Benefits and challenges of alternate wetting and drying in ... · Sustainable intensification:...

UCDAVISUniversity of California

Water seeded

Benefits and challenges of alternate wetting and drying in rice systems

Bruce Linquist, Daniela Carijo, Nimlesh Balaine, Nadeem Akbar, Gabe LaHue

University of California, Davis

International Temperate Rice Conference

Griffith, Australia

March 6-9, 2017

Agricultures major challenges

• Food security

• Water scarcity

• Environmental challenges• Climate change

• Pollution from agriculture

• Food safety

Rice• Provides more calories for humans than any

other crop• (Maclean et al., 2002)

• Is associated with high water use • (Bouman et al., 2007)

• Has a higher GWP than other cereal crops • (Linquist et al., 2012)

• Systems are associated with various heavy metal concerns• Arsenic and methyl mercury

http://blueandgreentomorrow.com/2012/09/07/calls-for-sustainable-investment-to-prevent-unmanageable-demand-for-food/

Sustainable intensification: win-win

EnvironmentalSocial, Health

Can this be achieved in rice systems with alternate wetting and drying (AWD)?

AWD in a water seeded system

Continuously Flooded

AWD alters soil chemistry

Areas covered• Can yields be maintained or increased?

• Our field studies and meta-analysis

• Water savings• Field study and meta-analysis

• Under what conditions are water savings realized?

• GHG emissions• Field studies and meta-analysis

• Arsenic• Field studies

• MeHg• Field study

Focus studies

• Arkansas (Linquist et al., 2015 Global Change Biology)• 3 years

• California (LaHue et al., 2016 AEE)• 5 years (2012-2016)

• Global meta-analysis of AWD (Carrijo et al., 2017 – Field Crops Research)

• Global meta-analysis of AWD and GHG (Balaine et al., In progress)

Two drains

Yields: Arkansas and CaliforniaCross year averages

• CA: no yield reduction with AWD or increased soil drying

• AR: decline with increased soil drying

California 2013-2014

Arkansas data: Linquist et al., 2015- Global Change BiologyCalifornia 2013/14 data: LaHue et al., 2016 -AEE

Arkansas-3yr

CF (control) AWD 35 AWD 25

CA Mean 2015/2016

AWD and yields

•Factors for maintaining yields in field studies•Not too dry•Avoid aerobic soil conditions when:

• High soil N• N losses

• Poor canopy coverage• Weeds

AWD and yields

• Results of a meta-analysis (Carrijo et al., 2017)• Severe vs mild AWD

WT>20kPa[23-80](152/15)

WL>15cm[20-50](40/8)

WT≤20kPa[5-20](76/12)

“MildAWD”

“SevereAWD”

WL≤15cm[1-15](117/14)

AWD and yields• Favorable soil characteristics

• Low soil pH

• High soil carbon

AWD and yields• Soil characteristics

more important under sever AWD

AWD and water use

• 18 – 44% reductions

• 18% were without yield loss

Flood (Control) AWD/40 – Flood AWD/60 AWD/40

Water use (m3 ha-1)

18% 44%31%

Linquist et al., 2015- Global Change Biology

AWD and water use

• Meta-analysis• (Carrijo et al., 2017)

AWD and water use

•Conditions for increased water use efficiency•Not likely reduced transpiration•Reduced evaporation•Reduced percolation and seepage• Increased use of precipitation

AWD and GHG emissions• CA and AR field studies (7 site yr)

• 50-90% reduction in GWP

• Mostly reduction in CH4

• Kept N2O very low

Date of sampling

May Jun Jul Aug Sep Oct Nov

CFAWD 25 AWD 35 AWDS

Year 2016

Date of sampling

Jun Jul Aug Sep Oct Nov

CFAWD 25 AWD 35 AWDS

Year 2016

AWD and GHG emissions

• Meta-analysis: (preliminary data)

• CH4 reduction – 60%• Similar to IPCC guidelines

• Some sites with higher N2O

AWD and GHG emissions: keeping N2O low

• Delaying 6 wk ensures N uptake

• Canopy coverage to prevent weeds

Water seeded

6 weeks

Fertilizer N

Topdressif necessary

NH4 NO3 N2

California

Anaerobic Aerobic

AWD and GHG emissions

• Lowering GWP requires• Careful management of both water and nitrogen

AWD and arsenic

• 2 dry down periods reduce total As in grain by over 40%• Similar in AR studies

• Reductions in inorganic and organic as well

• Safe AWD did not result in reductions

CF AWD35 AWD25

Concentration(mg/kg)

