Joint International Conference on Long-term Experiments ...

factor was at the minimum level and the remainder were optimum the highest values of
CV% were observed for weed control and fertilisation (36.6% and 34.8%, respectively).
T F D V W
0 0 0 0 0
1 1 1 0 1
1 0 1 1 1
1 1 0 1 1
1 1 1 1 0
0 1 1 1 1
1 1 1 1 1
Treatments
0 1 2 3 4 5 6 7 8 9
Maize grain yield t ha -1
Figure 2. Effect of crop production factors on maize grain yield increments in a longterm
experiment (Martonvásár 1960-2001). Treatments : T: Depth of soil tillage, F:
Fertilisation, D: Plant density, V: Variety, W: Weed control. Each factor at two levels:
0: Minimum level, 1: Optimum level. Treatments designated with the same letter did
not differ significantly according to Duncan’s test.
The magnitude of the ecovalence (W²) and stability variance (σ²) parameters expresses
the contribution of the treatments to the significant year × treatment interaction. It can
be seen that treatments in which weed control, fertilisation, genotype or all the factors
were minimum were chiefly responsible for the interaction. Based on the mean yield
response and the stability, the yield stability (YS) parameters indicated that Treatments
2, 3, 5 and 7 were the most favourable (Table 2).
When the effects of the treatments were investigated in diverse environments by
means of linear regression analysis (Fig. 3), the greatest difference in mean yield
response was observed between the treatments in which all the factors were minimum
or optimum. The yield difference between the two treatments (expressed as the distance
between the straight lines) increased with the environmental mean. The figure shows
that the slight effect of tillage depth could only be detected for a low environmental
mean. When fertilisation was at a minimum the magnitude of the yield reduction was
considerable and increased with the value of the environmental mean. The magnitude
and trend of yield reduction was similar when the genotype was at a minimum. There
was also a similar tendency for the plant density, but the yield reduction was smaller in
this case, particular in the case of a high environmental mean.
24
F
E
E
D
C
B
A