some rcts for improved irrigation water use productivity in rice
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Some RCTs for Improved Irrigation
Water Use Productivity in Rice
S S Kukal
Professor of Soil Conservation, PAU
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Direct dry-seeded rice
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Conventional practice of growing Rice
Puddling
Transplanting
Nursery
Puddled transplanted Rice(PTR)
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Constraints to PTR
Labour availability and cost
0
10
20
30
40
50
1960 1970 1980 1990 2000 2010
A g r i c u
l t u r e
l a b o u r
f o r c e
( %
o f t o t a l p o p u
l a t i o n )
0
1
2
3
4
2000 2002 2004 2006 2008 2010
L a b o u r w a g e s
( U S
$ )
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Ground water depletion
Humphreys et al. 2010
Depth of water table in the month of June, in Ludhiana district, PunjabIndia
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Reduced wheat yield
0
2
4
6
8
10
12
14
16
Y i e l d r e
d u c
t i o n d u e
t o p u
d d l i n g
( % )
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Dry Seeded Rice (DSR)
Land productivity•
t/ha• $/ha
Water productivity• WPi
• WPI+R
• WPET
Optimumirrigationscheduling
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Research Approach
EstablishmentMethod
Puddled TransplantedRice
DailyIrrigation
20 kPaSWT
40 kPaSWT
70 kPaSWT
Dry Seeded Rice
DailyIrrigation
20 kPaSWT
40 kPaSWT
70 kPaSWT
Field Experiment
Soil type: Clay loam
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PTR-40 kPa
PTR-20 kPa DSR-70 kPa
DSR-40 kPa
PTR- Daily
Crop growth at 105 DAS in 2008
DSR-20 kPa
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Grain Yield (t ha-1)
0
2
4
6
8
10
Dailyirrigation
20 kPa 40 kPa 70 kPa
PTR DSR
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Water Balance ComponentsI + R= ET +P + S + Roff + dSWC
Irrigation water Measurement Automatic Rain Gauge
Seepage & Runoff measurement Drainage measurement – Tritium Tagging Measurement of dSWC
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0
500
1000
1500
2000
25003000
3500
Daily 20 kPa 40 kPa 70 kPa
PTR DSR
47 %
63 %
0
200
400
600
800
1000
1200
Daily 20 kPa 40 kPa 70 kPa
PTR
DSR
0
500
1000
1500
2000
2500
Daily 20 kPa 40 kPa 70 kPa
PTR
DSR
Irrigation water input (mm)
Drainage (mm)Evapo-transpiration (mm)
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Water Productivity (g kg-1)
WPI
WPI+R
WPET
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.401.60
1.80
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SWT and Cracking intensity
0.0
5.0
10.0
15.0
20.0
25.0
30.0
0
2
4
6
8
10
12
2-days after irrigation 4-days after irrigation 6-day after irrigation
S W T ( k P a
)
P r o p o r t i o n a r e a o
f c r a c
k s
( % )
PTR DSR
PTR-20 DSR-20
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0.0
5.0
10.0
15.0
20.0
25.0
30.0
5/08/2009 17/08/2009 29/08/2009 10/09/2009 22/09/2009 4/10/2009 16/10/2009 28/10/2009
S W T ( k P a )
PTR-20
DSR-20
I
I
I
II I
I
I I
I
I
I
R
RRRR
I
Drying Pattern in -20 kPa2009
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Message
• Direct dry-seeded rice (DSR) has a potential as
RCT in the region especially in fine textured
soils
• DSR, however, still needs fine tuning in terms
of irrigation, weed management, nutrient
management particularly in coarse and
medium textured soils
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Raised beds for rice
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Why Raised Beds for Rice?
• Permanent beds
• Zero-tillage concept
• Irrigation water saving
• Fresh beds
• Irrigation water saving
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Fresh beds
TRFB-SMP
PTR-CF
Permanent BedsTRPB-2d
Rice - PR118
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IW applied to rice – sandy loam
mm
• Huge IW savings going from PTR-CF to PTR-2d – up to 2,000 mm ?
• IW on intermittently irrigated flats & beds similar ?
Longer duration ofDaily irrigation 50 d
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IW applied to rice - loam
• Huge IW savings going from PTR-CF to PTR-2d – up to 2,000 mm ?
• IW on intermittently irrigated flats & beds similar ?
Longer duration ofDaily irrigation 50 d
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Infiltration rate – sandy loam
Unpuddled ~12 mm/d
Puddled ~ 4 mm/d
10
0
20
mm/day
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Periodic amount of irrigation water (mm) applied to puddled flats and beds
Amount of irrigation water in
flats and beds during 0-15 DAT
--------------------------------------PTR-2d 389TRFB-2d 620--------------------------------------
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Soil tension – PTR-2d – sandy loam
Response
to irrig. &rain atdepth –
deepdrainage beyond thedepth of
wheat rootzone(~1.8 m)
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Water balance PTR-2d – sandy loam• irrigation amounts and seepage losses greatly reducedBUT still huge seepage losses
•
are irrigation & seepage data realistic ?
mm
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Water balance PTR-CF – loam• seepage losses from small plots >> real fields
• irrigation data from small plots unrealistic – un-useable
•
can plastic barriers reduce seepage losses to realistic proportion ?
