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
Reed canary grass, meadow fescue, tall fescue and goat’s rue had shown a high yielding capacity
in earlier studies, and especially the grass species had been found to be potential fibre crops Jan-
Table 4 Crude fibre contents of DM in different plant parts of reed
canary grass in autumn 1996 and in spring 1997
a
Harvest time Autumn
Spring P value
Reed canary grass 52.13 a
b
0.0001 39.70 a
b
Stem Leaf sheath
36.70 b 39.83 b
0.0032 26.97 c
0.0293 Leaf blade
30.13 c
a
The P value are given for the harvest time effect.
b
Means, which are written in columns, are not significantly different at the 0.05 probability level if they are followed by
the same letter.
son et al., 1994; Pahkala et al., 1995. In this study, the highest DM yield was obtained from
reed canary grass when the crop was harvested in spring as a dry senescent crop, and the yield level
remained constant from the second year through- out the experimental period of 6 years. In Swedish
studies Landstro¨m et al., 1996, the DM yield of reed canary grass increased at delayed harvest
with increasing age of the crop stand during the first three ley years.
The stem proportion of plant species studied varied greatly because of different growth habit of
the species. On average, more than half of the biomass of reed canary grass and goat’s rue con-
sisted of stem and the proportion of stem was higher in spring than in autumn. In fescues, the
major part of the harvested biomass consisted of leaf blades, and the proportion of stem even
decreased during winter. Reed canary grass is a strawy rhizomatous species and its growth habit is
vigorous and erect, while fescues form leafy tus- socks, which also lodge more easily during winter.
The total and stem yield losses during the winter are more common in fescues than in reed canary
grass or goat’s rue due to the lodging of the canopy.
The chemical composition of a plant part varies depending on the stage of development of the
plant when the mobile elements are moving from organ to organ as growth proceeds Jeffrey, 1988.
The concentrations of silicon, iron, manganese and copper have proved to increase at the late
stage of development Tyler, 1971, and also in this study the highest concentrations were found
in dead plants in spring. The reason for the great variation in the manganese and iron contents may
be connected to the lodging of the canopy and for possible soil contamination at harvesting. The
potassium content was clearly lower in spring than in autumn because of the leaching during
winter. An increase of fibre fraction in spring can be explained by ageing of the plant, when the
relative amount of plant cell walls increases with increasing amount of cellulose and lignin in the
secondary wall, as has been described in several forage crops Buxton and Hornstein, 1986; Bux-
ton and Russel, 1988; Albrecht et al., 1987; Gill et al. 1989.
Grasses seemed to accumulate more silica than goat’s rue. This result is comparable with earlier
findings which have shown high silica content typical for grass plants Marschner, 1995; Ilves-
salo-Pfa¨ffli, 1995. Grasses accumulate silicon as silica in epidermic cells where it protects the plant
against herbivores and fungi Jones and Han- dreck, 1965. Its role is different from that of
potassium, copper, iron and manganese, which take part more in cell metabolism.
From plant parts, leaf blades accumulated the highest concentrations of minerals. Removing the
undesirable minerals with the leaf blades would reduce the mineral content considerably and, at
the same time, would increase the relative propor- tion of stem, the most fibre-rich part of the plant.
On the one hand, sorting out the leaf blades would decrease the material usable for industry
from 11 to 67 depending on plant species. On the other hand, using more stem fraction increases
the pulp yield and improves the pulp quality Petersen, 1989; Hemming et al., 1994; Pahkala et
al., 1999. At the pulp mill, leaves, dust and dirt can be removed by air fractionation before cook-
ing. However, in grasses the leaf sheath is usually tightly rolled around the stem, and it can be more
difficult to remove than leaf blades. Mechanical pretreatment improves the quality of the pulp by
increasing the bleachability of the pulp and de- creasing the fines and silica particles in the raw
material. Silicon entering the process can be de- creased by pretreatment of the grass, removing
40 of the silica Paavilainen et al., 1996b. The dewatering and drying ability of pure grass pulps
can be improved by mechanical fractionation and blending the grass pulp with long-fibre soft wood
pulp Wisur et al., 1993; Paavilainen et al., 1996a,b.
5. Conclusion
