Recipient Organization
UNIV OF WISCONSIN
21 N PARK ST STE 6401
MADISON,WI 53715-1218
Performing Department
(N/A)
Non Technical Summary
Several farming practices (e.g., cover crops) are promoted to improve soil health, sequester carbon (SOC), and reduce greenhouse gas (GHG) emissions. However, the efficacy of such practices is highly variable and remains the subject of considerable debate. We believe the aspirational goal of building soil health and mitigating climate change through SOC sequestration and greenhouse gas (GHG) abatement can be met, but only when approached holistically through ecological intensification (EI).We will work at the Wisconsin Integrated Cropping Systems Trial (WICST) where a suite of EI interventions was established in 2019. Our goal, to provide a comprehensive evaluation of the soil health, carbon sequestration, and GHG mitigation potential of EI in Midwestern grain systems will be met by 1) Quantifying medium-term changes in soil health and SOC; 2) Tracking the fate and persistence of C inputs from manure and cover crops, and 3) Assessing the net ecosystem carbon and GHG balance of each system.Knowledge generated by this research will enhance our understanding of how EI can improve "overall soil health and the resilience and sustainability of agricultural production systems", in addition to "directly evaluating the effects of management practices on soil microbial community function and their contribution to healthy soils, carbon sequestration, and greenhouse gas mitigation" as specified under Program Area Priority A1401-Soil Health.Regular engagement with WICST stakeholders will ensure the relevance of our EI interventions and ensure high impact for our results, which will be shared at field days, through our website, and in several UW-Madison courses.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
0%
Goals / Objectives
Approach-Specific objectives:To provide a comprehensive assessment of the ecological intensification management practices at Wisconsin Integrated Cropping Systems Trial (WICST), we propose the following three-tiered approach:We will measure an improved suite of soil health metrics including SOC, POM-C, PLFA, aggregate stability, and 24-h mineralizable C following the sixth consecutive year of ecological intensification practices.We will track the fate and persistence of carbon additions from manure and cover crops in tilled and no-till system using 13C labeling techniques.We will quantify the net ecosystem carbon balance (NECB) and GHG balance (N2O and CH4) in grain systems with ecological intensification management practices.Activities proposed and their sequence:Direct assessment of SOC & soil health: We will assess cumulative changes in SOC and key soil health indicators (POM-C, PLFA, Aggregate Stability, 24 h C mineralization, and ACE protein) following 6 full seasons of ecological intensification interventions at WICST.Rationale: SOC changes slowly making direct measurement of ΔSOC a challenge. Soil and climate variability, as well as experimental design constraints (limitations on replication and therefore power) can complicate the matter. Nevertheless, direct measurement of SOC stocks via dry combustion coupled with adjustments for equivalent soil mass remains the "gold" standard for accurately quantifying ΔSOC. Past work has demonstrated the robust statistical nature of WICST's experimental design (Sanford et al., 2012), and recent results have shown that ecological intensification is making a difference in sensitive soil health parameters at the trial. While changes in SOC were not discernable at year 3, we believe that we will be able to detect management-induced changes in SOC at year 6. Moreover, a recent publication has indicated that aggregate stability and 24 h C mineralization are core components of the "minimum suite of soil health indicators for North American Agriculture" (Bagnall et al., 2023), but these indicators were not measured as part of the original ecological intensification project at WICST. We will add these indicators to the six-year measurement suite, thereby providing a comprehensive, medium-term soil health assessment of ecological intensification practices.Expected outcome: At the end of six years, SOC and soil health parameters will have all improved relative to the control treatments as a result of ecological intensification interventions. In line with our early soil health findings, we anticipate the manure and combined interventions (EI-3, EI-4, EI-5) showing the most significant gains in SOC and soil health. While SOC improvements in cover crop (EI-1) and no-till (EI-2) interventions will be roughly equivalent, we expect them to differentially affect soil health parameters with cover cropping resulting in higher POM-C levels than no-till and no-till leading to greater aggregate stability and 24 h mineralization than cover cropping.Fate and persistence of C additions: Carbon from manure and cover crops will be tracked into soil POM, MOAM, and microbial "guilds" in both tilled and no-till systems at three timepoints across one growing season.Rationale: POM is made of partially decomposed plant material, while MAOM is derived from microbial residues. Recent work at WICST has shown that adding manure or