Welcome

RAMESH ACHARYAAGR-05M-2013

DEPARTMENT OF AGRONOMYAGRICULTURE AND FORESTRY

UNIVERSITY

A graduate Seminar On

Drought and heat stress in late sown wheat and mitigation

strategies

INTRODUCTION

Wheat is the major cereal crop of world.89 nations have 2.5 million wheat consumers worldwide (CIMMYT,2013)

Wheat is grown on 215 million hectare of land each year which is equivalent to Greenland (CIMMYT,2013)

Used for food65%

Used in animal feed17%

Used in indus-tries

includ-ing bio-

fuel12%

others6%2013/14

Source: FAO statUse of wheat grain for 2013/14

Source: CIMMYT

Of the total cereal production area, wheat occupies 22.58% (MOAC,2014)

Of the total cereal production, wheat occupies 20.13%. (MOAC,2014)

2010/11 2011/12 2012/130

500000100000015000002000000250000030000003500000

Total cereal area(Ha)Total wheat area(ha)

2010/11 2011/12 2012/130

2000000

4000000

6000000

8000000

10000000

Total cereal production...

o In Nepal, 84% of wheat area comes under Rice –wheat system (Timsina & Conner,2001) which is 0.6 Mha (Timsina et al.,2007)

o There are 35 improved wheat cultivars, 40 landraces and 10 wild relatives of wheat in Nepal (Joshi et al., 2006)

o The productivity of wheat in Nepal is 2.29 t/ha which is much less than average productivity of world (MOAC,2014)

Contd.

Lack of irrigation

Major yield limiting factors

Late planting due

to longer window

period after rice harvestLack of wise use of plant

nutrientsAbiotic stress

Heat stress

Drought stress

Frost stress

Biotic stress

Plant diseases

Insects

Results and DiscussionsImportance of sowing date Early sowing provides longer period of maturation, earlier flowering and

higher yield potential (Coventry et al.,??).

Wheat in Nepal is generally sown in November to late December and harvested in March/April (Joshi et al.,2006).

Timely planting of wheat is often delayed by tillage and yield potential is also reduced. This is due to rice crop vacating the field late (Hobbs et al.,2005; Gupta et al.,2010).

With delay in sowing time from 1st fortnight of November to 1st fortnight of December, a decline in yield at 32 kg/ha /day is reported (Tripati et al.,2005).

A yield loss of 1-1.5% for delay of each day after the optimum sowing date of Nov 15 in wheat crop is recorded (Hobbs et al.,2005).

Contd..Effect of sowing date on grain yield of wheat

Effect of sowing date on grain yield and biomass

Grain yield Biomass yield 05

101520253035

7.56

32.6

5.49

26.6

Optimum sowing

Yiel

d in

t/h

a

21st Nov

5th Dec 19th dec

2nd Jan0

0.51

1.52

2.53

3.54

4.55 4.62

3.713.31 3.16

2009/10 2010/11

Date of sowing of wheat

Yiel

d in

t/h

a

Source: Aslani et al., 2011 , Iran

Contd..Grain Yield of different varieties affected by sowing date, Rampur ,Chitwan

Straw yield of different varieties affected by sowing date, Rampur , Chitwan

5-Nov 20-Nov 5-Dec 20-DecGrain yield on different dates

in t/hec

0123456 NL 297 BL 1443

yiel

d in

t/h

a

5-Nov 20-Nov 5-Dec 20-Decstraw yield on Dates of sowing

0123456789

Gautam NL 297 BL 1473

yiel

d in

t/h

a

Source: Nabaraj Acharya, 2008

Effect of sowing time on grain filling rate, yield per panicle and plant height on five cultivars named Seri I-84, Hartog, Bhrikuti, Gautam, Nl-2800

Normal sowing ( 22nd November)

Late sowing( 2nd January)

Mean Plan0t height (cm)

69.25 57.58

Seed filling rate (mg/day)

0.71 0.75

Yield per panicle(gm)

1.37 0.908

Source: P.R.Timsina,2008

Effect of sowing on Days to Booting, Days to Heading, Flag leaf duration, Days to maturity and Grain filling duration assessed on 5 varieties on Rampur, Chitwan

Normal sowing(22nd November)

Late sowing(2nd January)

Days to booting

57.73 51.79

Days to heading

68.86 63.00

Flag leaf duration

59.13 44.60

Days to maturity

122.40 103.26

Grain filling duration

53.56 39.53Source: P.R.Timsina, 2009

Contd…How terminal moisture stress limits the yield? Many Scientists and researchers have reported of this drop in grain

and biomass yield is due to exposure of plant to terminal heat and drought stress.

Terminal stress is the moisture stress mainly during dry seasons on heavy soil, where plants are grown on stored moisture and matures on progressively depleting moisture profile(Ludlow & Muchow,1988).

Nirman et al., 2013 simulated and concluded that yields of rainfed wheat was lower (1.7 t/ha) due to water stress during the post anthesis phase resulting in early senescence during dry years.

And wheat in case of Nepal is sown after rice and it grows and survives on the residual soil moisture and late monsoon rain or winter rain (Nirman et al.,2013) which is only 20% of the annual rainfall (Malla, 2008).

As 0.8 tons of water is required to produce 1 kg of wheat grain (Wani GM,2011),Wheat production falls short of moisture.

How water affects the grain yield?

