Tag: soil

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Assessing the impacts of crop and nutrient management practices on long-term water quality and quantity in a dairy intensive irrigated agricultural region using the SWAT model

Purpose

The dairy industry in Idaho has grown substantially over the past 30 years and is the state’s largest agricultural commodity, accounting for $3.7 billion in sales in 2022. Roughly 500,000 of Idaho’s 660,000 dairy cows reside in a six-county region known as the Magic Valley, a name originating in the early 1900s when large canal irrigation projects turned a dry landscape into verdant farmland. The Magic Valley is semi-arid, receiving around 254 mm of precipitation each year and requiring cropland to be irrigated throughout the growing season. Due to a limited amount of water available for irrigation each season cropland area has not expanded since the 1980s.

The large number of dairy cows in the Magic Valley has shifted crop production towards forage crops, predominantly silage corn and alfalfa. For example, between 1992 and 2022 the number of dairy cows in Twin Falls County increased from 18,000 to 108,000. During this same timespan corn silage and alfalfa saw a 14,000 and 5,000 hectare increases in land cover, respectively (Figure 1). This change in land cover has potentially increased consumptive water use within the region through the replacement of crops with shorter irrigation seasons (e.g., wheat and beans) with forage crops. In addition to changes in water use, the increase in dairy cattle has resulted in greatly increased manure applications to surrounding fields. It is typical for cropland to receive manure at rates of 52 Mg ha-1 year-1, which can input high amounts of nitrogen and phosphorus beyond what is removed by the crop. Over time, this could result in soil phosphorus enrichment and the leaching of nitrate to groundwater.

Figure 1. Population of dairy cows in Twin Falls County from 1992 to 2022 along with total hectares of corn silage and alfalfa.
Figure 1. Population of dairy cows in Twin Falls County from 1992 to 2022 along with total hectares of corn silage and alfalfa.

What Did We Do?

The study area for this project was the Twin Falls Canal Company, a large irrigation project in southern Idaho. Investigation into potential changes in water quality and quantity brought about by the growing dairy agriculture in southern Idaho was carried out using the Soil and Water Assessment Tool (SWAT) model. SWAT is a physically based geospatial watershed-scale hydrologic model that incorporates climate, topography, soils, land cover, and management practice data. Model scenarios included examining changes in consumptive water use over time, effects of irrigation practices on the leaching of water and nutrients, and the impact of continuous manure applications on the buildup and leaching of nutrients. Nutrient cycling and crop nutrient uptake were calibrated in the model using two USDA-ARS eight-year studies. The first study applied manure under a corn-barley-alfalfa rotation only when soil nutrient concentrations were deficient, and the second study applied manure on a yearly basis in the spring at a rate of 52 Mg ha-1 under a barley-sugar beet-wheat-potato rotation.

Table 1. Crop areas and percentages under the 1992 and 2022 scenarios.

1992 km2 (%) 2022 km2 (%)
Alfalfa 189 (25.3) 244 (32.8)
Barley 104 (13.9) 132 (17.7)
Beans 169 (22.7) 60 (8.0)
Corn Silage 55 (7.4) 191 (25.7)
Potatoes 35 (4.6) 34.5 (4.6)
Sugar Beets 46 (6.2) 26 (3.5)
Wheat 148 (19.8) 57 (7.6)

Table 1. Crop areas and percentages under the 1992 and 2022 scenarios.

Consumptive water use within the Twin Falls Canal Company was compared between two distinct time periods: pre-dairy and present. 1992 was selected as the pre-dairy benchmark due to being before large increases in dairy cattle numbers. Modeled crops were alfalfa, barley, beans, corn silage, potatoes, sugar beets, and wheat, which account for over 95% of irrigated cropland within the TFCC. Land cover in 2022 was used as the present scenario, and crop distributions were altered for the 1992 scenario based on USDA agricultural census data (Table 1). The model was run using climate data from 2002 to 2022 to have consistency between the two scenarios and to allow for year-to-year variability weather patterns. Automatic irrigation routines were used in the model, with a 9.1 mm irrigation event being triggered when soil water content dropped 5 mm below field capacity. 9.1 mm was chosen as the daily irrigation amount because it is roughly equivalent to the flow rate of an 850 gallon per minute center pivot. Irrigation schedules varied by crop within the April 15th – October 31st irrigation season (Table 2).

Table 2. Irrigation seasons for modeled crops.

Irrigation Season
Alfalfa April 15th – October 9th
Barley April 15th – July 25th
Beans June 26th – September 10th
Corn Silage May 25th – September 18th
Potatoes May 15th – September 1st
Sugar Beets April 20th – September 25th
Wheat April 15th – July 16th

What Have We Learned?

Modeled changes in land use within the Twin Falls Canal Company towards forage crops for dairy cattle have increased consumptive use during the year by 9% on average. June, August and September showed the greatest average increases in evapotranspiration (ET) (Figure 2). Irrigation amounts increased under the 2022 land use scenario for all months except April. Percolation under the 2022 scenario also increased to an average of 155 mm each year, up from 132 mm in the 1992 land use scenario.

Figure 2. Modeled monthly average cropland ET for the pre-dairy (1992) and post-dairy (2022) land cover scenarios.
Figure 2. Modeled monthly average cropland ET for the pre-dairy (1992) and post-dairy (2022) land cover scenarios.

Typical yearly water diversions for the Twin Falls Canal Company were sufficient to meet the current and future irrigation demand. Diversion reductions in August and September are common depending on reservoir storage and the timing and volume of snowmelt. A shift towards greater cropland area irrigated during those months could require deficit irrigation during extreme drought years, which are likely to become more common given climate change projections indicating reduced snowpack and earlier snowmelt runoff.

