gomez.nitrogen {agridat} | R Documentation

## Soil nitrogen at three times for eight fertilizer treatments

### Description

Soil nitrogen at three times for eight fertilizer treatments

### Format

A data frame with 96 observations on the following 4 variables.

`trt`

  nitrogen treatment factor

`nitro`

  soil nitrogen content, percent

`rep`

  replicate

`stage`

  growth stage, three periods

### Details

Eight fertilizer treatments were tested.

Soil nitrogen content was measured at three times. P1 = 15 days post transplanting. P2 = 40 days post transplanting. P3 = panicle initiation.

### Source

Gomez, K.A. and Gomez, A.A.. 1984, Statistical Procedures for Agricultural Research. Wiley-Interscience. Page 259.

Used with permission of Kwanchai Gomez.

### References

R-help mailing list, 9 May 2013. Data provided by Cyril Lundrigan. Analysis method by Rich Heiberger.

### Examples

    data(gomez.nitrogen)
    dat <- gomez.nitrogen

    # Note the depletion of nitrogen over time (stage)
    if(require(HH)){
      interaction2wt(nitro ~ rep/trt + trt*stage, data=dat,
                     x.between=0, y.between=0,
                     main="gomez.nitrogen")

      # Just the fertilizer profiles
      with(dat, interaction.plot(stage, trt, nitro,
                                 col=1:4, lty=1:3, main="gomez.nitrogen",
                                 xlab="Soil nitrogen at three times for each treatment"))
    }

    # Gomez table 6.16
    m1 <- aov(nitro ~ Error(rep/trt) + trt*stage, data=dat)
    summary(m1)

    # Gomez table 6.18
    # Treatment                    1 2 3 4 5 6 7 8
    cont <- cbind("T7 vs others" = c( 1, 1, 1, 1, 1, 1,-7, 1),
                  "T8 vs others"  = c( 1, 1, 1, 1, 1, 1, 0,-6),
                  "T2,T5 vs others"   = c(-1, 2,-1,-1, 2,-1, 0, 0),
                  "T2 vs T5"       = c( 0, 1, 0, 0,-1, 0, 0, 0))
    contrasts(dat$trt) <- cont
    contrasts(dat$trt)

    m2 <- aov(nitro ~ Error(rep/trt) + trt*stage, data=dat)
    summary(m2, expand.split=FALSE,
            split=list(trt=list(
                         "T7 vs others"=1,
                         "T8 vs others"=2,
                         "T2,T5 vs others"=3,
                         "T2 vs T5"=4,
                         rest=c(5,6,7)),
              "trt:stage"=list(
                "(T7 vs others):P"=c(1,8),
                "(T8 vs others):P"=c(2,9),
                "(T2,T5 vs others):P"=c(3,10),
                "(T2 vs T5):P"=c(4,11),
                "rest:P"=c(5,6,7,12,13,14))
              ))

[Package agridat version 1.16 Index]