Cereals 2024 Week 9-B Growth Regulation in Cereals Flashcards
How does lodging occur?
lodging occurs when the forces of gravity pulling
stem to ground are greater than those keeping it
standing
Whats the key parameters of lodging? (2)
key parameters are
– stem strength
– crown roots
when lodging occurs it may be as a result of
…
stem lodging, root lodging or a combination of
both stem and root lodging
If the centre of gravity is higher, there is…
A greater lodging force
the centre of gravity is determined by : (2)
– height of stem
– weight of stem (and ear
lodging occurs because of….
– bending or breaking of stem bases
the key stem characteristics are : (3)
- stem diameter,
- stem thickness,
- degree of
lignification
What do modern wheat varieties have?
modern wheat varieties have short, thick stems and
the forces required to break/bend stems are usually
far in excess of the self weight moment in most crops
What is not very common lodging ?
What can also lead to stem lodging?
-lodging due to stem failure is not very common in wheat
crops
– the occurrence of stem disease, eyespot can also lead to stem
lodging
What crop is much more prone to stem failure lodging and why?
barley crops are much more prone to this type of
lodging as they tend to be taller with weaker stem
bases
What is root lodging?
the ability of the cereal root system to keep
roots anchored in the ground depends largely
on the thick basal regions of the roots - crown
roots, which only extend a few cm’s into the soil
What are important crown characteristics?(2)
– number and spread of crown roots
– crown root length and strength
Root lodging with crown: how does it occur?
root lodging occurs when the crown root system
rotates through the soil profile under a high
lodging pressure (overturning force)
Reducing the risk of Lodging list factors that help: (3)
What can help reduce the risk of lodging (in terms of chemically?
1- decrease crop height
2-* increase stem strength
– increase stem diameter
– increase stem thickness
3* increase root anchorage
– by increasing crown root volume
– by having firm seedbed characteristics?
Growth regulators
How do you assess the lodging risk?
1* use the ‘standing power’ ratings when choosing
varieties
– shortness of straw
– strength of straw
2* site factors
– fertility of the field
– site aspect : is it exposed to wind effects
3* sowing date
– most relevant to winter wheat, e.g. higher lodging
risk with early sowings unless sowing rates are
reduced significantly
% Lodging in Winter Wheat across Nitrogen Progs.
First Wheat crop At UCD Lyons Farm
Slide 10
What was the results or the thrend?
As Fertiliser rate increased the higher % of lodging occurred
Plant growth regulators (PGR’s) what is this?
What are they controlled by?
What are the key growth hormones?
What can PGR’s be used to manipulate?
- plant growth and reproduction is controlled by
hormones
– key ‘growth’ hormones are auxins, gibberellins and
kinins
- PGRs can be used to manipulate the internal
hormone activity of the plant
Role of the PGR product CCC:
1- What does the gibberellin hormones do?
2- What is CCC?
3- How was this observed?
4- What does CCC have?
1- in cereals the gibberellin hormones increase
internode length and anti-gibberellins stop this
2-chlormequat (CCC) is a growth retardant which
inhibits gibberellin synthesis
3- this activity was observed by Tolbert (1960) and over
the last three decades, the use of CCC for straw
shortening has been an integral part of the crop
management in cereals
4- CCC has shortening and strengthening effects
– the time of application will determine the effect with
earlier timings giving more strengthening and later
timings giving more shortening
Use of CCC in practice :
1- What is very important with this?
2- What will rate depend on?
3- In high risk situations, what may be used?
4- On winter oats what sort of a split is used?
1- timing is very important
– key timing is before GS 31 (first node)
– temperature is critical (5-60 C air temp.)
2- rate will depend on timing and on crop
– lower rates used on spring-sown cereals
– typical rate is 1.5-2.0 l/ha of 75% CCC , - ~3 l/ha of
46% CCC
3- in high risk situations a split appl. may be used
– 2/3 of the total dose at GS. 22-23 (mid-tillering)
– 1/3 of the dose at GS. 30-31
4- on Winter Oats a split-appl. is used with GS 31-32
and GS37 timings
Other Useful PGR’s commonly used:
Whats the GS for them to be used on also?
1- Ethephon inhibits auxins and is sold as Cerone
– commonly used on winter barley at GS 32-45
2- Mepiquat chloride inhibits gibberellins and is sold as
Terpal
– key timing is GS 32 to GS 37-39 on wheat and barley
3- trinexapal ethyl is sold as Moddus and has uses on
winter cereals
– claims for its performance in reducing both stem and
root lodging risk
– variety profiling for risk of stem and root lodging
and product timed accordingly
4- Meteor is a chrormequat-based product with imazaquin
added to increase performance and also the spray-
window
UCD Spring Oats Trial 2021
Heritage Lines v Modern
Cultivars
Lodging Issues (2)
Lodging levels were extremely
high on many of the heritage
lines.
- All were salvageable but
caused a lot of mechanical
problems. 4 breakdowns due to
lodging, all attributable to older
genetic material.