mm
10.7 m x 12 mPerim/Area = 0.35
24 m x 80 m (0.5 acre)Perim/Area = 0.10
1 acre P/A = 0.07
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Farmers’ field scale plot experiments
F l h fi ld i
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Farmer length field experiments
Rice W
(m)
L
(m)
Area(acres)
Irrig mgt
PTR-CF 24 80 0.47 CF 50 mm
PTR-Farmer 50 80 1.0 CF 40 d
then weekly
TR FB-SMP –half F=fresh
7 80 -15 kPa @ 20 cmHalf furrow depth
TR PB-SMP-half 7 80 “ “ “ “
TR PB-2d-half 7 80 2d after water goneTR PB-2d-full 10 80 “ “ “ “
• All beds irrigated daily with full furrow-depth for first 15
DAT• Permanent beds 4th crop
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Fresh beds
TRFB-SMP
PTR-CF
Permanent BedsTRPB-2d
Rice on beds
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• Fresh beds irrig amt. ~40-60% of PTR-CF & PTR-Farmer
• Irrigation mgt affects irrig. amt on PBs, while similar yield
Irrigation amount in large fields/long runs
mm
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• WPi fresh bed ~2 x WPi of PTR-CF & PTR-Farmer• need to compare PTR and TRFB with same irrig mgt !
Irrigation water productivity (WPI)
g/kg
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Message
• The furrow irrigation in rice on raised beds withfull furrow depth irrigation at 2-d interval doesnot improve IW productivity in at least coarse
and medium textured soils• Still there is scope for improving IWUP in rice on
fresh raised beds, provided the irrigationscheduling is redefined in terms of amount and
frequency
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Conservation irrigation
• Intermittent irrigation in puddled rice (AWD)
•
2-d irrigation interval• Soil matric potential based irrigation
• Furrow irrigation
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Challenge for water-efficient riceproduction
“to reduce water inputs while maintainingyields at the same high level as thatunder continuously flooded conditions”
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Irrigation practice
What the farmers are doing?• Ponding water
• 40 days
• 50 days
• 60 days or even throughout the season
What the university recommends?
• Ponding water for first 15 days and then
irrigating 2 days after the ponded water has
disappeared
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The existing practice of irrigation schedulingdoes not consider the effect of
* Evaporative demand* At some instances, this 2-d interval may beprolonged without affecting the crop yield
during high relative humidity* Or even 2-d interval may prove detrimental to cropin case of harsh weather
* Soil texture* Finer soils may retain more water and for alonger period of time
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Soil matric potential
It is a criterion which takes into account
the atmospheric demand of water andthe moisture supplying capacity ofdifferent soils
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Soil matric potential ??
* It is a force with which water is held in the soil
matrix and determines the water availability to theplants
* It is a criterion which takes into account theatmospheric demand of water and the moisturesupplying capacity of different soils
It can be measured with the help of an instrument calledTensiometer
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Soil water content vs soil matric potential
Soil Texture Sa Si Cl Field Capacity(%) SWC Matric pot.
(g/g) (cm)
---------------------------------------------------------Loamy sand 88 08 04 10.8 -49Sandy loam 79 11 10 14.3 -48Sandy loam 75 12 12 15.1 -45
Loam 65 21 14 17.0 -48------------------------------------------------------------------
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This clearly shows that Soil matric potential can be successfully used
as a criterion for scheduling irrigation to ricein all types of soils.
It can be measured with the help of aninstrument called Tensiometer
T nsi m t s inst ll d in i fi lds
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Tensiometers installed in rice fields
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Tensiometer-principle
The water inside atensiometer wouldequilibrate with thewater in the soilthereby creating asuction in thetensiometer which is
measured by thevacuum gauge.
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Experimental results
Soil matric Paddy yield Irrigation % waterpotential water use saving(cm) (t/ha) (cm)
-----------------------------------------------------------------------------------------
100 20 6.44 111.8 24.6150 20 6.40 102.3 31.0200 20 6.21 89.5 39.6250 20 5.61 80.0 46.1
Recommended 6.43 148.3 --
----------------------------------------------------------------------
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Results of adaptive trials (2004)
District Paddy yield (t/ha) IrrigationTensiometer Existing water
saved (%)------------------------------------------------------------------------------Jallandhar (7) 6.42 6.46 16.3Ropar (3) 6.00 5.75 14.3Gurdaspur (3) 6.96 6.73 27.5Faridkot (4) 6.35 6.38 30.8Amritsar (4) 6.55 6.56 18.0
Sangrur (3) 6.46 6.40 34.0
Average (27) 6.46 6.38 21.5-----------------------------------------------------------------------------
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Proposed recommendation
Continuous flooding during first fortnight after
transplanting followed by irrigation with thehelp of tensiometers, installed at 15-20 cm soildepth, at soil matric potential of 150 ± 20 cm.
Tensiometers
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Tensiometers
Commerciallyavailable
Fabricatedby PAU Modified andfabricated by PAU
Si l d f f i dl T i t
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Simple and farmer-friendly Tensiometerdeveloped by PAU
F Ri i i t h th t l l
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For Rice crop, irrigate when the water levelcrosses Green zone
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• A hole of diameter slightly bigger thanthat of the ceramic cup is made in the soil
•
Slurry of soil and water is poured in to thehole to ensure proper contact between thecup and the surrounding soil
• The tensiometer body is filled with de-
aerated distilled water
How to install a tensiometer
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When to take the reading
• The reading is to be taken during
the early morning hours at sunrise
F t Ki l t ki k i t t i th
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Farmers at Kisan mela taking keen interest in theuse of tensiometers
Scientists explaining tensiometers to the
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farmers at PAU Kisan Mela
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Fabrication of Tensiometers in the
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Fabrication of Tensiometers in theDepartment of Soil Science
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Message
• The irrigation scheduling on the basis of soil
matric potential seems to be better criterion
as it takes into account the soil type as well as
the evaporativity
• The technique becomes much more important
in present day changing climatic patterns
where the irrigation practice can not begeneralized with respect to time and space
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Thanks a lot for your patience
KUKAL