--- tags: methane, rice, sulfate, mid-season drain, 13C --- [toc] # <center>Field-based assessment of enhanced rock weathering's potential remove atmospheric CO2 and its implications for net system emissions</center> ## Preamble and contact information This is project is led by Zhenglin ==**Zhang**==. Zhang will be holding two appointments during this period as the project lead. * Postdoctoral Scholar | Stanford | Dept of Earth System Science, Fendorf Group * Research associate | UC Davis | Dept of Plant Sciences, Linquist Group Email: <zhangzhl@stanford.edu> | <hcizhang@ucdavis.edu> Other collaborators and main points of contact * UC Davis, Linquist Lab, California * Bruce Linquist * Telha Rehman This is part of a larger project on ["scalable solutions for rice methane suppression"](https://hackmd.io/@xiaozhangzhang/rkxAbe0okx). ## Background Enhanced rock weathering (ERW) captures atmospheric CO2 through the weathering of silicate materials. Increasingly, it is touted as a technical option, especially in agricultural systems, to sequester atmospheric C. Thus far, there is no published research on field-based validation of ERW in rice systems. Previous work has shown that ERW can contributed to enhanced methanogensis [(Zhang et al. 2024)](https://pubs.acs.org/doi/10.1021/acs.est.4c04751). Consequently, the net effect of ERW may be negative even with atmospheric C removal. Additionally, pot studies have suggested that metal cations are released into soils from weathering. Base cations can improve crop fertility, but release of excessive heavy metal species can toxic for human consumption [(Uchibayashi et al. 2025)](https://doi.org/10.1080/00380768.2024.2448457). ## Location/Experiment arrangements * California: Rice Experiment Station, Biggs * Potential to also run this with IRRI or INIA ## Objectives Primary: Establish the effect of ERW on (1) methane emissions and (2) carbon capture through a dose response trial. Calculate net CO2eq balances. ==**Overall, we hypothesise an increase in methane with ERW and increase in CO2 capture with increasing rock application rates but changes to the two response variables will plateau at sufficiently high rock application rates.**== Secondary: Evaluate soil geochemical changes to soils, especially heavy metal concentrations. If specific metal species have high soils concentrations, proceed with elemental quantification in plant tissue. ## Treatments Treatments include a low to high rate of rock amendment application * Control: 0 Mg ha^-1^ * Agronomic rate: 10 Mg ha^-1^ * CDR rate: 50 Mg ha^-1^ (consider 40 Mg ha^-1^) ## Data collection Online data repository available on [GitHub](https://github.com/XiaoZhangZhangRice/ERW) * 10 by 20m plots - 8 to 12 cores. * 3 cores per plot * 0-15, 15-30, 30-50 cm * Thaicat method (read the paper) https://reinhard.gatech.edu/uploads/5/4/1/0/54106417/reershemius-et-al-2023.pdf#:~:text=The%20TiCAT%20mass%2Dbalance%20approach%20introduced%20here%2C%20which,and%201.04%20%C2%B1%200.37%20tCO2eq%20ha%E2%88%921%20(manure%2Dfertilized) * LLNL did 6 month and then 1 year soil cores. * Cations and * 6 months and a year * High speed centriguging methods * Metagenomes or 16s both can work. * Basalt rock power analyses * Minerology and chemical composition (initial data available) * Scanning electron microscopy will be useful - determine porosity of the material * Greenhouse gas (GHG) emissions * Weekly sampling of GHG emissions. Intensive sampling (daily or every other day) when rapid changes to soil moisture are expected (initial flood and drainages). Results allow the quantification of cumulative seasonal methane and nitrous oxide emissions. :::warning Use GC to gap fill, Li-Cor for day to day. ::: * Weekly redox and pH * Weekly