5.2 Effect of crop management on raw material for non-wood pulp
5.2.2 Age of reed canary grass ley
Dry matter yield
The effect of harvest timing on DM yields var-ied among years (P = 0.0001) (Table 50). The lowest DM yields (t ha-1) were harvested at the beginning of the experiment in 1991 (spring) and 1992 (autumn) (Fig. 7a). Subsequently the yields were significantly higher, ranging from 6 to 8 t Table 49. Effect of fertilizer application rate and row spacing on stem fraction, crude fibre and mineral content (ash, SiO2, N, P, K) in dry matter of tall fescue in June and August, 1994 and in May, 1995 on organic soil in Vihti.
N rate kg ha-1 Means for
Harvest 0 50 100 150 harvest*
Stem fraction % June 35.5 32.3 29.6 26.3 30.9a
Aug 36.6 38.1 38.8 36.3 37.4b
May 45.6 40.1 39.4 39.6 41.2c
*Means for N rate 39.2a 36.8ab 35.9b 34.0b
Crude fibre % June 36.4 35.4 34.8 34.5 35.3a
Aug 39.4 37.7 38.7 37.4 38.3b
May 46.8 44.5 43.1 41.1 43.9c
*Means for N rate 40.9a 39.2b 38.8b 37.7c
Ash % June 8.9 9.3 10.0 9.8 9.5a
Aug 9.2 9.4 9.0 9.5 9.3a
May 4.9 5.1 5.1 5.7 5.2b
*Means for N rate 7.7a 7.9a 8.0ab 8.3b
SiO2 % June 3.5 3.1 3.2 2.9 3.2a
Aug 3.7 3.3 2.9 2.9 3.2a
May 3.7 4.0 3.9 4.4 4.0b
*Means for N rate 3.6a 3.5ab 3.3b 3.4b
N % June 0.94 1.10 1.30 1.58 1.23a
Aug 0.73 0.90 0.91 1.21 0.94b
May 0.64 0.77 0.93 1.14 0.87b
*Means for N rate 0.77a 0.93b 1.05c 1.31d
P g kg-1 June 2.38 2.53 2.73 3.00 2.65a
Aug 1.69 2.10 2.05 2.60 2.11b
May 1.02 1.09 1.19 1.35 1.16c
*Means for N rate 1.70a 1.91b 1.99b 2.30c
K g kg-1 June 25.7 28.8 30.3 29.9 28.7a
Aug 25.9 27.2 27.2 27.7 27.0a
May 1.68 1.59 1.68 1.91 1.71b
*Means for N rate 17.8a 19.2b 19.7b 19.8b
* Means within the column or row followed by a different letter are significantly different (P<0.05).
ha-1 on average. At the lower fertilizer rate, the age of the ley did not affect the spring harvested DM yield significantly, and the DM yields were relatively constant throughout the period 1992 to 1998. Among the autumn yields, only the yield in 1992 was significantly lower than the yields in the following years. The DM yields varied more at the higher fertilizer application rate and consequently the yield was more than 9 t ha-1 at both harvest times in 1997 (Fig. 7a). No signif-icant decrease or increase in yield was recorded as the ley aged, either when measured in autumn or in spring.
Persistence of reed canary grass stand
The reed canary grass plots harvested in spring remained free of weeds for 8 years, i.e., until spring 1999 when a small number of Elymus repens L. seedlings was found in plots. At au-tumn harvest and especially at the lower ferti-lizer application rate, the weed infestation was greater and particularly in 1996 the total harvest-ed biomass consistharvest-ed of about 40% weharvest-eds in-cluding Taraxacum officinale L. and E. repens (Fig. 7b).
Number of stems
When number of stems and plant fractions were measured from the 25 x 50 cm sample taken in each plot before harvesting in 1992–1998, the results indicated that harvesting in spring result-ed in more straw (644 stems m-2) than harvest-ing at the seed stage (562 stems m-2). The results were, however, highly dependent on the year of harvest (Table 51). The older the stand, the few-er stems pfew-er m-2. At autumn harvest, the decrease was significant (3 first years vs. 3 last years) at both of the fertilizer application rates (P = 0.0036 and P = 0.0013). At spring harvest the decrease was smaller at the lower rate of 100 kg N ha-1 (P = 0.0782) and not significant at 200 kg N ha-1. Proportion of plant fractions
Plant fractions, such as stem, leaf sheath, leaf blade and panicle, were analysed from yields harvested in 1992–1998 (Fig. 8). The proportion of stems in reed canary grass biomass was
sig-Table 50. Significance (P values) of differences in fertilizer application rate, harvest timing and year effect on dry mat-ter (DM) yield, number of stems and proportion of stem fraction of reed canary grass harvested in 1991–1999.
Source DM yield Number Stem
of stems fraction
Fertilizer (F) 0.0636 0.1983 0.6622
Harvest (H) 0.3103 0.1171 0.0001
FH 0.1160 0.9870 0.9713
Year (Y) 0.0023 0.0112 0.0001
FY 0.1365 0.5326 0.3242
HY 0.0001 0.0001 0.0171
FHY 0.0794 0.0110 0.8201
Table 51. Number of stems of reed canary grass in autumn and in spring yield at 100 and 200 kg N ha-1.
