Fig. 1. Dry matter yield kg ha
− 1
of reed canary grass in autumn 1992 – spring 1998. Relative proportion of different plant parts in total DM are given in columns.
on a selected model 1. The covariance structure of the repeated measurements was chosen by com-
paring potential structures using Akaike’s infor- mation criterion Wolfinger, 1996.
Y
ij
= m + T
i
+ B
j
+ o
ij
+ P
k
+ T × P
jk
+ B × P
ik
+ d
ijk
1 where m, T
i
, B
j
and o
ij
are equivalent in the analysis of variance for the classical randomised
complete-block design. P
k
and T × P
jk
represent the fixed effect of plant part or year in reed
canary grass and plant part or year × harvest time interaction. B × P
ik
represents the random effect of plant part or year × block interaction.
d
ijk
are the experimental error terms. Assumptions of the model were checked by
graphical methods; box-plot for normality of er- rors and plots of residuals for constancy of error
variance Neter et al., 1996. The parameters of the models were estimated by the restricted maxi-
mum likelihood REML estimation method us- ing the SAS system for Windows 6.12.
3. Results
3
.
1
. Total yields and weight distributions of different plant parts
3
.
1
.
1
. Reed canary grass When harvested in spring, the total DM yield
of reed canary grass was on average 2025 kg ha
− 1
higher than at autumn harvest P 0.0012 Fig. 1. The age of the crop stand did not affect the
harvested DM yield significantly in spring, and the yield level remained constant throughout the
experiment period. In spring, the DM yield varied between 6408 1993 and 7716 kg ha
− 1
1997. Variation in yield was greater when harvested in
autumn; 3298 1992 to 6357 kg ha
− 1
1994. The variation was due to the climate and the age of
the crop stand. The lowest yield was obtained in the second harvest year at both harvest times
autumn 1992 and spring 1993. The total yields of the first harvest year have been reported earlier
Pahkala et al., 1994, but then we did not frac- tionate the biomass into the different plant parts.
The stem proportion of reed canary grass was significantly P 0.0133 higher in spring 61.3
than at autumn harvest 51.6 Fig. 1. The proportion of stem varied greatly depending on
the year P 0.0001. Variation in stem fraction ranged between 42.4 1993 and 61.8 1996 in
autumn and in spring between 46.6 1993 and 73.9 1997. The stem yield kg ha
− 1
varied yearly more than stem proportion. The stem yield
was lowest in 1992 2269 kg ha
− 1
and it in- creased later, varying from 2966 to 4311 kg ha
− 1
in older stands. The proportion of leaf blades averaged 28.2 in autumn and 20.1 in spring,
leaf sheaths 17.4 and 18.5 of the DM yield, respectively. Panicles were found only at seed
stage in autumn when their proportion was 3.3 of the DM yield.
3
.
1
.
2
. Fescues The total DM yields for both tall fescue and
meadow fescue over a period of several years have been presented earlier Pahkala et al., 1994. In
both fescues, the total biomass yield was lower and variation was greater in spring than in au-
tumn Fig. 2. The harvest effect was significant in tall fescue P 0.0450. In fescues, the major part of
the harvested biomass consisted of leaf blades Fig. 2, the stem fraction being a minor part and
the stem proportion even decreased during winter. In autumn, the proportion of stem varied from
24.1 to 33.1 in tall fescue and from 29.9 to 34.6 in meadow fescue and in spring from 11.1
to 39.9 and from 7.1 to 27.9, respectively. The proportion of panicles in tall fescue was 8.2, and
in meadow fescue 11.6 of the DM yield at seed ripening stage.
3
.
1
.
3
. Goat
’
s rue The spring yield of goat’s rue was significantly
lower than that harvested in autumn P 0.0299 Fig. 2. The proportion of stem was as high as
73.1 in spring, which was significantly higher P 0.0250 than in autumn 48.6. However, the
stem yield kg ha
− 1
was comparable at both harvest times.
Fig. 2. Dry matter yield kg ha
− 1
of tall fescue a, meadow fescue b and goat’s rue c in autumn 1992 – spring 1993. Relative proportion of different plant parts in total DM are given in columns.
Table 2 Ash, silica SiO
2
and potassium K contents in different plant parts of reed canary grass, tall fescue, meadow fescue and goat’s rue in autumn 1992 and in spring 1993
a
SiO
2
of DM K g kg
-1
of DM Ash of DM
Harvest time Harvest time
Harvest time Spring
P value Autumn
Spring P value
Autumn Autumn
Spring P value
Reed canary grass 5.04 a
b
0.4824 1.67 a
b
4.04 a
b
Stem 0.0005
4.71 a
b
14.47 a
b
2.77 a
b
0.0019 9.00 b
0.2572 4.27 b
7.40 b 0.0002
8.44 b 19.73 b
Leaf sheath 3.57 a
0.0004 11.53 c
Leaf blade 13.00 c
0.0263 5.73 b
10.67 c 0.0022
21.13 b 4.30 a
0.0001 Tall fescue
4.15 a 0.0132
0.67 a 1.94 a
0.0039 6.03 a
25.93 a Stem
8.83 a 0.0114
9.03 b Leaf sheath
8.53 b 0.5180
3.24 b 5.06 b
0.0029 28.30 ab
13.07 b 0.0336
10.07 b 0.1931
3.54 b 7.33 c
Leaf blade 0.0014
10.90 c 30.77 b
6.33 a 0.0007
Meadow fescue Stem
6.12 a 3.78 a
0.0077 0.53 a
2.54 a 0.0266
24.87 a 3.00 a
0.0001 7.76 b
0.1168 2.86 b
5.83 b 0.0071
Leaf sheath 23.90 a
8.71 b 4.30 a
0.0001 10.89 c
0.3735 2.63 c
8.51 c 0.0006
11.37 c 30.87 b
Leaf blade 4.47 a
0.0001 Goat
’
s rue 3.62 a
0.0012 0.08 a
0.48 a Stem
0.0766 4.89 a
12.57 a 2.50 a
0.0014 11.10 b
0.0166 0.34 a
2.03 b 0.0243
14.57 a 3.37 a
10.77 b 0.0012
Leaf blade
a
The P value are given for the harvest time effect.