SWAT was able to reasonably represent manure nitrification, including the increases in nitrification during the year following sugar beet and potato residue being left on the field (Table 3).  Crop nutrient uptake in the two USDA-ARS studies was also able to be accurately modeled after adjusting nutrient uptake parameters. Modeled soil nitrate and plant-available phosphorus concentrations were similar to field samples. Changes to SWAT source code was necessary to better partition “fast” and “slow” organic nitrogen fractions in manure between the two pools and limit mineralization when the air temperature is below 6 degrees Celsius. Under a manure application rate of 52 Mg ha-1 soil plant-available phosphorus levels exceed the allowed maximum of 40 mg kg-1 in just two years. Applying manure only when needed to satisfy crop nutrient requirements did not result in soil plant-available phosphorus approaching or exceeding the 40 mg kg-1 threshold. In addition to high soil phosphorus levels, nitrogen mineralization from yearly applications of manure resulted in high soil nitrate levels. Modeled percolation using actual irrigation amounts over the eight-year study totaled 1,176 mm and resulted in 1,256 kg ha-1 of leached nitrogen. This highlights the risk that yearly manure applications can have to water quality, especially if water is applied in excess of crop needs when also accounting for soil moisture. In addition, high variability in manure nitrogen and phosphorus concentrations suggests yearly fixed-rate applications are not the ideal for managing nutrient budgets.

Table 3. Yearly and in-season manure nitrogen mineralization from the SWAT model output compared to in-season nitrogen mineralization collected from field samples during the long-term manure study. Asterisks denote years in which sugar beet or potato residue was left on the field, resulting in greater N mineralization the following year.

Year SWAT N Mineralization SWAT In-Season N

Mineralization

 Field In-Season Mineralization
kg ha-1 kg ha-1 kg ha-1
2013 211 117 180
2014* 287 192 110
2015 442 308 280
2016* 321 205 190
2017 399 242 250
2018* 297 197 150
2019 393 285 230
2020 357 145 150
Total 2,707 1,690 1,540

Future Plans

Now that the SWAT model has been fully calibrated, the next step will be to test various scenarios in which yearly manure application amounts, crop rotations, and irrigation schedules are adjusted. Typical regional dairy crop rotations include silage corn, alfalfa, wheat, barley, triticale, and occasionally potatoes or sugar beets. Manure is not applied to alfalfa, possibly allowing for a drawdown of phosphorus that has accumulated over previous years. Changing irrigation schedules will alter the timing and quantity of percolated water which will change nutrient export characteristics. Incorporating these scenarios over a large irrigation district with variable soils should identify areas that are more at risk of nutrient losses through runoff or leaching. Results from this research will be used to inform management agencies on the water use and water quality implications of crop rotations, manure applications, and irrigation schedules in southern Idaho.

Authors

Presenting & corresponding author

Galen I. Richards, PhD Candidate, University of Idaho, grichards@uidaho.edu

Additional authors

Erin Brooks, Professor, Department of Soil and Water Systems, University of Idaho

Linda Schott, Assistant Professor and Nutrient & Waste Management Extension Specialist, Department of Soil and Water Systems, University of Idaho

Kossi Nouwakpo, Research Soil Scientist, USDA-ARS Northwest Irrigation and Soils Research Station

Daniel Strawn, Professor, Department of Soil and Water Systems, University of Idaho

Additional Information

https://www.uidahoisaid.com/

Acknowledgements

This research was funded under the University of Idaho Sustainable Agriculture Initiative for Dairy (ISAID) grant USDA-NIFA SAS 2020-69012-31871

I would like to thank USDA-ARS researchers April Leytem, Robert Dungan, and Dave Bjorneberg at the Northwest Irrigation and Soils Research Station in Kimberly, ID for providing me with data from their long-term research studies and general assistance in accurately modeling regional agricultural practices.

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. 2025. Title of presentation. Waste to Worth. Boise, ID. April 7-11, 2025. URL of this page. Accessed on: today’s date. 

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Managing Dairy Manure for Increased Soil Health and Forage Production Sustainability

Manure is a valuable source of crop-essential nutrients that, when managed carefully, can help build soil organic matter, enhance nutrient cycling, and improve overall soil health and climate resilience over time. In 2022, a statewide on-farm research project was initiated in New York State to quantify the nitrogen (N) replacement value, corn silage or grain yield, and soil health enhancements of various manure sources. Between 2022 and 2023, eleven on-farm field trials were implemented. Yield data are being used to quantify differences in most economic N rate between manured and non-manured strips, and to quantify the yield impact of the manure applications. In 2024, eight additional trials were added using various manure sources. Results so far indicate that manure can offset N fertilizer needs and increase corn silage yield beyond its nutrient contributions, but impacts are field-specific, reflecting differences in field histories and growing conditions. Assessments of soil microbial biomass for sites in 2023 and 2024 reflected the manure history for trial locations and suggest that mid-season assessments may help identify where nitrogen fertilizer addition is beneficial for the crop and where not. Assessment of variability of different manure sources point to the importance of manure sampling and analyses. Preliminary results will be shared. This presentation was originally broadcast on October 18, 2024. Continue reading “Managing Dairy Manure for Increased Soil Health and Forage Production Sustainability”

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Soil Type and Short-Term Survival of Porcine Epidemic Diarrhea Virus

Manure management practices recycle nutrients in animal manures for crop production.  Harmful microbes and viruses in the manure are generally reduced in the soil environment over time.  The soil properties influencing how long animal virus persistence are poorly understood and may be specific even down to the type of microbe present.  Recently, porcine epidemic diarrhea virus (PEDV), which causes nearly 100% mortality in newborn piglets, has become a serious challenge for swine production.  An important concern is whether PEDV in manure applied to nearby farmland may be a source for herd reinfection. How long will PEDV persist in the soil and still be infectious?  Are some soils better suited to reduce PEDV risk?

