Research & Projects

Perennial biofuel cultivation on low-productivity land offers an opportunity to improve soil health and increase soil organic carbon storage. More root trait research in subsurface depths (> 20 cm) would help inform this potential as root inputs strongly influence soil organic carbon dynamics. This study examined root traits across soil profiles (0–1 m) under contrasting biofuel systems at the Great Lakes Bioenergy Research Center Bioenergy Land Experiment at the three Michigan-based locations that differ in climate, soil type, and soil fertility. This project was funded by the Great Lakes Bioenergy Research Center and Natural Resource Conservation Service. 

Objectives

The objectives of this study were: 1) compare root biomass distribution, carbon storage, and biomass allocation across soil profiles (0–1 m) among switchgrass, miscanthus, and poplar systems; and 2) infer the relative roles of soil fertility and soil texture in shaping root traits and biomass allocation. 

Results

Treatment differences in root traits varied by location and soil depth. This study improves our understanding of biofuel root distribution and carbon storage at depth and informs biofuel management strategies in low-productivity lands. 

Naasko K, Gervase F, Mann M, Sprunger CD (In Prep) Biofuel crops differ in root biomass and carbon storage across soil profiles. To be submitted to Biomass and Bioenergy.

Forest management can enhance soil organic carbon storage and stabilization, particularly at depth. Integrating soil health indicators into forest assessments could strengthen management strategies aimed at optimizing soil organic carbon dynamics to support long-term ecosystem functioning. However, monitoring forest soil health remains uncommon. We examined the effects of manipulating aboveground and belowground plant inputs on soil health and soil organic carbon stocks across soil profiles (0–1 m) at the Detrital Input and Removal Treatment experiment at the University of Michigan Biological Station. This project was funded by the Natural Resource Conservation Service. 

Objectives

The objectives of this study were: 1) determine the extent to which long-term manipulations of aboveground and belowground plant inputs regulate soil health and soil organic carbon and nitrogen storage in temperate mixed hardwood forests in northern Michigan; 2) evaluate the effects of plant input manipulations on soil health and soil organic carbon at different depths; and 3) assess how soil health indicators relate to soil organic carbon stocks throughout the soil profile. 

Results

Soil health indicators were more sensitive to plant input manipulations than total soil organic carbon and nitrogen, especially autoclaved citrate extractable protein. Plant inputs predominantly impacted soil health and carbon storage in the O horizon, with little effects in the mineral soil profile. Yet, there were treatment differences in root biomass and root carbon storage in mineral soil depths. Our results show the regulating role of roots, in combination with litter inputs, in sustaining forest soil health. These findings demonstrate how plant inputs regulate forest soil health and highlight the value of integrating soil health metrics into forest management monitoring for long-term soil organic carbon stabilization. 

Naasko K, Robles A, Vergara I, Mann M, Sprunger CD (Under Review) Soil health indicators reveal above and belowground controls on forest soil carbon cycling. Soil Biogeochemistry.

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Understanding how agricultural systems change soil organic carbon over time and depth is critical for carbon accounting. Yet, knowledge is limited on how soil organic carbon trajectories vary across depth and among different fractions and soil health metrics. In this study, we leveraged soil archives from multiple long-term experiments across the Midwest including those managed by the Great Lakes Bioenergy Research Center and the United States Department of Agriculture Agricultural Research Service. This project was funded by the Environmental Defense Fund. 

Objectives

The objectives of this study were: 1) determine how management-driven changes in plant inputs regulate the temporal dynamics of total soil organic carbon and various carbon pools, clarifying differential component responses and the temporal direction of change; and 2) examine the influence of sampling depth on changes in soil organic carbon. 

Results

Long-term monitoring across multiple carbon fractions and depths is essential for accurately assessing soil organic carbon change under different management practices. Extending sampling beyond surface soils revealed larger changes in soil organic carbon, highlighting that surface-focused measurements alone can misrepresent soil organic carbon dynamics. Notably, soil organic carbon levels measured at single post-establishment timepoints did not reliably reflect gains and losses through time and may inaccurately estimate change relative to baseline conditions. 

Naasko K, Smychkovich A, Mahmood S, Cordova SC, Schmer M, Lavallee J, Lin Y, Sprunger CD (Under Review) Tracking soil organic carbon trajectories: Depth and fractions matter for carbon accounting in US midwestern long-term no-tilled systems. Soil Biogeochemistry.

