Progress 05/01/20 to 04/30/23
Outputs
Target Audience:The target audiences reached by this project include undergraduate students; faculty, staff, and students of Ursinus College from multiple academic disciplines; and agricultural scientists. Changes/Problems:The original timeline for project activities was significantly altered by the COVID-19 pandemic. The project was granted a one-year no cost extension in order to complete a final sample collection campaign and subsequent sample analyses. These activities were completed by the project end date. What opportunities for training and professional development has the project provided?Over the duration of this project, ten undergraduate students participated in the collection and processing of field samples, laboratory analyses, protocol development, and data analysis. All students engaged in the project participated in weekly discussions of relevant journal articles and developed scientific communication skills by presenting the results of their work at at least one undergraduate symposium at Ursinus College. In addition, three of these students designed and carried out independent experiments relevant to the project. One experiment investigated mechanisms of soil organic matter stabilization at varying depths in the soil profile using infrared spectroscopy. This work was the basis of the student's undergraduate honors thesis. Another student designed a laboratory incubation to quantify differences in decomposition rates and carbon dynamics among residues from crops included in the field study. She presented the results of her experiment at the Soil Science Society of America annual meeting. In a third undergraduate experiment, a student researcher measured nitrogen mineralization from decaying residues in a uniformity trial following forage crop termination. This project has also supported expanded teaching of soil science at Ursinus College. PI Finney adapted protocols developed for and utilized in the project (and written in a manner accessible to undergraduate students) to design three course-based undergraduate research experiences implemented in general ecology and agroecology courses she teaches. Finney also mentored an undergraduate student project to establish protocols for monitoring soil carbon and other soil health parameters in a campus food forest. These protocols will be used regularly in environmental studies courses and contribute to building a long-term dataset on food forest soils. How have the results been disseminated to communities of interest?Preliminary findings from this experiment have been disseminated to the scientific community through a peer-reviewed publication and research presentations at professional society meetings. Research results have been disseminated to faculty, staff, and students at Ursinus College, a primarily undergraduate institution, through a field day led by PI Finney in September 2021. Undergraduate summer research fellows also presented research findings to the Ursinus community through written papers and presentations at the Ursinus Summer Fellows Symposium held annually in July. This project provided the basis for an undergraduate honors thesis, the results of which were disseminated through an on-campus presentation (December 2021) and paper (April 2022). Students engaged in project research for academic credit also shared results through poster and oral presentations at an annual exhibition of undergraduate achievement in the arts, humanities, and sciences at Ursinus College. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Meeting the food, fiber, and energy needs of a growing global population in the face of a changing climate is among the most significant challenges of the 21st century. Developing agricultural systems that enhance carbon storage in soil is essential to increasing agricultural productivity while also mitigating climate change through reduced greenhouse gas emissions. This project investigated how cropping system diversification, specifically the practice of growing multi-species perennial forage crops to support livestock, impacts the capacity of agricultural soils to store carbon. We hypothesized that increasing the number of species present in forage crop stand would increase storage of soil organic carbon (SOC) relative to single-species plantings. We also expected that SOC concentrations would be influenced by the root systems and soil microbial communities associated with each crop stand. To test these hypotheses, we measured soil and crop parameters in a forage crop field experiment initially planted in April 2017. The experiment included three single-species (monoculture) crop stands, three two-species crop stands, and one three-species crop stand, each replicated four times. We collected soil samples for SOC quantification (Objectives 1 and 4), root biomass and quality estimation (Objectives 2 and 4), and microbial community characterization (Objectives 3 and 4) at four time points: September 2020 (the end of the fourth growing season), May/June 2021 (the beginning of the fifth growing season), September 2021 (the end of the fifth growing season), and May/June 2022 (the beginning of sixth growing season). At each spring sampling event, soil cores were collected to 60 cm and segregated into four depth categories: 0-15 cm, 15-30 cm, 30-45 cm, and 45-60 cm. In the fall, samples were collected from the 0-15 and 15-30 cm depth categories. Spring SOC measurements showed that crop selection (the choice farmers make regarding which species or species combination to grow) had a significant impact on SOC in perennial forage stands (Objective 1). The