Materials and methods Directory UMM :Data Elmu:jurnal:E:European Journal of Agronomy:Vol12.Issue1.Jan2000:
4 M. Hu¨hn European Journal of Agronomy 12 2000 1–12
variables are included in the analyses. The mean of resistances, strong branching ability Liberator.
The cultivars were randomly arranged on the test value for trait per area K can be approximated
site. Several problems arose with Phoma lingam by Hu¨hn, 1998, 1999a,b:
and Verticilium dahliae. Herbicide, fungicide and insecticide treatments as well as plant nutrition
K E
9 A
9 +
E 9
A 9
v A
− r
EA v
E v
A +
3v 3A,
5 regimes were applied according to standard cul-
tural practices. The 13 plots used for this study with E
: and A:=means of E and A; v E
and were selected from a large long-term field experi-
v A
= coefficients
of variation
of E
and A;
ment used for testing agronomic practices for r
EA =
correlation coefficient between E and A. monocultures of winter oilseed rape. The plots
For constant individual plant areas with were selected according to a differentiation of the
v A
= 0, the mean value for trait per area reduces
actual plant population densities at harvest, i.e. to the commonly used estimate E
: A:. In analogy they were chosen to obtain a range of mean
to the discussion of approach 1, it seems reason- population densities rather than to obtain a range
able to express all interesting terms relative to the of within-plot variabilities. As a consequence of
ratio E : A:=100
. For the relative amount of these requirements, the plot numbers were not
the second term on the right-hand side of Eq. 5, constant Table 1. Dinter 1991 describes the
one obtains: experimental details site, design, crop manage-
ment, weather conditions, cultivars, husbandry Second term of Eq. 5
details, disease assessment, etc.. =
100v A
− r
EA v
E v
A +
3v 3A relative to E9A9.
Separately for each individual plot, a system of Cartesian coordinates was introduced with axes at
6 the left and lower borders of the plots. Cartesian
This term can be interpreted as the effect of coordinates were determined at harvest for each
variable individual plant spaces on the mean value individual plant in the plot. In addition, the coordi-
of trait per area — expressed relative to E : A:.
nates of the adjacent neighbouring plants from out- Again, the second term in Eq. 5 can also be
side were determined. Based on these coordinates, expressed relative to the total K.
the Thiessen polygons were constructed, and their The main objective of this study is to obtain a
areas were calculated geometrically unit: cm 2.
deeper insight into the relationships between the The numbers of plots per cultivar and the
mean value of trait per area and the uniformity of numbers of plants per plot were not constant
the spatial distribution of the individual plants Table 1. In addition to the separate analyses for
over the area for agronomic traits of economic each individual plot, the different plots of the same
interest. cultivar were collected into one data set and ana-
lysed. Finally, the analysis was also carried out for the collected total plant material over plots and