Steps to determine differences in the slope and intercept components for linear equations from
the stability analysis were derived from Mead et al. 1993. The regression test for differences be-
tween level regressions was used from the MSTAT-C statistical program.
The data were processed on an IBM-compatible computer using the MSTAT-C and SPSS 9.0 for
Windows programs MSTAT-C, 1991; SPSS for Windows, 1999.
3. Results
3
.
1
. Effect of crop rotation and fertilisation on soil properties
The long-term effect of the crop rotation and fertilisation treatments on major soil properties is
summarised in Table 1. The humus content was significantly the greatest in treatments 3 and 4
where alfalfa was grown for 3 years as a previous crop to maize and wheat, respectively and in the
wheat monoculture. It was lowest in the maize monoculture. As regards the effect of fertilisation,
the humus was greatest in plots where both farmyard manure and NPK were applied. The soil
pH was greatest in the Norfolk rotation and lowest in the alfalfa – maize sequence. The pH was
significantly higher in control plots and in those treated with farmyard manure than in the other
fertiliser treatments. The P
2
O
5
and K
2
O contents of the soil were highest in the Norfolk rotation, in
the wheat monoculture and in the wheat – maize diculture, and the data also provided a good
reflection of the effect of the fertiliser treatment.
3
.
2
. Analysis of 6ariance In the combined analysis of variance over years
the effects of crop sequences containing various proportions of maize and wheat were compared
to the yields in maize and wheat monocultures. The main effects year, crop sequence, fertilisa-
tion were significant in all cases at the 0.1 level, but their relative importance on the basis of MQ
values varied according to the type of crop sequence.
In the case of maize – wheat diculture versus maize monoculture and maize – alfalfa diculture
versus maize monoculture the greatest effect was recorded for fertilisation, followed by the year
effect and the crop sequence. In the 3 years maize – 2 years wheat – 3 years alfalfa triculture
versus maize monoculture, the effect of crop se- quence increased substantially, becoming similar
in magnitude to that of fertilisation. When com- paring the Norfolk rotation with the maize mono-
culture the effect of crop rotation became the most important, followed by fertilisation and
year.
The crop rotation × year interaction was signifi- cant at the 1 and 0.1 level in the 2 years
maize – 2 years wheat and the 3 years maize – 2 years wheat – 3 years alfalfa sequences, respec-
tively, compared to the maize monoculture. The fertilisation × year interaction was significant at
the 0.1 level for all the crop sequences. The crop sequence × fertilisation interaction was significant
at the 0.1 level for all crop sequences except the maize – wheat diculture.
When comparing the 5 years wheat – 3 years alfalfa diculture with the wheat monoculture the
effect of fertilisation was the most important, followed by that of crop sequence and year. In the
case of wheat – maize diculture versus wheat monoculture the effect of crop sequence was the
most important; on the basis of MQ values the effect of fertilisation was only two-thirds and that
of the year only half that of crop sequence. In the case of 2 years wheat – 3 years alfalfa – 3 years
maize triculture versus wheat monoculture the effect of crop sequence was three times that of
fertilisation and almost ten times that of the year. When comparing the Norfolk rotation with the
wheat monoculture the effect of crop sequence was more than seven times that of fertilisation
and more than four times that of the year.
The crop sequence × year interaction was sig- nificant at the 0.1 or 1 level for all crop se-
quences and was the most important of the interactions on the basis of MQ values. The fertil-
isation × year interaction was significant at the 1 level in the triculture and at the 0.1 level in
the other crop sequences. The crop sequence × fertilisation interaction was significant at the 0.1
level in the wheat – maize diculture and at the 1 level in the Norfolk rotation.
3
.