SOC content in the top 60 cm of soil was higher in white clover monoculture (54.54 + 3.42 Mg C ha-1) and tall fescue and white clover biculture (53.77 + 2.47 Mg C ha-1) than orchardgrass monoculture (47.91 + 2.49 Mg C ha-1) five and six years after forage crop planting (values are averages across two spring sample collections). Concentrations of SOC also varied significantly with depth, declining from the top to the bottom of the soil profile as expected (0-15 cm: 15.83 + 0.25 g C kg-1 soil; 15-30 cm: 8.49 + 0.20 g C kg-1 soil; 30-45 cm: 3.84 + 0.17 g C kg-1 soil; and 45-60 cm: 2.35 + 0.11 g C kg-1 soil). Contrary to our expectations, we found no evidence that increasing crop diversity influenced the biomass or depth distribution of roots (Objective 2). Analysis of standing root biomass indicated that root biomass tended to be lowest in white clover monoculture and highest in tall fescue monoculture at all depths. Root quality decreased with depth (i.e. the carbon to nitrogen ratio of root material increased) in all crop stands. Root quality was highest in white clover monoculture (average carbon to nitrogen ratio across depths = 22.5 + 1.5), consistent with this species' identity as a nitrogen-fixing legume. Measurements of soil microbial community characteristics showed differences in microbial community size, but not structure or function in response to crop treatment (Objective 3). The abundance of soil microbes (determined by phospholipid fatty acid analysis) was variable across sampling dates and tended to be lowest in orchardgrass monoculture. Ordination analyses indicate that the structure of soil microbial communities was not influenced by crop treatment but was different between depths. The rate at which microbes mineralized carbon (an indicator of microbial community function) declined with depth but was not impacted by the identity or diversity of crops present in a stand. To elucidate drivers of SOC accumulation within each depth increment (Objective 4), we used correlation analyses and applied model selection procedures using data from the final soil collection to identify factors that best predicted SOC concentration. Candidate variables included were % sand, % clay, root quantity and quality, soil microbial biomass, and the rate of carbon mineralization. In the top 0-15 cm of soil, SOC concentration was strongly positively correlated with the size of the soil microbial community, with SOC increasing as microbial biomass increased (r=0.74, p<0.001). A statistical model that included microbial biomass, carbon mineralization rate, and root quantity and quality explained 68% of the variation in SOC concentration, indicating that crop roots and soil microbes are important drivers of carbon accumulation in the top layer of soil. In contrast, soil texture was a key determinant of SOC concentration in deeper soils. In the 15-30 cm soil layer, % sand was negatively correlated with SOC concentration (r=-0.38, P=0.048), indicating that as soil sand content increases, SOC concentration decreases. Sand content had similar correlation with SOC concentration in the 30-45 cm soil layer (r=-0.42, P=0.027). Soil texture is an inherent property of soil that does not change in response to management, therefore carbon storage in these deeper soil layers may be less responsive to crop selection. The results of this study demonstrate that farmers' choice of what crops to grow influences how much carbon is stored in an agricultural soil. This influence is particularly strong in the top layer of soil, where crop effects on root quantity and quality and the abundance soil microbes shape carbon storage. We expected that planting a diversity of crop species would positively impact SOC through effects on root characteristics and soil microbial communities, a hypothesis that was not supported by our data. What we did uncover, however, was that characteristics of individual crop species ("crop identity") play an important role in SOC outcomes. For example, farmers frequently choose forage legumes like white clover because of their nutritional value for livestock and lower fertilizer requirements. One potential drawback of forage legumes, however, is that they tend to have less extensive root systems relative to forage grasses, which could reduce their capacity to accumulate and store carbon in soil. Our work has shown that the choice to plant white clover does not, in fact, reduce soil carbon storage compared to grasses such as tall fescue that produce more root biomass. We attribute this capacity to store SOC to the high quality of legume roots, a hypothesis that warrants further investigation. This experiment has also shown that individual species can have traits that may reduce carbon storage. Orchardgrass is a popular forage grass often grown in monoculture or in combination with a forage legume. In our study, orchardgrass monoculture exhibited lower levels of SOC than white clover and the combination of white clover and tall fescue. Orchardgrass was also associated with lower microbial abundance and lower concentrations of fine roots, both characteristics that singly, or in combination, may have contributed to reduced SOC storage. For farmers seeking to use perennial forages to build soil carbon, knowing whether a crop has traits that could hinder SOC accumulation is essential to choosing an appropriate crop to achieve this goal. This project has demonstrated that further research to uncover the mechanisms linking the individual crop species' traits and soil carbon storage is essential to guide farmers to cropping choices that can enhance both productivity and soil carbon storage.
