Experimental designs in plant breeding like Latin square design and randomised block design are explained in this presentation.

1. Experimental Designs In
Plant Breeding
Dr. Ravindra D. Madhekar
Associate Professor and Head,
Dept. Of Botany,
S. B. E. S. College of Science,
Chhatrapati Sambhajinagar
(Maharashtra)

2. Terminology
• Design:- Whenever an agriculture experiment is done by using certain scientific
(statistical) procedure then it is called design.
• OR Experimental design are various types of plot arrangement which are used to test
a set of treatments to draw a valid conclusions about a particular problems.
• Treatment:- The objective under comparison is called treatment.
• Experimental material:- The material which is used in experiment is known as
experimental material . For example, a field, soil seeds etc.
• Experimental units:- Small plot of the block to which the treatment can apply are
called experimental unit.

3. • Experiment:- Experiment is a scientifically planned method. The experiment is
conducted to draw a valid conclusion about a particular problem. The conclusion
is based on statistical observation.
• Experimental error:- The variation due to environmental factor or due to
uncontrolled factor is called experimental error.
• Uniformity trail:- A uniformity trail consists in dividing the whole field into so
many small units of equal size. Uniformity trail are helps as know the nature of
soil fertility in agricultural/ experimental field.
• Sampling unit :- The object that is measured in an experiment is called the
sampling unit. This may be different from the experimental unit.

4. Why need experimental designs in Plant Breeding ?
1. Developing new varieties
2. Problems with regard to the estimation of differences between candidates and
testing their significance are not considered.
3. Getting an answer to a question which the experimenter wants to know.
4. The average value of all observations in a population.
5. Keep the design as simple as possible while satisfying the required level of
scientific soundness.

5. Introduction
• Definition of Experimental design :- The choice of treatment, the method
assigning treatments to experimental units and arrangement of experimental
units in various pattern to suit the requirements of particular problems are
commonly known as design of experiment.
Or
• Experimental design is the process of planning and study to meet a specific
objectives.
• Experimental design was developed by :- Prof. R. A. Fisher in 1920

6. Objectives:
1. To increase precision of experiment.
2. To reduce experimental error.
3. In screening off various treatments.
4. In partitioning of variation into different components.
5. Used in proper interpretation of scientific results and drawing valid conclusions.
6. In reducing the soil heterogeneity.
7. In assessment of variance and covariance.
8. Shows the direction of better results. 9. Includes the plan for analysis and
reporting of the results.

7. Principles of Experimental Design :
• There are three basic principles :
• Replication:- Repetition of the treatment under investigation Or To provide an
estimate of experimental error.
• Randomization:- The allocation of the treatment to the different
experimental units by a random process is known as randomization.
• Local control:- The principal of making use of greater homogeneity in groups
of experimental units for reducing experimental error.

8. Types Of Experimental Designs :
1. Randomized Block Designs
2. Completely Randomized Designs
3. Latin Square Designs
4. Randomized Complete Block Designs
5. Split Plot Designs
6. Augmented Design
7. Lattice Designs (Alpha Lattice Design)

9. Latin Square Designs (LSD):
• The experimental design which simultaneously controls the fertility variation in
two directions is called Latin square design (LSD).
• It is two factor design (row may present to level of one factor and column present
the another factor).
• The experimental material is divided into rows and columns.
• Each having the same number of experimental units which is equal to the
number of treatments.
• The treatments are allocated to the rows and the columns such that each
treatment occurs once and only once in the each row and in the each column.

10. • No. of Replication = No. of Treatments
• No. of rows = No. of Columns = No. of Treatments
T1 T2 T3 T4
T4 T1 T2 T3
T3 T4 T1 T2
T2 T3 T4 T1
Layout of field experiment

11. Advantages Of LSD :
• Statistical analysis is relatively simple
(complicated than CRD and RBD).
• Statistical analysis is simple if one
value is missing.
• Most efficient design when compared
to CRD and RBD.
• Standard error less than 1%.
Disadvantages of LSD :
 LSD is not suitable for agricultural
experiments.
 Statistical analysis is complicated
when two or more values are missing.
 Difficult when treatments are more
than ten.
 No. of treatment 5 to 12 no more
treatment or less treatment.

12. Randomized Block Designs (RBD) :
• RBD is used when the experimental material is not homogenous and fertility
gradient is moving one direction
• The no. of equal plot in each block is equal to the no. of treatment.
• The design is based on of three principles of experimental designs
(replication ,randomization and local control).
• In case of field experiment the experimental material is divided into a no. of
equal blocks.
• RBD is the most commonly used experimental design in agriculture.

13. Layout of field experiment
T1 T5 T2 T4 T3
T5 T4 T3 T2 T1
T3 T2 T1 T5 T4
Block 1
Block 2
Block 3
T1, T2, T3, T4 and T5 are treatments

14. • Advantages of RBD :
• RBD is more efficient and accurate when
compared to CRD.
• When material is heterogeneous and no.
of treatment more then 20.
• Chance of error in RBD is comparatively
less.
• Statistical analysis is relatively simple and
easy.
• Errors of any treatment can be isolated.
Disadvantages of RBD :
 RBD is not advised for very large
number of treatments.
 If the heterogeneity of the plot is
very high, RBD cannot be applied.
When the number of treatments is
very large then the size of each
block will be increased so that
there may be heterogeneous
blocks within.