agridat (version 1.23)

smith.wheat.uniformity: Uniformity trial of wheat

Description

Uniformity trial of wheat in Australia.

Usage

data("smith.wheat.uniformity")

Format

A data frame with 1080 observations on the following 4 variables.

row

row ordinate

col

column ordinate

yield

grain yield per plot, grams

ears

number of ears per plot

Details

Experiment was grown in Canberra, Australia, 1934.

The data are the yield of grain per plot and the number of "ears". Each plot was 1 foot long by 0.5 foot.

Field width: 36 columns x 1 foot = 36 feet.

Field length: 30 rows x 0.5 foot = 15 feet.

Notes:

There are 2 copies of the yield data at Rothamsted library. Let Copy A be the one with dark, hand-drawn grid lines, and Copy B be the one without hand-drawn grid lines. Both copies are hand-written, likely copied from the original data.

For row 4 (from top) column 34: Copy A has yield 164 while Copy B has yield 154. The value of 154 appears to be correct, since it leads to the same row and column totals as shown on both Copy A and Copy B.

For row 20, column 28, both Copy A and Copy B show yield 283. This appears to be a copy error. We replaced the value 283 by 203, so that the row and column totals match the values on both Copy A and Copy B, and also the variance of the data matches the value in Smith (1938), which is 2201 on page 7.

The documents at Rothamsted claim that the grain yield is shown as "Yields of grain in decigrams per foot length". However, we believe that that actual unit of weight is grams. Note that the yield values in the high-yielding parts of the field are close to 200 g per plot, and a plot is 0.5 sq feet. Multiply by 8 to get 1600 g per 4 sq feet. In Smith's paper, the fertility contour map in figure 1 shows the high-yielding part of the field having a yield close to "16 d.kg per 4 sq ft", and 16 d.kg = 16 kg = 1600 g.

This data was made available with special help from the staff at Rothamsted Research Library.

References

H. Fairfield Smith (1938). An empirical law describing heterogeneity in the yields of agricultural crops. The Journal of Agricultural Science, volume 28, Issue 1, January 1938, pp. 1 - 23. https://doi.org/10.1017/S0021859600050516

Peter McCullagh & David Clifford. (2006). Evidence for conformal invariance of crop yields. Proc. R. Soc. A (2006) 462, 2119–2143 http://www.stat.uchicago.edu/~pmcc/reml/ https://doi.org/:10.1098/rspa.2006.1667

Examples

if (FALSE) {
  
  library(agridat)
  data(smith.wheat.uniformity)
  dat <- smith.wheat.uniformity

  libs(desplot)
  desplot(dat, yield ~ col*row,
          main="smith.wheat.uniformity",
          flip=TRUE, aspect=15/30)

  xyplot(yield ~ ears, data=dat)

  libs(agricolae,reshape2)

  # Compare to Smith Fig. 2
  m1 <- index.smith(acast(dat, row~col, value.var='yield'),
                    main="smith.wheat.uniformity",
                    col="red")$uni
  m1 # Compare to Smith table I
  
}