Environmental Benefits of Manure Application

For centuries, animal manure has been recognized as a soil “builder” because of its contributions to improving soil quality. Environmental benefits are possible from manure application if manure and manure nutrients are applied and timing and placement follows best management practices. When compared to more conventional fertilizer, manure properly applied to land has the potential to provide environmental benefits including:

    • Increased soil carbon and reduced atmospheric carbon levels
    • Reduced soil erosion and runoff
    • Reduced nitrate leaching
    • Reduced energy demands for natural gas-intensive nitrogen(N) fertilizers

Manure Effects on Soil Organic Matter

Manure contains most elements required for plant growth including N, P, potassium, and micronutrients (Manure as a Source of Crop Nutrients and Soil Amendment). However, it is manure’s organic carbon that provides its potential environmental value. Soil organic matter is considered nature’s signature of a productive soil. Organic carbon from manure provides the energy source for the active, healthy soil microbial environment that both stabilizes nutrient sources and makes those nutrients available to crops.

photo of solid manure spreader
Manure is comparable to commercial fertilizer as a plant food and, if applied according to a sound nutrient plan, has environmental benefits over commercial fertilizer. cc2.5 manure nutrient management group

Several long-term manure application studies have illustrated its ability to slow or reverse declining soil organic levels of cropland:

  •  

    The ability of manure to maintain or build soil organic matter levels has a direct impact on enhancing the amount of carbon sequestration in cropped soils.Manure organic matter contributes to improved soil structure, resulting in improved water infiltration and greater water-holding capacity leading to decreased crop water stress, soil erosion, and increased nutrient retention. An extensive literature review of historical soil conservation experiment station data from 70 plot years at 7 locations around the United States suggested that manure produced substantial reductions in soil erosion (13%-77%) and runoff (1%-68%). Increased manure application rates produced greater reductions in soil erosion and runoff. Additional studies during years following manure application suggest a residual benefit of past manure application.

    Overview of Manure Impacts on Soil (Mark Risse, University of Georgia). Visit the archived webinar for additional videos on carbon, fertility, and soil health.

    Manure Effects on Soil Erosion

    In addition, surface application of manure behaves similarly to crop residue. Crop residue significantly decreases soil erosion by reducing raindrop impact which detaches soil particles and allows them to move offsite with water runoff. Data has been published showing how manure can coat the soil surface and reduce raindrop impact in the same way as crop residue. Therefore, in the short-term, surface manure applications have the ability to decrease soil erosion leading to a positive impact on environmental protection.

    Organic Nitrogen

    In addition, organic N (manure N tied to organic compounds) is more stable than N applied as commercial fertilizer. A significant fraction of manure N is stored in an organic form that is slowly released as soils warm and as crops require N. Commercial fertilizer N is applied as either nitrate or an ammonium (easily converted to nitrate). Nitrate-N is soluble in water and mobile. These forms contribute to leaching during excess precipitation (e.g., spring rains prior to or early in growing season) or irrigation. Manure N’s slow transformation to nitrate is better timed to crop N needs, resulting in less leaching potential. In fact, manure N is a natural slow-release form of N.

    Energy Benefits

    Recycling of manure nutrients in a cropping system as opposed to manufacturing or mining of a new nutrient resource also provides energy benefits. Commercial nitrogen fertilizers consume significant energy as a feedstock and for processing resulting in greenhouse gas emissions. Anhydrous ammonia requires the equivalent of 3300 cubic feet of natural gas to supply the nitrogen requirements of an acre of corn (assuming 200 lb of N application). Phosphorus and potassium fertilizers also have energy requirements for mining and processing. Substituting manure for commercial fertilizers significantly reduces crop production energy costs

    It is important to remember that the environmental benefits of manure outlined in this article are only beneficial when best management practices for reducing soil erosion are implemented in concert with proper levels of manure nutrient application and use.

    Recommended Reading on Environmental Benefits of Manure

     

  • Authors: Rick Koelsch, University of Nebraska, and Ron Wiederholt, North Dakota State University
  • Reviewers: Charles Wortmann, University of Nebraska, and Steve Brinkman, Iowa NRCS
    Last reviewed on October 25, 2022 by Leslie Johnson, Animal Manure Management Extension Educator, Nebraska Extension.

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.

