agridat (version 1.8.1)

gomez.nitrogen: Soil nitrogen at three times for eight fertilizer treatments

Description

Soil nitrogen at three times for eight fertilizer treatments

source

Gomez, K.A. and Gomez, A.A.. 1984, Statistical Procedures for Agricultural Research. Wiley-Interscience. Page 259. Used with permission of Kwanchai Gomez.

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.

References

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

Examples

dat <- gomez.nitrogen

# Note the depletion of nitrogren over time (stage)
library(HH)
interaction2wt(nitro ~ rep/trt + trt*stage, data=dat)
# Just the fertilizer profiles
with(dat, interaction.plot(stage, trt, nitro, col=1:4, lty=1:3))

# 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))
          ))