3
. Yield response Without fertilisation the yield in the 2 years
maize – 2 years wheat diculture was 0.61 t ha
− 1
higher than in the maize monoculture Table 2. Averaged over the B – E fertiliser treatments the
yield difference was 0.407 t ha
− 1
. Differences were observed in the maize yield depending on
whether it was grown in the first or second year after wheat 7.392 vs. 6.665 t ha
− 1
. In the 5 years maize – 3 years alfalfa sequence
the yield of maize without fertilisation was 1.201 t ha
− 1
higher than in a maize monoculture, while it was only 0.23 t ha
− 1
higher when a satisfactory level of fertilisation was applied mean of treat-
ments B – E Table 2. A detailed analysis of the data indicates that the yield of maize after alfalfa,
averaged over fertiliser treatments A – E, was 0.566 t ha
− 1
higher than that in a maize monocul- ture during the first 2 years, but only 0.408 t ha
− 1
higher in the 3rd – 5th years without fertilisation the yield increase over the same periods was 1.55
and 1.28 t ha
− 1
, respectively. In the 3 years maize – 2 years wheat – 3 years
alfalfa triculture Table 3 the mean yield surplus compared with the maize monoculture was 1.434 t
ha
− 1
without fertilisation and 0.717 t ha
− 1
at a satisfactory nutrient supply level mean of treat-
ments B – E. The greatest maize yield surplus was obtained in the Norfolk rotation maize – spring
barley – peas – wheat, where the maize yield aver- age exceeded that achieved in the maize monocul-
ture by 1.357 t ha
− 1
without fertilisation and by 0.787 t ha
− 1
in fertilised treatments Table 3. In the 2 years wheat – 2 years maize diculture
the yield without fertilisation was 0.376 t ha
− 1
higher than in the wheat monoculture Table 4. Averaged over the B – E treatments the yield dif-
ference was 0.860 t ha
− 1
. In the 5 years wheat – 3 years alfalfa diculture the wheat yield was 0.431 t
ha
− 1
greater without fertilisation and 0.444 t ha
− 1
greater at adequate fertiliser levels average of treatments B – E than in the monoculture.
There was a difference in the effect of the crop sequence, depending on which year the wheat was
grown after alfalfa. The yield surplus of wheat after alfalfa, averaged over treatments A – E, was
1.27 t ha
− 1
in the first year, 0.63 t ha
− 1
in the second year and only 0.055 t ha
− 1
in the 3rd – 5th years compared to the wheat monoculture the
magnitude of the yield increase was similar with- out fertilisation.
In the 2 years wheat – 3 years alfalfa – 3 years maize triculture Table 5 the average yield sur-
plus compared to the wheat monoculture was 0.856 t ha
− 1
without fertilisation and 1.115 t ha
− 1
with adequate nutrient supplies mean of treatments B – E. Differences were observed in
the wheat yield depending on whether it was grown in the 1st or 2nd year after maize. In the
triculture the yield of wheat after maize was 1.354 t ha
− 1
greater in the 1st year and 0.78 t ha
− 1
greater in the 2nd year than in the monoculture. The greatest wheat yield surplus was obtained in
the Norfolk rotation maize – spring barley – peas – wheat, where the wheat yield average exceeded
that of the monoculture by 1.614 t ha
− 1
without fertilisation and by 1.554 t ha
− 1
in fertilised plots Table 5.
In maize crop rotations the greater rotation effect observed without fertilisation and in rota-
tions including legumes could be attributed chiefly to the N effect. The increase in the yield of wheat
in crop sequences, however, was similar in magni- tude in the fertilised treatments and in the non-
fertilised control.
When the effect of fertilisation treatments was compared in various crop sequences, a signifi-
cantly higher yield was obtained at high rates of NPK fertilisation treatments D – E, especially in
rotations where the proportion of maize or wheat was 50 or higher. Farmyard manure and the
recycling of crop residues maize stalks, wheat straw with NPK supplementation were efficient
ways of fertilising maize and wheat.
The effect of crop rotation and fertilisation on the grain yield of maize and wheat over the
average of the years 1961 – 1998 is illustrated in Figs. 1 and 2. It can be seen that the yield of
maize and wheat in a monoculture was always lower than in crop rotation. The extent of yield
loss was greater in wheat than in maize. The effect of crop rotation without fertilisation was greatest
Z .
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Agronomy
13 2000
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244
Table 2 Stability parameters of a maize monoculture vs. maize–wheat diculture and maize monoculture vs. maize–alfalfa diculture in various fertilisation systems, 1961–1998
a
Yield response t ha
− 1
CV W
2
s
2
YS Fertilisation treatments
Yield response t ha
− 1
CV W
2
s
2
YS Maize monoculture
Maize monoculture 4.492
16.9 A
36.93 4.724
2.40 17.0
30.36 2.61
B 6.737
6.856 7.9
23.49 1.38
4.4 3.06
0.06
N.S.
+ 6.875
6.6 14.76
0.72 +
0.85
N.S.
C 6.966
6.2 6.26
6.941 4.7
6.13 0.07
N.S.
