caribbean.maize {agridat}

Multi-environment trial of maize with fertilization

Description

Maize fertilization trial on Antigua and St. Vincent.

Format

A data frame with 612 observations on the following 7 variables.

isle

island, 2 levels

site

site

block

block

plot

plot, numeric

trt

treatment factor

ears

number of ears harvested

yield

yield in kilograms

Details

Antigua is a coral island in the Caribbean with sufficient level land for experiments and a semi-arid climate, while St. Vincent is volcanic and level areas are uncommon, but the rainfall can be seasonally heavy.

Plots were 16 feet by 18 feet. A central area 12 feet by 12 feet was harvested and recorded.

The number of ears harvested was only recorded on the isle of Antigua.

The digits of the treatment represent the levels of nitrogen, phosphorus, and potassium fertilizer, respectively.

The TEAN site suffered damage from goats on plot 27, 35 and 36. The LFAN site suffered damage from cattle on one boundary–plots 9, 18, 27, 36.

Electronic version of the data was retrieved from http://lib.stat.cmu.edu/datasets/Andrews/

Source

D.F. Andrews and A.M. Herzberg. 1985. Data: A Collection of Problems from Many Fields for the Student and Research Worker. Springer.

References

Also in the DAAG package as data sets antigua, stVincent.

Examples

library(agridat)
data(caribbean.maize)
dat <- caribbean.maize

# Yield and ears are correlated
libs(lattice)
xyplot(yield~ears|site, dat, ylim=c(0,10), subset=isle=="Antigua",
       main="caribbean.maize - Antiqua")

# Some locs show large response to nitrogen (as expected), e.g. UISV, OOSV
dotplot(trt~yield|site, data=dat, main="caribbean.maize treatment response")

# The pattern is a bit hard to see, so we split the treatment factor
# into separate factors, and group sites by island
dat <- transform(dat, N=factor(substring(trt,2,2)),
                      P=factor(substring(trt,3,3)),
                      K=factor(substring(trt,4,4)))
dat <- transform(dat, env=paste(substring(isle,1,1),site,sep="-"))
# Now we can see the strong N*site interaction
bwplot(yield~N|env, dat,
       main="caribbean.maize", xlab="nitrogen")