Joint International Conference on Long-term Experiments ...

Table 2. Variance and regression parameters of the stability of the production factors
in the long-term experiment (1960-2001)
Stability
parameters
Coefficient of
1 2 3 4 5 6 7
variation (CV%)
Ecovalence
45.7 19.5 21.9 34.8 24.5 25.1 36.6
(W 2 )
Stability variance
117.7 51.0 53.5 219.2 57.1 163.2 325.9
(σ 2 )
Yield stability
3.22 0.94 1.02 6.68 1.15 4.77 10.32
(YS) **
Correlation
+ +
+
+
coefficient (r)
Regression
0.796 0.947 0.962 0.713 0.919 0.690 0.899
coefficient (b)
Mean yield
0.500 1.145 1.236 0.860 1.020 0.580 1.659
response t ha -1
2.094F 8.585A 8.315B 5.205E 6.355D 4.979E 7.014C
Treatments *
* Treatments: 1. Minimum values of all factors, 2. Optimum values of all factors, 3.
Minimum depth of soil cultivation, 4. Minimum level of fertilisation, 5. Minimum level
of plant density, 6. Minimum for variety, 7. Minimum weed control.
** +: variants selected by the STABLE programme.
Table 3. AMMI Analysis for the long-term experiment (1960-2001)
Source df SS MS F-value
Total 1175 8540
Treatments 6 5054 842.3 1969.7 ***
Environments 41 2091 51.0 76.1 ***
Block 126 84 0.67
Interactions 246 988 4.0 9.39 ***
IPCA1 46 467 10.2 23.8 ***
IPCA2 44 238 5.4 12.7 ***
Residuals 156 282 1.8 4.23 ***
Error 756 323 0.43
Compared with the other production factors the weed control minimum exhibited the
opposite environmental dependence, indicating that weed infestation had the greatest
yield-reducing effect at low environmental means and the smallest effect at an
environmental index of 10 t ha –1 . Consequently, it can be stated that Treatments 2, 3 and
5 have average stability (regression coefficients of around 1), while the approximately b
= 0.5 value recorded for Treatments 1 and 6 and the b