+ D
7.256 5.5
7.37 0.36
N.S.
+ 7.065
6.9 22.82
1.33 +
E 2.30
27.16 7.8
7.157 0.152
LSD
5
0.161 Maize–alfalfa diculture
Maize–wheat diculture 5.334
5.693 12.7
40.45 2.68
13.3 41.40
A 3.70
7.261 +
6.988 6.6
18.16 0.99
5.6 3.47
B 0.02
N.S.
6.984 6.8
16.91 0.89
N.S.
+ +
C 0.14
N.S.
5.04 5.0
7.458 0.35
N.S.
+ 7.244
4.5 11.51
0.48
N.S.
+ 7.604
D 5.9
7.20 7.322
6.0 15.40
0.78
N.S.
+ 1.25
E 7.541
8.6 16.40
0.190 LSD
5
0.174
a
A, control; B, farmyard manure+NPK; C, recycled crop residues+NPK; D, extracted NPK equivalent; E, NPK for high yield level. CV, coefficient of variance; W
2
, ecovalence; s
2
, stability variance; YS, yield stability; +, selected treatments.
N.S.
Non-significant at P\0.05; Significant at P50.05;
Significant at P50.01; Significant at P50.001.
Z .
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al .
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Agronomy
13 2000
225 –
244
233 Table 3
Stability parameters of a maize monoculture vs. alfalfa–maize–wheat triculture and maize monoculture vs. Norfolk crop rotation in various fertilisation systems, 1961–1998
a
Yield response t ha
− 1
CV W
2
s
2
Fertilisation treatments YS
Yield response t ha
− 1
CV W
2
s
2
YS Maize monoculture
Maize monoculture 4.715
15.5 A
32.44 4.442
5.48 16.9
32.10 3.30
6.727 7.092
5.0 1.76
0.20
N.S.
+ 8.4
21.79 2.07
B 7.145
9.2 10.83
1.48 0.97
C 6.824
8.2 12.54
7.220 6.1
2.10 0.14
N.S.
+ D
6.982 4.0
2.33 0.25
N.S.
+ 7.200
8.2 9.84
1.30 +
E 1.79
19.47 7.8
7.075 0.192
0.237 LSD
5
Norfolk crop rotation Maize–wheat–alfalfa triculture
6.072 8.8
A 14.97
5.876 2.50
9.3 10.49
1.05 8.199
5.4 B
3.25 7.547
0.33
N.S.
+ 4.5
5.26 0.43
N.S.
+ 8.208
5.8 3.62
0.40
N.S.
+ +
C 0.35
N.S.
4.62 5.2
7.594 +
7.577 7.821
3.7 1.90
0.08
N.S.
+ 4.1
1.95 0.04
N.S.
D 7.576
6.0 5.36
0.72
N.S.
+ 1.08
E 7.757
7.6 10.69
0.260 LSD
5
0.219
a
A, control; B, farmyard manure+NPK; C, recycled crop residues+NPK; D, extracted NPK equivalent; E, NPK for high yield level. CV, coefficient of variance; W
2
, ecovalence; s
2
, stability variance; YS, yield stability; +, selected treatments.
N.S.
Non-significant at P\0.05; Significant at P50.05;
Significant at P50.01; Significant at P50.001.
Z .
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al .
Europ .
J .
Agronomy
13 2000
225 –
244
Table 4 Stability parameters of a wheat monoculture vs. wheat–maize diculture and wheat monoculture vs. wheat–alfalfa diculture in various fertilisation systems, 1961–1998
a
Yield response t ha
− 1
CV W
2
s
2
Fertilisation treatments YS
Yield response t ha
− 1
CV W
2
s
2
YS Wheat monoculture
Wheat monoculture 2.387
23.51 A
13.80 2.266
0.89 28.26
14.25 1.09
3.333 3.549
13.98 6.30
0.32 12.69
5.03 0.29
B 3.740
15.84 5.22
0.24
N.S.
+ +
0.19
N.S.
C 3.492
9.80 3.92
3.812 13.73
5.22 0.24
N.S.
+ D
3.519 9.93
4.46 0.24
N.S.
+ 3.939
13.65 11.32
0.70 E
0.51 7.60
8.64 3.606
0.104 0.103
LSD
5
Wheat–alfalfa diculture Wheat–maize diculture
2.818 28.48
A 17.42
2.642 1.17
16.88 26.23
2.04 4.056
13.19 B
5.17 4.070
0.24
N.S.