b
Means for each species, which are written in columns, are not significantly different at the 0.05 probability level if they are followed by the same letter.
3
.
2
. Mineral and fibre contents of different plant parts
3
.
2
.
1
. Ash The ash content was lowest in the stem fraction
for all species and at both harvest times, in leaf sheaths and especially in leaf blades the ash content
was clearly higher Table 2. Harvest time had not a very clear effect on the ash content. Leaf blades
of reed canary grass and goat’s rue had a higher ash content in spring than in autumn, while the ash
content in the stem of fescues and goat’s rue decreased in spring.
3
.
2
.
2
. Silica SiO
2
The grass species had a higher silica content than goat’s rue. In spring, the silica content was higher
than in autumn in all plant parts. Silica was lowest in the stem fraction for all species at both
harvest times Table 2. The silica content in leaf sheaths and blades was almost the same
in autumn, but in spring the silica content was clearly higher in leaf blades than in leaf sheaths.
3
.
2
.
3
. Potassium K
Harvest time had a considerable effect on the potassium content in all plant species and plant
parts. The potassium content in all plant species and in all plant parts was clearly lower at spring
harvest than in autumn Table 2. Between plant parts the differences were small. In autumn, the
potassium content was lower in stem than in leaves.
3
.
2
.
4
. Copper Cu
, iron Fe
and manganese Mn
The copper content of leaf sheaths and blades in all plant species was higher in spring than in
autumn, but the difference was not so clear in stem Table 3. Except for tall fescue, in spring the
copper content was significantly lower in stem than in leaf blades. The copper content of goat’s rue was
higher than that of grasses.
The iron content was always higher in spring than in autumn Table 3. Also the differences
Table 3 Copper Cu, iron Fe and manganese Mn contents in different plant parts of reed canary grass, tall fescue, meadow fescue and
goat’s rue in autumn 1992 and in spring 1993
a
Fe mg kg
-1
of DM Mn mg kg
-1
of DM Cu mg kg
-1
of DM Harvest time
Harvest time Harvest time
Autumn Spring
P value Autumn
Spring P value
Autumn Spring
P value Reed canary grass
Stem 5.90 a
b
6.34 a
b
0.4946 18.70 a
b
61.37 a
b
0.1738 20.00 a
b
48.00 a
b
0.3998 4.11 b
Leaf sheath 7.33 ab
0.0055 66.67 b
267.00 b 0.0015
52.83 ab 140.33 b
0.0423 8.22 b
0.0193 110.33 b
491.00 c 0.0001
5.99 a 80.53 b
Leaf blade 213.67 c
0.0110 Tall fescue
4.65 a 0.0447
15.73 a 68.10 a
Stem 0.0090
2.47 a 35.73 a
62.67 a 0.0851
4.91 a 0.0228
48.00 a 148.33 b
2.19 a 0.0796
Leaf sheath 97.37 b
175.67 b 0.0027
3.63 a Leaf blade
6.72 a 0.0149
91.97 a 477.33 c
0.0044 105.10 b
186.00 b 0.0024
Meadow fescue 5.73 a
0.2692 25.30 a
157.33 a 4.23 a
0.0195 Stem
42.53 a 63.43 a
0.2313 3.31 a
Leaf sheath 8.54 b
0.0110 55.50 a
391.67 b 0.0019
84.70 b 117.70 b
0.2366 6.81 b
Leaf blade 12.07 c
0.0109 131.00 a
1176.33 c 0.0007
83.53 b 149.67 c
0.1155 Goat
’
s rue 12.40 a
0.0096 Stem
44.83 a 4.09 a
332.00 a 0.0507
18.33 a 48.57 a
0.0009 26.07 b
0.0512 125.00 a
1192.00 b 0.0215
85.80 b 194.00 b
10.67 a 0.0062
Leaf blade
a
The P value are given for the harvest time effect.
b
Means for each species, which are written in columns, are not significantly different at the 0.05 probability level if they are followed by the same letter.
between plant parts were significant in spring. The lowest contents were found in stem, the highest in
leaf blades. In autumn, the iron content varied greatly which is the reason why there were no
significant differences between the plant parts in iron content.
The manganese content varied considerably be- tween different plant parts. It was higher in spring
than in autumn Table 3. The contents were lowest in the stem of all species, the highest in leaf
blades.
3
.
2
.
5
. Fibre The fibre content in reed canary grass was
always clearly higher in spring than at autumn harvest Table 4. Even the differences between
plant parts were significant. The highest fibre content was observed in stem where the harvest
time effect was strongest. The amount of fibre was lowest in leaf blades.
4. Discussion
