Sustainable low-input cereal production: required varietal characteristics and crop diversity

1. Sustainable low-input cereal production:required varietal characteristics and crop diversity Working Group 4: plant-plant interactions

2. 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

3. Better use of crop genetic diversity (1) • Selection of suitable genotypes Better 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)

4. Better use of crop genetic diversity (2) • Use of mixtures Utilize more genotypes simultaneously • Heterogeneity contributes to stability (risk avoidance) • Generation of added value: • Facilitation • Competition

5. Crop - environment: mutual interaction environment Crop A

6. Facilitation: positive effect environment + crop Crop A Crop B

7. Facilitative production principle: insects

8. Competition: negative influence environment - crop Crop A Crop B

9. Competitive relations are important

10. 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

11. 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.

12. Facilitative production principle: weeds

13. Working group plant-plant interaction • Crop – weed interaction • Weed suppression • Which traits • General or environment specific • Easy screening procedures

14. In case of mixtures • Crop – crop interaction • Yield stability • Difference in stress-tolerance • Productivity • Niche differentiation • Intra-specific competition > inter-specific competition

15. 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

16. 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?

17. Time to decide on where to go …

19. Organisation of activities and reciprocal benefits WG 3 Plant – Soil Interactions WG 4 Plant – Plant Interactions WG 1 Genetics & Breeding WG 6 Variety testing & certification WG 2 Biostatistics WG 5 Plant Disease Complex

20. Facilitative production principle: diseases

21. Plant-plant interaction • Main issues: • Productivity • Stability • Weed suppression

22. 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

23. Multiple cropping Growing two or more crops on the same field in a year - sequential cropping - relay intercropping - full intercropping time

24. 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)

25. Facilitative production principle: diseases Causal organism: Magnaporthe grisea two phases: vegetative stage Leaf blast reproductive phase Neck or panicle blast

26. Intercropping as weed management component Leek monoculture weed-free period mechanical weeding manual weeding Weeds Leek-Celery Intercrop weed-free period mechanical weeding Weeds Transplanting Harvest

27. 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

28. Key to evaluation of intercrop productivity Quantification of competitive relations Example: Two-species mixture (sp 1 - sp 2) How many competition coefficients?

29. 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

30. Intraspecific competition Y=N/(b0+b1N)  W=Y/N=1/(b0+b1N)  1/W=b0+b1N

31. 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)

32. Intercropping: intra and interspecific 1/W1=b10+b11N1+ b12N2 b11/b12 relative competitive ability What does this value learn us?

33. 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

34. How can we determine these indices?

35. 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

36. 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

37. 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

38. k21=1.93 k12=0.58 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

39. k21=1.93 k12=0.58k12=0.58 Replacement design • k  intrasp/intersp comp. • Similar to b11/b12? • k*k • related to intercrop productivity • =1, >1, <1 • Similar to NDI?

40. 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)?