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tags: methane, rice, sulfate, mid-season drain
---

[toc]

# <center>Combination of sulfate and mid-season drain as a scalable methane suppression solution</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: <[e-mail]> | <[e-mail]>

Other collaborators and main points of contact

* UC Davis, Linquist Lab, California
* Bruce Linquist <[e-mail]>
* Telha Rehman <[e-mail]>

* IRRI, Phillipines
* Ando Radanielson
:::danger
Collaboration contigent on LOA - signing in process
:::

This is part of a larger project on ["scalable solutions for rice methane suppression"](https://hackmd.io/@xiaozhangzhang/rkxAbe0okx).

## Background

Rice is an important crop in meeting global calorie demand but its production contributes to 12% of global methane emissions. Various technical options, especially in-season drainages, have been empirically demonstrated to reduce methane emissions. However, few studies have examined stacked practices such as the combination of drainage with other management strategies, representing a knowledge gap. Preseason sulfate addition to rice fields increases soil redox potential, disrupting early-season methanogenesis and reducing methane emissions. A single mid-season drain suppresses late-season methane emissions and reduces total emissions by about 50%. Hence, the combination of preseason sulfate application and mid-season drainage can potentially suppress methane emissions both early and late in the season. This stacked practice only includes one amendment application and one drain, representing an easy-to-implement and more importantly, scalable solution.

## Objectives
* Primary: Evaluate preseason sulfate’s ability to suppress methane emissions in combination with a mid-season drain. ==**Overall, we hypothesize that the sulfate with drain treatment will have reduced methane emissions compared to continuous flood, midseason drain only, and preplant sulfate treatments.**==
* Secondary: Quantify soil biogeochemical changes, specifically changes in sulfate concentrations and soil microbial communities over time.

## Treatments
* CF – Continuous Flood
* CFS – Continuous Flood, Preplant Sulfate
* MD – Mid-season Drain
* MDS – Mid-season Drain, Preplant Sulfate
* MDSS - Mid-season Drain, Preplant & mid-season sulfate

:::info
Drain to occur before pannicle initiation for approximately 10 days. Sulfate to be applied at the end of the drain.
:::

:::info
Preplant S rate @ 300 kg S ha^-1^ for California
Preplant S rate @ 50 kg S ha^-1^ for IRRI
Mid-season S rate @ 50 kg S ha^-1^ for California
Mid-season S rate @ 30 kg S ha^-1^ for IRRI
:::

:::warning
Ando to get back on the midseason sulfate rates @ a later date
:::

## Data collection/Methods
* Baseline soils
* Collect soils from 0-15 cm between land preparation and fertilizer application. 8 subsamples into 1 composite sample.

* 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 from all treatments, addressing the primary objective.

* Sulfate concentrations
* Weekly pore water samples (0-15 cm) - 30 cm Irrometer lysimeters
* Results allow us to track sulfate transformations/concentrations and losses in the soil over time and its relationship with methane fluxes.
* Add on DOC
* Analyze on IC
:::info
0-15 cm chosen because there is a water restrictive layer at around 15 cm depth. Most soil chemical changes will be captured in the 0-15cm band.
:::

* Redox potential
* Weekly redox potential

* Soil samples (geochemical analyses)
* Sample soils (0-15 cm) at three time points (1) pre-MD (peak of methane emissions, right before PI), (2) right before flood (during drain), and (3) after re-flood (2-3 weeks post drain). Freeze for future analyses.

* Soil moisutre (MD plots only)
* Install soil moisture sensors for MD plots (0-15 cm).
* A total of 6 sensors were installed for the California site. 2 for a set of LD treatments per block (refer to the site map).
* Installing individual sensors in each ring would have messed more things up.

* Microbial structure and function
* Sample rhizosphere and bulk soils to evaluate microbial structure and function. Sample at three time points **add one more for preplant soil** (1) pre-MD, (2) drain (just before reflooding), and (3) after re-flood (2-3 weeks after reflood). Perform DNA extractions and sequence metagenome on the Illumina platform. Results allow us to track shifts in microbial structure, relative abundance of specific species, and extrapolate function in relationship to the drain and sulfate application.

:::danger
Scott: Potential to domicrobial work at Telha's other site - only mid-season drain + continuous flood
:::
* Growth stage
* Drone data NDRE for measure plant health
* Plant height, tiller number (PI, 50% heading)
* Plant density (stand count - GHG ring and yield ring)

* Yield
* Harest at maturity, report grain yield at 14% moisture. Can perform subsequent plant tissue analysis if needed (e.g. S uptake).