What did we do?

A laboratory study was conducted to mimic a standard manure application practice (manure slurry application into soil) to determine if it reduced the potential for PEDV reinfection.  In our study, we tested a range of soil types spiked with PEDV-positive manure slurry and evaluated how PEDV detection and potential infectious risk was affected by soil type. Quantitative PCR and live swine bioassays were used to enumerate PEDV and to determine whether manure and soil samples contained infectious PEDV (Stevens et al., 2018).

What have we learned?

Manure Slurry/Soil Incubations.  PEDV genomes declined at different rates depending upon the type of soil tested (Figure 1).  While PEDV declined rapidly and was not detected by PCR in Soil #1, #2, and #5 in just 24 hours, PEDV genomes in Soil #6 and #7 decreased more slowly the other soils.  Soils #3 and #4 displayed an intermediate rate of decline and reached our detection limit at 48 hours. Soil is an important factor on PEDV persistence.

Figure 1. Porcine epidemic diarrhea virus genomes in the manure slurry/soil incubation determined by reverse-transcriptase quantitative polymerase chain reaction.
Figure 1. Porcine epidemic diarrhea virus genomes in the manure slurry/soil incubation determined by reverse-transcriptase quantitative polymerase chain reaction.

 

Swine Bioassay.  Several of the samples tested positive for infections PEDV (Table 2) even when PCR indicated no virus was present; PCR molecular detection of the virus did not produce a complete picture of PEDV survival.  For instance, the PCR method indicated no virus in soil #1 or #2 at 24 hours, yet the soil-manure mixture caused disease in a swine bioassay test—the gold standard test for infectious PEDV.

 

Table 2. Outcome of Swine Bioassay
Manure-slurry Soil Composite
Time (hours) #1 #2 #3 #4 #5 #6 #6
24 Pos Pos Neg Pos Neg Neg Pos
48 Pos Neg Neg Neg Pos Neg Pos

†Animals inoculated by oral gavage of 10 mL of phosphate buffer-diluted sample.  A porcine epidemic diarrhea virus positive (Pos) or negative (Neg) score is based on fecal swab molecular diagnostic test (reverse transcriptase quantitative polymerase chain reaction).

Are there any soil environmental factors that can help predict whether/how long infectious PEDV lasts in soils?  Anything that would damage or disrupt the membrane or proteins on the outside of PEDV would render the virus non-infectious.  Theoretically moist soils with lots of active bacteria would release enzymes to chew up PEDV proteins or alkaline (high pH) soils may denature PEDV proteins and damage membranes to inactivate PEDV.  On the other hand, soils where manure rapidly dries would help preserve PEDV. None of these hypotheses could explain the PCR or swine bioassay results. Only one factor seemed related to PEDV persistence—high soil phosphorous seemed to protect the virus.  No single factor seemed to destroy the virus.

Future Plans

Additional studies are underway determining where PEDV is found within three production sites and the surrounding environment immediately after an outbreak of PEDV.  The sites will be monitored over 18 months to signs of PEDV re-emergence.

Authors

Corresponding author:  Dan Miller, Research Microbiologist, USDA Agriculture Research Service; email: Dan.miller@ars.usda.gov

Other authors:  Erin Stevens (Department of Animal Science, University of Nebraska – Lincoln); Amy Schmidt (Department of Biological Systems Engineering, University of Nebraska – Lincoln); Sarah Vitosh-Sillman and J. Dustin Loy (School of Veterinary Medicine and Biomedical Sciences, University of Nebraska – Lincoln).

Additional information

Stevens EE, Miller DN, Brittenham BA, Vitosh-Sillman SJ, Brodersen BW, Jin VL, et al. Alkaline stabilization of manure slurry inactivates porcine epidemic diarrhea virus. Journal of Swine Health and Production. 2018;26(2):95-100.

Acknowledgements

Funding for this research was provided by the National Pork Board and USDA Agriculture Research Service operational funds. USDA is an equal opportunity provider and employer.

 

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. 2019. Title of presentation. Waste to Worth. Minneapolis, MN. April 22-26, 2019. URL of this page. Accessed on: today’s date.

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Manure Treatment and Natural Inactivation of Porcine Epidemic Diarrhea Virus in Soils

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Purpose

The porcine epidemic diarrhea virus (PEDv) outbreak in North America has substantially impacted swine production, causing nearly 100% mortality in infected newborn piglets. Because manure may remain a source of reinfection, proper manure management practices to limit outbreaks need to be developed and evaluated. Two laboratory studies simulating manure pit treatment with increasing amounts of quicklime were conducted to determine PEDv susceptibility to increasing pH. Additionally, two laboratory soil incubation studies contrasting manure liming, multiple soil types, and two antecedent soil moistures were conducted over several months with incubation conditions mimicking the climates in Minnesota, Missouri, and Oklahoma to determine whether current manure application practices reduce the potential for PEDv reinfection via manure-amended soil. Quantitative PCR and live swine bioassays were used to enumerate PED virus and to determine whether manure and soil samples contained infectious PEDv.

What did we do?