+ 7.72
5.78 0.24
N.S.
+ 4.181
13.97 4.88
0.22
N.S.
+ C
0.34 6.87
10.94 4.421
+ 4.472
4.264 11.94
6.34 0.33
N.S.
+ 10.98
5.85 0.25
N.S.
D 4.316
11.77 5.91
0.30
N.S.
+ 1.06
E 4.425
15.49 15.12
0.115 LSD
5
0.104
a
A, control; B, farmyard manure+NPK; C, recycled crop residues+NPK; D, extracted NPK equivalent; E, NPK for high yield level. CV, coefficient of variance; W
2
, ecovalence; s
2
, stability variance; YS, yield stability; +, selected treatments.
N.S.
Non-significant at P\0.05; Significant at P50.05;
Significant at P50.01; Significant at P50.001.
Table 5 Stability parameters of a wheat monoculture vs. wheat–alfalfa–maize triculture and wheat monoculture vs. Norfolk crop rotation
in various fertilisation systems, 1961–1998
a
Yield response s
2
CV W
2
s
2
YS Yield response
YS Fertilisation
CV W
2
t ha
− 1
treatments t ha
− 1
Wheat monoculture Wheat monoculture
18.15 A
1.67 2.607
0.25
N.S.
2.441 22.62
6.57 1.20
B 13.50
3.771 2.81
0.52 3.702
11.84 1.70
0.19
N.S.
+ 9.41
1.97 0.32
N.S.
+ 3.728
3.891 14.84
C 2.97
0.45 9.34
1.83 0.28
N.S.
+ 3.934
D 7.92
4.132 1.80
0.21
N.S.
+ 8.70
4.38 0.89
4.075 4.209
6.65 E
2.98 0.45
+ 0.141
LSD
5
0.186 Norfolk crop rotation
Wheat–alfalfa–maize triculture 15.77
3.21 A
0.56 3.463
4.055 13.39
4.31 0.79
11.31 4.14
B 0.78
4.885 5.360
4.50 1.15
0.13
N.S.
+ 5.59
3.92 0.73
5.470 5.075
6.59 C
1.13 0.13
N.S.
+ 7.23
2.66 0.43
N.S.
+ 5.487
8.23 D
1.42 5.210
0.19
N.S.
+ 6.49
3.05 0.52
N.S.
+ 5.338
5.291 7.81
E 2.02
0.32
N.S.
+ 0.159
LSD
5
0.210
a
A, control; B, farmyard manure+NPK; C, recycled crop residues+NPK; D, extracted NPK equivalent; E, NPK for high yield level. CV, coefficient of variance; W
2
, ecovalence; s
2
, stability variance; YS, yield stability; +, selected treatments.
N.S.
Non-significant at P\0.05; Significant at P50.05;
Significant at P50.01; Significant at P50.001.
Fig. 1. Effect of crop rotation and fertilisation on maize grain yield compared with the monoculture 1961 – 1998. MW, 2 years maize – 2 years wheat; MA, 5 years maize – 3 years alfalfa; MWA, 3 years maize – 2 years wheat – 3 years alfalfa; NF, Norfolk crop
rotation. A, control; B, farmyard manure + NPK; C, recycled crop residues + NPK; D, extracted NPK equivalent; E, NPK for high yield level. Within rotation and fertilisation the same letter indicates non-significant differences at P B 0.05 according to LSD.
in the Norfolk rotation, followed by the tricul- ture, with the poorest effect for the two dicultures.
At a satisfactory nutrient supply level treatments B – E the yield-increasing effect of crop rotations
in wheat remained at a similar level while in maize it decreased significantly.
3
.
4
. Stability analysis Variance indices characteristic of the yield sta-
bility of maize or wheat were calculated for com- parable years for crop rotation and monoculture
for each fertiliser treatment Tables 2 – 5. The highest CV was obtained in the non-fertilised
treatment A for both the monocultures and the crop sequences. The CV values tended to be
higher in the maize and wheat monocultures than in the crop sequences. The lowest CV values
were generally recorded in treatments B and D. The significance level and numerical size of the
stability variance index s
2
express the extent to which different treatments are responsible for the
interaction. It can be seen that the effect of treat- ments B andor C and D was not usually signifi-
cant. On the basis of mean yield response and stability, the yield stability index YS consistently
selected fertiliser treatments B, C and D as the best treatments in maize and wheat crop rota-
tions. In maize monocultures comparable with the crop rotations treatment D was selected consis-
tently in all cases. In wheat monocultures the yield stability index YS selected fertiliser treat-
ments C and D in most cases as the best treat- ments.
