Quantifying Carbon Sequestration From an Enhanced Rock Weathering Application at an agricultural field in Nebraska
Description
This dataset supports a Master’s thesis at the University of Nebraska–Lincoln and includes results from inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectrometry (ICP-OES), particle size analysis, lysimeter water chemistry, electromagnetic induction (EMI) mapping, crop yield, and plant nutrient uptake. The study was conducted at the University of Nebraska's Eastern Nebraska Research Extension and Education Center (ENREEC) near Mead, Nebraska, as part of the Carbon Sequestration Project 3 (CSP3). The field site follows a no-till, rainfed corn–soybean rotation, with soybeans grown in even years. Yield and biomass data were provided by ENREEC farm management. The experimental design includes three treatments: olivine (sourced from Åheim, Norway), agricultural lime (Aglime), and a control. Each amendment was applied at a uniform rate of 3 metric tons per hectare on October 18, 2023, following harvest. The field is laid out in a strip design, with aglime applied to rows labeled 1–24, olivine to rows 25–48, and control treatments in rows 49–72. Soil samples are numbered accordingly, while lysimeter locations are identified with "L" labels. The field layout consists of a rectangular grid with sampling rows spaced 9.14 m (30 ft) apart lengthwise and 12.19 m (40 ft) apart widthwise. Each row includes 12 sampling points across two rows, with interspersed guest rows where no heavy machinery enters. Lysimeters were installed in the center of each treatment block, with five lysimeters per treatment (15 total) placed 36.58 m (120 ft) apart. Soil samples were collected within a 1-meter radius around each lysimeter. Sampling occurred at three time points: prior to amendment (October 18, 2023), immediately after amendment (same day), and at one year post-application (October 25, 2024). Soil sampling involved composite samples from two random points within a 1 m² area. Each sample was divided into two depths: 0–10 cm (topsoil) and 10–30 cm (subsoil). Approximately 200 g of topsoil and 400 g of subsoil were collected per location. All samples were duplicated to ensure reproducibility. In total, the study includes 72 distinct row soil samples and 15 lysimeter-adjacent samples, collected annually. With duplicates across two depths, this totals 174 soil samples per year. The EMI dataset was used to map soil texture, organic matter, pH, and cation exchange capacity. These data help assess how soil variability affects weathering processes and carbon sequestration potential across treatments.
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Field measurements were conducted during lysimeter sampling to capture ambient conditions. Dissolved oxygen (DO) was measured using a ThermoElectron Corporation DO meter, while water temperature, oxygen-reduction potential (ORP), and electrical conductivity were measured with an Oakton PCTS5 probe. The volume of lysimeter-collected water was recorded on-site in liters. Within 48 hours, samples were analyzed for pH using a Fisherbrand FE150 pH meter and for alkalinity via titration following APHA (1998) protocols. To assess field-scale hydrology, a potassium bromide (KBr) tracer (1.66 g Br L⁻¹, equivalent to 168 kg ha⁻¹) was applied to all 15 plots. Each 1×1 m plot received 252 g of KBr in 151.8 L of water. For enhanced rock weathering (ERW) treatments, 0.74 kg/m² of olivine was evenly incorporated into the topsoil under plastic cover to ensure uniform application. Geophysical mapping was conducted pre- and post-treatment using electromagnetic induction (EMI) with a Dualem-21S sensor, capturing both shallow (1 m) and deep (2.1 m) effective conductivity (ECa) data. EMI was used to infer soil texture and chemical properties, with references to previous applications (e.g., Becker et al., 2022; Doolittle & Brevik, 2014). Soil samples were analyzed at Waters Agricultural Lab for physical and chemical properties, including pH (water and buffer), cation exchange capacity (CEC), organic matter (OM), and nutrient content (P, K, Mg, Ca) using the Mehlich III extraction method. Percent base saturation for K, Mg, Ca, Na, and H was also measured. At WSL, elemental analyses were performed using inductively coupled plasma mass spectrometry (ICP-MS, Thermo iCAP RQ) and optical emission spectrometry (ICP-OES, Agilent 720). Samples underwent total digestion (EPA 1992) with hydrochloric and nitric acids using a CEM MARS XPress system. Ni was measured on the ICP-MS, while Al, Cu, Mg, Ca, K, Mn, Na, and Fe were analyzed on the ICP-OES. Three rounds of lysimeter porewater samples were analyzed at WSL for major cations (Mg²⁺, Ca²⁺, Fe, Al³⁺, Cu, Mn²⁺, Na⁺, K⁺) via ICP-OES and anions (Br⁻, Cl⁻, F⁻, NO₃⁻, NO₂⁻, SO₄²⁻, PO₄³⁻) via ion chromatography (Thermo Dionex ICS 5000+). Ni and Cr were measured on the ICP-MS. Additional parameters, including pH, alkalinity, bicarbonate, and total organic carbon, were recorded to support aqueous alkalinity calculations. Particle size distribution was determined for 15 soil samples (L1–L15) collected on October 18, 2025, using the Kettler et al. (2001) method. Soil textures were classified following Soil Survey Division Staff (1993) guidelines.
Institutions
- University of Nebraska-LincolnNE, Lincoln