Figure 1: Average percent change in soil organic carbon (SOC) and total nitrogen (TN) based on amendment type, application method, soil texture, and duration of swine manure application. Black circles represent outlier data, and diamonds represent mean. IF = inorganic fertilizer; LSM = liquid swine manure; M + IF = manure (liquid and solid) plus inorganic fertilizer; SM = solid swine manure

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.

Assessment of method of photo analysis for demonstrating soil quality

Purpose

The use of livestock manure as a soil amendment to benefit soil health by improvements to soil physical, chemical, and biological properties, has been documented. However, quantification of the impact of improved soil health metrics on nutrient cycling has lagged. The soil your undies experiment has been implemented in the past to visually demonstrate microbial activity (Figure 1). However, this demonstration is seldom quantified, and does not have the capacity to statistically show that the effects of different management practices are distinct. The goal for this study was to quantify the degradation of fabric on a similar experiment, using cotton fabric on agricultural soils through photographic editing software. This study was designed to assess a visual method for quantifying carbon cycling in soil, observed through the degradation of buried organic materials.

Figure 1. Soil your undies soil health demonstration. Credit Clackamas Soil and Water Conservation District.

What Did We Do?

White, 100% cotton fabric cloths were cut into 29.21 × 29.84 cm (871.62 cm2) (11.5 x 11.75 in, 135 in2) pieces and placed flat inside a non-degradable mesh bag (48 cm × 48 cm, 18.9 in x 18.9 in). Sixty of the mesh bags were buried at 5 cm (2 in) depth in a field planted with corn in May of 2021 (Figure 2). The sixty bags were arranged in 12 plots to which one of three soil treatments (swine slurry, swine slurry + woodchips, and control plots with no amendments) with four replications per treatment were also applied. Swine slurry was applied at a rate of 39,687.06 L-ha-1 (4,242 gal-ac-1) and woody biomass was applied at a rate of 21.52 Mg-ha-1 (9.6 tons-ac-1).

Figure 2. Fabric and mesh bag burial in research plots

Five times during the growing season (25, 54, 81, 99 and 128 days after establishment), one bag was retrieved from each plot and returned to the lab for analysis. For each bag, soil was gently removed from the surface of the mesh and then the bag was cut open to observe the cotton fabric remaining. All the fabric pieces were photographed after retrieval. Photographs of the fabric were taken with an iPad mounted on a tripod. Fabric samples were photographed in a premeasured area of 29.21 × 29.84 cm (11.5 x 11.75 in) on a black surface (Figure 3).

Figure 3. Fabric sample placement inside pre-measured area (29.21 × 29.84 cm) for photographing

Manual evaluation of percent fabric degradation for each sample was performed by overlaying a clear plastic grid (Figure 4) with primary graduations (darker lines) of 2.54 cm (1 in) and secondary graduations (lighter lines) of 6.4 mm (0.25 in) on fabric samples and counting grid squares that were void of fabric.

Figure 4. Grid overlayed on fabric sample for manual evaluation of percent fabric degradation

Each photograph was assessed using Adobe Photoshop 2020 and the free license program ImageJ. Briefly, each image was opened in the respective program and the initial fabric area (871.62 cm2) (135 in2) was delineated in the program, based on the premeasured area included in the photo to set a scale for the degradation measurement. The image was converted to black and white, and brightness and contrast were adjusted as needed to remove glare on the black background that might be misread by the program as fabric. Then, all the pixels within a specific color range – which was previously defined as fabric – were selected using the native editing tools in the two programs and this area was compared to the pixels in the initial fabric area to determine the percentage of fabric remaining.

What Have We Learned?

The three methods for estimating the area of the fabric did not show significant differences among each other, which means estimates of fabric degradation obtained with Photoshop and Image J accurately reflect manual hand counts, suggesting that these are reliable visual methods for determining the area of the remaining area of fabric (Figure 5, 6).

Figure 5. Linear regression model for degradation estimation via Photoshop relative to degradation value obtained by hand count
Figure 6. Linear regression model for degradation estimation via ImageJ relative to degradation value obtained by hand count

Future Plans

Future work will seek to validate this method according to standard measures of soil health and biological activity and ensure that the method has enough sensitivity to demonstrate statistical differences between soil treatments. Future studies should also focus on making the process of area estimation with the software an easier, less laborious process. Creating a cellphone app to determine degradation quickly and without the need for a computer could increase the adoption of the fabric degradation assessment method in field settings.

