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 A good experiment incorporates all the possible means of minimizing
the experimental error.
 Commonly used techniques in agricultural research to control
experimental error:
1. Blocking
2. Proper p[lot technique
3. Data Analysis
4.
1.2.1 BLOCKING

 Variation among blocks can be measured and removed from
experimental error by:
1. Putting together experimental units in the same group
that are as similar as possible (blocks)
2. Assigning all treatments into each block separately and
independently.

 This is suggested especially in an experimental field where
variation is expected.

1.2.2. PROPER PLOT TECHNIQUES
 VARIETY TRIALS consisting of test varieties the following

environmental factors are required to be maintained uniformly for
all plots in the experiment.
o Soil nutrients
o Solar energy
o Plant population
o Pest incidence etc.
o CHOICE OF The primary concern of proper plot technique is
to minimize variation.
 For field experiments sources of variation are the following:
o Soil heterogeneity
o Competition effects
o Mechanical errors
1.2.3 DATA ANALYSIS:

 Proper data analysis is recommended if experimental error could not
be adequately controlled by blocking.
 COVARIANCE ANALYSIS - is the most commonly used for this
purpose.
o This is done by measuring one or more covariates( characters
whose functional relationships to the character of primary
interest are known)
o It is done by adjusting their values to a common value of the
covariates.