sustainable low-input cereal production: required varietal characteristics and crop diversity...
TRANSCRIPT
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Sustainable low-input cereal production:
required varietal characteristics and crop
diversity
Working Group 4: plant-plant interactions
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About SUSVAR….
System characteristics: Cereal production Low-input conditions
Aims: Increased stability (yield and quality) Increased resource use efficiency
Main means: Better use of crop genetic diversity
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Better use of crop genetic diversity (1)
Selection of suitable genotypesBetter use of available gene-pool for low-input systems
Varieties that are well suited to low-input conditions in general
Varieties that are well suited to specific conditions (environmental conditions by definition more variable than under high-input conditions)
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Better use of crop genetic diversity (2)
Use of mixturesUtilize more genotypes simultaneously
Heterogeneity contributes to stability (risk avoidance) Generation of added value:
• Facilitation• Competition
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Crop - environment: mutual interaction
environment
Crop A
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Facilitation: positive effect
environment
cropCrop A Crop B
+
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Facilitative production principle: insects
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Competition: negative influence
environment
cropCrop A Crop B
-
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Competitive relations are important
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Competition also the basis for over-yielding
Competitive production principle
intra-specific competition > inter-specific competition
Niche-differentiation or complementarity
better exploitation of available resources
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Facilitative production principle: weeds
Facilitation
(the creation of a weed free environment)
is through
Competition
(suppression of weeds by other crop)
Challenge: avoid other crop from developing into a weed.
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Facilitative production principle: weeds
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Working group plant-plant interaction
Crop – weed interaction Weed suppression Which traits General or environment specific Easy screening procedures
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In case of mixtures
Crop – crop interaction Yield stability
• Difference in stress-tolerance
Productivity• Niche differentiation• Intra-specific competition > inter-specific competition
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Weed suppression of mixtures
Crop – crop – weed interaction How to maximize weed suppression?
• Combine most competitive cultivars• Maximize complementarity
– Complementarity in resource use and acquisition– Complementarity in weed suppression mechanism
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Currently many different questions ….
What do we want to obtain with mixtures?
(stability, productivity, weed suppression, others)
How can added value of mixtures be obtained?
(what is the best strategy)
How to select individual varieties for their performance in mixtures?
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Time to decide on where to go …
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WG 1Genetics & Breeding
WG 3Plant – Soil Interactions
WG 4Plant – PlantInteractions
WG 5Plant Disease
Complex
WG 6Variety testing &
certification
Organisation of activities and reciprocal benefits
WG 2Biostatistics
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Facilitative production principle: diseases
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Plant-plant interaction
Main issues: Productivity Stability Weed suppression
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Learning-objectives
To familiarise with options for evaluating: productivity competitive relations
within intercropping systems To be able to value the various methodologies To learn the relationship between some indices of
relative competitive ability
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Multiple cropping
Growing two or more crops on the same field in a year
- sequential cropping
- relay intercropping
- full intercropping
time
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Reasons for intercropping
Better use of available resources
(land, labour, light, water, nutrients) Reduction in pest pressure + associated damage
(diseases, insects, weeds) Socio-economic
(greater stability, risk avoidance, food/cash crops) Sustainability
(erosion, soil fertility)
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Facilitative production principle: diseases
Causal organism:Magnaporthe grisea
two phases:vegetative stageLeaf blast
reproductive phaseNeck or panicle blast
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Intercropping as weed management component
manual weeding
Transplanting Harvest
weed-free period
Leek monoculture
Leek-Celery Intercrop
Weeds
Weeds
weed-free period
mechanical weeding
mechanical weeding
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Competition the basis for over-yielding?
Niche-differentiation
better exploitation of available resources separation in time (relay) separation in space (rooting depth) different resource capture abilities different growth requirements
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Key to evaluation of intercrop productivity
Quantification of competitive relations
Example:
Two-species mixture (sp 1 - sp 2)
How many competition coefficients?
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Key to evaluation of intercrop productivity
Quantification of competitive relations
Example:
Two-species mixture (sp 1 - sp 2)
How many competition coefficients?
2 intraspecific competition coefficients: b11, b22
2 interspecific competition coefficients: b12, b21
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Intraspecific competition
Y=N/(b0+b1N) W=Y/N=1/(b0+b1N) 1/W=b0+b1N
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Measure of intraspecific competition
1/W1=b10+b11N1
b10 [plant/g]
b11 [m2/g]
b11/b10 [m2/plant]
crowding coefficient (de Wit) ecological neighbourhood area (Antonovics & Levin)
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Intercropping: intra and interspecific
1/W1=b10+b11N1+ b12N2
b11/b12 relative competitive ability
What does this value learn us?
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Intercrop productivity
1/W1=b10+b11N1+ b12N2
and
1/W2=b20+b22N2+ b21N1
b11/b12 and b22/b21
Niche differentiation index (NDI):
b11/b12 * b22/b21= (b11*b22)/(b12*b21)
NDI =1,<1,>1
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How can we determine these indices?
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Evaluation in practice Experiment with three treatments:
Monoculture of species 1 Y1,mono
Monoculture of species 2 Y2,mono
Mixture of species 1 and 2 Y1,mix, Y2,mix
Calculation of Relative Yield RY1 =Y1,mix/Y1,mono
RY2 =Y2,mix/Y2,mono
Land Equivalent Ratio (LER) LER = RY1 + RY2 relative land area under sole crops required to produce the yields
achieved in intercropping
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Two basic designs
Additive design
0 0 0 0 x x x x 0 x 0 x 0 x 0 x
0 0 0 0 x x x x 0 x 0 x 0 x 0 x
0 0 0 0 x x x x 0 x 0 x 0 x 0 x
0 0 0 0 x x x x 0 x 0 x 0 x 0 x
0 0 0 0 x x x x 0 x 0 x 0 x 0 x
species 1 species 2 mixture
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Two basic designs
Replacement design
0 0 0 0 x x x x 0 x 0 x
0 0 0 0 x x x x 0 x 0 x
0 0 0 0 x x x x 0 x 0 x
0 0 0 0 x x x x 0 x 0 x
0 0 0 0 x x x x 0 x 0 x
species 1 species 2 mixture
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Replacement design
Overall density constant Results represented in a
replacement diagram LER generally replaced by
Relative Yield Total (RYT) Relative crowding coefficient
(k) to express competitive relations:
k12=(1-z1)/(w11/w12-z1)
z1=fraction species 1 0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 0.5 1
0.0
0.2
0.4
0.6
0.8
1.0
1.2
k12=0.58
k21=1.93
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Replacement design
k intrasp/intersp comp. Similar to b11/b12?
k*k related to intercrop
productivity =1, >1, <1 Similar to NDI? 0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 0.5 1
0.0
0.2
0.4
0.6
0.8
1.0
1.2
k12=0.58
k12=0.58
k21=1.93
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Excercises
Complete calculations on two intercrops grown at two different densities in replacement and additive design
Focus on: What is the difference between outcomes from a
replacement and an additive design? What is the difference between relative crowding
coefficient (k) and the ratio of competition coefficients (e.g. b11/b12)?