Authors

Amy Schmidt, Associate Professor, University of Nebraska-Lincoln

Corresponding author email address

aschmidt@unl.edu

Additional authors

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

Mara Zelt, Research Technologist, University of Nebraska-Lincoln

Andrew Ortiz Balsero, Undergraduate Research Assistant, University of Nebraska-Lincoln

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 members of the Schmidt Lab who supported field and laboratory work: Juan Carlos Ramos Tanchez, Nancy Sibo, Andrew Lutt, Seth Caines and Jacob Stover.

Potential soil health improvement through the integration of cover crops and manure in the upper Midwest

Purpose

Oftentimes fall manure application is associated with significant offsite transport of nitrogen and phosphorus into nearby bodies of water and the atmosphere. Mechanisms of losses include leaching, runoff, sediment transport, and volatilization processes. This is becoming more common as there has been a trend of increased wet springs that create difficult planting conditions. This prolonged period without an active root system leaves more time for nutrient loss from fall-applied manure to occur.

A strategy to offset nutrient losses in the fall and early spring is to plant a cover crop. The uptake of nutrients during this time in the field, which would otherwise be left fallow, allows for nutrients to be stored in the tissue of the cover crops, minimizing nutrient loss risk. Upon terminating the cover crops, the decomposing residues can supply nutrients to the succeeding row-crop. However, cover crop adoption is low in the upper Midwest US stemming from a short cover crop growing season due to the cold climate. This is especially the case for crops utilizing manure. A strategy to expand the cover crop growing season may be to interseed a cover crop into a maturing row-crop prior to harvest. Previous studies investigating the integration of manure and cover crops have seeded the cover crop after manure application. We wanted to measure the impacts of first planting a cover crop then applying manure once the cover crop has had ample time to get established. This may help expand the cover crop growing season and potentially limit the offsite transfer of pollutants to our water and air.

What Did We Do?

A small plot study was started in fall 2019 at the University of Minnesota West Central Research and Outreach Center near Morris, MN. We tested the effect of nitrogen source and cover crops on soil health, nutrient cycling, and agronomic responses using a randomized complete block design with split plots.

Cover crop mixtures of cereal rye and annual ryegrass were interseeded near corn’s fifth leaf collar (V5) growth stage, physiological maturity (R5 to R6 growth stage), or drilled after corn harvest. Dairy manure was sweep-injected to minimize soil disturbance in early and late fall, when soil temperatures were above and below 10°C (50°F), respectively. Non-manured plots received urea in the spring prior to corn planting. Urea applied plots (no manure) with no cover crops served as the control. Soil samples were taken throughout the cover crop and row-crop growing season from the 0-15, 15-30, and 30-60 cm (0-6, 6-12, and 12-24 in) soil layers. Cover crop biomass samples were taken in the late fall prior to the first frost event and prior to cover crop termination in the spring.

What Have We Learned?

Sweep injection is a reliable method to apply liquid manure to a field with an established stand of cover crops with minimal noticeable damage to the cover crops in the spring (Figure 1). Planting cover crops as soon as possible ensures more biomass is produced; planting after harvest consistently had lower cover crop yield than interseeding. Spring cover crop yield, right before termination, was highest when planted near physiological maturity [110 kg ha-1 (98 lb ac-1)] compared to drilling after harvest [87 kg ha-1 (78 lb ac-1)]. Nutrient source had a significant effect on silage yield. Manure, either applied in the early or late fall, had greater silage yield [58.5 and 58.7 Mg ha-1 (26.1 and 26.2 ton ac-1), respectively] than spring applied urea [53.6 Mg ha-1 (23.9 ton ac-1)]. Plots with cover crops interseeded at V5 had greater silage yield [59.5 Mg ha-1 (26.5 ton ac-1)] than all other treatments [54-56 Mg ha-1 (24-25 ton ac-1)] except no cover crops [57.8 Mg ha-1 (25.8 ton ac-1)].

Figure 1. Cover crops planted prior to late manure application. Photo was taken in the spring at cover crop termination.

Future Plans

Soil samples collected throughout the study are currently being analyzed for nutrient content and other soil health parameters. Results from this study will be used to develop best management practices for integrating cover crops and liquid injected manure in the upper Midwest.