Quicklime-Manure Slurry Incubations: An initial short-term manure slurry study was conducted on fresh PEDv-positive manure slurry collected in 2015 from the shallow pit of a commercial swine facility in southeast Nebraska. Manure was sampled prior to treatment (0 h) and then distributed among glass beakers (250 mL) to accommodate triplicates of three treatments: liming to pH 10, liming to pH 12, and unlimed manure. Following pH adjustment, aliquots of each sample were collected at 1 and 10 h, immediately neutralized with 10 mM HCl and stored at -80°C for subsequent analysis. In a second manure slurry incubation, triplicate PEDv-positive manure samples collected from a commercial swine operation in south central Nebraska site in December 2016 were mixed in equal portion (w:v) with distilled water to mimic manure slurry consistency observed in swine production pit storages. Quicklime was added stepwise (0.25 g addition) to each manure slurr! y sample with continuous stirring to gradually increase manure slurry pH. After each addition of quicklime, pH was measured and an aliquot of manure slurry was collected for subsequent quantitative PCR PEDv enumeration and infectivity in a pig bioassay.

Long-term manure and soil incubation. Initial tests determined appropriate initial soil moisture contents (representing a ‘dry’ and ‘moist’ soil condition) and manure:soil ratios (1 g slurry:3 g soil) to best represent the manure:soil within an injection furrow when slurry is injected into soil, and appropriate liming source (ag lime vs. quicklime). PEDv-positive manure slurry collected from a commercial swine operation in southeast Nebraska was divided between two 3-L containers, one for limed treatment (LIME) and the other for the control, or no-lime, treatment (CNL). Quicklime (30 g) was added to one 3 L portion (equivalent to an application of 80 lbs. quicklime per 1000 gallons of slurry) to achieve a final pH of 12. Both treated and untreated slurry stocks were incubated at room temperature for 24 hours. Distilled water was added to two soils, a silty clay loam (pH 7.0) and a loamy fine sand (pH 6.9), to attain 10% and 30% water holding capacity! (dry and moist soil condition). Thirty grams (dry weight) of soil was apportioned to multiple 50 mL screw top conical tubes and a cavity was made in the center of the soil by pressing a 10 mL pipet tip into the soil. Ten mL of slurry (LIME or CNL) were then added to each soil tube via pipet. Four replicate tubes were immediately frozen at -80°C for each combination of soil, moisture, and manure treatment to represent initial soil application (day 0). The tubes were loosely capped and placed into one of three incubators operated independently throughout the trial to simulate soil temperatures between November 1 and May 1 at one of three geographic locations: southern Minnesota, northern Missouri, and central Oklahoma (Figure 1). Twenty replicate tubes were created for each combination of soil, moisture, incubation, and manure treatment, and a set of four tubes were collected for each treatment combination on days 30, 60, 90, 120 and 150 of the incubation and immediately transfer! red to a -80°C freezer for storage.

Molecular detection and quantification of PEDv. Prior to analysis, soil and manure samples were removed from -80°C storage and allowed to thaw at room temperature. The RNA in each sample was extracted using the RNA PowerSoil Total RNA Isolation kit (Mo Bio, Carlsbad, CA). PEDv was detected in samples by reverse transcription and quantitative polymerase chain reaction (RT-qPCR).

Swine bioassay. To confirm that conditions yielding a PCR negative result actually inactivated the PED virus and rendered the manure non-infectious, a live pig bioassay was conducted with the limed and non-limed manure slurry samples from the initial short-term manure slurry incubation (quicklime addition). Fifteen pigs, approximately 21 days old, were sourced from a high-health facility whose dams tested negative for PEDv antibodies and virus by PCR. Piglets were tested for PEDv upon arrival and confirmed negative. Piglets were randomly assigned to individual housing in BSL-2 rooms at the University of Nebraska-Lincoln Life Sciences Annex as follows: control (3 piglets), pH 10 (6 piglets), and pH 12 (6 piglets), and allowed to acclimate for three days. Each pig was then administered a 10-mL oral gavage of manure slurry: three piglets in the control room received one of the three un-limed slurry samples; six piglets in the pH 10 room received one of the six limed (pH 10) sl! urry samp les (three limed for 1 h and three limed for 10 h); and six pigs in the pH 12 room received one of the six limed (pH 12) slurry samples (three limed for 1 h and three limed for 10 h). Piglets were monitored for fecal shedding of PEDv for four days until control animals began to demonstrate clinical signs of PEDv infection, at which time all piglets were humanely euthanized. Fecal swabs, and duodenum, ileum, jejunum, and cecum samples were collected from each animal and fixed in formalin. All fecal and tissue samples were analyzed for the presence of detectable PED virus by immunohistochemistry and PCR.

PEDv, log # g soil

What have we learned?

Manure Slurry Incubation: Manure limed to pH 10 and pH 12 for 1 and 10 h yielded no detectable PEDv RNA. Live swine bioassay results confirmed that these samples were not infective while control samples resulted in PEDv infection of piglets. These results indicate that a final manure slurry pH of 10 (equivalent to 50 lbs. of quicklime added to 1000 gallons manure slurry) is sufficient to reduce PEDv RNA to an undetectable concentration after 1 hour of contact time. All pigs receiving limed manure (pH 10 or 12 maintained for 1 or 10 h) during the live swine bioassay tested negative for PEDv infection while control pigs (un-limed treatment) all tested positive for PEDv infection (Figure 1). The pig bioassay results confirmed that the PCR assay is a reliable predictor for the presence of infectious PEDv in these matrices and that lime addition to achieve pH 10 for just one hour is sufficient to deactivate the virus in stored manure.