Publications
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2022
Citation:
Mickles, A. and D.M. Finney. 2022. The Effect of Crop Legacy on Nutrient Cycling in Litters of Varying Quality. ASA/CSSA/SSSA International Annual Meetings. Baltimore, MD.
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Progress 05/01/21 to 04/30/22
Outputs
Target Audience:This project reached three target audiences through efforts during this reporting period: 1. Undergraduate students at Ursinus College, a primarily undergraduate institution. The project provided students with hands-on experience conducting agricultural research through a 10-week summer research fellowship program in 2021 and research for academic credit in the fall 2021 and spring 2022 semesters. 2. Faculty, staff, and students of Ursinus College from multiple academic disciplines 3. Agricultural scientists Changes/Problems:I have been granted a no-cost extension in order to complete the final plant and soil sample collection in May 2022. This is a deviation from the original project timeline that was created by the COVID-19 pandemic. There have been significant delays in the determination of microbial carbon use efficiency (obj. 3) due to extremely slow turn around times at external labs used for isotopic analysis (9 months) and total carbon and nitrogen determination in liquid extracts (12 months and counting). We have begun using an alternative lab for isotopic analysis and anticipate no further challenges in acquiring the data needed. Issues with the carbon and nitrogen analysis are not yet resolved. In addition, the lab we had used for PLFA analysis recently discontinued this service, so we are in the process of identifying an alternative provider for this analysis. What opportunities for training and professional development has the project provided?During the current reporting period, seven undergraduate students participated in the collection and processing of field samples, laboratory analyses, and protocol development. This number includes one student who completed an honors thesis from this project and is currently a graduate student in soil science at the University of Illinois. How have the results been disseminated to communities of interest?The findings of this project have been disseminated to the scientific community through a peer-reviewed publication. Research results have been disseminated to faculty, staff, and students at Ursinus College, a primarily undergraduate institution, through a field day led by PI Finney in September 2021. Undergraduate summer research fellows presented research findings through written papers and a presentation at the Ursinus Summer Fellows Symposium in July 2021. This project also provided the basis for an undergraduate honors thesis, the results of which were disseminated through an on-campus presentation (December 2021) and paper (April 2022). Students engaged in project research for academic credit shared results through two student posters and one oral presentation at an annual exhibition of undergraduate achievement in the arts, humanities, and sciences. What do you plan to do during the next reporting period to accomplish the goals?We will carry out the final plant and soil collection from the experiment in May 2022. We will use these samples to quantify soil carbon and nitrogen pools (obj 1). Roots will be isolated for biomass estimation and carbon and nitrogen analysis (obj 2). We will also assess differences in microbial community size, structure, and physiology across treatments and depths through PLFA analysis and CUE determination (obj 3). All data will be analyzed to assess relationships among root, soil, and microbial traits (obj 4). The project will continue to engage undergraduate students in agricultural research, supporting two summer research fellows who will participate in sample collection and analysis in 2022. Summer researchers will assess the impact of crop treatment and depth on rates of carbon and nitrogen mineralization (obj 3).
Impacts
What was accomplished under these goals?
Aboveground biomass, root, and soil samples from an established perennial forage diversity experiment were collected in May 2021 and September 2021. These collections occurred during the fifth growing season following forage crop planting (April 2017). All soil samples have been analyzed to quantify total soil carbon and nitrogen (obj 1). In addition, mineralizable carbon analysis, permanganate oxidation, and infrared spectroscopic analysis were performed on all May 2021 samples. Plant samples have been analyzed to determine aboveground yield and root quantity and depth distribution; root quality assessment is in progress (obj 2). Soil microbial community size and structure were characterized on May 2021 samples by phospholipid fatty acid analysis (PLFA) (obj. 3). In addition, we developed a protocol for the determination of microbial carbon use efficiency (CUE) that measures incorporation of isotopically labeled water into microbial DNA and performed this analysis on all samples collected in 2021 (obj. 3). Preliminary analyses of relationships among SOC pools, root traits, and microbial community characteristics have been performed using data available on soils collected in May 2021 (obj. 4).
