Trial Designs
- May Ann Sallan
- Rica Aicel Mariano
- Alaine Gulles (IRRI)
- Pedro Barbosa
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The EBS supports several experimental designs for Breeding Trials that can be generated using different models as described in the table below.
The design parameters of the selected design model should be set, and there is also an option to define the shape of the field trial by moving the toggle switch to “Yes” position and then, setting up the field layout parameters.
Trial Designs and Models
Design | Model name | Description |
|---|---|---|
Alpha-Lattice | A kind of resolvable Incomplete Block design, wherein, not all treatments are tested in the same block. It is a resolvable design because blocks can be arranged and grouped together to form complete replications. Design parameters: Number of Occurrences (Trials), Number of Replicates, Number of Blocks. Layout parameters: Number of Rows per Block, Number of Rows per Replicate, Total Number of Field Rows, Plot Ordering (serpentine or not) Usage: When the number of treatments being tested (entries, genotypes) is very large, it is difficult to have a uniform field that can support this large number of plots, so we build small blocks (incomplete blocks) within the replication. The block size need not be large even when the number of treatments is large. This design is more flexible than the Lattice designs (which require that number of treatments should be a perfect square and block size or number of plots in each block is equal to the square root of the number of treatments). | |
Same as Alpha-Lattice. Differences:
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This model is usually used to generate the Breeding trials that are also considered International Nurseries, it generates an Alpha-Lattice design, however, there are two more options to restrict the randomization process. It is the same as Alpha-Lattice | CIMMYT, with the follow difference:
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Randomized Complete Block Design | Is the standard design for agricultural experiments, the replication is arranged in group, creating a local control factor that is called “Block”. Each block contains one plot of each entry. There are no theoretical limit for the number of blocks. The entries are randomized within the blocks. In this design, the block and the replication are the same entity. Design parameters: Number of Occurrences (Trials) and Number of Replicates (Blocks) Layout parameters: Rows per Replication (Block), Number of Field Rows and Plot Ordering (serpentine or not). Usage: When the experimental units are not homogeneous and it is possible to group the experimental units into blocks such that experimental units within each block are more homogeneous than those between blocks. It is not recommended when the number of entries are too large, being impossible to have field with a little variation even within the blocks. | |
Same as RCBD Differences:
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OFT | RCBD | It is a regular RCBD but each block will be assigned to a occurrence, with that, each block can be planted in a different location. Design parameters: Number of Farms (In the case of OFT, it is the same as number of blocks or even number of locations) Layout parameters: Layout parameters are not used for this design. Usage: To be used exclusively for “On-farm trials”, that is an experiment usually for late stages of a breeding program evaluating a small number of genotypes (<15). | |
Incomplete Block Design | OFT | Incomplete Block | Is an incomplete block design where each block is assigned to an occurrence, with that, each incomplete block can be planted in a different location. Design parameters: Number of Farms (In the case of OFT, it is the same as number of blocks or even number of locations) and Block size (plots per block). Usage: To be used exclusively for “On-farm trials”, that is an experiment usually for late stages of a breeding program evaluating a small number of genotypes (<15). Is there some restrictions in terms of number of farms, as it is the number of blocks and it is dependent of the number of entries. This design tries to create a balanced design considering the test and the check entries. The entry list must have at least 2 check entries. |
Row and Column Design | Another kind of resolvable Incomplete Block design, it is like Alpha-Lattice but with better field variation since this design allows blocking in two directions that are perpendicular to each other. Design parameters: Number of Occurrences (Trials), Number of Replicates, Number of Row Blocks. Layout parameters: Total Number of Field Rows, Plot Ordering (serpentine or not) Usage: When the number of treatments being tested (entries, genotypes) is very large, it is difficult to have a uniform field that can support this large number of plots, so we build small blocks (incomplete blocks) within the replication. This design is appropriate if there are two sources of variation and the dimension of the field per replicate is squarish as possible. | |
Augmented RCBD | Another type of Incomplete Block design wherein some of the treatments (entries, genotypes) are replicated while the the other treatments are unreplicated. The Replicated treatments are referred to as the check while the unreplicated ones are referred to as the test. The replicated treatments follow the randomization of the RCBD (all treatments are present in each block) while the unreplicated treatments are distributed and embedded within each block. Design parameters: Number of Occurrences (Trials), Number of Blocks. Layout parameters: Total Number of Field Rows, Plot Ordering (serpentine or not) Usage: This design is often used in the early generation, when the seeds or resources are limited, when the user wants to evaluate as many genotypes as possible, and when it is difficult to maintain homogeneous blocks when comparing many genotypes. | |
Augmented designs with diagonal checks | P-rep w/ diagonal systematic checks | An Incomplete Block design wherein some treatments (entries, genotypes) are replicated while the other treatments are unreplicated. The replicated treatments are referred to as the check which can then be further classified as spatial or repeated. The repeated checks and the unreplicated treatments are completely randomized across the field, while the spatial checks are positioned in a diagonal pattern. Design parameters: Number of Occurrences (Trials), Entry Role, Number of Replicates. Layout parameters: Total Number of Field Columns, Percentage of Check Plots Usage: This design is often used in the early generation, when the seeds or resources are limited and when the user wants to evaluate as many genotypes as possible. |
Partially replicated design | P-Rep | A special case of Augmented design where 20% of the test entries are replicated, check entries are not classified as either spatial or repeated and no diagonal plots are included. Design parameters: Number of Occurrences (Trials), Number of Replicates. Layout parameters: Total Number of Field Rows, Plot Ordering (column order, column serpentine, row order, row serpentine) Usage: This design is often used in the early generation, when the seeds or resources are limited, when the user wants to evaluate as many genotypes as possible, and when it is difficult to maintain homogeneous blocks when comparing many genotypes. |
Alpha Lattice
The number of entries should not be a prime number.