Smychkovich A, Naasko K, Mahmood S, Cordova C, Schmer M, Liebig M, Lavallee J, Lin Y, Sprunger CD (In Prep) Sensitive soil health measurements predict long-term SOC changes in agricultural systems. 

Conservation tillage and diversified crop rotations are known to enhance soil organic carbon storage in surface soils (0-20 cm), while their long-term effects on subsurface soil organic carbon storage remain poorly understood. This study examined the 60+ year impacts of tillage and rotation on surface and subsurface soil organic carbon storage and aggregation at the Triplett-Van Doren Experiment in Ohio, at two locations with contrasting soil types (Wooster silt loam and Hoytville clay loam). The Sprunger lab collaborated with researchers from The Ohio State University and Colorado State University for this project. 

Objective

The main objective of this study was to evaluate the long-term (60+ years) effects of tillage and crop rotation practices on total soil organic carbon, mineral-associated organic carbon, and particulate organic carbon storage, and aggregation across soil profiles (0–1 m) in Midwest corn production systems. 

Results

Tillage and soil depth had greater influence on SOC stocks than crop rotation. Surface soils (0-10 cm) stored more SOC and MAOC under NT than MP and CP, more POC at Hoytville, and had greater MWD at Wooster. In subsurface soils, MP stored more SOC and MAOC than NT and CP (30-50 cm) and more POC at Hoytville than NT (50-100 cm). The depth-dependent nature of SOC storage after six decades underscores the importance of including subsurface soils in SOC assessments. 

Naasko K, de Camargo Santos A, Sprunger CD, Deiss L (2026) Tradeoffs Between Soil Organic Carbon Surface Gains and Subsurface Losses Following 60 Years of Contrasting Tillage and Crop Rotations. Soil Science Society of America Journal. https://doi.org/10.1002/saj2.70267 

Short-term flooding from extreme rainfall is becoming more frequent, with implications for aboveground and belowground agroecosystem function. However, few studies have explored how flooding affects the soil microbiome and plant growth in agroecosystems. We investigated how a four-day flood influenced soil microbial communities, soil nitrogen and maize (Zea mays L.) productivity in a split-plot randomized complete block design field trial in Custar, Ohio. This project was funded by the United States Department of Agriculture National Institute of Food and Agriculture. 

Objectives

The objectives of this study were: (1) evaluate changes in soil microbial community structure after the flood, over both short-term (3 and 8 days after flooding) and long-term (3 months after flooding) periods; and (2) investigate the relationship between soil microbial community structure and agroecosystem function in fertilized and unfertilized systems, with respect to soil nitrogen and maize growth, after the flood. 

Results

Soil microbial community structure was not impacted by the flood or fertilizer treatments in contrast to soil nitrogen and corn biomass at the end of the growing season. Autoclaved citrate extractable protein was an early indicator of reduced agroecological function as it was lower in the flood treatment compared to the control 8 days after flooding. The flood treatment also increased the number of differentially abundant fungal and bacterial taxa across time. This work advances understanding of agroecological responses to flooding in field conditions.

Naasko K, Zakolski E, Martin TK, Mann M, Malacrinò A, Lindsey A, Sprunger CD (2026) The impact of short-term flooding on soil microbial communities, soil nitrogen, and maize productivity in clay loam soils of Ohio, United States. Annals of Applied Biology. https://doi.org/10.1111/aab.70107  

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Monitoring soil nitrogen dynamics in agroecosystems is foundational to soil health management and is critical for maximizing crop productivity in contrasting management systems. More work is needed that investigates the relationship between the newly established soil health indicator, autoclaved-citrate extractable (ACE) protein, an organically bound pool of nitrogen, and other nitrogen-related soil health indicators. In this study, ACE protein is investigated in relation to other soil nitrogen measures at four timepoints across a single growing season at the W K Kellogg Biological Station Long-Term Ecological Research experiment.

Objectives

The objectives of this study were: (1) determine how ACE protein varies across a management intensity gradient that varies in perenniality and diversity; (2) measure ACE protein over the course of a single growing season to assess short-term fluctuations; and (3) assess the relationship of ACE protein with and other nitrogen related soil health indicators across a single growing season to better understand how to incorporate ACE protein into the soil health framework.