integrating manure, cover crops, and no-till generally increases POM, microbial biomass, and AMF fungi. However, no changes have been detected when no-till and cover crop practices have been implemented individually. Furthermore, no changes to MAOM have been detected under any interventions, yet MAOM is the largest and most stable store of soil C and N (Rocci et al., 2021; Schrumpf et al., 2013). It is unclear why manure C is incorporated into the soil more efficiently than cover crop residue, why no-till practices have not enhanced C storage, and whether changes in MAOM are simply too small to detect using non-isotopic methods. This work will provide novel mechanistic detail about the pathways of POM and MAOM formation under various soil health interventions. This information will serve as the schematic for designing new systems that enhance SOC storage and will fill critical voids in current mechanistic SOC models.Expected outcome: Compared to cover crop-C, manure-derived C will have a longer POM residence time, be acquired more efficiently by fungi, and more quickly become stabilized as MAOM (Wang et al., 2022). No-till will slow the transfer of C into POM, microbes, and MAOM, but a greater proportion of C will be stabilized to MAOM compared to tilled systems.NECB and GHG footprint: The annual net ecosystem carbon balance and greenhouse gas footprint of six EI interventions will be quantified over three years.Rationale: The SOC impact of ecological intensification practices such as cover cropping, no-till, and manure can take several years to fully quantify, confounding adaptive management decisions. A NECB approach provides valuable "real time" information on the flux of carbon in an agroecosystem which can be used to validate direct measures of SOC stock change and assist farmers in management decisions. While soil carbon sequestration is of critical importance for climate mitigation and the provisioning of valuable ecosystems services (e.g. crop water regulation), ecological intensification interventions may unintentionally enhance the loss of climate warming GHGs, potentially negating the climate mitigating effects of gains in SOC (Lawrence et al., 2021). While soil organic carbon is the primary focus of this project, any effort to understand the climate mitigation potential of ecological intensification must account for the impacts of EI interventions on N2O or CH4. This work will help to validate the findings from our long-term direct assessment of SOC change and provide a comprehensive picture of the potential for ecological intensification interventions to serve as natural climate solutions.Expected outcome: Consistent with the soil health findings from the first three years of ecological intensification research, we anticipate a net flux of carbon into the EI systems at WICST, with the greatest carbon gains in manured (EI-3) and integrated interventions (EI-4 and EI-5). We further anticipate that systems receiving manure rather than synthetic N will emit less soil N2O than other systems, thus having the smallest GHG footprint.
Project Methods
Methods (abridged to meet character limit)Unabridged methods presented in full proposalDirect assessment of ΔSOC & soil health:Soil sampling: Samples (0 to 15 cm) will be collected from three locations within each 9 x 15-m EI plot, avoiding an area of 1.5 m from each plot edge. At each location a set of six 2 x 15-cm cores will be taken (2 in row, 2 between row, 2 intermediate), thoroughly homogenized, and composited.Bulk density: To relate all soil parameters to an area basis, calculate SOC stocks, and perform equivalent soil mass corrections, soil bulk density will be estimated in the surface 30 cm (0 to 15 and 15 to 30 cm) using a hand-held 7.6 x 15-cm hammer core. Soil cores will be carefully extracted to avoid compaction and dried at 60° C.Total C and N: Soil will be sieved to 2 mm, picked clean of all visible plant material, pulverized, and analyzed for CN using a Thermo-Finnigan EA 1112 flash combustion analyzer (Robertson et al., 2009).POM-C: POM will be separated by dispersing a 5-g soil subsample in sodium hexametaphosphate, shaking for 18 h, then poured onto a 53-µm sieve (Cotrufo et al. 2019). Material that remains in the sieve, which is classified as POM, will be thoroughly rinsed with DI water, dried at 60 °C, and weighed. The POM mass fraction will be determined by dividing the mass of POM by the mass of soil analyzed (Cates et al., 2016).PLFA: Phospholipid fatty-acid analysis (PLFA) will be used to quantify microbial groups as outlined by Herzberger et al. (2014). Lipids will be related to total microbial biomass as well as bacterial and fungal functional groups. PLFA has been shown to provide robust information on microbial community composition (Liang et al., 2016) and is very sensitive to shifts in management (Oates et al., 2012).Aggregate stability: Aggregate stability will be determined by wet sieving with an apparatus modified from the design of Yoder (1936) with 4 sieve mesh sizes: 2mm, 1mm, 500µm, 53µm. 24-h C mineralization (C-min): C-min will be determined by measuring the flush of carbon dioxide released by air-dried soil rewetted to 50% water filled pore space and incubated for 24-hours at 25°C (Franzluebbers, 