Soil Incubations: At the completion of the long-term (150-day) soil incubation, a subset of the frozen samples (LIME and CON soil samples collected on day 0 and 30) was selected for RNA extraction and qPCR analysis. The qPCR results from days 0 and 30 yielded no detectable PEDv RNA in either the limed or un-limed manure-amended soils (Figure 1). Furthermore, manure-amended soils did not differ from soil-only controls even though PEDv RNA was still detectable in the original manure slurry at high concentrations. No differences in PEDv abundance were detected on either day when initial soil moisture (10% vs 30% water holding capacity), incubation condition (MN vs. MO vs. OK), or soil type (silty clay loam and loamy fine sand) were varied. For these soils, the concentration of PEDv in limed or un-limed manure decreased immediately to a non-detectable level. These results indicate that manure-amended soil with pH 6.9 or greater is not a vector for transmission of the PED virus.

A consistent finding from all of the studies is that pH of media (slurry or soil) strongly influences PED virus survival.

Future Plans

Additional studies are underway to identify the lowest pH at which the PED virus is rendered non-infectious in slurry manure.

Corresponding author, title, and affiliation

Amy Millmier Schmidt, Assistant Professor, Departments of Biological Systems Engineering and Animal Science, University of Nebraska – Lincoln

Corresponding author email

aschmidt@unl.edu

Other authors

Stevens, E., A. Schmidt, D. Miller, J.D. Loy and V. Jin

Additional information

Dr. Amy Millmier Schmidt, corresponding author, can also be reach at (402) 472-0877.

Acknowledgements

Funding for this research was provided by the National Pork Board. Gratitude is extended to Ashley Schmit for assistance with laboratory activities and animal care. Special thanks to the Nebraska pork producers who granted access to their farms for collection of PEDv-positive manure.

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Sensitivity of Soil Microbial Processes to Livestock Antimicrobials

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Purpose

Many of the antimicrobials administered to livestock are excreted in manure where they may undergo natural breakdown, become more tightly associated with the manure and soil, or become mobilized in wastewater/runoff. Both liquid and solid manure is usually applied to nearby crop fields as a manure fertilizer, recycling the nutrients in the manure. Public concerns about the overuse of antimicrobials leading to greater antibiotic resistance and potentially greater risk for human health have led to new regulations limiting the use of antimicrobials in animal production. However, there are several significant research questions that need to be explored in order to determine how important the links are between antimicrobial use in livestock production and increased antibiotic resistance in humans.

One important issue involves how important soil processes (decomposition, nutrient transformation, and gas emissions) could be altered by antimicrobial compounds in manures and wastewater. In a previous study at a cattle feedlot in central Nebraska, we found typical antimicrobial concentrations in feedlot runoff at low part per billion (ppb) levels and were detected infrequently (<20% of the time). One exception, monensin, was usually detected with an average concentration of 87 ppb and peak concentrations above 200 ppb. Adding complexity to this issue is that soils may experience a variety of conditions ranging from fully aerobic, to denitrifying (using nitrate as a terminal electron acceptor), to anaerobic, and a diverse variety of microbes may predominate in these various conditions. How might soil functions be affected under a range of conditions experiencing differing concentrations of antibiotic? Are there clear very high concentration thresholds that completel! y inhibit specific soil functions? The purpose of this study was to determine the effects of three common livestock antibiotics at multiple concentrations on decomposition, nutrient transformation, and gas production in pasture soil under aerobic, denitrifying, and anaerobic conditions.

What did we do?

A soil slurry incubation study was conducted with pasture soil where runoff from a nearby cattle feedlot was occasionally applied. Monensin, sulfamethazine, and lincomycin were amended (0, 5, 500, and 5000 ppb) to mason jars and serum bottles containing soil and simulated cattle feedlot runoff. The mason jars were flushed with air (aerobic) while serum bottles were flushed with nitrogen gas (anaerobic). Denitrifying conditions were established initially in a subset of anaerobic serum bottles which were supplemented with nitrate (100 mg NO3-N L-1). All antimicrobial amendments and conditions were replicated in triplicate and incubated at 20°C. Headspace gas composition and decomposition products were both measured using gas chromatography and monitored over several weeks.Table 1. Summary of the effects of various livestock antibiotics on decomposition under aerobic, anaerobic, and denitrifying conditions

What have we learned?

Soil processes were generally affected only at the highest antibiotic concentrations, which are 10x greater than observed levels in feedlot runoff. Furthermore, the effects on soil processes depended upon the antibiotic tested (Table 1). Monensin, a broad-range antimicrobial, had the greatest effect on a number of processes. At highest monensin concentrations tested (5000 ppb), both aerobic and anaerobic decomposition (including denitrification) were affected as shown by greater VFA concentrations and low to no gas production (CO2, N2O, and CH4). Even at 500 ppb, monensin had some effect—CO2, N2O, and CH4 gas production were reduced. Sulfamethazine at 5000 ppb inhibited full denitrification (no N2O produced), but there was no effect on other gases or VFA. At 500 ppb sulfamethazine, N2O production was reduced by half. Lincomycin’s only observable effect was lower (0.5x) N2O production at the 5000 ppb level under denitrification conditions.

These results show important soil processes can be blocked by high levels of antibiotics found in animal manures, but inhibition depends upon the antibiotic.  A general antimicrobial like monensin affected microbial processes far more than antimicrobials with a specific mode of action.  The highest antibiotic levels evaluated were 5 to 10 times higher than levels found in animal manures, so soils are likely not impacted under normal conditions where manures mixed and distributed into soils.  Antibiotic breakdown in the soil further helps reduce the potential for antibiotics to build up in the soils.

