Sugar beet trial with competition effects
Yield of sugar beets for 36 varieties in a 3-rep RCB experiment. Competition effects are present.
A data frame with 108 observations on the following 5 variables.
gengenotype, 36 levels
reprep, 3 levels
rowrow
colcolumn
yieldyield, kg/plot
Entries are grown in 12m rows, 0.5m apart. Guard rows were grown alongside replicate boundaries, but yields of these plots are not included.
R Kempton, 1982. Adjustment for competition between varieties in plant breeding trials, Journal of Agricultural Science, 98, 599-611. https://doi.org/10.1017/S0021859600054381
## Not run:
library(agridat)
data(kempton.competition)
dat <- kempton.competition
# Raw means in Kempton table 2
round(tapply(dat$yield, dat$gen, mean),2)
# Fixed genotype effects, random rep effects,
# Autocorrelation of neighboring plots within the same rep, phi = -0.22
libs(nlme)
m1 <- lme(yield ~ -1+gen, random=~1|rep, data=dat,
corr=corAR1(form=~col|rep))
# Lag 1 autocorrelation is negative--evidence of competition
plot(ACF(m1), alpha=.05, grid=TRUE, main="kempton.competition",
ylab="Autocorrelation between neighborning plots")
# Genotype effects
round(fixef(m1),2)
# Variance of yield increases with yield
plot(m1, main="kempton.competition")
## End(Not run)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.