Design parameters
No. Of Occurrences: Number of locations that the experiment will be planted. The default value is 1 and valid value is greater than or equal to 1.
No. Of Replicates: The number of replicates. The default value is 2 and the valid value is greater than or equal to 2.
No. Of Blocks Per Rep: The number of blocks per replicate. The possible values are system-generated which must be a factor of the total number of entries, except 1 and total number of entries, since the the number of entries will be divided by the number of blocks per rep to define the block size (number of plots per block).
Field layout parameters
No. Of Rows Per Block: Used to define the shape of each block. Must be a factor of the block size, since the model requires rectangular blocks. E.g. number of entries is 25, blocks per rep is 5, the rows per block only options will be 1 or 5, that is, the block is a “vertical bar” of 5 plots or a “horizontal bar” of 5 plots.
No. Of Rows Per Rep: Used to define the shape of the rep, or, how to assemble the blocks, if side-by-side or in front of each other in the field.
Rows: Used to define the shape of the field trial, using the same logic as No. Of Rows per Rep, the user can define how the reps would be positioned in the field. The restriction is always generate a rectangular field shape.
Field Order: If the plots will be assigned to the field in plot order or in serpentine order.
Alpha-Lattice | CIMMYT
The number of entries should not be a prime number.
Design parameters
No. Of Occurrences: Number of locations that the experiment will be planted. The default value is 1 and valid value is greater than or equal to 1.
No. Of Replicates: The number of replicates. The default value is 2 and the valid value is greater than or equal to 2.
No. Of Plots Per Block: It is the block size. Must be a factor of the number of entries.
Field layout parameters
Rows: Used to define shape of the field trial, used to define how the reps would be positioned in the field. In this model is possible to generate non-rectangular blocks.
Field Order: There is two options of serpentine, horizontal or vertical, as showed but the arrows. The plots will be assigned to the field in serpentine, the first plot will always be at the plot R1C1 (row 1 column 1), if is vertical serpentine the second plot will be positioned in R2C1, if horizontal R1C2, that is, in one case the following plot is added in the next row in other case in the next column.
Plots Until Turn The Serpentine: The plots will be assigned to the field in serpentine will determine when the process of add a plot will move to the subsequent column (if vertical serpentine) or row (if horizontal serpentine).
Example of Plots Until Turn The Serpentine.
25 entries, 5 rows, horizontal serpentine and 5 or 10 plots until turn the serpentine.
IWIN Design
The number of entries should not be a prime number.
Design parameters
No. Of Occurrences: Number of locations that the experiment will be planted. The default value is 1 and valid value is greater than or equal to 1.
No. Of Replicates: The number of replicates. The default value is 2 and the valid value is greater than or equal to 2.
No. Of Plots Per Block: It is the block size. Must be a factor of the number of entries.
Randomize the 1st Rep: The default (Yes) runs a randomization for all the reps, the alternative (NO) fixes the first rep to receive the entries in the order they are in the entry list, and the subsequent replicates are randomized to follow the Alpha-Lattice restriction.
Randomize Each Occurrence: The default (Yes) runs a randomization to each occurrence, the alternative (NO), runs only one randomization and reuse the same result for all the occurrences.
Field layout parameters
Rows: Used to define shape of the field trial, used to define how the reps would be positioned in the field. In this model is possible to generate non-rectangular blocks.
Field Order: There is two options of serpentine, horizontal or vertical, as showed but the arrows. The plots will be assigned to the field in serpentine, the first plot will always be at the plot R1C1 (row 1 column 1), if is vertical serpentine the second plot will be positioned in R2C1, if horizontal R1C2, that is, in one case the following plot is added in the next row in other case in the next column.
