Trial Designs v1
- Heide Mae Balcera (Unlicensed)
- May Ann Sallan
- Alaine Gulles (IRRI)
- 1 Trial Designs and Models
- 1.1 Alpha Lattice
- 1.1.1 Alpha-Lattice | CIMMYT
- 1.2 IWIN Design
- 1.3 RCBD
- 1.3.1 RCBD | CIMMYT
- 1.4 Row-Column
- 1.5 Augmented RCBD
- 1.1 Alpha Lattice
Can’t find what you’re
looking for? Search here!
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 treatment are tested in the same block, and it is a resolvable design because blocks are arranged and group together to form complete replications. Design parameters: number of occurrences (trials), number of replicates, number of blocks. Layout parameter: 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 supports this large number of plots, so we build small blocks (incomplete blocks) within the replication. Block size need not be large even when the number of treatments is large. More flexible than 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:
| ||
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:
| ||
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 block and replication are the same entity. Design parameters: number of occurrences (trials) and number of replicates (blocks) Layout parameters: number of field rows, rows per replication (block) 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:
| ||
Row and Column Design | Another kind of resolvable incomplete block design, 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 parameter: 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 supports 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. Replicated treatment are referred as check while the unreplicated are referred as the test. The replicated treatment follows the randomization of the RCBD (all treatments are present in each block) while the unreplicated treatment are distributed and embedded within each block. Design parameters: number of occurrences (trials), number of replicates, number of blocks. Layout parameter: total number of field rows, plot ordering (serpentine or not) Usage: This design is often used in the early generation, when seed is limited or resources are limited, want to evaluate as many genotypes as possible, difficult to maintain homogeneous blocks when comparing so 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.
No. Of Replicates: The maximum number of replicates is 166., default is 2.
No. Of Blocks Per Rep: 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.
No. Of Replicates: This model
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 col.
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
This is he number of entries should not be a prime number
Design parameters
No. Of Occurrences: Number of locations that the experiment will be planted.
No. Of Replicates: This model
No. Of Plots Per Block: It is the block size. Must be a factor of the number of entries.
Randomize the first 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 col.
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.
No. Of Replicates: The minimum number of replicates is 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.
No. Of Replicates: The minimum number of replicates is 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 col.
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).
Row-Column
Design parameters
No. Of Occurrences: Number of locations that the experiment will be planted.
No. Of Replicates: The maximum number of replicates is 166., default is 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.
No. Of Replicates: Must be greater enough to result in a minimum degree of freedom of 12. Number of occurrences should 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 reps.
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.