Category: Waste to Worth

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Evaluating Full-Scale Greenhouse Systems for Lagoon Sludge Drying and Pathogen Reduction

Purpose

This study aims to assess the performance of solar greenhouse drying as a management strategy for swine lagoon sludge. In North Carolina, swine lagoons are heavily concentrated in a small geographic area (Figure 1), which overlaps with a high concentration of poultry operations. This results in a challenge for identifying suitable acres for sludge application, particularly for nursery operations with high concentrations of zinc (Zn) in the sludge. Drying the sludge creates opportunity for long-distance transportation, further processing to produce marketable granules/pellets, as well as co-firing to produce energy and concentrate minerals in ash form. While a useful strategy, drying is an energy-intensive process and often requires significant capital investment and trained operators, both of which are a barrier for on-farm adoption. Solar drying using greenhouses is a low-cost technology that requires minimal oversight and management. While successfully adopted in wastewater treatment applications, solar drying has not been fully evaluated in manure management contexts.

Figure 1. Distribution of swine operations (red dots) in Eastern North Carolina (Source: NC Department of Environmental Quality)

What Did We Do?

Figure 2. Novel lagoon sludge drying system showing: (A) entrance and air inlet louvers, (B) exhaust fans, (C) sludge layer at beginning of drying test, and (D) panoramic view of drying bed at end of drying test.

We conducted two sludge drying tests in Summer 2021 using a greenhouse structure we built on NC State University campus (Figure 2). The tests utilized freshly dredged sludge with a total solid concentration of 8%. The sludge was in a pumpable state and was applied to the drying bed in a uniform layer. The drying bed consists of a concrete floor (17m long, 6 m wide) with a sweeping mechanism to level the sludge and facilitate removal at the study termination. Two different loading rates were tested in this study: 13.9 kg-m-2 (low loading density test), and 28.3 kg-m-2 (high loading density test). Only the two middle fans for the greenhouse structure were operated continuously during the testing period. Each fan had a nominal flowrate of 20,000 cubic feet per minute. The sweeping mechanism was operated twice daily to mix the material in the drying bed. Temperature and relative humidity were monitored inside the greenhouse structure near the air inlet, at the middle of the building, and near exhaust fans. Ambient conditions were monitored using an on-site weather station. At the completion of each test, the recovered material was analyzed for moisture, nutrient, ash, and energy content.

What Have We Learned?

The daily weather conditions during the two drying tests are summarized in Table 1. Ambient temperature and relative humidity within the greenhouse structure were greater for the high-loading density test than the low-loading density test by around 3℃ and 17% relative humidity points, respectively. This data suggests favorable drying conditions for low loading density. Wide variability in weather conditions during the spring and summer seasons in North Carolina are common and likely to be a significant factor in the performance of similar drying systems.

Table 1. Daily weather conditions during test periods (Source: Lake Wheeler Road Field Laboratory Weather station)

Test Date Temperature (C) Relative Humidity (%) Rain (mm)
 Avg. Solar Radiation (W.m-2) ETo* (mm)
Mean Max. Min. Mean Max. Min.
Low Loading Density 5/19 20.2 28.3 11.2 55.5 91.7 25.1 0.0 334.3 5.2
5/20 22.0 29.8 11.4 54.9 91.9 27.5 0.0 318.5 5.5
5/21 20.9 27.8 14.7 47.8 78.2 22.6 0.0 296.4 5.7
High Loading Density 5/25 22.9 29.6 17.6 76.7 92.5 53.0 0.0 211.3 4.2
5/26 26.3 34.3 20.6 65.4 86.4 34.4 0.0 281.4 6.1
5/27 26.5 33.5 18.9 70.4 86.6 42.4 0.0 280.2 5.8
5/28 25.9 33.0 18.7 62.1 91.3 30.5 1.8 267.7 6.4
5/29 20.8 30.3 12.4 76.0 43.0 43.0 1.8 162.8 4.6

*Penman-Monteith Estimated Evapotranspiration at 2-meter height

Cross-greenhouse variability in air temperature and relative humidity was greatest between sunrise and sunset (7AM and 6PM) indicating active drying. Mechanical mixing of the sludge (Figure 3, denoted by vertical yellow lines) appears to have had a positive impact on the drying process as evidenced by the increase in average air temperature and relative humidity after mixing. This effect can be attributed to exposing more water-saturated sludge to drying air, which increases the moisture gradient, thus boosting convective drying. In addition, wet sludge is darker in color, which increases its radiation heat absorption.