TotalAs As(III) DMA

CF AWDSafe AWD35 AWD25

Concentration(m

TotalAs As(III) DMA

AWD and arsenic: timing

• Drains at PI and booting - lowest grain As

• Safe AWD did not reduce (2016)

CF PI BOOT HEAD

Concentra

on(mg/kg)

TotalAs

As(III)

2016PI Booting Heading

AWD and methylmercury

• Flood water concentrations• Main concern in CA

AWD CF

Growing FallowLe

AWD CF

AWD and methyl mercury

• Rice grain MeHg levels a health concern in some areas

• AWD reduced MeHg in grain by almost 50%

• Grain MeHg: good integrator of seasonal Hg dynamics

• Suggests that AWD may reduce overall MeHg production

Harvest2014

August2015

Harvest 2015

) Grain Total Hg CF AWD

Grain MeHgCF AWD

Challenges

• N management• In conjunction with water management to keep N2O

emissions low

• Water management• Requires ability to control water

• The timing and severity of drain events.

• Up to 11 days drain without yield reductions

• Scaling up to commercial fields

• Can we use AWD to increase yields?

Sustainable intensification: win-win a possibility

• On farm incomes increased through reduced water use and pumping

• Yields maintained

• GWP reduced by 45-90%• Water resources conserved

• Grain arsenic reduced by 50%• MeHg production

Thankyou

GWP: (CH4 + N2O)

• GWP reductions of 45 – 90%.

• N2O kept low

• Yield-scaled emission reduction similar• Yields were similar

• See Balaine et al (Tue 10:35 am)

GWP: (CH4 + N2O)

• GWP reductions of 45 – 90%.

• N2O kept low

• Yield-scaled emission reduction similar• Yields were similar

• See Balaine et al (Tue 10:35 am)

Flood 338 a -57 a 11262 a -

AWD-35 92 b -111 a 3003 b 73

AWD-25 111 b -32 a 3681 b 67

Flood 105 a 0.03 b 3520 a -

AWD/40–flood 55 b 0.17 ab 1922 b 45

AWD/60 7 c 0.28 ab 359 c 90AWD/40 8 c 0.51 a 494 c 86

Treatment CH4(kg CH4-C ha-1)

N2O(kg N2O-N ha-1)

GWP(kg CO2-eq ha-1)

Reduction

Flood 133 a -0.02a 6035a -

WS AWD 52 b -0.03a 2361b 61

DS AWD 18 b 0.21a 903c 85

CA 2013-2014

CA 2015

AR 2012-2013

Yield-scaled GWP

• Yield-scaled GWP• kg CO2 Mg-1 grain

• Yield-scaled GWP decrease similar to GWP• GWP decreased

while yields changed little

Flood 13.36 11,262 a 947 a -

AWD-35 13.32 3,003 b 253 b 73

AWD-25 13.56 3,681 b 305 b 68

Flood 10.26 3520 a 347 a -

AWD/40–flood 10.17 1922 b 190 b 45

AWD/60 9.73 359 c 37 c 89AWD/40 8.97 494 c 55 c 84

TRT Yield(Mg ha-1)

GWP(kg CO2-eq ha-1)

GWP-Y(kg CO2-eq

Mg-1 grain)

GWP-Y%Reduction

Flood 9.38 6035a 667a -

WS AWD 9.66 2361b 251 b 62

DS AWD 10.71 903c 84 b 87

CA 2013-2014

CA 2015

AR 2012-2013

Managing N fertilizer and water

• Eliminated or reduced N2O emissions

• Little to no N additional losses • Same N rate to

achieve optimum yield

NH4 NO3 N2

California

Anaerobic Aerobic

Meta-analysis: Soil moisture and yields

• > 20kPa resulted in 23% yield loss

• <20 kPa or “Safe AWD” resulted in 2-4% yield loss.

• Safe AWD • measured water table below soil

surface <15cm• Conservative measure

• No difference between < or >15cm

• CA occurred 2 days after soil saturation.

• AWD treatments were reflooded5 to 10 days after soil saturation.

• Useful?