Authors

Manuel J. Sabbagh, Graduate Research Fellow, University of Minnesota

Corresponding author email address

sabba018@umn.edu

Additional authors

Melissa L. Wilson, Assistant Professor, University of Minnesota; Paulo H. Pagliari, Associate Professor, University of Minnesota

Additional Information

Twitter: @mannyandmanure @manureprof

Lab website: https://wilsonlab.cfans.umn.edu/

Acknowledgements

This work is supported by the Conservation Innovation Grants program at the Natural Resources Conservation Service of the USDA, the Minnesota Corn Research and Promotion Council, and the Foundation for Food and Agriculture Research.

University of Idaho Sustainable Agriculture project seeks to create a bioeconomy from dairy byproducts to increase nutrient recycling

Purpose

This Sustainable Agriculture Systems project is called “Idaho Sustainable Agriculture Initiative for Dairy (ISAID).” Its main purpose is to create a bioeconomy around dairy manure and its byproducts, generating a circular use and economy of nutrients (Figure 1). Idaho is currently the third largest milk-producing state in the USA (USDA-NASS, 2021). Idaho dairy farms typically operate as confined operations that concentrate a significant amount of manure and nutrients in relatively small areas. Over the years, this situation has increased the concentration of nutrients in farms surrounding dairies. Meanwhile, distant farms may not benefit from using those nutrients (Leytem, et al. 2021). Except for its exceptional fertilizer and soil amendment value (USEPA, 2015), dairy manure is seen as a nuisance that needs to be managed well. Manure handling and use generate expenses for the producers and may be a nuisance for the neighboring communities and a potential environmental risk for the areas surrounding dairy production (Berg, et al. 2017; Moore and Ippolito, 2009; Sheffield, et al. 2008). This multidisciplinary project aims to create bioproducts from manure to significantly change the nutrient balance and the economic impact for producers in the region. Implementing the various strategies included in the project will help export nutrients to in-need areas within the region or outside the watershed altogether. In addition, increased income from manure processing would allow for better management and reduction of overall costs associated with nutrient management in the region.  The ISAID project includes three main areas that are integrated to generate the highest impact possible. Research, Extension, and Education are the distinctive areas of work. Still, these areas don’t work as silos, having a lot of integration to get the most of everybody’s work in the project.

What Did We Do?

Figure 1. Dairy bioeconomy

A group of 25 researchers in diverse areas of expertise obtained a USDA-NIFA Sustainable Agricultural Systems grant to conduct long-term (five years or more) projects. On the research side, the multifaceted studies that are under development include: use of amendments in manure composting to increase compost quality and value, reducing air emissions; nutrients’ extraction from various fractions of manure treatment to concentrate specific nutrients for individual commercialization (including nitrogen, phosphorous, and carbon); generation of hydrochar and biochar from dairy manure; bio-plastics production; cover crops use to increase nutrient extraction and soil health; fine-tuning fertilizer guides for crops using manure, compost, and other bioproducts. Analysis of each product’s economic and social impact separately and as a multi-prong approach. The extension component includes outreach to livestock and crop producers, local authorities, and communities to communicate the applicability of researched technologies and techniques, their impacts, benefits and challenges. The development of programs to train producers, allied industry, their workforce government employees on the diverse applications resulting from the project. The education component includes the participation of graduate and undergraduate students in all facets of the project and the development of educational programs for undergraduate and graduate students on topics associated with manure and nutrient management, bioeconomy, and on-farm application and management of these technologies and techniques.

What Have We Learned?

This project just finished the first of its five years; most of the projects are in the inception phase. We are generating baseline data and linking together diverse processes to determine possible interactions and needed extension and instructional needs. The corresponding poster includes a detailed list of projects associated with the grant, their corresponding principal investigators, and any recent advances. Some examples of project outcomes include the Water Machine that extracts phosphorous from waters with high nutrient content. Ammonia extraction from dairy wastewater. Enhanced composting using zeolites, pumice, biochar, and balanced carbon. Cover crops and corn silage as dual and double cropping. Hydrochar production from dairy manure and bioplastics. We are working on obtaining stakeholders’ input through diverse methods to help assess the needs of the industry and communities and guide the evolution of the research, extension, and education processes.

Future Plans

The project will continue to gather data and evolve. Collaborations and graduate student inquiries about inclusion in some projects are welcomed. We will offer updates at various conferences, including the next Waste to Worth.