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2021
Citation:
Finney, D.M., S. Garritano, and M. Kenwood. 2021. Forage species identity shapes soil biota in a temperate agroecosystem. Sustainability. 13(10):5689. doi: 10.3390/su13105689.
- Type:
Other
Status:
Other
Year Published:
2022
Citation:
Doherty, Finnleigh Shane. Digging Deeper: The Impact of Depth on Soil Organic Matter Stabilization Dynamics in a Forage System. Undergraduate Honors Thesis in Biology. April 2022. Held in the Ursinus College Digital Commons.
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Progress 05/01/20 to 04/30/21
Outputs
Target Audience:In the current reporting period, this project served a target audience of undergrdaute students at Ursinus College, a primarily undergraduate institution, by providing hands-on experience conducting agricultural research. Students engaged in project research for academic credit in the fall 2020 and spring 2021 semesters. Changes/Problems:I originally proposed collecting plant and soil samples in May 2020, however, due to a later than anticipated grant start date and work restrictions related to the COVID-19 pandemic, it was not possible to adhere to this timeline. I was able to use the summer to secure equipment and a research assistant to conduct the fall 2020 sampling described under accomplishments. I anticipate that because of the missed sampling opportunity in spring 2020, I may need an extension in order to conduct a second springtime sampling in 2022. What opportunities for training and professional development has the project provided?During the 2020-21 academic year, seven undergraduate students participated in the collection and processing of field samples, laboratory analyses, and protocol development. How have the results been disseminated to communities of interest?Research results have been disseminated to faculty and students at Ursinus College, a primarily undergraduate institution, through three student poster presentations at an annual exhibition of undergraduate achievement in the arts, humanities, and sciences. What do you plan to do during the next reporting period to accomplish the goals?We will carry out a second plant and soil collection from the experiment in May 2021. We will use these samples to quantify soil carbon and nitrogen (obj 1). Roots will be isolated for biomass estimation and carbon and nitrogen analysis (obj 2). We will also assess differences in microbial community size, structure, and physiology across treatments and depths through PLFA analysis and CUE determination (obj 3). All data will be analyzed to assess relationships among root, soil, and microbial traits (obj 4). In order to adequately assess treatment effects on above and below-ground productivity, shoot and root biomass will be sampled again in mid-summer and fall, and data from the spring, summer, and fall biomass collections will be combined to provide a second approach to addressing objective 2. The project will continue to engage undergraduate students in agricultural research, supporting two summer undergraduate researchers in 2021 who will participate in sample collection and analysis. Summer researchers will assess the impact of crop diversity and soil depth on rates of carbon and nitrogen mineralization (obj 3). Additionally, an undergraduate researcher will analyze spring collected soils to quantify and characterize labile soil carbon as part of an honors thesis project in fall 2021 (obj 1).
Impacts
What was accomplished under these goals?
Aboveground biomass, root, and soil samples from an established perennial forage diversity experiment were collected in fall (August and September) 2020. This collection time corresponded with the final hay cutting of the fourth growing season. Soil samples have been analyzed to quantify total soil carbon and nitrogen (obj 1). Plant samples have been analyzed to determine aboveground yield and root quantity, depth distribution and quality (obj 2). Soil microbial community size and structure have been characterized by phospholipid fatty acid analysis (PLFA) and microbial physiology was assessed by community level physiological profiling (obj. 3). In addition, we have developed a protocol for the determination of microbial carbon use efficiency (CUE) that measures incorporation of isotopically labeled water into microbial DNA and performed this analysis on a subset of samples collected in fall 2020. We have also developed a protocol to quantify and characterize labile carbon pools using permanganate oxidation and infrared spectroscopy.
Publications
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