Future Plans

These incubations only assessed the effect of a one-time dose of antimicrobials. Future studies will examine how longer soil exposures affect soil processes. Additional studies will also compare how soils that have different manure exposure histories (cattle feedlot soil with heavy exposure versus protected prairie soils with very low manure exposure) would react to higher levels of antimicrobials.

Corresponding author, title, and affiliation

Dan Miller, Microbiologist, USDA-ARS

Corresponding author email

dan.miller@ars.usda.gov

Other authors

Matteo D’Alessio, Postdoctoral Researcher, Nebraska Water Center; Dan Snow, Director of Services, Water Sciences Laboratory

Additional information

151 Filley Hall, UNL East Campus, Lincoln, NE 68583

Ph: 402-472-0741

https://dl.sciencesocieties.org/publications/csa/pdfs/61/8/4?search-result=1

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. 2017. Title of presentation. Waste to Worth: Spreading Science and Solutions. Cary, NC. April 18-21, 2017. URL of this page. Accessed on: today’s date.

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Legacy Phosphorus in Calcareous Soils: Effects of Long-Term Poultry Litter Application on Phosphorus Distribution in Texas Blackland Vertisol

Why Study the Impacts of Poultry Litter on Phosphorus Cycling?

Livestock manures, including poultry litter, are often applied to soil as crop fertilizer or as a disposal mechanism near livestock housing. Manures can improve soil quality and fertility; however, over-application can result in negative environmental consequences, such as eutrophication of surface waters following runoff of soluble or particulate-associate phosphorus (P). In soil, P exists in many forms (inorganic/organic, labile/stable) and the fate of manure P is highly dependent upon soil properties, including soil texture and microbial activity. The Houston Black series is a calcareous (~17% calcium carbonate), high-clay soil that occupies roughly 12.6 million acres in east-central Texas. These Blackland vertizols are agronomically important for the production of cotton, corn, hay, and other crops, but their high calcium and clay content could lead to accumulation of P in forms that are not readily available for plant utilization. Accumulated P could serve as a source of legacy P if mineralized or otherwise transformed in situ or transported with soil particles in runoff.

Very few studies have investigated the long-term effects of manure or litter application on soil P distribution: almost no data exist on manure impacts on calcium-associated organic P in soil. Sequential fractionation techniques, coupled with phosphatase hydrolysis, have allowed for greater understanding of manure/litter effects on soil P distribution and transformation. A fairly standardized designation is separation of extracted P into labile P (H2O- and NaHCO3-P), moderately labile P (NaOH-P; assumed to be associated with amorphous Al/Fe oxides and organic matter), and stable P (HCl-P; assumed to be Ca-associated phosphates). Incubation of the extracted fractions with excess P hydrolyzing enzymes enables further characterization of organic P as phosphomonoester-like, nucleotide-like, phytate-like, or non-hydrolyzable organic P.

The specific objectives of this study were to investigate effects of long-term poultry litter application and land-use type (cultivated, grazed/ungrazed improved pasture, native rangeland) on soil P distribution in watershed-scale plots. The goal of this work is an improved understanding of how litter impacts P cycling and availability in these agronomically important calcareous soils.

What did we do?

We evaluated the effect of long-term (> 10 years) poultry litter (broiler and turkey litter) application at rates of 4.5, 6.7, 9.0, 11.2, and 13.4 Mg/ha (wet weight) on P distribution in cultivated (4.0 to 7.4 ha) and pasture (1.2 to 8.0 ha) watersheds near Riesel, Texas. The experiment was initiated in 2000 by the USDA-ARS Grassland Soil and Water Research Laboratory in Temple, Texas (Harmel et al., 2004), where cultivated fields were in a 3-year corn-corn-wheat rotation and received an annual application of poultry litter at predetermined rates. Litter was incorporated into cultivated plots with a disk or field cultivator. Improved pastures received surface-application of litter. Control treatments (no litter application) included cultivated, native rangeland, and grazed improved pasture.

Soil samples were collected from each watershed and subjected to sequential fractionation with water (H2O), sodium bicarbonate (0.5 M NaHCO3), sodium hydroxide (0.1 M NaOH), and hydrochloric acid (1.0 M HCl) (He et al., 2006; Waldrip-Dail et al., 2009). Total P in the extracts was determined by inductively coupled optical-emission plasma spectroscopy. Inorganic P was determined colorimetrically using a modified molybdenum blue method (He and Honeycutt, 2005). Concentrations of organic P forms (monoester-, DNA- phytate-like, and non-hydrolyzable organic P) were determined following enymatic hydrolysis with acid phosphomonoesterases and nuclease P1 (He and Honeycutt, 2001; He et al., 2003, 2004).

What have we learned?

This research clearly showed that use of poultry litter as a nutrient source for both cultivated and pasture watersheds increased concentrations of total P in all extractable fractions, especially at high litter application rates (Figure 1).

Figure 1. Total extractable phosphorus (sum of P in H2O, NaHCO3, NaOH, and HCl extracts) from 2002 to 2012 in cultivated fields and pasture following application of poultry litter.

The majority of the total extractable P was found in the fractions that are associated with calcium in the soil (HCl and NaHCO3). An average of 68% of total P was extractable with HCl. However, differences were observed in extractable P distribution due to land-use type and litter application rate. In cultivated watersheds, the inorganic pools primarily affected were H2O- and NaHCO3-P, with some treatments having as much as four times more inorganic P in the labile pool compared with the stable pool. Whereas in the pastureland, increases in soil inorganic P were only found in pasture when either cattle was grazed or when poultry litter was applied at the highest rate.