porewater - see below for visual schemetic * 15 cm: Base cation, heavy metal (Fe, Co, and Ni) and CO~3~^-^ concentrations in active root zone across time. This allows quantification of atmospheric C capture. Combined with downward percolation, we can calulate amount of C removed from atmospher for long term storage. Net CO2eq can be calcuated as the difference between C captured and methane released in kg CO2eq ha-1. :::danger Scott: Will the 65 cm depth be a good representation of long term storage? There is a water restrictive layer at about 15 cm. FYI the longest lysimters we have are 90 cm. 15 cm is subtracted to account for floodwater depth. ::: ![image](https://hackmd.io/_uploads/ryYm-MFxxg.png) * Weekly irrigation water * Quantify original CO3- levels in * Water entry - before interaction with rocks * Water exit - after interaction with rocks * Downward water percolation * Quatify downward water movement (m^3^day^-1^) * Use findings from [LaHue et al. 2021](https://doi.org/10.1016/j.agwat.2020.106445) becuase percolation rate has been measured for the Rice Experiment Station site. * Soil biogeochemical properties * Sample soils at pannicle initiation (PI), 50% heading (H), and maturity (M). * Section off into 0-15, 15-30, 30-60 cm * Quantify concentration of base cations and other heavy metal species. * Can also perform microbial analysis - novel * Also perform analysis on basalt - minerology transformation over time. * Yield * Harest at maturity, report grain yield at 14% moisture. Perform tissue analysis of heavy metals if a particular species have high concentrations. ## California experiment - 2025 ### Site map Plot maps - to scale with all the different kinds of rings when final treatments are confirmed. ![image](https://hackmd.io/_uploads/rJYsn44bgx.png) :::danger Scott: Do you think we need some kind of implement to minimise lateral water movement - which may also cause CO3 movemenet? See below for a potential solution using PVC rings. ::: ![image](https://hackmd.io/_uploads/BkQhCrnyex.png) ### Logistics * 15 plots, RCBD * Each plot to be 2mx3m * Lysimeters x15 of each * 30 cm * 60 cm * 90 cm * 30x GHG collars * 15x yield rings (1 m^2^) * Seeds (2.8 kg total) - seeding rate 180 lb/ac $$Seed\ weight\ per\ plot: \frac{453.592g}{lb} \times \frac{180lb}{acre} \times \frac{acre}{4046.86m^2} \times \ (2\times 3)m^2 = 187.4g $$ * Boardwalks * Basalt rock powder * Provider: SunRock * [Metabasalt rock](https://www.thesunrockgroup.com/construction-materials/trap-rock/) product * Total amount of product needed :::warning To change all plots calculations to 2x3 m ::: $$\frac{[(0+10+50)/3]Mg}{ha}\times\frac{ha}{10000m^2}\times\ (2\times 3)m^2 \times\frac{1000kg}{Mg}\times\ 15\ plots = 180kg $$ * Amount of product needed per plot, where x is the rate in Mgha^-1^. $$\frac{xMg}{ha}\times\frac{ha}{10000m^2}\times\ (2\times 3)m^2 \times\frac{1000kg}{Mg}\ =0.6x\ kg $$ <center> | Rate (Mgha^-1^) | Weight per plot (kg) | | --------------- | -------------------- | | 0 | 0 | |10 | 6 | |50 | 30 | </center> * Basalt elemental analyses ![Slide1](https://hackmd.io/_uploads/HkW9QGtgge.png) ![Slide2](https://hackmd.io/_uploads/B1WqXMtglg.png) ### Soil sampling dates * 7 July 2025 (47 days after seeding) - if possible * 8 Aug 2025 (79 days after seeding) * 12 Sep 2025 (114 days after seeding) ### Field notes ##### 15 May 2025 * All plots marked out. * From east to west, plots had a spacing of 50 cm * For the boardwalk, plots had a spacing of 70 cm * Total set up was 10.4m (North to south) by 12 m (East to West) * Soils were sampled from the 3 following depths - 1 per plot * 0-15 cm * 15-30 cm * 30-60 cm * See below for more information about this * No shields will be installed between plots because