Authors

Mario E. de Haro Martí, Extension Educator, University of Idaho Extension, Central District

Corresponding author email address

mdeharo@uidaho.edu

Additional authors

Mireille Chahine, Extension Dairy Specialist, Department of Animal, Veterinary and Food Science, University of Idaho

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

Additional Information

ISAID Website: https://www.uidaho.edu/extension/nutrient-management/isaid

Facebook: https://www.facebook.com/uofiisaid

Instagram: https://www.instagram.com/uofiisaid/

Acknowledgements

This ISAID project is supported by USDA-NIFA SAS award #2020-69012-31

References

Berg, M., Meehan, M., and Scherer T. 2017. Environmental Implications of Excess Fertilizer and Manure on Water Quality. NM1281. https://www.ag.ndsu.edu/publications/environment-natural-resources/environmental-implications-of-excess-fertilizer-and-manure-on-water-quality

Leytem, A. B., Williams, P., Zuidema, S., Martinez, A., Chong, Y. L., Vincent, A., Vincent, A., et al. 2021. Cycling Phosphorus and Nitrogen through Cropping Systems in an Intensive Dairy Production Region. Agronomy, 11(5), 1005. MDPI AG. http://dx.doi.org/10.3390/agronomy11051005

Moore, A. and Ippolito, J. 2009. Dairy Manure Field Applications—How Much is Too Much? CIS1156. http://www.extension.uidaho.edu/publishing/pdf/CIS/CIS1156.pdf

Sheffield, R. E., Ndegwa, P., Gamroth, M., and de Haro Martí, M. E. 2008. Odor Control Practices for Northwest Dairies. CIS1148. http://www.extension.uidaho.edu/publishing/pdf/CIS/CIS1148.pdf

USDA-NASS. 2021. Quick Stats. Retrieved 02 27, 2022, from National Agricultural Statistics Service: https://quickstats.nass.usda.gov

USEPA. 2015. Beneficial Uses of Manure and Environmental Protection. Fact Sheet. https://www.epa.gov/sites/default/files/2015-08/documents/beneficial_uses_of_manure_final_aug2015_1.pdf

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

Microarthropods as Bioindicators of Soil Health Following Land Application of Swine Slurry


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*Purpose 

As producers of livestock and agricultural crops continue to focus significant efforts on improving the environmental, economic, and social sustainability of their systems, increasing the utilization of livestock manure in cropping systems to offset inorganic fertilizer use benefits both sectors of agriculture. However, promoting manure based purely upon nutrient availability may not be sufficient to encourage use of organic versus inorganic fertilizer. The value of livestock manure could increase significantly with evidence of improved soil fertility and quality following manure application. Therefore, understanding the impact of manure addition and application method on both soil quality and biological health is an important step towards improving the value and desirability of manure for agricultural cropping systems.

For edaphic ecosystems, collection, analysis, and categorization of soil microarthropods has proven to be an inexpensive and easily quantified method of gathering information about the biological response to anthropogenic changes to the environment (Pankhurst et al., 1995; Parisi et al., 2005). Arthropods include insects, crustaceans, arachnids, and myriapods; nearly all soils are inhabited by a vast number of arthropod species. Agricultural soils may contain between 1,000 and 100,000 arthropods per square meter (Wallwork, 1976; Crossley et al., 1992; Ingham, 1999). Soil microarthropods show a strong degree of sensitivity to land management practices (Sapkota et al., 2012) and specific taxa are positively correlated with soil health (Parisi et al., 2005). These characteristics make soil microarthropods exceptional biological indicators of soil health.

This study focused on assessing the chemical and biological components of soil health, described in terms of soil arthropod population abundance and diversity, as impacted by swine slurry application method and time following slurry application.

What did we do? 

A field study was conducted near Lincoln, Nebraska from June 2014 through June 2015 on a site that has been operated under a no-till management system with no manure application since 1966. Experimental treatments included two manure application methods (broadcast and injected) and a control (no manure applied).

Soil samples were collected twelve days prior to treatment applications, one and three weeks post-application of manure, and every four weeks, thereafter, throughout the study period. Samples were not collected during winter months when soil was frozen.

Two types of soil samples were collected. Samples obtained with a 3.8-cm diameter soil probe were divided into 0-10 and 10-20 cm sections for each of the plots for nutrient analysis at a commercial laboratory. Samples measuring 20 cm in diameter and 20 cm in depth, yielding a soil volume of 6,280 cm3, were stored in plastic buckets with air holes in the lids, placed in coolers with ice packs, and transported to the University of Nebraska-Lincoln West Central Research & Extension Center in North Platte, Nebraska within 12 h of collection. These samples were then transferred to Berlese-Tullgren funnels 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.