The addition of litter increased all forms of labile, enzyme hydrolyzable organic P in cultivated plots, compared to plots that did not receive litter (Figure 2).

Figure 2. Distribution of inorganic phosphorus, enzymatically hydrolyzable organic phosphorus (monoester-, DNA, and phytate-like P), and nonhydrolyzable organic phosphorus.

In cultivated fields, litter application significantly increased monoester-, DNA-, and phytate-like P; in contrast, only monoester-like P was increased in pasture, and phytate- and DNA-like P concentrations were actually lower in litter-amended pasture than native rangeland. The majority of the extractable organic P was non-hydrolyzable calcium-associated P (HCl-P), and this fraction was increased up to 217% by 10 years of poultry litter application. Thus, we concluded that repeated litter application increased levels of both soluble inorganic P and stable, non-hydrolyzable organic P, but specific response varied with application rate and management.

Future Plans

The fate of manure P in the environment is not yet well understood, and the fact that a large fraction of calcium-associated P was not accessible to the enzymes used in this study does not necessarily indicate that this fraction is not accessible to other soil phosphatases. Only very limited studies have been conducted on organic P in the HCl fraction, and more work is required to provide a clearer understanding of how this fraction interacts with soil minerals and organic matter. Results like this long-term study show the potential for high levels of accumulation of P that is not readily available for plant uptake and that could be transferred to surface or groundwaters. In addition, further applications of poultry litter, other livestock manure, or inorganic fertilizer, could lead to increased concentrations of labile P due to lack of available sorption sites in soil. Further study is warranted to evaluate the long-term effects on P distri bution and accumulation of legacy P following application of different manure types (e.g., beef and dairy cattle, swine) and on soils with contrasting physicochemical properties.

Authors

Heidi M. Waldrip, Research Chemist at USDA-ARS Bushland, TX heidi.waldrip@ars.usda.gov

Paulo Pagliari, Univ. Minnesota; Zhongqi He, Research Chemist at USDA-ARS, New Orleans, LA; R. Daren Harmel, Agricultural Engineer at USDA-ARS, Temple, TX; N. Andy Cole, Animal Scientist at USDA-ARS, Bushland, TX; Mingchu Zhang, Univ. Alaska

Additional information

Heidi M. Waldrip, Research Chemist, USDA-ARS Conservation and Production Laboratory, PO Drawer 10, Bushland, TX 79012. Tel: 806-356-5764. email: heidi.waldrip@ars.usda.gov.

Harmel, R. D., H. A. Torbert, B. E. Haggard, R. Haney, and M. Dozier. 2004. Water quality impacts of converting to a poultry litter fertilization strategy. J. Environ. Qual. 33: 2229-2242.

References:

He, Z., T. S. Griffin, and C. W. Honeycutt. 2006. Soil phosphorus dynamics in response to dairy manure and inorganic fertilizer applications. Soil Sci. 171: 598-609.

He, Z., and C. W. Honeycutt. 2001. Enzymatic characterization of organic phosphorus in animal manure. J. Environ. Qual. 30: 1685-1692.

He, Z., and C. W. Honeycutt. 2005. A modified molybdenum blue method for orthophosphate determination suitable for investigating enzymatic hydrolysis of organic phosphates. Commun. Soil Sci. Plant Anal. 36: 1373-1385.

He, Z., C. W. Honeycutt, and T. S. Griffin. 2003. Enzymatic hydrolysis of organic phosphorus in extracts and resuspensions of swine manure and cattle manure. Biol. Fertil. Soils. 38: 78-83.

He, Z., T. S. Griffin, and C. W. Honeycutt. 2004. Enzymatic hydrolysis of organic phosphorus in swine manure and soils. J. Environ. Qual. 33: 367-372.

Waldrip-Dail, H., Z. He, M. S. Erich, and C. W. Honeycutt. 2009. Soil phosphorus dynamics in response to poultry manure amendment. Soil Sci. 174: 195-201

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. 2015. Title of presentation. Waste to Worth: Spreading Science and Solutions. Seattle, WA. March 31-April 3, 2015. URL of this page. Accessed on: today’s date.

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Swine Manure Application Method Impact on Soil Arthropods


Does Manure Application Impact Soil Arthropods? *

Soil arthropod populations and diversity provide an indication of the biological quality of soil, which can impact soil fertility. Arthropods include insects, crustaceans, arachnids, myriapods, and scorpions and nearly every soil is inhabited by many different arthropod species. Row-crop soils may contain several dozen species. One particular arthropod species, mites, can have a significant impact on nutrient release in soil. For this study, the impact of swine manure slurry applied via broadcast and injection at a rate designed to meet the agronomic nitrogen needs of corn was investigated to determine the manure application method impact on soil arthropod population and diversity.

What did we do?

Treatments include broadcasted swine slurry, injected swine slurry, and non-manured check plots with four replications per treatment. Plots have been monitored following manure application in June 2014 and will continue through June 2015. Soil samples were removed 4 d prior to manure application and at 1, 2, and 4 weeks and monthly thereafter from 0 to 8 inches on each plot. Arthropods were extracted by use of Burlese funnels and collected species are being sorted and characterized.

What have we learned?

Species characterization is on-going and will be summarized for presentation in the poster session at the conference.

Future Plans

Results of this work will allow us to better understand the impact of manure application on soil biological properties, a component in defining the overall fertility or “health” of soil.