WT>20kPa[23-80](152/15)

WL>15cm[20-50](40/8)

WT≤20kPa[5-20](76/12)

“MildAWD”

“SevereAWD”

WL≤15cm[1-15](117/14)

“Safe AWD”-IRRI

Managing water

(528/58)

(453/39)

(452/39)

EffectofAWD(%)

Water use: meta-analysis

Water use: Causes of lower water use

• Fields are not drained but water is allowed to subside naturally due to ET and percolation

• Decreased percolation and seepage• During drain times

• Takes full advantage of rainfall capture• Provided boards are high enough

Greenhouse gas emissions

Soil water content

Flooded

AWD/60

AWD/40

• CH4 emissions increase until first drain then drop.• In CA, very little CH4 after first drain

• In AR, N2O emissions increased during drain events. Not seen in CA

California Water-seeded Arkansas Drill-seeded

Outline

•What is AWD?

•Benefits•Water, GHG, As, Hg

•Managing drain timing and duration to achieve desired outcomes

•Challenges

Greenhouse gas emissions

Soil water content

Flooded

AWD/60

AWD/40

No emissions

Kept seasonal emissions low

Is there a GHG benefit to extended dry times?

TRT CH4

kg CH4-C ha-1

N2Okg N2O-N ha-1

Flood 338 a -57 a

AWD-35 92 b -111 a

AWD-25 111 b -32 a

TRTCH4

kg CH4-C/ha

N2Okg N2O-N/ha

Flood 105 a 0.03 bAWD/60 7 c 0.28 abAWD/40 8 c 0.51 a

• Allowing fields to dry longer did not reduce GHG emissions

Arkansas

California

Nitrogen management

• Keeping GWP low requires optimal N and water management to minimize N2O losses

• Introducing aerobic periods into system increases opportunities for losses via denitrification

2008, USEPA

Managing N fertilizer and water

• Italian study

• Permanent flood vs AWD

• Used nitrification inhibitor

• Drained randomly

• CH4

• N2O

Lagomarsino et al., (2015) Pedosphere

PF=Permanent flood

N2OCH4

PF AWD PF AWD

2012 2013

Heavy metals

• Arsenic (As)• Present in rice grain• Human health concern• Babies and populations with high rice

intake

• Mercury (Hg)• Ecosystem concern• Flooding leads to methylation of Hg =

methyl mercury (MeHg)• MeHg is toxic• MeHg bio-accumulates in food systems

Sustainable intensification

YieldEconomic

AWD drain timing and grain As

Water seeded Water seeded-AWD Drill seeded AWD

Drill seeded conventional Drill seeded- early AWD Drill seeded AWD

352(µg kg-1)

55(µg kg-1)48(µg kg-1)114(µg kg-1)

176(µg kg-1)367(µg kg-1)

Early season aerobic periods had little impact on grain As concentrations

Arkansas

California

Length of drain time and grain As

State Treatment Polished rice total As (ug/g)

% reduction

Arkansas-RS Flood 343 -

AWD/60 165 52

AWD/40 114 67

Arkansas-RR Flood 370 -

AWD/60 199 46

AWD/40 149 60

California Flood 111 -

35% 44 60

25% 36 68

• Possibly a small effect of longer drain times on rice grain As.

• On average a 12% further reduction in grain As with increased drain times.

• In no individual study was this significant.

Drain time

• Longer drain times lead to:• Increased risk of yield loss

• Increased water savings

• Lower As???

• Longer drain times do not:• Reduce GWP

In Summary

• AWD presents a real win-win-win opportunity• Farm: save water/pumping costs, no yield reduction

• Health: reduce grain As

• Environment: water resources, GHG, MeHg

Challenges and opportunities

• Field scale• Variability in soils/moisture

• Rapid/timely application of water• Wells and poly-pipe are big advantage

• Grower comfort• Programs that allow testing with minimal risk

• Future research• Identify dry-down windows where desired benefits are achieved without yield

risk• Time during season and length

• Develop technologies to monitor soil moisture conditions

UCDAVIS

University of California

Thank youN2

AWD - GHG

Soil water content

Flooded

AWD/60

AWD/40

Linquist et al., 2015 Global Change Biology

TRT CH4 N2Okg CH4-C/ha kg N2O-N/ha

Flood 105 a 0.03 bAWD/40–flood 55 b 0.17 abAWD/60 7 c 0.28 abAWD/40 8 c 0.51 a

Factors affecting yields

• Meta-analysis (Daniela Carrijo – poster - #76)• Primary factor affecting yields is water management (discussed further)

• Secondary factors that can reduce yields are• High pH soil

• High clay soils

• Low carbon soils

• Use of inbred vs hybrid varieties

Sustainable Intensification• Defined as a process or system

where agricultural yields are increased without adverse environmental impact.

