2. RAMESH ACHARYA
AGR-05M-2013
DEPARTMENT OF AGRONOMY
AGRICULTURE AND FORESTRY UNIVERSITY
A graduate Seminar On
Drought and heat stress in late sown
wheat and mitigation strategies
3. 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
food
65%
Used in
animal
feed
17%
Used in
industries
including
biofuel
12%
others
6%
2013/14
Source: FAO statUse of wheat grain for 2013/14
Source:
CIMMYT
4. Of the total cereal production area,
wheat occupies 22.58%
(MOAC,2014)
Of the total cereal production,
wheat occupies 20.13%.
(MOAC,2014)
0
500000
1000000
1500000
2000000
2500000
3000000
3500000
2010/11 2011/12 2012/13
Total cereal area(Ha)
Total wheat area(ha)
0
2000000
4000000
6000000
8000000
10000000
2010/11 2011/12 2012/13
Total cereal production (mt)
Total wheat production (mt)
o In Nepal, 84% of wheat area comes under Rice โwheat 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)
5. Contd.
Lack of
irrigation
Major yield
limiting factors
Late planting
due to longer
window period
after rice
harvest
Use of late
maturing rice
varieties
Lack of wise
use of plant
nutrients
Abiotic
stress
Heat stress
Drought
stress
Frost stress
Biotic stress
Plant
diseases
Insects
6. Results and Discussions
Importance 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).
7. Contd..
Effect of sowing date on grain
yield of wheat
Effect of sowing date on grain
yield and biomass
0
5
10
15
20
25
30
35
Grain yield Biomass yield
7.56
32.6
5.49
26.6
Yieldint/ha
Optimum sowing Late sowing
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
21st
Nov
5th Dec 19th
dec
2nd Jan
4.62
3.71
3.31 3.16
Yieldint/ha
Date of sowing of wheat
2009/10 2010/11
Source: Aslani et al., 2011 , Iran
8. Contd..
Grain Yield of different varieties
affected by sowing date, Rampur
,Chitwan
Straw yield of different varieties
affected by sowing date, Rampur ,
Chitwan
0
1
2
3
4
5
6
5-Nov 20-Nov 5-Dec 20-Dec
Grain yield on different dates in
t/hec
yieldint/ha
NL 297 BL 1443
0
1
2
3
4
5
6
7
8
9
5-Nov 20-Nov 5-Dec 20-Dec
straw yield on Dates of sowing
yieldint/ha
Gautam NL 297
Source: Nabaraj Acharya, 2008
9. 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
10. 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 39.53
Source: P.R.Timsina, 2009
11. Contdโฆ
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.
12. How water affects the grain yield?
Water
Water lost
Runoff
Deep drainage
Soil
Evaporation
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
13. 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
1-3ยฐC in
maximum temp
8-31% Nepal Pandey et
al.,2007
1ยฐC in mean
temperature
5% Australia Tashiro &
Wardlow, 1989
2ยฐC in mean
seasonal
temperature
50% Australia Foster et al.,2011
Rise in night
temperature
5.8% India Gupta et al.,2010
14. 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 ยฐC.
๏ 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).
15. How heat stress affects on wheat plant?
Wheat organ Effect on wheat plant
Spikes o Kernel abortion at supra-optimal
temperature
For photosynthetic
canopy
o Photo-inhibition due to excess light
o 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
16. Reduction (%) in various wheat traits under
drought and
heat stress conditions
Trait Drought stress Heat stress
Plant height 11.6 6.5
Productive tillers 19.7 -31.1
Days to heading 6.2 10.1
Days to anthesis 3.8 10.1
Days to maturity 4.5 10.7
Grain filling duration 6.7 11.3
No of grains per spike 4.4 3.3
Grain 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
17. 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 โAdoption of early maturing varieties showed
10% yield advantage over long duration varieties(Joshi et al.,2012).
18. 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
convention
al practices
(ha-cm)
Increase in
water
productivit
y (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.,2010
Source: Chauhan et al.,2012
19. 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 โwise use of irrigation by scheduling on critical
stages
๏ Balanced plant nutrition
20. 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.
