Non-regular fields

library(ofpetrial)

When the field is curved

When the field is curved, make_exp_plots() makes no effort to keep the length of plots across strips the same. Rather, it will find the best plot width within [min_plot_width, max_plot_width] that makes the most use of the available space. Also, make_exp_plots() does not try to start strips so that the bottom line of their first plots are lined up to be stratight. Consequently, when the field is curved, experiment plots will look like this.

n_plot_info <-
  prep_plot(
    input_name = "NH3",
    unit_system = "imperial",
    machine_width = 30,
    section_num = 1,
    harvester_width = 20,
    headland_length = 30,
    side_length = 60
  )
#> Since plot width was not provided via the `plot_with` option`, it was set to a least common multiplier of the widths of the machines.

exp_data <-
  make_exp_plots(
    input_plot_info = n_plot_info,
    boundary_data = system.file("extdata", "boundary-irregular1.shp", package = "ofpetrial"),
    abline_data = system.file("extdata", "ab-line-irregular1.shp", package = "ofpetrial"),
    abline_type = "free"
  )
#> Linking to GEOS 3.11.0, GDAL 3.5.3, PROJ 9.1.0; sf_use_s2() is TRUE
#> Warning: There was 1 warning in `dplyr::mutate()`.
#> ℹ In argument: `experiment_plots_dissolved = list(...)`.
#> ℹ In row 1.
#> Caused by warning:
#> ! package 'sf' was built under R version 4.2.3

viz(exp_data, type = "layout")

In this kind of spatial arrangement of experiment plots, some blocks can be shaped not so rectangular and it is simply impossible to define regular rectangular blocks. 5 by 5 blocks would look like below for this field if you try to assign blocks regardless.

#> Warning: Removed 1 row containing missing values or values outside the scale range
#> (`geom_text()`).

This means that designing trial using a randomized block design for this type of field may not produce a design you might have intended.

Field with ditches and holes

More often than not, fields have ditches (or parts where crops cannot be grown). The make_exp_plots() function avoids such areas automatically in creating experiment plots like below:

n_plot_info <-
  prep_plot(
    input_name = "NH3",
    unit_system = "imperial",
    machine_width = 30,
    section_num = 1,
    harvester_width = 20,
    headland_length = 30,
    side_length = 60,
    min_plot_length = 250
  )
#> Since plot width was not provided via the `plot_with` option`, it was set to a least common multiplier of the widths of the machines.

exp_data <-
  make_exp_plots(
    input_plot_info = n_plot_info,
    boundary_data = system.file("extdata", "field_boundary_with_holes.shp", package = "ofpetrial"),
    abline_data = system.file("extdata", "ab_line_for_field_with_holes.shp", package = "ofpetrial")
  )

viz(exp_data, type = "layout")