The QBS method of classification was employed to assign an eco-morphological index (EMI) score on the basis of soil adaptability level of each arthropod order or family (Parisi et al., 2005). Preserved arthropods from each soil sample were identified and quantified using a Leica EZ4 stereo microscope (Leica Biosystems, Inc., Buffalo Grove, IL) and a dichotomous key (Triplehorn and Johnson, 2004). Arthropods were classified to order or family based on the level of taxonomic resolution necessary to assign an EMI value as described by Parisi et al. (2005). For some groups, such as Coleoptera, characteristics of edaphic adaptation were used to assign individual EMI scores.

The impacts of swine slurry application method and time following manure application on soil arthropod populations and soil chemical characteristics was determined by performing tests of hypotheses for mixed model analysis of variance using the general linear model (GLM) procedure (SAS, 2015). The samples were tested for significant differences resulting from time and treatment, as well as for variations within the treatment samples. Following identification of any significant differences, the least significant differences (LSD) test was employed to identify specific differences among treatments. P <0.05 was considered statistically significant.

What have we learned? 

A total of 13,311 arthropods representing 19 orders were identified, with Acari (38.7% of total arthropods), Collembola: Isotomidae (26.8%), Collembola: Hypogastruridae (10.4%), Coleoptera larvae (1.6%), Diplura (1.2%), Diptera larvae (0.9%), and Pseudoscorpiones (0.6%) being the most abundant soil-dwelling taxa. These taxa had the greatest relative abundance in samples throughout the study and were, therefore, chosen for statistical analysis of their response to manure application method and time since application.

The most significant responses to application method were found for collembolan populations, specifically for Hypogastruridae and Isotomidae. However, Pseudoscorpiones were also significantly affected by application method. Time following slurry application had a significant impact on most of the analyzed populations including Hypogastruridae, Isotomidae, mites, coleopteran larvae, diplurans, and dipteran larvae. The positive response of Hypogastruridae and Isotomidae collembolans to broadcast swine slurry application was likely due to the addition of nutrients (in the form of OM and nitrates) to the soil provided by this form of agricultural fertilizer.

Future Plans   

Research focused on the role of livestock manure in cropping systems for improved soil quality and fertility is underway with additional soil characteristics being monitored under multiple land treatment practices with and without manure.

Corresponding author, title, and affiliation       

Dr. Amy Millmier Schmidt, Assistant Professor, University of Nebraska – Lincoln

Corresponding author email 

aschmidt@unl.edu

Other authors   

Nicole R. Schuster, Julie A. Peterson, John E. Gilley and Linda R. Schott

Additional information               

Dr. Amy Millmier Schmidt can also be reached at (402) 472-0877.

Dr. Julie Peterson, Assistant Professor of Entomology, University of Nebraska – Lincoln can be reached at (308) 696-6704 or Julie.Peterson@unl.edu.

Acknowledgements      

Eric Davis, Ethan Doyle, Mitchell Goedeken, Stuart Hoff, Kevan Reardon, and Lucas Snethen are gratefully acknowledged for their assistance with field data collection. Kayla Mollet, Ethan Doyle, and Ashley Schmit are acknowledged for their assistance with data processing. This research was funded, in part, by faculty research funds provided by the Agricultural Research Division within the University of Nebraska-Lincoln Institute of Agriculture and Natural Resources.

 

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.

Utilization of Woody Biomass and Manure as Agricultural Soil Amendments in Nebraska


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Purpose 

While Eastern Redcedar are native to Nebraska and much of the Central U.S., the ability of these trees to thrive in many soils and under a broad range of climatic conditions has contributed to their designation as an invasive species. Cedar tree proliferation negatively impacts agriculture by reducing groundwater availability, compromising grazing land, impeding forage production for cattle, and altering surface water flows. Agricultural crop and livestock producers depend on affordable access to water, healthy and productive soils, and quality grazing land to remain profitable. Land treatment practices that return organic matter to soil improve soil health, which in turn positively impacts crop productivity, soil water holding capacity, soil fertility, and grazing land forage quality and productivity. This project is investigating the use of two readily available by-products in Nebraska, livestock manure and cedar tree wood chips,  as amendments on agricultural land to improve soil productivity metrics. The overall goal of this project is to demonstrate a value-added use for woody biomass to offset the cost of tree management activities and encourage landowner management of cedars.

