. The samples were submerged in 9.5 inch of water oscillating up and down 1.5 inch at 30 oscillations per minute for 10 minutes. A CSI was used to measure soil aggregate stability at the heights of 1, 3, and 5 feet. The CSI operated at a constant rainfall rate of 0.79 inch of rainfall per 10 min of operation. Runoff rate and rainfall before runoff were calculated based on the values collected from the CSI using the equations listed in van Es and Schindelbeck (2001). The CSI was placed on top of a metal ring (9.5 inch diameter), and a runoff tube was fitted in the metal ring to measure runoff. The CSI had an air entry of 3.9 inch, and data was recorded every 2 minutes once runoff started to occur until the outflow reached steady state. Because each measurement took a minimum of one hour, only one block was measured each day for a total of four days. Bulk density measurements were taken at depths of 0-2, 2-4, and 4-6 inch at each plot. Compaction was measured using a penetrometer to measure a total depth of 12 inch at increments of 1 inch.
What Have We Learned?
Two methods (wet sieving and CSI hybrid) were compared for accessing soil aggregate stability among the two studies. No differences in aggregate stability were found when the wet sieving method was used among treatments for both studies (Figure 1). However, the CSI hybrid method was found to be statistically different at an operational height of 1 foot among treatments at mean values of 0.147 ± 0.005 inch (CC + M), 0.145 ± 0.005 inch(CC only), and 0.146 ± 0.005 inch (M only) as compared to the control (0.124 ± 0.005 inch) for the Cover Crop study. It is also clear that there are large numerical differences in mean weight diameters between the operational heights for the Cover Crop study.
Significant differences in rainfall before runoff were found between treatments in the Cover Crop study, and the mean values were 2.26 ± 0.23 in (CC + M), 1.70 ± 0.23 in (CC only), and 1.53 ± 0.23 in (M only) when compared to the control (1.45 ± 0.23 in) (Figure 2). No differences were found in the Long-Term Manure study. When measuring bulk density, it was found that measurements at the 0–2-inch depth were found to be statically significant (p≤0.05) with means of 52.7 ± 3.7 pound per cubic foot (CC + M), 59.6 ± 3.7 pound per cubic foot (CC only), and 49.4 ± 3.7 pound per cubic foot (M only) when compared to the control (65.9 ± 3.7 pound per cubic foot), respectively. Compaction was found to be statistically significant at the depths of 1 through 4 inch and 10 and 12 inches. The tillage by treatment effect was also found to be statistically significant at 2 and 3 inches. Assessing physical properties among management practices can give producers a clearer insight into soil health in the Magic Valley.
Future Plans
At the Long-Term Manure study site, dairy manure was applied annually or biannually from 2013-2019. The project now focuses on nutrient drawdown and manure will no longer be applied. Cover crops may be incorporated into the project. At the Cover Crop study site, inversion tillage will be performed spring of 2022 prior to planting silage corn to incorporate the dairy manure into the topsoil. Dairy manure has not been applied to the field since fall of 2020. Inorganic fertilizer will be applied if needed.
Authors
Presenting author
Kevin Kruger, Research Support Scientist, University of Idaho
Corresponding author
Linda R. Schott, Nutrient and Waste Management Extension Specialist, University of Idaho
Corresponding author email address
Additional authors
Jenifer L. Yost, Research Soil Scientist, USDA-ARS; April B. Leytem, Research Soil Scientist, USDA-ARS; Robert S. Dungan, Research Microbiologist, USDA-ARS; Amber D. Moore, Soil Fertility Specialist, Oregon State University
Additional Information
Part of this research was presented at the ASA, CSSA, SSSA International Annual Meeting in Salt Lake City, Utah, in November of 2021. The link to the recorded presentation is found in the citation below:
Yost, J.L., Kruger, K., Leytem, A.B., Dungan, R.S., & Schott, L.R. (2021). Measuring Soil Aggregate Stability Using Three Methods in Aridisols Under Continuous Corn in Southern Idaho [Abstract]. ASA, CSSA, SSSA International Annual Meeting, Salt Lake City, UT.
https://scisoc.confex.com/scisoc/2021am/meetingapp.cgi/Paper/138171
More information about the Long-Term Manure project can be found in the following scientific papers:
Leytem, A.B., Moore, A.D., & Dungan, R.S. (2019). Greenhouse gas emissions from an irrigated crop rotation utilizing dairy manure. Soil Science Society of America Journal, 83, 137-152.
https://eprints.nwisrl.ars.usda.gov/id/eprint/1693/
Bierer, A.M., Leytem, A.B., Dungan, R.S., Moore, A.D., & Bjorneberg, D.L. (2021). Soil organic carbon dynamics in semi-arid irrigated cropping systems. Agronomy, 11, 484.
https://doi.org/10.3390/agronomy11030484
The papers that were referenced in this proceedings paper are:
Reynolds, W. D., & Elrick, D. E. (1990). Ponded infiltration from a single ring: I. Analysis of steady flow. Soil Science Society of America Journal, 54, 1233–1241.
https://doi.org/10.2136/sssaj1990.03615995005400050006x.
Tetra Tech. (2014). Reevaluation of Mid Snake/Upper Snake-Rock Subbasin TMDL: Data Summary, Evaluation, and Assessment.
van Es, H. & Schindelbeck, R. (2001). Field Procedures and Data Analysis for the Cornell Sprinkler Infiltrometer. Department of Crop and Soil Science Research Series R03-01. Cornell University.
