agridat (version 1.8.1)

broadbalk.wheat: Long term wheat yields on Broadbalk fields at Rothamsted.

Description

Long term wheat yields on Broadbalk fields at Rothamsted.

source

D.F. Andrews and A.M. Herzberg. 1985. Data: A Collection of Problems from Many Fields for the Student and Research Worker. Springer. Retrieved from http://lib.stat.cmu.edu/datasets/Andrews/.

Details

Rothamsted Experiment station conducted wheat experiments on the Broadbalk Fields beginning in 1844 with data for yields of grain and straw collected from 1852 to 1925. Ronald Fisher was hired to analyze data from the agricultural trials. Organic manures and inorganic fertilizer treatments were applied in various combinations to the plots. N1 is 48kg, N1.5 is 72kg, N2 is 96kg, N4 is 192kg nitrogen. ll{ Plot Treatment 2b manure 3 No fertilizer or manure 5 P K Na Mg (No N) 6 N1 P K Na Mg 7 N2 P K Na Mg 8 N3 P K Na Mg 9 N1* P K Na Mg since 1894; 9A and 9B received different treatments 1852-93 10 N2 11 N2 P 12 N2 P Na* 13 N2 P K 14 N2 P Mg* 15 N2 P K Na Mg (timing of N application different to other plots, see below) 16 N4 P K Na Mg 1852-64; unmanured 1865-83; N2*P K Na Mg since 1884 17 N2 applied in even years; P K Na Mg applied in odd years 18 N2 applied in odd years; P K Na Mg applied in even years 19 N1.5 P and rape cake 1852-78, 1879-1925 rape cake only }

References

Broadbalk Winter Wheat Experiment. http://www.era.rothamsted.ac.uk/index.php?area=home&page=index&dataset=4

Examples

dat <- broadbalk.wheat

require(lattice)
xyplot(grain~straw|plot, dat, type=c('p','smooth'), as.table=TRUE,
       main="broadbalk.wheat")
xyplot(grain~year|plot, dat, type=c('p','smooth'), as.table=TRUE,
       main="broadbalk.wheat") # yields are decreasing

# See the treatment descriptions to understand the patterns
levelplot(grain~year*plot, dat, main="Grain")
levelplot(straw~year*plot, dat, main="Straw")