Results

This study highlights the potential for ACE protein as a sensitive indicator of sustainable management practices, SOM cycling, and soil health. ACE protein was more responsive to management and less variable across time than the other soil nitrogen fractions. In particular, polyculture perennial systems that promote soil health had between 2 and 12 g per kg higher ACE protein compared to annual cropping and monoculture perennial systems. 

Naasko K, Martin T, Mammana C, Murray J, Mann M, Sprunger CD (2024) Soil protein: A key indicator of soil health and nitrogen management. Soil Science Society of America Journal. https://doi.org/10.1002/saj2.20600 

Featured in March 2024 by CSA News and MSU CANR News

Calcareous soils may partially mitigate these losses via carbon capture and storage. This study aimed to determine how irrigation-supplied soil moisture and perennial tall wheatgrass impact biotic and abiotic soil properties that underpin deep soil carbon chemistry in an unfertilized calcareous soil. Amplicon sequencing was coupled with a multi-omics approach to characterize the soil microbiome composition, diversity, metabolome, lipidome, and proteome. The project was completed as part of my time in the Washington State University-Pacific Northwest National Laboratory Distinguished Graduate Research Program.  

Objectives

The objectives of this study were: (1) test for irrigation, cultivar, and depth effects on the soil microbiome and metaphenome; and (2) assess relationships between soil chemical and biological properties across depths and treatments. 

Results

Deep soil (>50 cm) had higher soil pH and calcium concentrations and higher levels of organic acids, bicarbonate, and triacylglycerides. By contrast, surface soil (0–5 cm) had higher concentrations of soil organic matter, organic carbon, oxidizable carbon, and total nitrogen. Surface soils also had higher amounts of sugars, sugar alcohols, phosphocholines, and proteins that reflect osmotic and oxidative stress responses. The lipidome was more responsive to perennial tall wheatgrass treatments compared to the metabolome or proteome, with a striking change in diacylglyceride composition. Permanganate oxidizable carbon was more consistently correlated to metabolites and proteins than soil organic and inorganic carbon and soil organic matter. This study reveals specific compounds that reflect differences in organic, inorganic, and oxidizable soil carbon fractions that are impacted by interactions between irrigation-supplied moisture and plant cover in calcareous soil profiles.

Naasko K, Naylor D, Graham E, Couvillion S, Danczak R, Tolic N, Nicora C, Fransen S, Tao H, Hofmockel K, Jansson J (2023) Influence of soil depth, irrigation, and plant genotype on the soil microbiome, metaphenome, and carbon chemistry. mBIO. https://doi.org/10.1128/mbio.01758-23  

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Deep soil health (>30 cm) supports deep roots in dryland wheat cropping systems. However, few studies examine how tillage and climate impact soil health indicators deeper than 30 cm in dryland wheat systems. We evaluated how select soil chemical (i.e., nutrients and pH), biological (i.e., carbon and nitrogen pools), and physical (i.e., mean weight diameter of soil aggregates) health indicators were impacted by depth, tillage, and climate. We sampled soil profiles of the Palouse soil series at three no-till and three conventional till sites across a mean annual precipitation gradient in the Palouse River watershed. This was my first PhD project in cooperation with the Natural Resource Conservation Service as part of the initial Dynamic Soil Properties for Soil Health assessment. 

Objectives

The objectives of this study were: (1) measure variability in soil biological, physical, and chemical health indicators with soil depth; and (2) assess how tillage and climate impact these soil properties in winter wheat cropping systems. 

Results

Soil depth, tillage, and climate had interactive effects on soil chemical, biological, and physical health indicators in Palouse soil series. Some of these effects were absent or reversed when analyzing only surface soil depths or when averaging across the whole soil profile. This study provided a snapshot of how management and inherent factors impact soil profile health in semi-arid dryland regions with deep-rooting crops that scavenge for soil moisture and nutrients in subsurface soil depths. Our study illustrates the importance of whole-profile soil sampling in soil health assessments of dryland wheat cropping systems.

Naasko K, Pan W, Huggins D, Reganold J, Sullivan T, Madsen I, Wills S, Tao H (2023) Soil profile health in the Palouse soil series: carbon, nitrogen, nutrients, and aggregates. Agroecosystems, Geosciences, & Environment. https://doi.org/10.1002/agg2.20421