mead.cowpeamaize {agridat} | R Documentation

## Maize/Cowpea intercropping experiment

### Description

Maize/Cowpea Intercropping experiment with multiple nitrogen treatments.

### Format

A data frame with 72 observations on the following 6 variables.

`block`

  block, 3 levels

`nitro`

  nitrogen, 4 levels

`cowpea`

  cowpea variety, 2 levels

`maize`

  maize variety, 3 levels

`cyield`

  cowpea yield, kg/ha

`myield`

  maize yield, kg/ha

### Details

An intercropping experiment conducted in Nigeria. The four nitrogen treatments were 0, 40, 80, 120 kg/ha.

### Source

Roger Mead. 1990. A Review of Methodology For The Analysis of Intercropping Experiments. Training Working Document No. 6. CIMMYT. http://repository.cimmyt.org/xmlui/handle/10883/868

### References

Roger Mead, Robert N Curnow, Anne M Hasted. 2002. Statistical Methods in Agriculture and Experimental Biology, 3rd ed. Chapman and Hall. Page 390.

### Examples

    data(mead.cowpeamaize)
    dat <- mead.cowpeamaize

    # Cowpea and maize yields are clearly in competition
    if(require("latticeExtra")){
      useOuterStrips(xyplot(myield ~ cyield|maize*cowpea, dat, group=nitro,
                            main="mead.cowpeamaize - intercropping",
                            xlab="cowpea yield",
                            ylab="maize yield", auto.key=list(columns=4)))
    }

    # Mead Table 2 Cowpea yield anova...strongly affected by maize variety.
    anova(aov(cyield ~ block + maize + cowpea + nitro +
              maize:cowpea + maize:nitro + cowpea:nitro +
              maize:cowpea:nitro, dat))
    # Cowpea mean yields for nitro*cowpea
    aggregate(cyield ~ nitro+cowpea, dat, FUN=mean)
    # Cowpea mean yields for each maize variety
    aggregate(cyield ~ maize, dat, FUN=mean)

    # Bivariate analysis
    aov.c <- anova(aov(cyield/1000 ~ block + maize + cowpea + nitro +
              maize:cowpea + maize:nitro + cowpea:nitro +
              maize:cowpea:nitro, dat))

    aov.m <- anova(aov(myield/1000 ~ block + maize + cowpea + nitro +
              maize:cowpea + maize:nitro + cowpea:nitro +
              maize:cowpea:nitro, dat))

    aov.cm <- anova(aov(cyield/1000 + myield/1000 ~ block + maize + cowpea + nitro +
              maize:cowpea + maize:nitro + cowpea:nitro +
              maize:cowpea:nitro, dat))

    biv <- cbind(aov.m[,1:2], aov.c[,2], aov.cm[,2])
    names(biv) <- c('df','maize ss','cowpea ss','ss for sum')
    biv$'sum of prod' <- (biv[,4] - biv[,2] - biv[,3] ) /2
    biv$cor <- biv[,5]/(sqrt(biv[,2] * biv[,3]))
    signif(biv,2)
    ##                    df maize ss cowpea ss ss for sum sum of prod    cor
    ## block               2    0.290    0.0730      0.250      -0.058 -0.400
    ## maize               2   18.000    0.4100     13.000      -2.600 -0.980
    ## cowpea              1    0.027    0.0060      0.058       0.013  1.000
    ## nitro               3   29.000    0.1100     25.000      -1.800 -0.980
    ## maize:cowpea        2    1.100    0.0099      0.920      -0.099 -0.950
    ## maize:nitro         6    1.300    0.0680      0.920      -0.200 -0.680
    ## cowpea:nitro        3    0.240    0.1700      0.150      -0.130 -0.640
    ## maize:cowpea:nitro  6    1.300    0.1400      1.300      -0.033 -0.079
    ## Residuals          46   16.000    0.6000     14.000      -1.400 -0.460

[Package agridat version 1.16 Index]