blackman.wheat {agridat} | R Documentation

## Multi-environment trial of conventional and semi-dwarf wheat varieties

### Description

Yield for conventional and semi-dwarf wheat varieties at 7 locs with low/high fertilizer levels.

### Format

A data frame with 168 observations on the following 5 variables.

`gen`

  genotype

`loc`

  location

`nitro`

  nitrogen fertilizer, low/high

`yield`

  yield (g/m^2)

`type`

  type factor, conventional/semi-dwarf

### Details

Conducted in U.K. in 1975. Each loc had three reps, two nitrogen treatments.

Locations were Begbroke, Boxworth, Crafts Hill, Earith, Edinburgh, Fowlmere, Trumpington.

At the two highest-yielding locations, Earith and Edinburgh, yield was _lower_ for the high-nitrogen treatment. Blackman et al. say "it seems probable that effects on development and structure of the crop were responsible for the reductions in yield at high nitrogen".

### Source

Blackman, JA and Bingham, J. and Davidson, JL (1978). Response of semi-dwarf and conventional winter wheat varieties to the application of nitrogen fertilizer. The Journal of Agricultural Science, 90, 543–550. http://doi.org/10.1017/S0021859600056070

### References

Gower, J. and Lubbe, S.G. and Gardner, S. and Le Roux, N. (2011). Understanding Biplots, Wiley.

### Examples

    data(blackman.wheat)
    dat <- blackman.wheat

    require(lattice)

    # Semi-dwarf generally higher yielding than conventional
    # bwplot(yield~type|loc,dat, main="blackman.wheat")

    # Peculiar interaction--Ear/Edn locs have reverse nitro response
    dotplot(gen~yield|loc, dat, group=nitro, auto.key=TRUE,
            main="blackman.wheat: yield for low/high nitrogen")

    # Height data from table 6 of Blackman.  Height at Trumpington loc.
    # Shorter varieties have higher yields, greater response to nitro.
    heights <- data.frame(gen=c("Cap", "Dur", "Fun", "Hob", "Hun", "Kin",
                                "Ran", "Spo", "T64", "T68","T95", "Tem"),
                          ht=c(101,76,76,80,98,88,98,81,86,73,78,93))
    dat$height <- heights$ht[match(dat$gen, heights$gen)]
    xyplot(yield~height|loc,dat,group=nitro,type=c('p','r'),
           main="blackman.wheat",
           subset=loc=="Tru", auto.key=TRUE)

    ## Not run:
      require(reshape2)
      # AMMI-style biplot Fig 6.4 of Gower 2011
      dat$env <- factor(paste(dat$loc,dat$nitro,sep="-"))
      datm <- acast(dat, gen~env, value.var='yield')
      datm <- sweep(datm, 1, rowMeans(datm))
      datm <- sweep(datm, 2, colMeans(datm))
      biplot(prcomp(datm), main="blackman.wheat AMMI-style biplot")

    ## End(Not run)

[Package agridat version 1.16 Index]