Crop Yield Maximization

SRI Seminar

FasoulaJuly, 2008

55

65

75

85

95

105

115

3 4.5 6

Density (plants/m2)

Yie

ld (

t/ha)

Source: adapted from Russell (1986)

1970 era single-cross hybrids

1930 era double-cross hybrids

Crop yield maximization – 1. Use of monogenotypic cultivarsto erase the plant differences due to genetic competition

2

3

4

5

6

7

Inbredlines

open-poll

doublecrosses

3-waycrosses

hybrids

Gra

in y

ield

(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 cultivarsthat possess high individual homeostasis (stability)

Crop yield maximization

3. Utilization of density-independentmonogenotypic cultivars

Choice of the plant ideotypeMany fertile tillersDeep and extensive root system

Maize ideotype: uni-culmed and single-eared

Maize hybrids have become heavilydependent on a specific plant density

The case of density-dependence in maize

0

2

4

6

8

10

0.5 1 2 4 8 12 18 24

Density (plants/m2)

Cro

p y

ield

(t/h

a)

Pioneer 3902

Maize hybrids tend to be density-dependent

Source: Fasoula and Tollenaar 2005

Year of introduction

1930 1940 1950 1960 1970 1980 1990

Yie

ld (

t/h

a)

0

2

4

6

8

10

12

14

1 plant/m2, r

2= 0.06

7.9 plants/m2 , r

2 = 0.86

3 plants/m2 , r

2= 0.56

Maize hybrids were not selected for high plant yield

Source: Duvick 1997

Example of density-independent and density-dependentcultivars in tomato

Density (Plants/m2)

Yie

ld (

t/ha

)

Source: Fery and Janick 1970

0,75 1,75 4,25 10,25 2511

22

34

4556

112

IndeterminateJointlessDeterminateMiniatureDwarf

MULTIPLE HARVEST

DisadvantagesMore frequent weeding (farmers may favor

high densities as a means to suppress weeds)

Medium plant densities

AdvantagesLower seed cost

Better drought and lodging resistance

Fewer disease problems

Security in adversity

SRI advantage

Wider plant spacing – many tillers

Source: Uphoff 2006

AdvantagesMany 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

Growth resources must be ample, readilyavailable, and evenly distributed across the field

Crop yield maximization – Precondition 2

SRI advantageCareful field and soil preparationEnhanced soil organic matterIncreased soil aerationCareful water management

1. Germination and growth of plants must be fast and synchronous

SRI advantage: early transplantingYounger 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

SRI achieves better stand uniformity and thus higher crop yield

Source: Uphoff 2006

Smaller CV

Cultivars selected for the environments that aredestined 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 visuallyselect the best plants for the following year(Participatory Breeding)

Frequent weedingweeds will interfere with the even growth

Cultivars not adapted to the environmentsutilized 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

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