Some RCTs for Improved Irrigation Water Use Productivity in Rice

8/3/2019 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



Direct dry-seeded rice



Conventional practice of growing Rice

Puddling

Transplanting

Nursery

Puddled transplanted Rice(PTR)



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

$ )



Ground water depletion

Humphreys et al. 2010

Depth of water table in the month of June, in Ludhiana district, PunjabIndia



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

( % )



Dry Seeded Rice (DSR)

Land productivity•

t/ha• $/ha

Water productivity• WPi

• WPI+R

• WPET

Optimumirrigationscheduling



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



PTR-40 kPa

PTR-20 kPa DSR-70 kPa

DSR-40 kPa

PTR- Daily

Crop growth at 105 DAS in 2008

DSR-20 kPa



Grain Yield (t ha-1)

0

2

4

6

8

10

Dailyirrigation

20 kPa 40 kPa 70 kPa

PTR DSR



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



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


PTR

DSR

0

500

1000

1500

2000

2500


PTR

DSR

Irrigation water input (mm)

Drainage (mm)Evapo-transpiration (mm)



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



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



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



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



Raised beds for rice



Why Raised Beds for Rice?

• Permanent beds

• Zero-tillage concept

• Irrigation water saving

• Fresh beds

• Irrigation water saving



Fresh beds

TRFB-SMP

PTR-CF

Permanent BedsTRPB-2d

Rice - PR118



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



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



Infiltration rate – sandy loam

Unpuddled ~12 mm/d

Puddled ~ 4 mm/d

10

0

20

mm/day



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--------------------------------------



Soil tension – PTR-2d – sandy loam

Response

to irrig. &rain atdepth –

deepdrainage beyond thedepth of

wheat rootzone(~1.8 m)





Water balance PTR-2d – sandy loam• irrigation amounts and seepage losses greatly reducedBUT still huge seepage losses

•

are irrigation & seepage data realistic ?

mm



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



Farmers’ field scale plot experiments

F l h fi ld i



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



Fresh beds

TRFB-SMP

PTR-CF

Permanent BedsTRPB-2d

Rice on beds



• 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



• 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



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



Conservation irrigation

• Intermittent irrigation in puddled rice (AWD)

•

2-d irrigation interval• Soil matric potential based irrigation

• Furrow irrigation



Challenge for water-efficient riceproduction

“to reduce water inputs while maintainingyields at the same high level as thatunder continuously flooded conditions”



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



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



Soil matric potential

It is a criterion which takes into account

the atmospheric demand of water andthe moisture supplying capacity ofdifferent soils



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





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------------------------------------------------------------------



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



Tensiometers installed in rice fields



Tensiometer-principle

The water inside atensiometer wouldequilibrate with thewater in the soilthereby creating asuction in thetensiometer which is

measured by thevacuum gauge.



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 --

----------------------------------------------------------------------



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-----------------------------------------------------------------------------



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



Tensiometers

Commerciallyavailable

Fabricatedby PAU Modified andfabricated by PAU

Si l d f f i dl T i t



Simple and farmer-friendly Tensiometerdeveloped by PAU

F Ri i i t h th t l l



For Rice crop, irrigate when the water levelcrosses Green zone



• 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



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



Farmers at Kisan mela taking keen interest in theuse of tensiometers

Scientists explaining tensiometers to the



farmers at PAU Kisan Mela



Fabrication of Tensiometers in the



Fabrication of Tensiometers in theDepartment of Soil Science



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



Thanks a lot for your patience

KUKAL

Documents

Some RCTs for Improved Irrigation Water Use Productivity in Rice