Figure 3. Average greenhouse temperature (upper) and relative humidity (lower) during high-loading test. Vertical yellow lines indicate drying bed turning using the mechanical sweeping mechanism.

For the high-loading rate test, observing temperature and relative humidity on Day 4 (Figure 3) during daytime (hours 77 to 80) indicates the drying process has slowed down considerably with average air temperature and relative humidity inside the greenhouse closely matching inlet air. These observations suggest that accessible water in the sludge has been effectively removed.

Moisture content of sludge in the low-loading rate test decreased by 88% over 46 h while the high-loading rate treatment yielded a 91% reduction in moisture over 101 h. Using the starting total solids content of 7.9%, Using the drying bed dimensions and test duration, the average drying rates observed were 0.26 and 0.25 kgH2O.m-2.h-1 for low and high loading density tests, respectively. Over the drying duration, the average evapotranspiration, estimated using Penman-Monteith equation, was 0.23 kgH2O. m-2.h-1 (with a standard deviation of 0.03 kgH2O. m-2.h-1) which is 9% and 13% lower than observed evaporation rates for low and high loading density tests. These observations indicate the depth of material addition had minimal effect on the drying rate. In addition, these observations suggest the combined effect of mechanical ventilation and energy gain due to the greenhouse effect, increased the evaporation rate beyond average evaporation rate estimates. The air use efficiency was estimated as the amount of water removed during the test to the maximum amount of water removable (i.e., resulting in drying air saturation). Air quality at inlet and exhaust were used to estimate moisture ratio at both points. The air use efficiency for low and high sludge loading density were 21.1% and 21.0%, respectively.

Future Plans

These findings suggest opportunities to improve the drying efficiency. We are currently assessing different controllers in terms of their ability to manage mechanical ventilation to minimize energy use in low-drying conditions. Similarly, we are planning a series of tests to capture seasonal weather conditions. Gaseous emissions (ammonia and greenhouse gases (GHG) will be evaluated on full scale operation). Pathogen count for the starting and ending material will be quantified and reported to assess any risk associated with wider distribution of the dewatered material. Currently, a full-scale sludge drying compound (929square meters) has been built and operated on a swine operation in Eastern North Carolina. Our team is collecting data on the system operation and will be reporting system performance and energy use in upcoming meetings.

Authors

Mahmoud Sharara, Assistant Professor and Extension Specialist, North Carolina State University
msharar@ncsu.edu

Christopher Hopkins, Research Associate, Department of Forest Biomaterials, College of Natural Resources, NC State University
Joseph Stuckey, Research Operations Manager, Animal Poultry Waste Management Processing Facility, Prestage Department of Poultry Science, NC State University

Additional Information

https://animalwaste.ces.ncsu.edu/2021/08/drying-sludge-critical-to-improving-nutrient-distribution-and-utilization/

Acknowledgements

  • NC Department of Agriculture and Consumer Services, Bioenergy Research Initiative (BRI) – Contract No #17-072-4015, Potential for Integrating Swine Lagoon Sludge into N.C. Bioenergy Sector
  • Virginia Pork Council, Optimizing Greenhouse Drying of Swine Lagoon Sludge to Support Implementation in NC and VA.

 

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.

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A Workshop to Review BMPs and BATs for Control of Dust, Ammonia, and Airborne Pathogen Emissions at Commercial Poultry Facilities (Zhao)

Purpose

Poultry production is a significant source of air pollutant emissions including particulate matter (PM), ammonia (NH3), and  pathogens, which negatively impact bird health and performance, human respiratory health, food safety, and local environmental quality. Effective and economically feasible management practices and technologies to mitigate air pollutant emissions and pathogen transmission are urgently needed.

