Balwinder Singh, IRRI, PhilippinesLiz Humphreys, IRRI, PhilippinesDon Gaydon, CSIRO, AustraliaPhil Eberbach, CSU, Australia

Effect of mulch on water use and productivity of wheat in Punjab, India-Field and simulation studies

1

Methodology • Field experiments (2006-07 and 2007-08)

• Crop model application

2

Ludhiana, Punjab

Treatments

Mulch treatments • With mulch (8 t/ha)• Without mulch

3

Irrigation management

-First irrigation at -40kPa SMP at 15-20 cm soil depth

- Subsequent irrigations at -40kPa SMP at 35-40 cm soil depth

4

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 1061131201271341411481550

10

20

30

40

50

60

70

80

Days after sowing

Rain

/irr

igati

on (m

m)

Rainfall/irrigation- 2006-07

Rain- 160 mm

Mulch irrigation = 75 mm

Non-mulch irrigation= 150 mm

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106 113 120 127 134 141 148 1550

10

20

30

40

50

60

70

80

Days after sowing

Rain

/irr

igati

on (m

m)

5

Rainfall/irrigation- 2007-08

Rain- 88 mm

Non-mulch irrigation= 225 mm

Mulch irrigation = 150 mm7 days28 days

Grain yield (kg/ha)

Total biomass production (t/ha)

6

2006-07 2007-080

1

2

3

4

5Mulch Non mulch

Gra

in y

ield

(k

g/h

a)

2006-07 2007-080

2

4

6

8

10

12

Mulch Non mulch

Bio

ma

ss

pro

du

cti

on

(t/

ha

)

NS

Evapotranspiration (ET)

7

.

ET= R+I-D-R-Δ(θv)

R = Rainfall

I = irrigation (volume was measured with a Woltman helical turbine meter)

D= drainage below root zone (1.8 m) (zero) ( based soil matric potential gradients to 180

cm depth)

R= runoff, zero as the plots had small bunds

Δ(θv) = change in soil water content (0-180 cm) between sowing and harvesting

Water balance equation

Evapotranspiration (ET)

8

.

2006-07 2007-080

50

100

150

200

250

300

350

400

450

Mulch Non mulch

ET

(m

m)

N/SN/S

Grain water productivity based on ET (kg/ha.mm)

Biomass water productivity based on ET (kg/ha.mm)

9

WPET = grain yield or biomass/ET

Units, kg/ha.mm

Water productivity

2006-07 2007-080

2

4

6

8

10

12

14Mulch Non mulch

Gra

in W

PE

T (

kg

/ha

/mm

)

2006-07 2007-080

5

10

15

20

25

30

35

40

Mulch Non mulch

Bio

ma

ss

WP

ET

(k

g/h

a/m

m)

APSIM application

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APSIM validation

Balwinder-Singh, Gaydon DS, Humphreys E, Eberbach PL (2011). Evaluating the performance of APSIM for irrigated wheat in Punjab, India. Field Crops Research, 124, 1-13.

Model attribute R2 (co-efficient of determination)

Grain yield 0.89

Biomass 0.95

ET 0.86

• Weather data at Ludhiana, Punjab (1970-2006) (36 years)

• Soil type-Sandy loam (290 mm PAWC, 0-180 cm)

Variables• ±mulch ( 0, 8 t/ha)

• 8 irrigation schedules

(10%, 20%, 30%, 40%, 50%, 60% and 70%SWD of 0-60 cm soil layer, rainfed)

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Simulation set up

12

• Wheat var. PBW 343 sown 10 November

• 150 plants/m2

• Initial soil water content at field capacity

0 1 2 3 4 5 6 7 8 90

0.2

0.4

0.6

0.8

1

1.2

10%-NM

10%-M

40%-NM

40%-M

70%-NM

70%-M

0-NM

0-M

Grain yield (t ha-1)

Cu

mu

lati

ve

Pro

ba

bili

ty

Grain yield - mulch and irrigation interactions

13

Yield ranged from 3 to 8 t/ha

~ 0.5 t/ha

In 60% years yield < 7 t/ha

Biomass production

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4000 6000 8000 10000 12000 14000 16000 18000 200000

0.2

0.4

0.6

0.8

1

1.2

40%-NM

40%-M

0-NM

0-M

Biomass production (kg/ha)

Cum

ulati

ve p

roba

bilit

y

0 100 200 300 400 500 6000

0.2

0.4

0.6

0.8

1

1.2

10%-NM

10%-M

40%-NM

40%-M

70%-NM

70%-M

Irrigation water (mm)

Cu

mu

lati

ve p

rob

abili

ty

Irrigation water input

15

At 40% SWD, mulch reduced irrigations by 1 in ~50% years

Average reduction ~40 mm

0 20 40 60 80 100 120 140 160 180 2000

0.2

0.4

0.6

0.8

1

1.2

10%-NM

10%-M

40%-NM

40%-M

0-NM

0-NM

Soil Evaporation (mm)

Cu

mu

lati

ve p

rob

abili

ty

Soil evaporation

16

Es reduced

by ~ 40mmIn irrigated wheat

by ~20 mm in rainfed wheat

50 100 150 200 250 300 350 400 4500

0.2

0.4

0.6

0.8

1

1.2

10%-NM

10%-M

40%-NM

40%-M

70%-NM

70%-M

0-NM

0-M

Transpiration (mm)

Cu

mu

lati

ve p

rob

abili

ty

Transpiration

17

Followed the same trends as by grain yield

No effect in frequent irrigation treatments

0 100 200 300 400 500 6000

0.2

0.4

0.6

0.8

1

1.2

10%-NM

10%-M

40%-NM

40%-M

70%-NM

70%-M

0-NM

0-NM

ET (mm)

Cu

mu

lati

ve p

rob

abili

ty

Evapotranspiration

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ET reduced by mulch ~ 40mm (same as Es) in frequent irrigation treatments

However, No difference for ET was observed in field study

No difference in rainfed treatment

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5 7 9 11 13 15 17 19 210

0.2

0.4

0.6

0.8

1

1.2

10-NM

10-M

40-NM

40-M

70-NM

70-M

Grain WPET (kg ha-1 mm-1)

Cu

mu

lati

ve

pro

ba

bili

ty)

Grain water productivity (WPET)

Highest WP at 40% SWD

Conclusions• Mulch reduced irrigation requirement when irrigated

according to soil water status (by 1 irrigation in ~50% of years)

• Mulch reduced Es of well-irrigated wheat by ~40 mm• No effect of mulch on grain yield of irrigated wheat• APSIM Wheat predicted ET lowered by mulch

BUT field study showed no effect of mulch on ET (due to increased T) – a worry!

Which is right? - needs further investigation.

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