Soil nitrogen and carbon in two fields

Format

A data frame with 200 observations on the following 6 variables.

field: field name, 2 levels
sample: sample number
x: x ordinate
y: y ordinate
nitro: nitrogen content, percent
carbon: carbon content, percent

Details

Two fields were studied, one at University Farm in Davis, the other near Oakley. The Davis field is silty clay loam, the Oakley field is blow sand.

Source

Waynick, Dean, and Sharp, Leslie. (1918). Variability in soils and its significance to past and future soil investigations, I-II. University of California press. https://archive.org/details/variabilityinsoi45wayn

Examples

if (FALSE) { # \dontrun{

library(agridat)
data(waynick.soil)
dat <- waynick.soil

# Strong relationship between N,C
libs(lattice)
xyplot(nitro~carbon|field, data=dat, main="waynick.soil")

# Spatial plot
libs(sp, gstat)
d1 <- subset(dat, field=="Davis")
d2 <- subset(dat, field=="Oakley")
coordinates(d1) <- data.frame(x=d1$x, y=d1$y)
coordinates(d2) <- data.frame(x=d2$x, y=d2$y)
spplot(d1, zcol = "nitro", cuts=8, cex = 1.6,
       main = "waynick.soil - Davis field - nitrogen",
       col.regions =  bpy.colors(8), key.space = "right")

# Variogram
v1 <- gstat::variogram(nitro~1, data=d1)
plot(v1, main="waynick.soil - Davis field - nitrogen") # Maybe hasn't reached sill

} # }