Water

Water lostRunoff

Deep drainage

Soil Evaporati

on

Water stored in

soil

Water not extracted by

crop

Plant survival

Water use efficiency

Partitioning efficiency

Water used by crop

Dry matter production

Fig: Schematic Diagram between water and grain yield Source: Ludlow & Muchow

Effect of terminal heat stress on yield Terminal heat stress is due to mean daily temp exceeding

17.50C in the coolest month in wheat growing region(Fischer & Byerlee, 1991).

Increase in temperature reduces crop duration, increase crop respiration rates, reduces crop yield , increased sterility that reduced the no. of grains formed, inhibit sucrose assimilation in grain, affect survival and distribution of pest populations (Hundal & Kaur,2007).

Change in Temperature

Decrease in yield

Place of experiment

Source

1-3°C in maximum temp

8-31% Nepal Pandey et al.,2007

1°C in mean temperature

5% Australia Tashiro & Wardlow, 1989

2°C in mean seasonal temperature

50% Australia Foster et al.,2011

Rise in night temperature

5.8% India Gupta et al.,2010

Contd.. Rane et al.,2002 reported that thirty million hectares of

crop was affected by terminal heat stress in temperate growing regions.

In wheat, the grain filling duration continued to decrease at temperatures above 26.7 °C.

Similarly heat induced spikelet sterility and increased in the respiration losses from the crops during the grain filling also caused by rising temperatures (Timsina and Humphrey,2006).

Heat stress affects the grain set if occurred during flowering and terminal heat stress reduces number of grains, weight of grain and grain filling duration (Chenu et al.,; Wall et al., ;Aggrawal &Kalra,1994).

Wheat crop experiment conducted in open top chamber in NARC showed that decrease in the growth stage like spike initiation, heading, flowering, milking and physiological maturity by 14, 5, 9, 6 and 14 days respectively due to increase in temperature(Malla,2008).

How heat stress affects on wheat plant?

Wheat organ Effect on wheat plantSpikes o Kernel abortion at supra-optimal

temperature For photosynthetic canopy

o Photo-inhibition due to excess lighto Impaired metabolism

Stems o Hydraulic resistance to high transpiration rate is likely to become rate limiting

Roots o Limited capacity for water uptake to match evaporative demand at high vapor pressure deficit may cause stomatal closure

Source: Cossani and Reynolds,2012

Reduction (%) in various wheat traits under drought andheat stress conditions

Trait Drought stress Heat stressPlant height 11.6 6.5Productive tillers 19.7 -31.1Days to heading 6.2 10.1Days to anthesis 3.8 10.1Days to maturity 4.5 10.7Grain filling duration 6.7 11.3No of grains per spike 4.4 3.3Grain weight per spike

3.7 16.8

Thousand grain weight

-1.1 14.1

Grain yield 29.1 26.4

Source: Sarren et al., 2014

Mitigation strategies Advancing in plant date No-till method A yield increase up to 41% is recorded by zero till plot over conventional

tilled due to 24 days earlier in planting date(Hobbs & Gupta, 2003). Planting the wheat in advance using zero-till ,sowing of the varieties that can

either adapt or escape terminal stress, using of crop residues./mulching, wise use of irrigation (irrigation scheduling) and plant nutrients (site specific nutrient management) are suggested as possible solutions for combating the terminal stress in wheat production (Jat et al.,2009).

Use of early maturing rice varieties in rice-wheat cropping system.

Cultivar choices Use of varieties that can either tolerate heat, avoid heat or escape

drought/heat. Early maturing varieties –Adoption of early maturing varieties showed 10%

yield advantage over long duration varieties(Joshi et al.,2012).

Effect of conservation practices on crop yields, water saving and water productivity

Cultivation Practices

Location/ Country

Yield gain over conventional practices (kg/ha)

Water saving over conventional practices (ha-cm)

Increase in water productivity (kg/m3

)

Source

No till Karnal, India

140-400 2-4 0.10-0.21 Malik et al.,2005

No till Meerut, India

610 2.2 0.28 Gathala et al.,2010

No till with surface residue

Karnal, India

500 6.1 0.24 Gathala et al.,2010

No till with surface residue

Meerut, India

410 1.0 0.13 Jat et al.,2010Source: Chauhan et

al.,2012

Contd.. An experiment conducted at 14 sites of various countries , Nepal(1), India

(6), Bangladesh (2), Pakistan (1)and Mexico(4), by CEISA as Heat trial-Early maturity trial during 2009-10 showed superiority (>10%) of 10% lines over local checks.

Stay green varieties- As there is positive association between duration of photosynthetically active leaf area and grain yield, identification of molecular markers for stay green trait can further open doors to fight heat stress( Singh et al., 2012).

Using varieties with higher water-use efficiency. Using varieties with heat tolerance traits as membrane thermostablity,

stomatal conductance and heat shock proteins (Slafer & Whitechurch,2001).

Use of mulching-decreases evaporation and increases water availability Irrigation management –wise use of irrigation by scheduling on critical

stages Balanced plant nutrition

Conclusion Late planting of wheat is one of the major cause for exposure

of wheat plants to terminal heat and drought stress.

Terminal stress of heat and drought affects on wheat phenology and all yield attributing traits resulting in significant drop in biomass and grain yield.

Use of better cultivation practice (Zero-tillage) with retention of crop residues/mulching, selection of early maturing varieties with better management practices and breeding works over identification of molecular markers for heat and drought tolerance is the future to solve the above mentioned stress.

Thank you for your patience