In the past decade, a variety of management practices and control technologies have been developed and preliminarily tested in commercial poultry facilities, with varying degrees of success. Technologies that have been applied for PM control include air filtration, impaction curtains, oil/water spraying, wet scrubbers, electrostatic precipitation, and electrostatic spray scrubbing. Among these, electrostatic methods and wet scrubbing achieve high removal efficiencies for both fine and coarse PM. For NH3 gas mitigation, various forms of scrubbing technologies such as trickling biofilters, acid spray scrubbers, and electrolyzed water spraying have been tested in commercial poultry facilities, alongside management practices such as feed additives and litter amendments. Acid spray scrubbers can be particularly attractive to poultry facilities since the sulfuric acid from the scrubber reacts with NH3 to create ammonium sulfate, which can be used as fertilizer to offset scrubber operating costs. A new technology using artificial floor was recently studied and demonstrated significant reduction in ammonia and PM concentrations and emissions at laying hen housing.

The avian influenza outbreak in 2014/15 and the current spread of the Highly Pathogenic Avian Influenza (HPAI) remind us that pathogen control at poultry facilities is crucial. Technologies such as electrostatic precipitators, electrostatic spray scrubbers, and electrolyzed water spraying systems have been tested to assess their capacities for airborne bacteria reduction.

The technical and economic feasibilities of these methods need to be evaluated for proper consideration by poultry producers and their stakeholders. All the above research results need to be introduced to producers for practical applications.

What Did We Do?

This workshop is organized for the researchers and Extension specialists to review the latest BMPs and BATs on control of dust, ammonia, and pathogens at poultry facilities for improved biosecurity, food safety, environmental quality, and the overall sustainability of poultry production.  We have developed the following presentations and will present them at 2022 W2W.

    1. Manure Drying Methods to Control Ammonia Emissions (Dr. Albert Heber-Professor Emeritus, Purdue University)
    2. A Spray Wet Scrubber for Recovery of Ammonia Emissions from Poultry Facilities (Dr. Lingying Zhao, Professor, Ohio State University)
    3. Electrostatic Precipitation Technologies for Dust and Pathogen Control at Poultry Layer Facilities (Dr. Lingying Zhao, Professor, The Ohio State University)
    4. Field Experiences of Large-Scale PM Mitigation (Dr. Teng Lim, Professor, University of Missouri)
    5. Mitigation of Ammonia and Particulate Matter at Cage-free Layer Housing with New Floor Substrate (Dr. Ji-Qin Ni, Professor, Purdue University)

What Have We Learned?