The regression method of stability analysis was used to evaluate interactions between fertilisation
and environment in different crop rotations and monocultures. The results of the F-test for signifi-
cant differences in regressions, as well as in the slope and intercept components are shown in
Table 6. The regression equations characterising the stability of various crop sequences including
maize differ significantly from those of the mono- cultures in fertiliser treatments A – D. On the basis
of the F-test, the difference between the regres- sions can be attributed mainly to the significant
differences between the intercepts. In some fer- tiliser treatments B, C and D in the maize – wheat
diculture, B and C in the maize – alfalfa diculture and A, C and D in the triculture significant
Fig. 2. Effect of crop rotation and fertilisation on wheat grain yield compared with the monoculture 1961 – 1998. WM, 2 years wheat – 2 years maize; WA, 5 years wheat – 3 years alfalfa; WAM, 2 years wheat – 3 years alfalfa – 3 years maize; NF, Norfolk crop
rotation. A, control; B, farmyard manure + NPK; C, recycled crop residues + NPK; D, extracted NPK equivalent; E, NPK for high yield level. Within rotation and fertilisation the same letter indicates non-significant differences at P B 0.05 according to LSD.
Fig. 3. Stability analysis of maize grain yield for different fertilisation treatments according to rotations vs. monoculture 1961 – 1998. A, control; B, farmyard manure + NPK; C, recycled crop residues + NPK; D, extracted NPK equivalent; E, NPK for
high yield level. n, number of years. , Significant at P 5 0.01 and P 5 0.001, respectively.
differences in slope also contributed to the differ- ences in the regression functions. According to the
results of the regression analysis, the stability of the crop rotations including wheat differed signifi-
cantly in all the fertiliser treatments A – E from that of the monoculture and this difference was
due exclusively to differences in the intercepts Table 6.
The effect of crop rotation versus monoculture and fertilisation on maize and wheat yield stabil-
ity in different environments was characterised by parallel or intersecting straight lines Figs. 3 – 6.
On the whole, the unfertilised control treatment A differed markedly from other fertilisation
treatments under high-yield conditions; the differ- ences, however, were smaller or non-existent un-
der low-yield conditions. In crop rotations the greater slope of treatment A, compared to the
monoculture, can be interpreted as the rotation effect.
In the maize – wheat diculture the highest yield in all environments was achieved with the D, E
and C treatments, where no differences in stability were observed Fig. 3. In the monoculture treat-
ments C, B and D showed an above-average response to poor environmental conditions and
their yield levels were higher up to an environ- ment mean of 5 t ha
− 1
. In the maize – alfalfa diculture the stability of treatments E and D was
greater than that of treatments B and C Fig. 3. In the monoculture comparable with this dicul-
ture the stability of treatments C, D and E were
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Berzsenyi et
al .
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Agronomy
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244
Table 6 Differences in regressions, slopes and intercepts for the regression equations of various treatments in a crop rotation experiment, 1961–1998
a
Difference in regressions Comparison
Difference in intercepts Difference in slopes
D E
A B
C D
E A
B C
D E
B C
A F-values
†
F-values
†
F-values
†
Maize monoculture 6s. 5.15
2.64
N.S.
7.84 B
1 10.64
5.55 3.53
N.S.
2.18
N.S.
19.92 9.10
4.60 1.69
N.S.
9.98 11.18 MW
5.38 22.43
3.70
N.S.
1.51
N.S.
B 1
3.06
N.S.
3.77
N.S.
4.26 1.57
N.S.
8.42 13.86
B 1
B 1
MA B
1 5.10
4.12 5.34
26.36 20.48
23.88 13.86
22.43 8.59
18.77 B
1 10.80
11.69 1.83
N.S.
11.51 14.84 21.51
MWA 6.55
1.25
N.S.
21.16 36.90
18.31 13.69
2.65
N.S.
B 1
B 1
B 1
B 1
B 1
10.79 NF
19.41 8.62
Wheat monoculture 6s. 6.66
38.55 49.77
50.61 21.21 B1
20.61 1.82
N.S.