What did we do? 

Crop year 2016 was the first year of the Woody Biomass and Manure Project. Six treatments were applied to 12-m x 10-m plots within cooperators’ fields following the 2015 harvest:

1. woody biomass (WB1), 6 ton/ac

2. woody biomass (WB2), 12 ton/ac

3. woody biomass with liquid N (WBLN), 6 ton/ac

4. woody biomass with swine manure (WBSM), 6 ton/ac

5. woody biomass with cattle manure (WBCM), 6 ton/ac

6. control (Cont), no amendments

Manure and liquid nitrogen treatments received less than 30 lbs ac-1 of N in the fall. The experiment is a completely randomized block design with four replications of each treatment, for a total of 24 plots, at each of the sites. Since the plots were established within existing crop fields, the producers were encouraged to continue their current management strategies. Both sites were irrigated, and fertilizer was applied uniformly across all plots using the pivot throughout the growing season.

Soil was sampled for chemical and biological properties in the spring and fall of 2016 and sent to a commercial lab for analyses. Rye was sampled by hand harvesting 0.25 square feet from four locations within each plot for a total of 1 square foot. Corn was sampled by hand harvesting six plants from each plot. Stand counts were also completed. WATERMARK sensors were installed at three depths (1, 2, and 3 ft) in two replications of four treatments (WBCM, WB1, WB2, Cont) at both sites. Additionally, temperature sensors were installed at a depth of 1 ft. A total of 16 plots were monitored (8 plots per site with 2 replications of 4 treatments).

What have we learned? 

Soil biological and chemical characteristics have not been affected during the first year. There were no differences in the amount or type of soil microbes due to treatment. WBCM and WBLN had greater soil nitrate than WB1 and WBSM early in the spring. Additionally, WBCM had greater soil K than the other treatments. Other than these two instances, there were no differences in organic matter, pH, and macronutrients. However, this is not surprising since measurable changes in soil properties typically occur over many years and manure application rate was relatively low. More importantly, though, is that microbial populations were not decreased by the cedar mulch.

Cedar mulch applications did not decrease biomass yield of corn and rye when applied with nitrogen. In fact, in the rye, WBLN had the greatest biomass yields followed by WBCM, WB1, WBSM, and Cont. WB2 had the lowest rye biomass, which was probably due to nitrogen tie-up by the wood chips due to the initially higher C:N ratio. There was no treatment effect for corn biomass or stand counts.

At the site planted to corn at a depth of one foot, the three woody biomass treatments monitored (WB1, WB2, and WBCM) were significantly wetter and cooler than the control from mid-June until mid-July. WBCM was also wetter at a depth of two feet than the control. Unfortunately, due to rodent activity, statistical analyses at the rye site and other times of the growing season are not possible. The differences in soil moisture and temperature are probably due to shading and the physical barrier to evaporation that the wood chips supply. The increased soil moisture under the woody biomass treatments could reduce irrigation.

Future Plans  

In order to apply for competitive funding, we need more supporting data. We are going to increase monitoring of soil moisture and temperature, so that three replications of all six treatments are monitored at both sites. Additionally, a greenhouse study will be conducted to provide water quality data and rate of decomposition of the wood chips.

Corresponding author, title, and affiliation       

Linda Schott, Extension Graduate Research Assistant, University of Nebraska-Lincoln

Corresponding author email   

linda.rae.schott@gmail.com

Other authors   

Amy Schmidt, Assistant Professor, University of Nebraska-Lincoln; Amy Timmerman, Associate Extension Educator, University of Nebraska-Lincoln; Adam Smith, Assistant Forester, Nebraska Forest Service

Additional information               

More information can be found at: manure.unl.edu

Acknowledgements       

This project is funded by the Nebraska Forest Service. We would like to thank the Middle Niobrara Natural Resource District, especially Mike Murphy, Travis Connot, and Zach Peterson, for their assistance to this project. We would also like to thank the Nebraska Forest Service, especially Richard Woollen, Adam Smith, and Heather Nobert, for their assistance to this project. Additionally, this project would not be possible without our two farmer cooperators, Leonard Danielski and Greg Wilke.