1999; Franzluebbers et al., 2000).ACE protein: ACE protein will be measured on air-dried soils sieved to 2mm (Hurisso et al., 2018) following the method described in (Stott, 2019). Briefly, sodium citrate is used to extract 3 g air-dried soil. The extractant is mixed with bicinchoninic acid reagent, incubated for 60 minutes, and absorbance is quantified using a plate reader at 562 nm and a standard curve.Fate and persistence of C additions13C-labeled manure: Alfalfa will be 13C-labeled in a non-research field during the 2025 growing season. In July 2025, a Holstein heifer located at the USDA Dairy Forage Research Center will be fed unlabeled alfalfa for one day followed by the 13C-labeled alfalfa the next day. All liquid and solid excrement will be collected in separate batches for labeled and unlabeled material. Subsamples from this collection will be taken for δ13C analysis via IRMS to ensure sufficient 13C incorporation. The remaining manure will be frozen for use during the following field season. In April 2026, the labeled manure will be adjusted to 97% water to emulate typical dairy slurry manure, and a subsample will again be taken for δ13C analysis via IRMS. The labeled and unlabeled manure will then be applied by hand in the 13C-manure and unlabeled manure subplots (1 x 1 m), respectively, at a rate of 5,000 gallons per acre.13C-labeled cereal rye: Cereal rye will be 13C-labeled within designated 1 x 1 m subplots during April and early May 2026 when the rye plants are actively growing. The 13C-labeling procedure will follow the previously described procedure used to label the alfalfa. To ensure uniform 13C label, rye will be pulse labeled once per week. Using twelve labeling chambers, all 13C rye subplots will be labeled on the same days.Plant and soil sampling: Aboveground rye will be sampled for δ13C endmembers one day after the first cover crop labeling event (April 2026) and one day after the final cover crop labeling event (May 2026). Belowground samples will be collected in all subplots (including manure treatments) 6 months after cover crop termination (November 2026) in addition to the two aboveground biomass sampling dates. Above- and below-ground biomass will be dried at 60 °C, weighed, and analyzed δ13C analysis via IRMS. The remaining soil will be sieved to 2 mm, frozen, and saved for the 13C-POM, 13C-MAOM, and 13C-PLFA procedures.13C-POM and 13C-MAOM tracing: 13C will be traced from manure and the rye cover crop into POM and MAOM at the three timepoints corresponding to the aforementioned belowground sample collection (April, May, November). The contribution of 13C-labeled rye and manure to POM-C and MOAM-C will be calculated using a two-source isotope mixing model (e.g., Austin et al., 2017)13C-PLFA stable isotope probing: 13C will be traced from the manure and rye cover crops into the phospholipid fatty acids (PLFA) of gram-negative, gram-positive, saprotrophic fungi, arbuscular mycorrhizal fungi, actinomycetes, and anaerobic bacteria. PLFA biomarker abundance and δ13C will be quantified using a coupled GC-IRMS system, and the contribution of 13C-labeled rye and manure to each microbial functional group will be calculated using a two-source isotope mixing model (e.g., Kong et al. 2011).NECB and GHG balanceANPP: Above ground biomass will be collected from both corn and cereal rye each year. Corn biomass will be collected as close to peak standing biomass as possible (~R6) in two 1 m2 areas (2 corn rows x 0.66 m each). Cereal rye biomass will be collected using two 0.5 m2 quadrats in the spring just prior to cover crop termination (~May 5). Biomass will be dried at 60 °C, weighed, pulverized, and analyzed for total C and N.BNPP: Root biomass will be sampled in six locations within the center of each experimental unit following cereal rye termination and corn harvest in spring and fall, respectively.RH: Heterotrophic CO2 respiration (RH) will be measured using a LI-COR LI-7810 trace gas analyzer equipped with an LI-8200-01S smart chamber. To avoid the CO2 contribution from roots (autotrophic respiration), which is not soil-derived and therefore does not contribute to the NECB, a 1.5 m x 1.5 m section of each experimental unit will be kept free of all plant and weed biomass. Two RH measurements will be collected near the center of each plant-free area at 10-day intervals during the growing season (April 15 to Oct. 31), and at monthly intervals during the off-season (Nov. 1 to April 14). Annual RH will be assessed by linear interpolation and summation of measured instantaneous RH fluxes.GHGs: Trace gas fluxes of soil N2O, CO2, and CH4 will be measured using a LI-COR LI-7810 coupled with a LI-7820 and equipped with an LI-8200-01S smart chamber. Two trace gas measurements will be collected in each experimental unit at 10-day intervals during the growing season (April 15 to Oct. 31), and at monthly intervals during the off-season (Nov. 1 to April 14). Additional measurements will be made following application of manure and N fertilizer to capture ephemeral N2O pulses. Annual soil GHG exchange will be assessed by linear interpolation and summation of measured instantaneous GHG fluxes.Yield: Corn yields (grain & silage) will be collected using field scale agricultural equipment.