Authors

Amy Millmier Schmidt, Assistant Professor and Livestock Bioenvironmental Engineer, University of Nebraska – Lincoln aschmidt@unl.edu

Nicole R. Schuster, Graduate Research Assistant, University of Nebraska – Lincoln; Julie Peterson, Assistant Professor and Entomologist, University of Nebraska – Lincoln

Additional information

Dr. Amy Millmier Schmidt; (402) 472-0877; aschmidt@unl.edu

Acknowledgements

We would like to recognize a number of individuals who assisted with soil sample collection, arthropod extractions, and other laboratory activities over the course of this project, including Keith Miller, Ethan Doyle, Mitch Goedeken, Eric Davis, Lucas Snethan, Kevan Reardon and Kayla Tierramar

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. 2015. Title of presentation. Waste to Worth: Spreading Science and Solutions. Seattle, WA. March 31-April 3, 2015. URL of this page. Accessed on: today’s date.

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Soil Nitrate Testing Protocol Development for Lands Receiving Injected Manure

Injection of liquid manure provides a number of benefits to the environment and cropping systems. Manure placement under the soil surface conserves nitrogen by decreasing ammonia loss. Injection can be conducted in a manner consistent with no-till farming practices resulting in greater conservation of both soil and manure nutrients. Thus the value of manure to the crop is increased.

Traditional soil nitrate testing protocol recommendations were developed on lands that received evenly distributed broadcast manure applications. However, the banding of manure during injection presents a challenge for soil testing. Random placement of soil probes in banded fields could result in artificially high or low nitrate analysis depending on the sampling distance from manure bands.

Many states recommend such nitrate testing when the corn is about 12 inches tall. In the weeks following the soil test the crop will grow quickly with high N demand. Soil testing at this time allows the producer to determine if it will be profitable to sidedress the crop with an additional N source. For example, in Pennsylvania, the Pre-Sidedress Nitrate Test (PSNT) is utilized to measure soil nitrate when corn is around the six-leaf stage (about 12-18 inches). Sidedress nitrogen need is calculated using the soil nitrate test level, expected yield, and nitrogen available from previous legumes or manure applications.

Research was conducted to explore nitrate distribution in a two dimensional view perpendicular to manure injection bands. In the proposed presentation the research results and new soil testing protocol for early-season nitrate will be discussed. This work provides an excellent tool to assure economic and environmental optimization of manure nitrogen.

What is the Pre-Sidedress Nitrate Test (PSNT)?

In the mid-Atlantic region the Pre-Sidedress Nitrate Test (PSNT) is an accepted tool for measurement of Nitrogen availability to a growing corn crop. The test is conducted when corn reaches the six-leaf stage by taking a number of twelve-inch deep soil samples. The samples are quickly dried or frozen to halt microbial N transformations and sent to a soils laboratory. A measure of soil Nitrate (NO3) level provides an indication whether the soil contains enough N to sustain maximum yield through the remainder of the growing season. The PSNT provides guidance to determine supplemental N fertilizer rates needed for soil with a low measured NO3 level. The PSNT becomes suspect on grounds receiving manure injection. Random sampling near manure bands may give artificial confidence in NO3 availability, while samples away from bands may indicate unnecessary need for commercial fertilizer.

The purpose of this work was to determine a PSNT sampling protocol for soils receiving injected manure.

What did we do?

Dairy manure was injected prior to planting of corn using shallow-disc injection spaced at 30 inches. When corn was at the six-leaf stage a ‘Monolith’ soil sampler was used to remove blocks of soil in a perpendicular direction to manure injection bands. Twelve-inch deep PSNT soil cores were systematically removed every inch across the thirty-inch sample. Each of these was evaluated individually for NO3 concentration. Composite cores of all thirty samples were also evaluated. To provide comparison, similar samples were attained in Monolith samples from Control (no manure) and Broadcast Manure plots.

What have we learned?

Others have suggested pairing manure samples to attain an average for manure-injected soils, with one sample attained in the band and one between bands. In our study, analysis of NO3 levels in a perpendicular direction to travel of manure injection equipment demonstrated concentrations in a sine wave pattern with higher concentrations located near the injection bands. Further analysis showed that five samples taken at any positions perpendicular to the manure band, and spaced six inches apart provide a reliable and repeatable sampling method. Four sets of samples taken in this manner (20 soil cores in total) were statistically better at predicting soil Nitrate level then ten paired soil sample sets (20 soil cores in total). Using this sampling protocol, marking of manure bands is not necessary. Testing can be performed at random locations in the field.

Future Plans

Manure injection conserves Nitrogen in comparison to broadcast application. Some manure injection implements can be used with minimal soil surface disturbance that is acceptable within no-till guidelines. In the mid-Atlantic region, manure injection is expected to become more common as economics and regulations drive increased Nitrogen conservation. Release of this PSNT soil sampling protocol will allow producers to accurately manage N in growing corn. The protocol will assist in adoption of manure injection utilization by providing a tool by which producers can gain confidence and knowledge centered on their manure nutrient management. Utilization of this sampling protocol will advance environmental goals in water and air quality.

Authors

Robert Meinen, Senior Extension Associate, Penn State University rjm134@psu.edu

Douglas Beegle, Peter Kleinman, Heather Karsten, Glenna Malcolm

Additional information

Penn State NorthEast SARE Sustainable Dairy Cropping Systems Project

http://plantscience.psu.edu/research/areas/crop-ecology-and-management/c…

Video of research manure injection system

http://extension.psu.edu/plants/crops/cropping-systems/video/sdmi-1

Acknowledgements

NRCS CIG and NESARE grants supported this 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. 2015. Title of presentation. Waste to Worth: Spreading Science and Solutions. Seattle, WA. March 31-April 3, 2015. URL of this page. Accessed on: today’s date.

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