    1. Newly developed BMPs and BATs can improve air quality in commercial poultry facilities: Manure belt layer houses reduce ammonia emissions by removing manure from the layer houses in 1 to 7 days. Belt aeration using blower tubes is one method that has been used to dry the manure on the belt.  Drying tunnels take manure from layer houses and utilize ventilation exhaust air to further dry the manure before it enters the manure storage or compost facilities or transfers to pelletizing operations.  Manure sheds and compost facilities are ventilated with building exhaust air or fresh air to dry manure in storage.
    2. The use of acid spray scrubbing is promising, as it simultaneously mitigates and recovers ammonia emission for fertilizer. Its low contribution of backpressure on propellor fans makes it applicable on US farms. A full-scale acid spray scrubber was developed to recover ammonia emissions from commercial poultry facilities and produce nitrogen fertilizer. The scrubber performance and economic feasibility were evaluated at a commercial poultry manure composting facility that released ammonia from exhaust fans with concentrations of 66–278 ppmv and total emission rate of 96,143 kg yr−1. The scrubber achieved high NH3 removal efficiencies (71–81%) and low pressure drop (<25 Pa). Estimated water and acid losses are 0.9 and 0.04 ml m−3 air treated, respectively. Power consumption rate was between 90 and 108 kWh d−1. The scrubber effluents containing 22–36% (m/v) ammonium sulphate are comparable to commercial-grade nitrogen fertilizer. Preliminary economic analysis indicated that a break-even of one year is achievable. This study demonstrates that acid spray scrubbers can economically and effectively recover NH3 from animal facilities for fertilizer.
    3. Two types of electrostatic precipitation-based dust control technologies have been developed at the Ohio State University: the electrostatic precipitator (ESP) and the electrostatic spray scrubber (ESS). Field tests of the ESP and ESS conducted at a commercial layer facility indicated that (1) the fully optimized ESP achieved respective mean PM5, PM10, and TSP removal efficiencies of 93.6% ±5.0%, 94.0% ±5.0%, and 94.7% ±4.4% and (2) the ESS exhibited respective mean PM2.5, PM10, and TSP removal efficiencies of 90.5% ±10.0%, 91.9% ±8.2%, and 92.9% ±6.9%.  A system of 88 large ESP units to treat exhaust air from the 4-house poultry facility at the minimum required ventilation rate of 24.8 m3 s-1 would have an initial cost of $757,680 and an annual operating cost of $10,831 ($13.43 per 1,000 birds), increasing annual facility electricity consumption by 54.2%. A system of ESS units designed to treat exhaust air for six exhaust fans in each of the 4 poultry houses that operated continuously year-round for minimum ventilation, is estimated to have an initial cost of $71,280 with an annual operating cost of $21,663 for water consumption and electricity usage. The ESP is more effective, and the ESS is more economically feasible to mitigate PM at a commercial egg production facility.
    4. The field-scale measurements of PM mitigation technologies are usually time-consuming to set up and maintain, and often only limited replications can be obtained. It is important to minimize interference to the routine farm operation. The use of different PM measurements, setup and maintenance required to ensure data quality, and differences between the mitigation technologies are discussed. It is important to consider practicality of the mitigations, along with safety, and long-term use of the different technologies.
    5. A new mitigation approach, using AstroTurf ® as floor substrate, reduced indoor concentrations and emissions of ammonia and PM at cage-free aviary-style layer rooms in a recent study. Results demonstrated that the average daily mean ammonia concentration in the two AstroTurf® floor rooms (7.5 ppm) was significantly lower (p < 0.05) compared with that in the two wood shaving floor rooms (15.2 ppm) with a reduction rate of 51%. Average daily mean large particles (all particles detected above ~2.5 µm) and small particles (all particles detected below ~0.5 µm) in the two AstroTurf® floor rooms were significantly reduced (p < 0.05) by 70% (501,300 vs. 1,679,700 per ft3) and 63% (906,300 vs. 2,481,100 per ft3), respectively, compared with those in the two wood shaving floor rooms. With the controlled and consistent ventilation rates among the rooms in the study, the emissions of ammonia and PM (large and small particles) from the two AstroTurf® floor rooms had similar reduction rates.

Future Plans

More workshops to review BMPs and BATs for mitigation of air emissions and pathogen transmission in poultry facilities will be organized as new research development and findings emerge.  The workshop will target audiences of researchers, farmers, and professionals working with farmers.

Authors

Presenting authors

Lingying Zhao, Professor and Extension Specialist, The Ohio State University

Albert Heber, Professor Emeritus, Purdue University

Teng Lim, Professor, University of Missouri

Ji-Qin Ni, Professor, Purdue University

Corresponding author

Lingying Zhao, Professor and Extension Specialist, The Ohio State University

Corresponding author email address

Zhao.119@osu.edu

Additional authors

Matt Herkins, Graduate Research Associate, The Ohio State University

Albert Heber, Professor Emeritus, Purdue University

Teng Lim, Professor, University of Missouri

Ji-Qin Ni, Professor, Purdue University

Additional Information

Airquality.osu.edu

Hadlocon, L. J., A. Soboyejo, L. Y. Zhao, and H. Zhu. 2015. Statistical modeling of ammonia absorption efficiency of an acid spray scrubber using regression analysis. Biosystems Engineering 132: 88-95.

Hadlocon, L. S., R.B. Manuzon, and L. Y. Zhao. 2015. Development and evaluation of a full-scale spray scrubber for ammonia recovery and production of nitrogen fertilizer at poultry facilities. Environmental Technology 36(4): 405-416.

Hadlocon, L.J. and L.Y. Zhao. 2015. Production of ammonium sulfate fertilizer using acid spray wet scrubbers. Agricultural Engineering International: CIGR Journal. 17 (Special Issue: 18th World Congress of CIGR): 41-51.

