benefits and challenges of alternate wetting and drying in ... · sustainable intensification:...
TRANSCRIPT
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
100
0
-100
EnvironmentalSocial, Health
Can this be achieved in rice systems with alternate wetting and drying (AWD)?
AWD in a water seeded system
Continuously Flooded
AWD
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
N2
• 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
UCDAVISUniversity of California
Yields: Arkansas and CaliforniaCross year averages
N2
• CA: no yield reduction with AWD or increased soil drying
• AR: decline with increased soil drying
5
6
7
8
9
10
11
Gra
in y
ield
(t/
ha)
aaaa
cbab
California 2013-2014
Arkansas data: Linquist et al., 2015- Global Change BiologyCalifornia 2013/14 data: LaHue et al., 2016 -AEE
Arkansas-3yr
5
6
7
8
9
10
11
12
13
CF (control) AWD 35 AWD 25
CA Mean 2015/2016
a aa
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”
D
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
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
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
g C
H4
-C h
a-1
d-1
0
2000
4000
6000
8000
10000
CFAWD 25 AWD 35 AWDS
Year 2016
Date of sampling
Jun Jul Aug Sep Oct Nov
g N
2O
-N h
a-1
d-1
-20
-10
0
10
20
30
40
50
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
UCDAVISUniversity of California
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
UCDAVISUniversity of California
NH4 NO3 N2
California
Anaerobic Aerobic
+N
-N
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
a
bb
a
bb
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
CF AWD35 AWD25
Concentration(mg/kg)
TotalAs As(III) DMA
2015
a
a
b b
aa
b b
a
a
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
CF AWDSafe AWD35 AWD25
Concentration(m
g/kg)
TotalAs As(III) DMA
2016
AWD and arsenic: timing
• Drains at PI and booting - lowest grain As
• Safe AWD did not reduce (2016)
a
b
b
a
a
bb
a
a
b
b
a
0.000
0.010
0.020
0.030
0.040
0.050
0.060
0.070
0.080
0.090
CF PI BOOT HEAD
Concentra
on(mg/kg)
TotalAs
As(III)
DMA
A
2015
2016PI Booting Heading
AWD and methylmercury
• Flood water concentrations• Main concern in CA
0
0.1
0.2
Leas
t-sq
uar
es m
ean
M
eHg
(ng
L-1
)
MeHg
AWD CF
0
5
10
Growing FallowLe
ast-
squ
ares
mea
n
THg
(ng
L-1
) THg
AWD CF
AWD and methyl mercury
N2
• 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
0
1
2
Harvest2014
August2015
Harvest 2015
THg
(ng
g-1
) Grain Total Hg CF AWD
0
0.5
1
MeH
g (n
g g-
1)
Grain MeHgCF AWD
UCDAVISUniversity of California
Challenges
N2
• 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
EnvironmentalSocial, Health
• 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)
N2
• GWP reductions of 45 – 90%.
• N2O kept low
• Yield-scaled emission reduction similar• Yields were similar
• See Balaine et al (Tue 10:35 am)
UCDAVISUniversity of California
GWP: (CH4 + N2O)
N2
• 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)
GWP %
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
UCDAVISUniversity of California
Yield-scaled GWP
N2
• 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
UCDAVISUniversity of California
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
+N
-N
UCDAVISUniversity of California
Meta-analysis: Soil moisture and yields
N2
• > 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”
D
WL≤15cm[1-15](117/14)
“Safe AWD”-IRRI
UCDAVISUniversity of California
Managing water
N2
(528/58)
(453/39)
(452/39)
EffectofAWD(%)
UCDAVISUniversity of California
Water use: meta-analysis
-26%
-5.5%
+27%
UCDAVISUniversity of California
Water use: Causes of lower water use
N2
• 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
UCDAVISUniversity of California
Greenhouse gas emissions
N2
So
il w
ate
r c
on
ten
t, m
3 m
-3
0.0
0.1
0.2
0.3
0.4
kg
CO
2 e
q h
a-1
da
y-1
0
30
60
90
120
150
180
Soil water content
CH4
N2O
Flooded
So
il w
ate
r c
on
ten
t, m
3 m
-3
0.0
0.1
0.2
0.3
0.4
kg
CO
2 e
q h
a-1
da
y-1
0
10
20
30
Time
May
25
Jun 0
1
Jun 0
8
Jun 1
5
Jun 2
2
Jun 2
9
Jul 0
6
Jul 1
3
Jul 2
0
Jul 2
7
Aug 0
3
Aug 1
0
Aug 1
7
Aug 2
4
Aug 3
1
Sep 0
7
So
il w
ate
r c
on
ten
t, m
3 m
-3
0.0
0.1
0.2
0.3
0.4
kg
CO
2 e
q h
a-1
da
y-1
0
10
20
30
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
UCDAVISUniversity of California
Greenhouse gas emissions
N2
So
il w
ate
r c
on
ten
t, m
3 m
-3
0.0
0.1
0.2
0.3
0.4
kg
CO
2 e
q h
a-1
da
y-1
0
30
60
90
120
150
180
Soil water content
CH4
N2O
Flooded
So
il w
ate
r c
on
ten
t, m
3 m
-3
0.0
0.1
0.2
0.3
0.4
kg
CO
2 e
q h
a-1
da
y-1
0
10
20
30
Time
May
25
Jun 0
1
Jun 0
8
Jun 1
5
Jun 2
2
Jun 2
9
Jul 0
6
Jul 1
3
Jul 2
0
Jul 2
7
Aug 0
3
Aug 1
0
Aug 1
7
Aug 2
4
Aug 3
1
Sep 0
7
So
il w
ate
r c
on
ten
t, m
3 m
-3
0.0
0.1
0.2
0.3
0.4
kg
CO
2 e
q h
a-1
da
y-1
0
10
20
30
AWD/60
AWD/40
No emissions
Kept seasonal emissions low
Is there a GHG benefit to extended dry times?