Acknowledgements
This project was funded by a USDA ARS Cooperative Agreement and USDA NIFA Project Number IDA01657. The authors would like to thank Emerson Kemper for assisting with the lab work and Peiyao Chen for assisting with field work.
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 swine manure on soil health properties: A systematic review
Purpose
As the campaign to improve agricultural soil health has gained momentum among conservationists and researchers worldwide, a comprehensive assemblage of outcomes from manure and soil health-related research studies is important. Particularly, the identification of knowledge gaps is an important step to direct future research that informs soil health improvement outreach programs. A thorough review of data reporting the effects of swine manure on soil health properties that is applicable to agricultural producers is lacking. Although previous research studies have looked at the effects of manure on individual soil properties, there are conflicting conclusions. Livestock manure literature reviews fail to consider inconsistent methodologies between individual research studies and whether research is applicable to producers utilizing manure as amendments to improve soil health, and none of the reviews focus on swine manure or swine manure by-products. The objectives of this review were (a) to synthesize literature describing effects of swine manure on soil properties that affect soil health and (b) to identify knowledge gaps and research needs to further our understanding of this topic.
What Did We Do?
We conducted a systematic literature review based on peer-reviewed studies that evaluated the effect of swine manure on soil health properties. First, we identified studies using three criteria: species (swine, pig, hog), manure source (i.e., solid [SM] or liquid manure [LSM], compost, deep pack), and soil property (i.e., soil organic carbon [SOC], total nitrogen, soil pH, bulk density, available water capacity). Second, studies had to meet the following criteria in order to be included: (a) the studies were replicated field experiments, (b) manure was the only differing factor between or among treatments, and (c) data means of organically amended treatments and controls were included. In total, 40 peer-reviewed studies were included in this review.
What Have We Learned?
Recycling of manure locally prior to importing inorganic fertilizer (IF) has the potential to reduce nutrient imbalances and improve soil health. Based on this review, swine manure has the potential to add significant amounts of organic carbon to the soil and to improve soil health metrics. In general, the application of swine manure increases soil organic matter (SOM) and SOC, decreases soil bulk density, and increases microbial biomass carbon Soil organic carbon and total N tended to be highest when manure and inorganic fertilizer were applied to the field (Figure 1). Soil chemical properties did not seem to change much when manure was applied to the soil surface or incorporated into the topsoil. The duration of swine manure application (annually) did not seem to increase the percent change in most chemical properties; however, this could be due to a lack of data. The percent change in SOC did increase when the swine manure was applied for a longer time period (Figure 1), and we would expect to see a similar trend with SOM and total carbon if there were more data. Few articles had data on soil physical and biological properties. Depending on soil type, swine manure has the potential to increase available water holding capacity and saturated hydraulic conductivity. Although more research is needed, it can be inferred that swine manure additions increase microbial activity, which promotes healthier soils and better crop yields.
Future Plans
Previous literature reviews failed to account for differences in methodologies between individual research studies and whether research is applicable to producers utilizing swine manure as amendments to improve soil health (i.e., unreasonable application rates of swine manure, overapplication of nutrients). The evaluation of the effect of swine manure on soil health properties is difficult to do based on current literature because (a) there are few comprehensive studies (i.e., only one study reported properties from chemical, physical, and biological categories) and (b) there are non-consistent research methodologies between studies. Therefore, we recommend redirecting research studies to demonstrate the value of manure to the suitability of agricultural cropping systems. Future swine manure research should include (a) a range of soil physical, chemical, and biological properties, (b) initial soil data prior to manure application, and (c) manure type, application method, application rate, total carbon and nitrogen of the manure, duration of swine manure application, and swine manure application timing. In addition, future research should also focus on the short- and long-term effects of a single application of manure to support an effort to identify optimal frequency of application for improving soil health. More research is also needed to compare the effects of manure and inorganic fertilizer additions on crop yield and soil health by balancing nitrogen, phosphorus, and potassium additions.
Authors
Jenifer L. Yost, Research Soil Scientist, USDA-ARS
Corresponding author email address
jenifer.yost@usda.gov
Additional authors
Amy M. Schmidt, Livestock Manure Management Engineer, University of Nebraska-Lincoln; Rick Koelsch, Livestock and Bio Environmental Engineer, University of Nebraska-Lincoln; Kevin Kruger, Research Support Scientist, University of Idaho; Linda R. Schott, Nutrient and Waste Management Extension Specialist, University of Idaho
Additional Information
For more information about this project, please check out our Open Access journal article. The citation for the journal article is:
Yost, J.L., Schmidt, A.M., Koelsch, R., and Schott, L.R. (2022). Effect of swine manure on soil health properties: A systematic review. Soil Science Society of America Journal.
https://doi.org/10.1002/saj2.20359
This research was presented at the ASA, CSSA, SSSA International Annual Meeting in Salt Lake City, Utah, in November of 2021. The link to the recorded presentation is found in the citation below:
Yost, J. L., Schmidt, A. M., Koelsch, R., & Schott, L. R. (2021). Impact of Swine Manure on Soil Health Properties: A Systematic Review [Abstract]. ASA, CSSA, SSSA International Annual Meeting, Salt Lake City, UT. https://scisoc.confex.com/scisoc/2021am/meetingapp.cgi/Paper/138180
Acknowledgements
This project was supported by funding from the National Pork Checkoff. The authors would also like to thank Meg Clancy and Drew Weaver for their assistance.
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.
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.
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.
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.
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.
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.