## California Experiment - 2025

### Data and important files

* [Linquist lab drive](https://drive.google.com/drive/folders/1Z3wR5hLPU6M0w9wiAJ89Bc7sGm0WgaWS?usp=drive_link)
* [GitHub repo](https://github.com/XiaoZhangZhangRice/Sulfate_Drain)

### Site

* Knight's landing: [River garden farms](https://maps.app.goo.gl/wiL1k5R2WsS4PcTs8)

### Site map and experimental design

Experiment set up as randomised complete block design (RCBD). Project done in collaboration with Telha Rehman.

:::info
The MD for this project is denoted by the LD (long mid-season drain) in the map below
:::


### Logistical prep

* Seeds
* 180 lb/ac
* 30 plots per site
* Each plot is 30 inches in diameter
* 9.2 g of seed need per plot
* Other seeds needed to fill up around the area: 10 kg approx

$$Seed\ weight\ per\ plot:
\frac{453.592g}{lb} \times \frac{180lb}{acre} \times \frac{acre}{6,272,640in^2} \times \pi \left(\frac{30in}{2}\right)^2 = 9.2g
$$

* Sulfate (gypsum: CaSO₄·2H₂O)

Preplant S rate = 300 kg S ha^-1^

$$Gypsum\ rate = \frac{300kgS}{ha} \times \frac{100kg\ gypsum}{17kgS}\ = 1764.71 kg \ gypsum/ha
$$

$$Gypsum\ weight\ per\ plot:
\frac{1000g}{kg} \times \frac{1764.71kg}{ha} \times \frac{ha}{15,500,031.000062in^2} \times \pi \left(\frac{30in}{2}\right)^2 = 80.5g
$$

Midseason S rate = 50 kg S ha^-1^

$$Gypsum\ rate = \frac{50kgS}{ha} \times \frac{100kg\ gypsum}{17kgS}\ = 294.117647 kg \ gypsum\ ha^-\ ^1
$$

$$Gypsum\ weight\ per\ plot:
\frac{1000g}{kg} \times \frac{294.117647kg}{ha} \times \frac{ha}{15,500,031.000062in^2} \times \pi \left(\frac{30in}{2}\right)^2 = 13.4g
$$

* Lysimeters (30 cm) x15
* 36x 30in PVC ring
* 18x GHG collar
* Other GHG sampling equipment
* Labelled stakes
* 9x moisture sensors
* 3x data logger
### Soil sampling dates

* Pre-drain:
* Post-drain:
* Maturity:

### Dates of agronomic importance
* Pre season sulfate application: 1 May 2025
* Planting date: 10 May 2025
* Initial Flood: 7 May 2025
* MD drain start: 21 June 2025
* MD reflood: 1 July 2025
* Top dress N: 7 July 2025
* End-of-season drain:
* Harvest date:
* Pre-season sulfate: 1 May 2025
* Herbicide application: 14 May 2025 (Cerrano, Cliffhanger)
* 1st Propanil: 14 June 2025
* Mid-season sulfate: 1 July 2025 (50 kgS/ha)

### Management

* N rate: kgN/ha, aqueous NH3 (aqua) ()
* Top dress N: kgN/ha Urea, 7 July 2025
* P rate: kgP/ha
* K rate: kgK/ha
* Seeding rate: 180 lb/ac
* Plot dimension: 30 inches (76.2 cm)
* Variety: M211
* Field history

2022        2023        2024             2024                       
Tomato     tomato      wheat     Flooded for shorebird program         

### Field notes

#### 1 May 2025
* Experiments set up
* PVC rings arranged. CF, SD, and LD rings are bunched together to prevent leakage and irrigation cross containmination
* Gympsum (sulfate) applied at a rate of 300 kg S ha-1.
* Final weight of SO4 applied per ring (30 in diameter): 80.5 g. Product has 12% S.
* Lysimeters will be installed when wet.
* Preplant soil samples taken


#### 5 May 2025
* Stakes installed
* Very very strong wind. Some sulfate may have been blown out but visual assessment looks okay!


#### 6 May 2025
* Telha did first GHG sample

#### 7 May 2025
* Bang in all rings to achieve good seal
* Install lysimeters - really good. About depth of 15 cm

#### 9 May 2025
* GHG sample for N2O

#### 13 May 2025
* GHG sample
* Lysimeter first measurement!
* Today's protoccol
* Remove all water by piping out with a syringe
* Apply pressure to approximately 70-80 kPa. Where pump fail to get to appropiate pressure, a syringe was used (approx 3 evacs).
* Pressue was present for about 2 hours.
* A clean syringe was used for each sample
* A syringe was attached to a lysimeter without opening the valve
* Accumulated porewater was pulled out. For lysimeters that yielded substantial amounts of water, only 12ml was collected into 15ml falcon tubes.
* Collected samples were immediately placed into an ice box for cooling.
* The vaccum of the lysimeter was then released with the valve kept open. Extra precaution was taken to ensure no water was left in the lysimeter.
* Tape was placed over the valve opening to prevent dust entry but allow aeration.
* Samples once brought to the lab were immediately frozen for subsequent analyses.
* 204-306 side had a couple of lysimters that yielded less than 2 ml - investigating
* First redox and pH reading
* Some preplant sulfate plots had a shade of colour to it.