N2
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
UCDAVISUniversity of California
Nitrogen management
N2
• 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
UCDAVISUniversity of California
Managing N fertilizer and water
• Italian study
• Permanent flood vs AWD
• Used nitrification inhibitor
• Drained randomly
• CH4
• N2O
Italy
Lagomarsino et al., (2015) Pedosphere
NH4
PF=Permanent flood
GW
P
N2OCH4
PF AWD PF AWD
2012 2013
UCDAVISUniversity of California
Heavy metals
N2
• 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
Be
nef
it100
0
-100
YieldEconomic
EnvironmentalSocial, Health
100
0
-100
UCDAVISUniversity of California
AWD drain timing and grain As
N2
Water seeded Water seeded-AWD Drill seeded AWD
N2
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
UCDAVISUniversity of California
Length of drain time and grain As
N2
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.
UCDAVISUniversity of California
Drain time
N2
• Longer drain times lead to:• Increased risk of yield loss
• Increased water savings
• Lower As???
• Longer drain times do not:• Reduce GWP
UCDAVISUniversity of California
In Summary
N2
• 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
UCDAVISUniversity of California
Challenges and opportunities
N2
• 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
UCDAVISUniversity of California
AWD - GHG
So
il w
ate
r c
on
ten
t, m
3 m
-3
0.0
0.1
0.2
0.3
0.4
kg
CO
2 e
q h
a-1
da
y-1
0
30
60
90
120
150
180
Soil water content
CH4
N2O
Flooded
So
il w
ate
r c
on
ten
t, m
3 m
-3
0.0
0.1
0.2
0.3
0.4
kg
CO
2 e
q h
a-1
da
y-1
0
10
20
30
Time
May
25
Jun 0
1
Jun 0
8
Jun 1
5
Jun 2
2
Jun 2
9
Jul 0
6
Jul 1
3
Jul 2
0
Jul 2
7
Aug 0
3
Aug 1
0
Aug 1
7
Aug 2
4
Aug 3
1
Sep
07
So
il w
ate
r c
on
ten
t, m
3 m
-3
0.0
0.1
0.2
0.3
0.4
kg
CO
2 e
q h
a-1
da
y-1
0
10
20
30
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
UCDAVISUniversity of California
Factors affecting yields
N2
• 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/
UCDAVISUniversity of California
Grain arsenic: Arkansas and California - cross year averages
Arkansas data: Linquist et al., 2015- Global Change BiologyCalifornia data: LaHue et al., Submitted
0
100
200
300
400
500
Flood (Control) AWD/40 –Flood
AWD/60 AWD/40 Water seeded(Control)
Water-seeded:AWD
Dry seeded:AWD
Arsenic (µg kg-1)
bba
a bba
Arkansas California
See Parikh et al., Tue 9:35
Grain arsenic concentration (AWD 2015)
Brown rice White rice
a
b b
a
bc
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
CF AWD35 AWD25
Concentration(mg/kg)
TotalAs As(III) DMA
a
bb
a
bb
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
CF AWD35 AWD25
Concentration(mg/kg)
TotalAs As(III) DMA
Grain arsenic concentration (AWD 2016)
Brown rice White rice
a a
b ba a
a a
a
a
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
CF AWDSafe AWD35 AWD25
Concentration(m
g/kg)
TotalAs As(III) DMA
a a
b ba a
a a
a
a
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
CF AWDSafe AWD35 AWD25
Concentration(m
g/kg)
TotalAs As(III) DMA
AWD: Grain yield and As concentrations as affected by a single drain time.
a
b
b
a
a
bb
a
a
b
b
a
0.000
0.010
0.020
0.030
0.040
0.050
0.060
0.070
0.080
0.090
CF PI BOOT HEAD
Concentra
on(mg/kg)
TotalAs
As(III)
DMA
A
AWD: Grain yield and As concentrations as affected by a single drain time.
a
b
b
a
a
bb
a
a
b
b
a
0.000
0.010
0.020
0.030
0.040
0.050
0.060
0.070
0.080
0.090
CF PI BOOT HEAD
Concentra
on(mg/kg)
TotalAs
As(III)
DMA
A
0
2000
4000
6000
8000
10000
12000
CF PI BOOT GF
Yie
ld (
kg/h
a)
UCDAVISUniversity of California
Water use: Arkansas cross year averages
N2
Linquist et al., 2015- Global Change Biology
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
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)
CF
AWD-Safe
AWD 35
AWD 25
13.8 a
na
13.7 a
14.1 a
11.4 a
11.4 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
2015
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
2016
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
(CF)
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