Joint International Conference on Long-term Experiments ...

mean (fixed, i.e. systematic effect) and the variance (random element) are the two main
parameters describing the response pattern of a cropping system. Variations in the
measurements or in the treatment differences across years are simultaneously due to
both the fixed and the random effects, and the two sets are often inseparable from each
other.
The improvement in maize production realized in the fields is the result of the
combined effects of genetic, ecophysiological and technological changes superimposed
on short- and long-term climatological variations. The simple partitioning of yield
improvement into a genetic and an agronomic component assumes the lack of
interaction between the two components. Although the increase has been the result of
both genetic and agronomic-management improvements, most of this improvement is
the result of the genotype x management interaction (Tollenaar and Lee 2002).
The effect of major crop production factors has been investigated in long-term
experiments in Martonvásár since 1960 (Győrffy 1969, Berzsenyi and Győrffy 1995).
The aim of the present work was to carry out a biometric analysis on the 42-year data
series from the experiments in order to determine how the minimum and optimum
levels of five production factors (tillage, fertilisation, plant density, variety, weed
control) influenced the yield of maize, and to use the single-variable and multi-variable
methods of stability analysis to determine the stability of these production factors in
diverse environments.
MATERIAL AND METHODS
The effect of five crop production factors on maize yields has been investigated since
1960 in a long-term experiment set up on medium heavy loam soil. Each factor is
represented by two treatments, one minimum and one optimum. The treatments applied
for each factor were as follows:
Factor Minimum level Optimum level
Tillage * Shallow ploughing Deep ploughing
to a depth of 12–14 cm to a depth of 24–28 cm
Fertilisation ** No fertilisation 60 t ha –1 farmyard manure
every 4 years;
N140P60K60 annually
Plant density ‡ 35,000 plants ha –1 70,000 plants ha –1
Variety Open-pollinated: Hybrid
Aranyözön and
Mindszentpusztai Sárga
Weed control Poor: late thinning and Good: complete freedom
two delayed hoeings from weeds; timely
thinning
* From 1985 onwards the optimum level was deep loosening every four years
** From 1980 onwards the fertiliser rate was doubled
‡ Until 1980 the minimum plant density was 20,000 plants ha –1 and the optimum 40,000
Seven treatment combinations were used in the experiment. In Treatment 1 all the
factors were at the minimum level and in Treatment 2 all were optimum. In Treatments
3–5 one of the crop production factors was at a minimum, while all the others were
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