• Why?• Decreasing amount of arable land

per capita

• Increasing populations/demand for food

• Limited availability of new arable land

• Environmental consequences

• Loss of biodiversity

• Pollution

http://blueandgreentomorrow.com/2012/09/07/calls-for-sustainable-investment-to-prevent-unmanageable-demand-for-food/

Grain arsenic: Arkansas and California - cross year averages

Arkansas data: Linquist et al., 2015- Global Change BiologyCalifornia data: LaHue et al., Submitted

Flood (Control) AWD/40 –Flood

AWD/60 AWD/40 Water seeded(Control)

Water-seeded:AWD

Dry seeded:AWD

Arsenic (µg kg-1)

Arkansas California

See Parikh et al., Tue 9:35

Grain arsenic concentration (AWD 2015)

Brown rice White rice

CF AWD35 AWD25

TotalAs As(III) DMA

CF AWD35 AWD25

TotalAs As(III) DMA

Grain arsenic concentration (AWD 2016)

Brown rice White rice

b ba a

Concentration(m

TotalAs As(III) DMA

b ba a

Concentration(m

TotalAs As(III) DMA

AWD: Grain yield and As concentrations as affected by a single drain time.

CF PI BOOT HEAD

Concentra

on(mg/kg)

TotalAs

As(III)

AWD: Grain yield and As concentrations as affected by a single drain time.

CF PI BOOT HEAD

Concentra

on(mg/kg)

TotalAs

As(III)

CF PI BOOT GF

Water use: Arkansas cross year averages

Linquist et al., 2015- Global Change Biology

Flood (Control) AWD/40 – Flood AWD/60 AWD/40

Water use (m3 ha-1)

18% 44%31%Reduction

Carrijo et al., submited

AWD and yields

• 4 yrs study NO difference in rice yields in any AWD treatment.

• 2 drains to 35 and 25% volumetric moisture content (8-12 days of drying).

• Similar results in Arkansas, although some yield declines under dryer conditions.

Treatment Grain Yield (t ha-1)

(2015) (2016)

AWD-Safe

AWD 35

AWD 25

13.8 a

13.7 a

14.1 a

11.4 a

11.1 a

Year Treatments Total CH4 emissions Total N2O emissions

kg CH4-C ha-1

season-1

kg CO2 eq ha-1

season-1

kg N2O-N ha-1

season-1

kg CO2 eq ha-1

season-1

Continuous

Flooded (CF)

338 a 11288 a -0.06 a -27 a

AWD 35 92 b 3055 b -0.11 a -52 a

AWD 25 111 b 3696 b -0.03 a -15 a

Year Treatments Total CH4 emissions Total N2O emissions

kg CH4-C ha-1

season-1

kg CO2 eq ha-1

season-1

kg N2O-N ha-1

season-1

kg CO2 eq ha-1

season-1

Continuous

Flooded (CF)

216 a 7201 a -0.1 a -45 a

AWDS 128 ab 4272 ab -0.09 a -41 a

AWD 35 96 ab 3218 ab -0.04 a -18 a

AWD 25 87 b 2902 b -0.13 a -62 a

Treatments GWP (2015) GWP ( 2016)

kg CO2 eq ha-1

season-1

kg CO2 eq t-1

season-1

kg CO2 eq ha-1

season-1

kg CO2 eq t-1

season-1

Continuous

Flooded (CF)

11262 a 813 a 7158 a 627 a

AWDS 4231 ab 371 ab

AWD 35 3003 b 222 b 3201 b 280 b

AWD 25 3681 b 271 b 2840 b 256 b

Treatments Cumulative CH4 emissions from first

day of drying till end (Year 2015)

Cumulative CH4 emissions from first

day of drying till end (Year 2016)

kg CH4-C ha-1 kg CO2 eq ha-1 kg CH4-C ha-1 kg CO2 eq ha-1

Continuous Flooded

178 a 5737 a 116 a 3878 a

AWDS 62 b 2064 b

AWD 35 5 b 170 b 13 c 446 c

AWD 25 6 b 210 b 10 c 350 c

Sustainable intensification

YieldEconomic

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