100 kg N ha-1 200 kg N ha-1 Means for Year Autumn Spring Autumn Spring year
1992 586 635 713 729 666a
1993 555 604 591 955 676a
1994 696 667 869 573 701a
1995 445 624 624 608 575ab
1996 344 549 464 853 553b
1997 472 425 530 512 485b
1998 456 629 523 653 565b
* Means within the column followed by a different letter are significantly different (P<0.05).
Table 52. Proportion of stem fraction (% of dry matter) in reed canary grass yield harvested in autumn and in spring as a mean of fertilizer rates of 100 and 200 kg N ha-1 in
* Means within the column or row followed by a differ-ent letter are significantly differdiffer-ent (P<0.05).
nificantly (P = 0.0001) higher at spring (61.8%) than at autumn harvest (53.1%) (Table 52). The proportion of stem varied greatly depending on the year (P = 0.0001), being lowest in spring yield of 1992 and in autumn yield of 1993, whereas fertilizer had only a minor effect on pro-portion of stem. The stem yield (kg ha-1) varied depending on year (P = 0.0001), harvest timing (P = 0.0011) and fertilizer application rate (P = 0.0390) (Fig. 8). The stem yield harvested in spring (P = 0.0011) was on average 1200 kg ha
-1 higher than that harvested in autumn. The pro-portion of leaf blades averaged 27.1% and 19.4%, and leaf sheaths 16.9% and 18.8% of the DM yield, from autumn and spring harvests,
re-Fig. 7. a) Dry matter (DM) yield kg ha-1, b) proportion of reed ca-nary grass (RCG) % of dry matter in 1991–1998 on clay soil in Jokioinen. N fertilizer rates 100 and 200 kg ha-1.
spectively. Panicles were present only at the seed stage in autumn when they contributed 2.9% to DM yield (Fig. 8).
Crude fibre content
The crude fibre content of reed canary grass was analysed in 1991–1994. Only the harvest time and the harvest year affected the fibre content (Table 53). The content was higher when bio-mass was harvested in spring rather than in au-tumn (P = 0.0001). The fibre content increased significantly as plant stand aged (P = 0.0001) at both fertilizer application rates and harvests (Ta-ble 54).
Fig. 8. Total dry matter (DM) yield of reed canary grass and proportion of plant fractions (1992–1999) harvested in August (A) and in spring (S) at 100 kg N ha-1 (1) and 200 kg N ha-1 (2) on clay soil in Jokioinen.
Ash content
The ash content of reed canary grass was meas-ured only in the initial four years of the experi-ment (Fig. 9a). The ash content was 6.7% of DM when the crop was harvested in spring, and the content decreased when the higher fertilizer ap-plication rate was used and in plants of aged stands (P<0.01). In autumn, the percentage was significantly higher (P = 0.0001); 8.4% on aver-age. Neither the fertilizer application rate nor the age of the grass stand affected ash content when harvested in autumn.
Silica
In addition to harvest timing and harvest year, fertilizer application rate affected the silica tent of reed canary grass (Table 53). Silica con-tent was significantly higher in material ed in spring (5.3% of DM) than in that harvest-ed in autumn (3.8% of DM) (Fig. 9b). Silica con-tent decreased from 6.2% to 4.2% in spring yield during the four years, but this was not the case for autumn yields. The higher fertilizer applica-tion rate resulted in lower silica content in both autumn and spring yields.
Table 54. Content of crude fibre (% of dry matter) in har-vested reed canary grass yield in autumn and in spring at 100 and 200 kg N ha-1 in 1991–1994.
Year Autumn Spring Means
for year
1991 30.5a 38.5a 34.5a
1992 28.6a 37.5a 33.0b
1993 32.8b 41.2b 37.0c
1994 36.1c 44.2c 40.1d
Means for harvest 32.0a 40.3b
* Means within the column or row followed by a differ-ent letter are significantly differdiffer-ent (P<0.05).
Table 53. Significance (P values) of difference in fertilizer application rate, harvest timing and year effect on crude fibre, ash and SiO2 content of reed canary grass in 1991–
1994.
Source Crude fibre Ash SiO2
Fertilizer (F) 0.5158 0.0881 0.0271
Harvest (H) 0.0001 0.0001 0.0004
FH 0.1634 0.0270 0.8551
Year (Y) 0.0001 0.0053 0.0024
FY 0.2058 0.3260 0.4425
HY 0.6917 0.0001 0.0003
FHY 0.2153 0.5162 0.3640
Pulping characteristics
Pulp yield, kappa number and screenings were measured only in the first and second years of harvest from two replicates. Harvest timing
con-tributed most to the pulping characteristics (Ta-ble 55). Significantly higher pulp yield (P = 0.0010) and kappa number (P = 0.0045) were recorded from spring (41% of DM and 24.4, re-spectively) than from autumn harvests (35.1%
and 18.5, respectively) (Fig. 10). Biomass har-vested in autumn was easier to pulp than bio-mass harvested in spring, and less screenings was recorded (P = 0.0009). The screenings averaged from 1.1% to 1.6% of DM in autumn and from 1.7% to 2.9% in spring harvests (Fig. 10).