WM B
1 B
1 B
1 3.27
24.93 25.19
10.33 4.92
3.13
N.S.
4.83 10.47
5.77 8.86
5.75 2.07
N.S.
B 1
1.89
N.S.
B 1
B 1
5.37 WA
3.89 3.51
12.75 19.00
WAM 40.53
5.91 33.56
34.67 B1 B
1 3.06
N.S.
B 1
1.98
N.S.
8.82 29.12
16.38 19.62
46.52 101.96 59.66
73.56 60.54 B1
B 1
1.11
N.S.
29.49 B
1 34.34
B 1
30.72 NF
22.55 48.61
a
MW, 2 years maize–2 years wheat; MA, 5 years maize–3 years alfalfa; MWA, 3 years maize–2 years wheat–3 years alfalfa; NF, Norfolk crop rotation; WM, 2 years wheat–2 years maize; WA, 5 years wheat–3 years alfalfa; WAM, 2 years wheat–3 years alfalfa–3 years maize. A, control; B, farmyard manure+NPK; C, recycled crop residues+NPK; D, extracted NPK equivalent;
E, NPK for high yield level.
N.S.
Non-significant at P\0.05; Significant at P50.05;
Significant at P50.01; Significant at P50.001.
†
F-test for homogeneity of error variance.
similar and they showed better adaptation to poor environments.
In the maize – wheat – alfalfa triculture the sta- bility of the fertilised treatments was similar, but
the yield level of treatments E and B was higher up to an environment mean of 5.8 t ha
− 1
Fig. 4. In the monoculture comparable with the triculture
treatments C, E and D showed good adaptation to poor environment. In the Norfolk rotation the
stability and yield of farmyard manure and recy- cled crop residues treatments B and C was the
greatest in all environments, while the stability of the NPK mineral fertiliser treatments D and E
was lower Fig. 4. It is interesting to note that in the Norfolk rotation the yield was smallest in
treatment E in all environments. The Norfolk cropping system, with an estimate of b close to
unity treatments B – D, shows an average re- sponse to environmental conditions, as measured
by the environment mean.
In the wheat – maize diculture Fig. 5 the stabil- ity of fertiliser treatments B – E was similar,
though the yield in treatment B was slightly lower. In the comparable monoculture the stability of
the fertiliser treatments differed to a lower extent; above an environment mean of 3 t ha
− 1
the yield level was greater in treatments E and C. In the
wheat – alfalfa diculture Fig. 5 the linear func- tions characterising the stability of fertilised treat-
ments B – E did not differ significantly. In the
Fig. 4. Stability analysis of maize grain yield for different fertilisation treatments according to rotations vs. monoculture 1961 – 1998. A, control; B, farmyard manure + NPK; C, recycled crop residues + NPK; D, extracted NPK equivalent; E, NPK for
high yield level. n, number of years. , Significant at P 5 0.05 and P 5 0.001, respectively.
Fig. 5. Stability analysis of wheat grain yield for different fertilisation treatments according to rotations vs. monoculture 1961 – 1998. A, control; B, farmyard manure + NPK; C, recycled crop residues + NPK; D, extracted NPK equivalent; E, NPK for
high yield level. n, number of years. , Significant at P 5 0.01 and P 5 0.001, respectively.
relevant monoculture treatment C was more stable in a low-yielding environment, but at environment
means of above 3.0 t ha
− 1
the yield gradually dropped to below the level of the other treatments.
In the wheat – alfalfa – maize triculture Fig. 6 treatments E and D showed an above-average
response to poor environmental conditions and their yield levels exceeded those of the other treat-
ments up to an environment mean of 5 t ha
− 1
. In the monoculture comparable with the triculture
treatments E and D showed an above-average response to improved environmental conditions as
indicated by the environment mean. In the Norfolk rotation treatments B, C and D indicated an
above-average response in superior environments Fig. 6. In the relevant monoculture treatment C
was most stable at low environmental means, while treatments E and D produced greater yields at an
environment mean of over 3 t ha
− 1
. Stability analysis suggests that recycled crop
residues had an increasingly greater effect in mono- culture and in a low-yielding environment B 4 t
ha
− 1
than when the environment mean was greater than 4 t ha
− 1
Figs. 3 – 6. In contrast, the farmyard manure treatment demonstrated a supe-
rior response in a high yielding environment versus a lower yielding environment when compared to
other fertilisation treatments.
4. Discussion