Hadlocon, L.J., L.Y. Zhao, B. Wyslouzil, and H. Zhu. 2015. Semi-mechanistic modeling of ammonia absorption in acid spray scrubbers based on mass balances.  Biosystems Engineering 136:14-24.

Heber, A. J., T.-T. Lim, J.-Q. Ni, P. C. Tao, A.M. Schmidt, J. A. Koziel, S. J. Hoff, L.D. Jacobson, Y.H. Zhang, and G.B. Baughman. 2006. Quality-assured measurements of animal building emissions: Particulate matter concentrations. Journal of the Air & Waste Management Association. 56(12): 1642-1648.

Knight, R. M. L.Y. Zhao, and H. Zhu. 2021. Modelling and optimisation of a wire-plate ESP for mitigation of poultry PM emission using COMSOL. Biosystems Engineering 211: 35-49.

Knight, R., X. Tong, L. Zhao, R. B. Manuzon, M. J. Darr, A. J. Heber, and J. Q. Ni. 2021. Particulate matter concentrations and emission rates at two retrofitted manure-belt layer houses. Transactions of the ASABE 64(3): 829-841. (doi: 10.13031/trans.14337)

Knight, R., X. Tong, Z. Liu, S. Hong, and L.Y. Zhao. 2019. Spatial and seasonal variations of PM concentration and size distribution in manure-belt poultry layer houses. Transactions of the ASABE 62(2):415-427. doi: 10.13031/trans.12950

Lim, T. T., H. W. Sun, J.-Q. Ni, L. Zhao, C. A. Diehl, A. J. Heber, and P.-C. Tao. 2007. Field tests of a particulate impaction curtain on emissions from a high-rise layer barn. Transactions of the ASABE 50(5): 1795-1805.

Lim, T.-T., Y. Jin, Ni, J.-Q., and A. J. Heber. 2012. Field evaluation of biofilters in reducing aerial pollutant emissions from commercial finishing barn. Biosytems Engineering 112(3): 192-201.

Lim, T.-T., C. Wang, A. J. Heber, J.-Q. Ni, and L. Zhao. 2018. Effect of electrostatic precipitation on particulate matter emissions from a high-rise layer house. In Air Quality and Livestock Farming, 372 p. T. Banhazi, A. Aland, and J. Hartung, eds. Australia: CRC Press, Taylor and Francis Group.

Ni, J.-Q., A.J. Heber, M. J. Darr, T.-T. Lim, Diehl, and B. W. Bogan. 2009. Air quality monitoring and on-site computer system for livestock and poultry environment studies. Transactions of the ASABE 52(3): 937-947.

Ni, J.-Q., A. J. Heber, E. L. Cortus, T.-T. Lim, B. W. Bogan, R. H. Grant, and M. T. Boehm. 2012. Assessment of ammonia emissions from swine facilities in the U.S. – Application of knowledge from experimental research. Environmental Science & Policy 22(0): 25-35.

Ni, J.-Q., L. Chai, L. Chen, B. W. Bogan, K. Wang, E. L. Cortus, A. J. Heber, T.-T. Lim, and C. A. Diehl. 2012. Characteristics of ammonia, hydrogen sulfide, carbon dioxide, and particulate matter concentrations in high-rise and manure-belt layer hen houses. Atmospheric Environment 57(0): 165-174.

Ni, J.-Q., S. Liu, C. A. Diehl, T.-T. Lim, B. W. Bogan, L. Chen, L. Chai, K. Wang, and A. J. Heber. 2017. Emission factors and characteristics of ammonia, hydrogen sulfide, carbon dioxide, and particulate matter at two high-rise layer hen houses. Atmospheric Environment 154: 260-273. http://dx.doi.org/10.1016/j.atmosenv.2017.01.050.

Tong, X., L.Y. Zhao, A. Heber, and J. Ni. 2020.  Mechanistic modelling of ammonia emission from laying hen manure at laboratory scale. Biosystems Engineering. 192:24-41.

Tong, X., L.Y. Zhao, A. Heber, and J. Ni. 2020. Development of a farm-scale, quasi-mechanistic model to estimate ammonia emissions from commercial manure-belt layer houses. Biosystems Engineering 196, 67-87.

