Fasoula SRI Seminar

1. Crop Yield Maximization SRI Seminar Fasoula July, 2008

2. Density (plants/m 2 ) Yield (t/ha) Source: adapted from Russell (1986) 1970 era single-cross hybrids 1930 era double-cross hybrids Crop yield maximization – 1. Use of monogenotypic cultivars to erase the plant differences due to genetic competition

3. Grain yield (t/ha) Source: Jugenheimer 1976; Fasoula and Tollenaar 2005 CV=33% CV=26% CV=24% CV=23.5% CV=22% Crop yield maximization – 2. Use of monogenotypic cultivars that possess high individual homeostasis (stability)

4. Crop yield maximization 3. Utilization of density-independent monogenotypic cultivars Choice of the plant ideotype Many fertile tillers Deep and extensive root system

5. Maize ideotype: uni-culmed and single-eared Maize hybrids have become heavily dependent on a specific plant density The case of density-dependence in maize

6. Density (plants/m 2 ) Crop yield (t/ha) Pioneer 3902 Maize hybrids tend to be density-dependent Source: Fasoula and Tollenaar 2005

7. Maize hybrids were not selected for high plant yield Source: Duvick 1997

8. Example of density-independent and density-dependent cultivars in tomato Density (Plants/m 2 ) Yield (t/ha) Source: Fery and Janick 1970

9. Disadvantages More frequent weeding (farmers may favor high densities as a means to suppress weeds) Medium plant densities Advantages Lower seed cost Better drought and lodging resistance Fewer disease problems Security in adversity

10. SRI advantage Wider plant spacing – many tillers Source: Uphoff 2006

11. Advantages Many tillers Extensive and deep root system (less water) Better resistance to drought and lodging Fewer disease problems Crop yield compensation in case of adversity Exploitation of the plant yield genetic potential SRI Rice plant ideotype in wider spacing

12. Growth resources must be ample, readily available, and evenly distributed across the field Crop yield maximization – Precondition 2 SRI advantage Careful field and soil preparation Enhanced soil organic matter Increased soil aeration Careful water management

13. 1. Germination and growth of plants must be fast and synchronous SRI advantage: early transplanting Younger seedlings can achieve more uniform growth and will mature quicker SRI advantage: square grid pattern 2. Plants must be evenly distributed across the field Crop yield maximization – Precondition 3

14. SRI achieves better stand uniformity and thus higher crop yield Source: Uphoff 2006 Smaller CV

15. Cultivars selected for the environments that are destined to exploit marginal environments (poor soils, drought, etc) favorable environments Monogenotypic cultivars with high stability Density-independent cultivars (less variable yields) 25 × 25, 30 × 30, 50 × 50 Conditions that will maximize SRI efficiency Wider spacings (50 × 50) can allow farmers to visually select the best plants for the following year (Participatory Breeding) Frequent weeding weeds will interfere with the even growth

16. Cultivars not adapted to the environments utilized by the farmers Density-dependent cultivars Cultivars with low tillering capacity (i.e., NPT of IRRI) Conditions that will minimize SRI yields Weeds in the field

17. A final thought The plant genome is dynamic and plastic and can activate mechanisms that release adaptive variation to the constantly changing environmental conditions, whether these are favorable or unfavorable