Performing Department
(N/A)
Non Technical Summary
Organic agriculture, long associated with sustainability, faces uncertainty aligning with theemerging demand for climate-smart food. While organic farming promotes many sustainabilitypractices, its contribution to CO2 drawdown into soil carbon for climate change mitigation is stilldebated. Building soil carbon is challenging for organic systems in the southeast U.S. due to themild, humid climate, weathered soils, and heavy reliance on tillage. In this context, enhanced rockweathering (ERW) emerges as a promising scale-neutral strategy for carbon sequestration. Whenadded to soils, crushed silicate minerals react with atmospheric CO2 to form stable carbonates,removing CO2 from the atmosphere, regardless of soil disturbance. ERW also acts a limealternative raising soil pH and releases plant nutrients. Global estimates show ERW sequestrationpotentials at the same magnitude as more well-known climate-smart strategies. North Carolina hasactive quarries producing ERW as a by-product and organic growers are already applying it to theirfields. However, this is a nascent climate-smart practice and there is currently no information onERW in organic systems in the U.S.This proposal is a collaboration with North Carolina State University and North CarolinaAgricultural and Technical State University. The objectives of this project are: 1) Evaluate theagronomic and soil fertility impacts of substituting lime for ERW in both organic row crop (12 siteyears) and small-scale organic vegetable (6 site years); 2) Estimate carbon dioxide removal rates forSoutheast soils; 3) Measure GHG mitigation potential and 4) Empower organic stakeholdersseeking to adopt ERW through Extension activities.
Animal Health Component
50%
Research Effort Categories
Basic
35%
Applied
50%
Developmental
15%
Goals / Objectives
The use of ERW for carbon capture is a nascent climate-smart practice with much of the information on its use still at the research stage. Despite this, the carbon markets are expanding rapidly and this form of agricultural carbon sequestration offers the highest payback to farmers and one of lowest barriers to entry being scale-neutral and simply used as a liming agent. While publications are beginning to emerge on efficacy on carbon dioxide removal potential there is extremely limited information on agronomic and soil fertility implication of its use. To our knowledge there is no information on ERW in organic systems in the U.S in any crop type. This is despite the fact the land application has begun at scale throughout the U.S. and in particular in North Carolina with such a large deposit of available material and an active carbon market. The goal of this research is to conduct foundational research on the both applied and basic understanding of integrating this climate smart practice into U.S. organic systems in the south east. Objectives:1. Evaluate the agronomic and soil fertility impact of substituting agricultural lime for ERW materials in organic row crop systemsGenerate liming equivalence estimates for improved target pH changes from field and lab incubationsQuantify plant available soil nutrients over 3 years after applicationMeasure yield, plant nutrient uptake and grain quality compared to conventional lime products2. Evaluate the agronomic and soil fertility impact of substituting agricultural lime for basalt materials in organic small acreage vegetable crops with the same sub-objectives as in Obj. 1. Led by NC&AT Co-PI Binswanath3. Evaluate the potential co-benefit of ERW application on greenhouse gas emissions (CO2 and N2O) mitigation in the field and lab4. Fully characterize basalt ERW, calculate weathering rates and estimate Carbon Dioxide Removal rates for the ERW product across varying soil types and the impact of biological weathering, using experimental data from the field, greenhouse and lab column trials5. Use a suite of extension strategies to build an information platform for this new climate-smart practice for organic growers
Project Methods
EWR Basalt Characterization: At field delivery a subsample of ERW will be collected and characterized. The following will be characterized:Specific Surface Area: Brunauer Emmet Tell (BET) surface area analyzerParticle Size Distribution: Laser DiffractionMineralogy: X-ray diffraction (XRD), including screening for presence of existing carbonate materials.Carbon Dioxide Removal Potential: Calculated using Steinour formulation (Equation from Reershemius et al. 2023) which is the maximum amount of CO2 removed if all basalt were to react with carbonic acid and is ultimately captured as bicarbonateNorth Carolina Department of Agriculture Waste Analysis ReportCarbon Dioxide Removal Estimate Approach: In the greenhouse and columns we are able to use a mass balance approach, where we sample from specific chemical pools including the soil exchangeable fraction, plant material and leachate to represent the speed of weathering (Reershemius et al. 2024). In addition, a solid phase elemental analysis using a lithium borate fusion at the start and end of the experiment will provide an estimate of weathering. Using all of these chemical pools a presumed carbon dioxide reduction (CDR) in t CO2 ha-1 yr-1 estimate will be calculated (Almaraz et al. 2022). In the field trials we are using change over time of the solid phase of the soil+basalt mixture compared to the unamended control and time 0, as an estimate of weathering over three time periods. Including samples of the basalt rock, ERW+Soil at time 0, end of year 1 and end of year 3. The two sampling times will allow some inference on potential weathering rate changes over time.Leachate/Pore Water: Water samples will be measured for pH, Dissolved Inorganic Carbon, Cations and Metals and total alkalinityPlant Tissue: Digestion and Analysis on ICP-OES for Mg, Ca, K, NaSoil Weather Analysis: Soil samples will be taken from the Greenhouse Mesocosms, the row crop on-farm trials and the GHG field trials. For the field trials two depths will be used 0-30 cm and 30-90 cm. Surface samples (0-30cm) will be homogenized from 8-10 samples per plot using a push probe and 30-90 cm samples will be taken from two samples from plot using AMS UTV mounted hammer probe. All samples will be processed through a 2mm sieve. For solid phase analysis samples will be submitted to ALS laboratories for a lithium borate fusion and analysis on a ICP-OES. In addition an ammonium acetate extraction will be performed to remove elements bonded to exchangeable sites and some carbonates. Subtracting the ammonium acetate leach from the solid phase prevents underestimating weathering that has occurred.Soil Inorganic Carbon: Lastly, soils will be analyzed for total carbon on the LECO, a subsample will be treated with an acid pre-treatment to remove organic carbon and then analyzed on the LECO for total inorganic C. Soils in the coastal plain of NC do not have inherent soil inorganic carbon, if weathering has occurred and carbonate formation is detected this quantity will be attributed to the weathering of the material.Soil Nutrient Properties: Samples submitted to the North Carolina Department of Agriculture will return the following parameters: "Mehlich-3 extractable phosphorus, potassium, calcium, magnesium, sulfur, sodium, zinc, manganese, and copper, humic matter, pH and Mehlich buffer pH, weight per volume, cation exchange capacity (CEC), and base saturation" (NCDA 2024)Plant Tissue Analysis: Samples submitted to the North Carolina Department of Agriculture will return the following parameters:Nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, sodium, iron, zinc, manganese, copper, boron and aluminum.