Plots Until Turn The Serpentine: The plots will be assigned to the field in serpentine will determine when the process of add a plot will move to the subsequent column (if vertical serpentine) or row (if horizontal serpentine).
RCBD
Design parameters
No. Of Occurrences: Number of locations that the experiment will be planted. The default value is 1 and valid value is greater than or equal to 1.
No. Of Replicates: The number of replicates. The default value is 2 and the valid value is greater than or equal to 2.
Field layout parameters
No. Of Rows Per Rep: Used to define the shape of the replicate, if side-by-side or in front of each other in the field.
Rows: Used to define the shape of the field trial, using the same logic as No. Of Rows per Rep, the user can define how the reps would be positioned in the field. The restriction is always generate a rectangular field shape.
Field Order: If the plots will be assigned to the field in plot order or in serpentine order.
RCBD | CIMMYT
Design parameters
No. Of Occurrences: Number of locations that the experiment will be planted. The default value is 1 and valid value is greater than or equal to 1.
No. Of Replicates: The number of replicates. The default value is 2 and the valid value is greater than or equal to 2.
Field layout parameters
Rows: Used to define shape of the field trial, used to define how the reps would be positioned in the field.
Field Order: There is two options of serpentine, horizontal or vertical, as showed but the arrows. The plots will be assigned to the field in serpentine, the first plot will always be at the plot R1C1 (row 1 column 1), if is vertical serpentine the second plot will be positioned in R2C1, if horizontal R1C2, that is, in one case the following plot is added in the next row in other case in the next column.
Plots Until Turn The Serpentine: The plots will be assigned to the field in serpentine will determine when the process of add a plot will move to the subsequent column (if vertical serpentine) or row (if horizontal serpentine).
OFT | RCBD
Design parameters
No. Of Farms: Number of locations that the experiment will be planted. It is the same as the number of blocks. The default value is 10 and valid value is greater than or equal to 10.
Field layout parameters
Field layout is generated for On-Farm Trials
OFT | Incomplete Block
Design parameters
No. Of Farms: Number of locations that the experiment will be planted. It is the same as the number of blocks. The default value is 100 and valid value is greater than or equal to 60.
No. Of Plots Per Farm: Must be > 2 and smaller than the total number of entries. It cannot be greater than the number of test or check entries.
Field layout parameters
Field layout is not genereated for On-Farm Trials.
Row-Column
Design parameters
No. Of Occurrences: Number of locations that the experiment will be planted. The default value is 1 and valid value is greater than or equal to 1.
No. Of Replicates: The number of replicates. The default value is 2 and the valid value is greater than or equal to 2.
No. Of Row Blocks: Must be a factor of number of entries except 1 and number of entries.
Field layout parameters
Rows: Used to define the shape of the field trial, the user can define how the reps would be positioned in the field. The restriction is always generate a rectangular field shape.
Field Order: If the plots will be assigned to the field in plot order or in serpentine order.
Augmented RCBD
Design parameters
No. Of Occurrences: Number of locations that the experiment will be planted. The default value is 1 and valid value is greater than or equal to 1.
No. Of Replicates: The number of replicates. The default value is 2. Must be enough to result to a minimum degrees of freedom of 12. Must be a factor of the number of test entries. The number of test entries will be divided by the number of replicates. Each replicate will receive a complete set of the check entries and a portion of the test entries equal to the number of test entries divided by the number of replicates.
Field layout parameters
No. Of Rows per Rep: Used to define the shape of the replicate, if side-by-side or in front of each other in the field.
Rows: Used to define the shape of the field trial, using the same logic as No. Of Rows per Rep, the user can define how the reps would be positioned in the field. The restriction is always generate a rectangular field shape.
Field Order: If the plots will be assigned to the field in plot order or in serpentine order.
Augmented Design with diagonal checks
Design parameters
Entry Role: Identify the role of each check whether it is Spatial Check or Repeated Check. Default value is Spatial Check.
No. of Reps: The minimum number of replicates and its default value is 2.
No. Of Occurrences: Number of locations that the experiment will be planted. The default value is 1 and valid value is greater than or equal to 1.
Field layout parameters
Columns: Used to define the shape of the field trial. Default value is 20 and Minimum value is 10.
Percentage of Check Plots: Used to define how many plots in the diagonal spatial check will occupy. Default value is 10, minimum value is 5 and maximum value is 20.
Partially Replicated Design
Design parameters
Specify Groups
Group type: Identify the different check group and test group.
No. Of Replicates: For check group, the minimum number is 2. For test group, at least 20% of the test entries are replicated.
No. Of Occurrences: Number of locations that the experiment will be planted. The default value is 1 and valid value is greater than or equal to 1.
Field layout parameters
Rows: Used to define the shape of the field trial.
Field Order: If the plots will be assigned to the field in column serpentine, column order, row serpentine and row order.