kempton.competition {agridat} | R Documentation

## Sugar beet trial with competition effects

### Description

Yield of sugar beets for 36 varieties in a 3-rep RCB experiment. Competition effects are present.

### Format

A data frame with 108 observations on the following 5 variables.

`gen`

  genotype, 36 levels

`rep`

  rep, 3 levels

`row`

  row

`col`

  column

`yield`

  yield, kg/plot

### Details

Entries are grown in 12m rows, 0.5m apart. Guard rows were grown alongside replicate boundaries, but yields of these plots are not included.

### Source

R Kempton, 1982. Adjustment for competition between varieties in plant breeding trials, Journal of Agricultural Science, 98, 599-611. http://doi.org/10.1017/S0021859600054381

### Examples

    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
    require("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")

[Package agridat version 1.16 Index]