we are on a Cerano regime - pesticide needs to move through water. * Deal with the shields at a later date ![image](https://hackmd.io/_uploads/Bkxfn4EZxg.png) ![PXL_20250516_041511218.MP](https://hackmd.io/_uploads/rJAvhN4-gl.jpg) Dots here refer to the sampled location ##### 16 May 2025 * Rocks applied to all plots * 6 kg per plot for 10 Mg/ha plots * 30 kg per plot for 50 Mg/ha plots * After applying by hand, the rock powder was raked into the soil gently for incoporation * Subsequent and rolling will allow for for more incorporation * 10 ton ha-1 (before and after) ![image](https://hackmd.io/_uploads/HkHWRDH-le.png) ![image](https://hackmd.io/_uploads/SkPXAvBZge.png) * 50 ton ha-1 (before and after) ![image](https://hackmd.io/_uploads/HyZ8RPHZlx.png) ![image](https://hackmd.io/_uploads/Bk9wRwSZxe.png) * Baseline GHG taken - to get from Nawal (we are the in the most Southeast plot at the RES systems site) ##### 19 May 2025 * Aqua applied (N rate 180 kgN/ha) and plots rolled - these both count as tillage events * Square off plots after rolling * Make sure plots are the right size, place flags back in place - stake afterwards * 50 cm gap from east to west between plots, 70 cm gap between plots * Add boards, cinder blocks and rebars to the plot. Extra bricks to be installed at the perimeter of plots. * GHG rings to go in, all to be on the West, 50 cm from borders inside the plot. 2 GHG rings per plot. * One yield ring per plot - if we can find it - if not I will use a quadrat at the end of the season - **no yield rings found - to use quadrat at the end of the season** #### 20 May 2025 * Initial flood * Added in 0-15 cm lysimeters * Not that 30 cm and 60 cm lysimeters were not installed - change in experimental design * Added 1x GHG ring - to add one more next week * A brick was added around the parameter of each plot ![image](https://hackmd.io/_uploads/rka1KQT-gx.png) #### 21 May 2025 Scott meeting - To install peziometers - use this to get pH, redox, and DIC - Use lysimters as well to sample - use this to get total akalinity and major cations - Do about 4 times of of porewater samples below the root zone using alternative methods. - Install metal shields 2 weeks from now - Cerrano (herbicide) will likely be going on #### 21 May 2025 - Plots got seeded - everything went on by blower LOL - just Bruce going at it in the field. Visually it looks like about 200 kg/ha. In the publication, it will be good to say seeded at a non-limiting rate. - Took GHG sample - likely will have some N2O flux (GC) #### 29 May 2025 - GHG sample (GC) #### 2 June 2025 - GHG sample with Li-Cor - Built additional boardwalks - Built shields ![image](https://hackmd.io/_uploads/SyOvPl3zxl.png) ![image](https://hackmd.io/_uploads/S18uwxnGex.png) ![image](https://hackmd.io/_uploads/r1nKvl2Gle.png) ![image](https://hackmd.io/_uploads/rJwcwxhMxg.png) #### 9 June 2025 - Added PVC pieziometers - Took first sample - Redox super low and pH super high - not sure why - Algae issues ![image](https://hackmd.io/_uploads/Skl3QBSQgx.png) ![image](https://hackmd.io/_uploads/BkapXHB7gl.png) - Final set up - ![image](https://hackmd.io/_uploads/Bklx4rS7gg.png) - GHG sample #### 18 June 2025 - Sampled full porewater - piez as well as lysi - GHG sample Lots of weeds ![image](https://hackmd.io/_uploads/r13cuvs4lx.png) ![image](https://hackmd.io/_uploads/SJl2_ws4xg.png) #### 27 Jun 2025 - Full porewater - GHG sample - Herbicide went on on 24 June 2025 - Basalt transported back to Davis - deal with it on Monday. #### 4 Jul 2025 - Full porewater - GHG sample #### 9 Jul 2025 - Soil sample (0-15 cm) - microbial and others Sampling scheme for microbial samples, two more cores were taken after microbial sample. All soil samples were taken from the **roadside**. * Clean dutch with eliminase right before taking a sample, make sure that it is dry with paper towel. Make sure it is dry - it will chew up DNA if not dry. * Wear rubber gloves and clean gloves. * Auger and get a full core * Using clean hands, place soil into a clean bag. * Change to a new pair of gloves before the next sample * Freeze all samples once back in the lab. #### 11 Jul 2025 - Full porewater - GHG sample - 2 ft extensions now #### 18 Jul 2025 - Full porewater - GHG samples #### 25 Jul 2025 - Full porewater - GHG samples #### 4 Aug 2025 - Full porewater - GHG samples #### 11 Aug 2025 - Full porewater - GHG samples #### 13 Aug 2025 - bulk density for all plots - soil sample for all plots - microbial and others #### 18 Aug 2025 - Fixed B0 Piez - Full porewater - GHG samples #### 25 Aug 2025 - Fixed B0 Piez - Full porewater - GHG samples #### 1 Sep 2025 - Fixed B0 Piez - Full porewater - GHG samples #### 3 Sep 2025 - Maturity soil samples - microbial and others #### 7 Sep 2025 - End of season drain commenced #### 8 Sep 2025 - Full porewater - GHG samples: commence intense sampling - Licor only - Assume N2O = 0 - Lysimeters removed from plots (3 more outside of plots to remove) #### 10 Sep 2025 - GHG samples: GC protoccol #### 12 Sep 2025 - GHG sample: Licor, assume N2O = 0 #### 19 Sep 2025 - Seasonal last GHG sample #### 2 Oct 2025 DIC run - all DIC samples completed #### 7/8 Oct 2025 - Harvesting (south two rows completed on 7th) # Li-Cor code steps 1. load raw licor output into R and extract relavant info (done) 2. Have a separate file (field-data), that gives meta data information, mostly chamber volume and temperature, and plot by time. 3. Use the metadata to annotate the Li-Cor data, add only plot at this time. 4. Clean data, chop first and last minute of chamber 5. Use lm to run linear regressions for each chamber on each sampling day. 6. check R2 value. keep to more than 0.85? 7. some how get the slope, whereby the slope is change in ppm/min? 8. Then use math to go from ppm/min to g CH4 ha-1 9. And that should be it????? Boy this is complicated as heck ### May also consider: LCA, mineral transformation and microbial stuff ### Selected readings * * [The contribution of percolation to water balances in water-seeded rice systems](https://doi.org/10.1016/j.agwat.2020.106445) * [Reduced accrual of mineral-associated organic matter after two years of enhanced rock weathering in cropland soils, though no net losses of soil organic carbon](https://link.springer.com/article/10.1007/s10533-024-01160-0) * [Quantifying enhanced weathering](https://carbonplan.org/research/ew-quantification-explainer) * [Potential for large-scale CO2 removal via enhanced rock weathering with croplands](https://www.nature.com/articles/s41586-020-2448-9) * [Enhanced Rock Weathering as a Source of Metals to Promote Methanogenesis and Counteract CO2 Sequestration](https://pubs.acs.org/doi/10.1021/acs.est.4c04751) * [Co-Benefits of Wollastonite Weathering in Agriculture: CO2 Sequestration and Promoted Plant Growth](https://pubs.acs.org/doi/10.1021/acsomega.8b02477) * https://www.thesunrockgroup.com/construction-materials/trap-rock/ cascade climate incorporate into lime * https://www.thesunrockgroup.com/construction-materials/trap-rock/ * [Wollastonite powder application increases rice yield and CO2 sequestration in a paddy field in Northeast China](https://doi.org/10.1007/s11104-024-06570-5) * [Enhanced Weathering May Benefit From Co-Application With Organic Amendments](https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2025AV001693) * [Enhanced Rock Weathering as a Source of Metals to Promote Methanogenesis and Counteract CO2 Sequestration](https://pubs.acs.org/doi/10.1021/acs.est.4c04751)