Tong, X., L.Y. Zhao, R. B. Manuzon, M. J. Darr, R. M. Knight, C. Wang, A. J. Heber, and J.Q. Ni. 2021. Ammonia concentrations and emissions at two commercial manure-belt layer housed with mixed tunnel and cross ventilation. Transactions of the ASABE 64(6): 2073-2087. (doi: 10.13031/trans.14634)

Tong, X., S. S. Hong., and L.Y. Zhao 2019. Development of upward airflow displacement ventilation system of manure-belt layer houses for improved indoor environment using CFD simulation. Biosystems Engineering 178:294-308.

Zhao, L.Y., L. J. S. Hadlocon, R. B. Manuzon, M.J. Darr, H. M. Keener, A. J. Heber, and J.Q. Ni. 2016. Ammonia concentrations and emission rates at a commercial manure composting facility. Biosystems Engineering  150: 69-78.

Acknowledgements

The wet scrubber development was supported by National Research Initiative Competitive Grant 2008-55112-1876 from the USDA Cooperative State Research, Education, and Extension Service Air Quality Program. The ammonia emission modelling work was supported by the USDA-NIFA Grant 2018-67019-27803.

The electrostatic precipitation-based dust control work was supported by the USDA National Institute of Food and Agriculture Grant 2016-67021-24434.

The Project funding for the Mitigation of Ammonia and Particulate Matter at Cage-free Layer Housing with New Floor Substrate presentation was provided by the U.S. Poultry & Egg Association. GrassWorx LLC provided the AstroTurf and financed the building of the flooring systems.

Appreciation is also expressed to the U.S. EPA, and participating producers and staff for their collaboration and support.

 

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.

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Swine manure and cedar woodchip applications improve soil ecological indicators and improve moisture retention

Purpose

Manure application has long been used as a soil amendment to supply nutrients for crop growth. However, the effects of manure on many other aspects of soil health have been less fully explored, especially in on-farm research settings. The health of soil biological communities has been shown to be positively correlated with the addition of organic materials and soil moisture. This study looked to confirm these observations in an on-farm setting using two types of organic treatments: swine manure and cedar woodchips and their impact on arthropod abundance and soil biological quality (QBS), measured through arthropod adaptations to deep soil living conditions (ecomorphological index).

What Did We Do?

12 plots were established (10 ft x 10 ft) on a commercial farm with clay loam soils, near Julian, Nebraska on a field planted in the second year of a corn-corn-soybean rotation. Plots were assigned to one of three treatments: swine slurry, swine slurry + woodchips, and control plots with no amendments with 4 replications per treatment. Swine slurry was applied at a rate of 4200 gal/ac. Woody biomass was applied at a rate of 10 ton/ac. Swine slurry was applied on all plots in April and woodchips were applied roughly 4 weeks later at the time when plots were established (Day 0).

At establishment (Day 0) and at 5 other days during the growing season (25, 54, 81, 99 and 128 days after establishment) roughly 1 gal of soil was collected from each plot by randomly sampling using a 2-in diameter sampler to a depth of 8-in. These samples were then transferred to Berlese-Tullgren funnels (Figure 1) for extraction of arthropods, a commonly used technique to assess microarthropods in the soil (Ducarme et al., 2002). A 70% ethanol solution was used to preserve the organisms for later analysis. Additionally, a 50 g subsample of the collected material was used to determine the moisture content of the soil at the time of sampling.

Figure 1. Berlese funnel uses light and heat to drive arthropods out of soil or litter sample. Photo credit University of Tennessee Extension.

The QBS method of classification was employed to assign an eco-morphological index (EMI) score based on soil adaptability level of each arthropod order or family (Parisi et al., 2005). Preserved arthropods from each soil sample were identified and quantified using light microscopy. For some groups, such as Coleoptera, characteristics of edaphic adaptation were used to assign individual EMI scores for each arthropod. Each sample was then assigned a total QBS score, which is the sum of the EMI values for each category of arthropod found in the sample.

What Have We Learned?

We observed that on days when soil moisture content was higher, QBS differed significantly among treatments, while no differences among treatments were evident during periods of low soil moisture content. This indicates that soil moisture is the most important soil factor for soil arthropods collected from the top 8 in of soil because they tend to migrate away from heat and drying to more favorable conditions (cooler and wetter environment).