* Plot 203 yield got smacked when we were pounding in rings - looks okay today


#### 20 May 2025

* GHG sample
* Porewater sample
* All lysimter straws replaced with new ones

#### 27 May 2025

* GHG sample
* Porewater
* Redox

#### 3 June 2025

* GHG sample
* Porewater
* Install 2x dataloggers for Blk 1 and Blk 2
* Transplanted for 105 yield due to low plant counts

#### 10 June 2025
* Routine GHG, porewater, and redox
* Redox super super low for all plots (<200 mV)
* pH (according to the probe is very high)
* Installed one more datalogger for Blk 3

#### 17 June 2025
* Routine GHG, porewater, and redox
* Pre-drain soil sample - to be used for microbial analysis and other things

Method used for sampling was as follows (certainly not the best but was practical):

Here we refer to eliminase as any product that can effectively remove RNA and DNA contamination.

Dirty hand:

* Clean the dutch auger, making sure that there is no soil residue
* Put out the auger for the clean hand to spray down with eliminase.
* Auger 0-15 cm
* Place tip of the auger into a clean bag and allow clean hand to remove all soil.
* Repeat

Clean hand:

* Wear rubber gloves and clean gloves with eliminase.
* Wait for dirty hand to clean the dutch auger
* Clean dutch auger 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.
* Hold out clean bag for dirty hand to place soil into clean bag
* Use sterile hands to remove all soil into the clean bag.
* Seal bag and place into ice chest
* Change to a new pair of gloves repeat
* Freeze all samples once back in the lab.

We acknowledge that the Ziplock was not sterile but it should affect results minimally - periodic error

#### 20 June 2025
* Pre T-0 GHG sample
* Replaced Blk2 data logger
* Set up irrigation for all CF treatments


#### 21 June 2025
T0

#### 23/25/27 June 2025
* GHG sample
* Porewater on 25 and 27 June 2025
* 27 June porewater only from continuously flood rings
* No leaks in continuously flooded rings
* Drained rings are drying out nicely

#### 1 July 2025
* GHG sample
* Porewater (continuous flooded only)
* Grower will reflood field and end of mid season drain!!
* LD rings moisture at around 30%
* Adding sulfate to CF-MS plots @ a rate of 50 kgS/ha. This translates to 13.4g of gypsum per plot

#### 3 July 2025

* GHG sample - first one post drain

#### 7 July 2025
* GHG sample, porewater sample
* Topdress N (Urea)

#### 8 July 2025
* Grandstand (herbicide application)
* 20 day water hold and 48 hours REI

#### 14 July 2025
* Porewater and GHG
* Soil sample from all rings

#### 21 July 2025
* Porewater and GHG
* Taped up extensions to 3 ft
* Cleaned out extra irrigation tubing

#### 28 July 2025
* Porewater and GHG

#### 1 Aug 2025
* Porewater and GHG

#### 8 Aug 2025
* Porewater and GHG

#### 15 Aug 2025
* Porewater and GHG

#### 19 Aug 2025
* soil samples for all plots

#### 22 Aug 2025
* Porewater and GHG

#### 29 Aug 2025
* Porewater and GHG

#### 5 Sep 2025
* Porewater and GHG
* Last porewater sample of the season

#### 7 Sep 2025
* End of season drain commenced

#### 9 Sep 2025
* End of season drain GHG samples
* Rest of the field still very much flooded
* Lysimeters removed
* 3ft extensions
* Cleaned out the site

#### 11 Sep 2025
* GHG sample

#### 13 Sep 2025
* GHG sample

#### 19 Sep 2025
* GHG sample

#### 24 Sep 2025
* GHG sample, CH4 @0. Seasonal last

#### 29 Sep 2025
* All yield rings harvested. Experiment ends

### Lab notes

#### 16 Sep 2025
* Transferred all samples to carnegie
* Prepped the last samples of the season for IC

## IRRI experiment

:::info
[Lysimeter usage guide](https://hackmd.io/@xiaozhangzhang/B1oBIppfll)
:::

Credit to Ando Radanielson and the IRRI team for the below proposed plan and mirror study