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Potato yields in response to potash and nitrogen fertilizer.
Data from Fisher's 1929 paper *Studies in Crop Variation 6*.
A different design was used each year.

A data frame with 225 observations on the following 9 variables.

`year`

year/type factor

`yield`

yield, pounds per plot

`block`

block

`row`

row

`col`

column

`trt`

treatment factor

`nitro`

nitrogen fertilizer, cwt/acre

`potash`

potash fertilizer, cwt/acre

`ptype`

potash type

The data is of interest to show the gradual development of experimental designs in agriculture.

In 1925/1926 the potato variety was Kerr's Pink. In 1927 Arran Comrade.

In the 1925a/1926a qualitative experiments, the treatments are O=None, S=Sulfate, M=Muriate, P=Potash manure salts. The design was a Latin Square.

The 1925/1926b/1927 experiments were RCB designs with treatment codes defining the amount and type of fertilizer used. Note: the 't' treatment was not defined in the original paper.

T Eden and R A Fisher, 1929.
Studies in Crop Variation. VI. Experiments on the response of the
potato to potash and nitrogen.
*Journal of Agricultural Science*, 19: 201-213.

McCullagh, P. and Clifford, D., (2006).
Evidence for conformal invariance of crop yields,
*Proceedings of the Royal Society A: Mathematical, Physical and
Engineering Science*, 462, 2119–2143.
https://doi.org/10.1098/rspa.2006.1667

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 | ```
library(agridat)
data(eden.potato)
dat <- eden.potato
# 1925 qualitative
d5a <- subset(dat, year=='1925a')
libs(desplot)
desplot(d5a, trt~col*row,
text=yield, cex=1, shorten='no', # aspect unknown
main="eden.potato: 1925 qualitative")
anova(m5a <- aov(yield~trt+factor(row)+factor(col), d5a)) # table 2
# 1926 qualitative
d6a <- subset(dat, year=='1926a')
libs(desplot)
desplot(d6a, trt~col*row,
text=yield, cex=1, shorten='no', # aspect unknown
main="eden.potato: 1926 qualitative")
anova(m6a <- aov(yield~trt+factor(row)+factor(col), d6a)) # table 4
# 1925 quantitative
d5 <- subset(dat, year=='1925b')
libs(desplot)
desplot(d5, yield ~ col*row,
out1=block, text=trt, cex=1, # aspect unknown
main="eden.potato: 1925 quantitative")
# Trt 't' not defined, seems to be the same as 'a'
libs(lattice)
dotplot(trt~yield|block, d5,
# aspect unknown
main="eden.potato: 1925 quantitative")
anova(m5 <- aov(yield~trt+block, d5)) # table 6
# 1926 quantitative
d6 <- subset(dat, year=='1926b')
libs(desplot)
desplot(d6, yield ~ col*row,
out1=block, text=trt, cex=1, # aspect unknown
main="eden.potato: 1926 quantitative")
anova(m6 <- aov(yield~trt+block, d6)) # table 7
# 1927 qualitative + quantitative
d7 <- droplevels(subset(dat, year==1927))
libs(desplot)
desplot(d7, yield ~ col*row,
out1=block, text=trt, cex=1, col=ptype, # aspect unknown
main="eden.potato: 1927 qualitative + quantitative")
# Table 8. Anova, mean yield tons / acre
anova(m7 <- aov(yield~trt+block+ptype + ptype:potash, d7))
libs(reshape2)
me7 <- melt(d7, measure.vars='yield')
acast(me7, potash~nitro, fun=mean) * 40/2240 # English ton = 2240 pounds
acast(me7, potash~ptype, fun=mean) * 40/2240
``` |

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