Table 1. Differences in QBS index by treatment at different soil moisture content ranges.
Moisture % Treatment p-value
< 3.3 CON vs SS 0.16
CON vs SSW 0.24
SS vs SSW 0.99
3.4-4.0 CON vs SS 0.08
CON vs SSW 0.03
SS vs SSW 0.73
4.1-5.0 CON vs SS <0.0001
CON vs SSW <0.0001
SS vs SSW <0.0001
CON=control, SS=swine slurry, SSW=swine slurry and woodchips; (p-values are shown for each comparison between treatments at different moisture content ranges)

Thus, it was only when soil moisture was higher overall that arthropod populations in the soil were high enough to show a difference between treatments. For example, on day 54, a more variable moisture content of the soil was observed, with SSW, SS and CON having moisture contents of 4.16, 3.92, and 3.75%, respectively (Table 2).

Table 2. Mean soil moisture content by treatment and time since treatment application
Treatment Moisture %
Day 0 Day 25 Day 54 Day 81 Day 99 Day 128
CON 4.65 3.43 3.75a 3.95 4.77ab 4.31
SS 4.63 3.42 3.92ab 3.71 4.38a 4.1
SSW 4.68 3.72 4.16b 4.27 5.54b 4.63
Effect p-value
Moisture level 0.47
Moisture*treatment 0.05
CON=control, SS=swine slurry, SSW=swine slurry and woodchips; values within columns having the same superscript are not significantly different (p>0.05).

On this same day, QBS was also significantly greater for SSW (QBS=1350) compared to SS (110) and CON (97). Similarly, on day 99 the mean moisture content for the SSW treatment (5.54%) was greater than for SS (4.38%) and CON (4.77%; p<0.05) (Table 3).

Table 3. QBS index by treatment and sampling day
Treatment Day
0 25 54 81 99 128 Mean QBS
CON 156 115 97a 141 105a 150 127.17a
SS 125 106 110ab 135 135b 140 125ab
SSW 140 105 135b 160 141b 160 137b
QBS values having the same superscript within each sampling day are not significantly different. Absence of subscript represent no significant difference between treatments on that day (p≥0.05). CON=control, SS=swine slurry, SSW=swine slurry and woodchips.

In general, we observed that the application of swine slurry with woodchips has a positive effect on soil quality biological index, likely because it also had a positive effect on soil moisture. The application of red cedar woodchips seemed to provide with a good habitat for soil arthropods, which in the future may increase microbial activity and soil aggregation through decomposition of organic matter and binding.

Future Plans

Further analysis will be conducted to examine the arthropod classifications and their role on nutrient cycling more closely. Future research should also seek to confirm these observations in different climates and seasons of the year to observe the efficiency of the treatments, especially woodchips, to preserve soil characteristics that are favorable to microbes and arthropods.

Author

Mara Zelt, Research Technologist, University of Nebraska-Lincoln

Corresponding author email address

mzelt2@unl.edu

Additional authors

Karla Melgar Velis, Graduate Research Assistant, University of Nebraska-Lincoln

Amy Schmidt, Associate Professor, University of Nebraska-Lincoln

Agustin Olivo, Graduate Research Assistant, Cornell University

Eric Henning, Graduate Research Assistant, Iowa State University

Additional Information

Parisi, V., Menta, C., Gardi, C., Jacomini, C., & Mozzanica, E. (2005). Microarthropod communities as a tool to assess soil quality and biodiversity: a new approach in Italy. Agriculture, Ecosystems & Environment, 105, 323-333.

Acknowledgements

Funding for this study was provided by the Nebraska Environmental Trust and Water for Food Global Institute at the University of Nebraska-Lincoln. Much gratitude is extended to collaborating members of the On-Farm Research Network, Nebraska Natural Resource Districts, Nebraska Extension Agents and Michael Hodges and family for providing the land, manure, and effort for this research project. Much appreciation to lab and field workers members of the Schmidt Lab: Mara Zelt, Juan Carlos Ramos, Nancy Sibo, Andrew Ortiz, Andrew Lutt, Seth Caines and Jacob Stover

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