Electronic Journal of Polish Agricultural Universities (EJPAU) founded by all Polish Agriculture Universities presents original papers and review articles relevant to all aspects of agricultural sciences. It is target for persons working both in science and industry,regulatory agencies or teaching in agricultural sector. Covered by IFIS Publishing (Food Science and Technology Abstracts), ELSEVIER Science - Food Science and Technology Program, CAS USA (Chemical Abstracts), CABI Publishing UK and ALPSP (Association of Learned and Professional Society Publisher - full membership). Presented in the Master List of Thomson ISI.
2009
Volume 12
Issue 1
Topic:
Agronomy
ELECTRONIC
JOURNAL OF
POLISH
AGRICULTURAL
UNIVERSITIES
Stolarski M. , Szczukowski S. , Tworkowski J. , Bieniek A. 2009. PRODUCTIVITY OF WILLOW COPPICE Salix spp. UNDER CONTRASTING SOIL CONDITIONS, EJPAU 12(1), #10.
Available Online: http://www.ejpau.media.pl/volume12/issue1/art-10.html

PRODUCTIVITY OF WILLOW COPPICE SALIX SPP. UNDER CONTRASTING SOIL CONDITIONS

Mariusz Stolarski1, Stefan Szczukowski1, Józef Tworkowski1, Arkadiusz Bieniek2
1 Department of Plant Breeding and Seed Production, University of Warmia and Mazury in Olsztyn, Poland
2 Department of Soil Science and Soil Protection, University of Warmia and Mazury in Olsztyn, Poland

 

ABSTRACT

In the present work, the yield of oven dry matter and morphological traits of seven willow genotypes grown on alluvial humus silty soil (Mollic Fluvisols) and on alluvial sandy soil (Eutric Fluvisols) in an annual cutting cycle are presented. In seasons 2001-2004, the average yield of oven willow dry matter amounted to 10.09 Mg·ha-1. Willow grown on Mollic Fluvisols gave a significantly higher yield than the one grown on Eutric Fluvisols, 13.32 and 6.96 Mg·ha-1, respectively. Among the studied genotypes, the significantly highest yield of oven dry matter was found for Salix viminalis 1061 and 1059 on Mollic Fluvisols. The highest yield was obtained in the third season after willow planting – on average on Mollic Fluvisols 16.51 Mg·ha-1. The yield of oven dry matter of willow was positively correlated with stem diameter, plant density, and stem height – values of correlation coefficients 0.57; 0.46; and 0.31, respectively. Willow stem height on average amounted to 2.60 m and plants grown on Mollic Fluvisols were significantly taller than the ones grown on Eutric Fluvisols – 2.96 and 2.23 m, respectively. Willow from Eutric Fluvisols showed thinner stems than willow grown on Mollic Fluvisols. Stems of all genotypes of the species Salix viminalis were thicker than other genotypes studied in the experiment.

Key words: alluvial soils, short rotation coppice, solid fuels, yield of wood dry matter.

INTRODUCTION

Gradual replacement of fossil fuels by biomass in the process of energy generation is perceived as an important strategy for inhibiting climate changes and improving the of energy safety of the European Union [18]. Therefore, in some EU Directives bioenergy is promoted [7,8].

Accepted in Poland "Strategy of development of renewable energy" assumes that the share of renewable energy in the balance of primary energy on a national scale should reach 7.5% (ca 250 PJ) in 2010 and 14% (ca. 470 PJ) in 2020 [5,26]. Reaching this goal will depend on proper mechanisms in the fields of production and utilization of biomass as a renewable source of energy.

In Poland, the development of the utilization of renewable energy based on energy crops biomass can promote the growth of the following crops of willow coppice – Salix spp., miscanthus – Miscanthus sinensis giganteus, Virginia mallow – Sida hemaphrodita Rusby or other crops on lands which are excluded from traditional food production in agriculture [28,30]. In our country, the best energy crop seems to be willow coppice of the following species: Salix viminalis, Salix dasyclados, Salix amygdalina, and Salix acutifolia, which are natural components of our vegetation. The base for establishing energy plantations can be set-aside grounds. Willow can be grown on polluted soils where food cannot be produced. Due to its phytoremediation properties, willow can be used for reclamation and simultaneously a high biomass yield can be harvested [19,32,33]. Willow biomass from arable lands can be utilized as a solid fuel (wood chips, briquettes or pellets) for heat itself or for heat and power (CHP) generation [10,22,23,24,25].

In many trials conducted in several countries it was shown that productivity of willow coppice is related to the choice of proper species, conditions of a given habitat, maintenance, as well as to cutting frequency [3,9,12,13,15,16,20,26,27,29].

It was hypothesized that short-rotation willow coppice grown on alluvial soil is able to give a high biomass yield. The presented studies were aimed at the determination of the yield of biomass and morphological features of seven clones of willow coppice grown on alluvial humus soil and sandy alluvial soil in an annual cutting cycle.

MATERIAL AND METHODS

A field trial was established in the spring of 2000 in Obory, mesoregion of the Kwidzyn River Valley, macroregion of the Lower Vistula River Valley. In the decimal system of physiogeographic regions by FID (Federation Internationale de Documentation), this region is denoted as 1-924.314.815 [11]. Kwidzyn Vistula River Valley is the north part of the Lower Vistula River Valley – 6 to 9 km wide. The climate in this part of the Valley is very unique due to high air humidity, lower precipitation, frequent fog occurrence and local frosts. High annual amplitude of air temperature is typical of this region – in Kwidzyn it amounts to 20°C. The highest annual temperature reaches 33°C. The warmest month is July with the mean temperature of 17.5 to 18°C and the coldest one is February with the mean temperature of -3.5°C. Number of days with temperature below zero amounts to 30-50 annually. Growing period lasts for 200-210 days. This region is considered to be rain-deficient with the annual precipitation sum of 400-500 mm. The number of days with precipitation amounts to 160-170 annually and with snowfall to 30-40. Snow cover lasts for 60-70 days annually. In the spring and summer, western winds are predominant while in the autumn and winter west and north-west winds are more frequent [14].

The first factor in the experiment was soil: alluvial humus clay soil, i.e. Mollic Fluvisols or sandy alluvial soil Eutric Fluvisols. The second factor was willow genotype. There were genotypes from the Collection of the Department of Plant Breeding and Seed Production, University of Warmia and Mazury in Olsztyn. The following genotypes were studied: Salix viminalis (1059 – number in collection), Salix viminalis (1060), Salix viminalis (1061), Salix viminalis (1066), Salix viminalis x S. purpurea (1067), Salix viminalis (1089), and Salix americana (1043).

In total, 84 plots were taken into consideration, each of the area of 21.78 m2. Cuttings were planted at the density of 40,000 ha1, which corresponded to the spacing of 0.75 × 0.33 m. Results from the first season of the plant growth (2000) were treated and presented separately. Results from the seasons from 2001 to 2004 were presented in factorial design.

Before-crop for willow coppice was permanent grassland. Before establishing the experiment in the summer of 1999, Glyphosate was applied at the rate of 5 dm3·ha-1 for weeds control. Then, disk harrowing was performed. In the late autumn of 1999, deep (35 cm) ploughing was done. In the season of trial the establishment of shallow harrowing was performed. The planting material was cuttings 25 cm long and of 7-15 mm in diameter. Right after the planting, simazine was applied at the rate of 2 kg·ha-1. Later during the season, mechanical weeding was performed twice. In the next seasons, no other management practices were carried out. In the season of trial, establishing mineral fertilisation did not take place. In the succeeding seasons, the following rates of nutrients were applied: N – 90 kg·ha-1, P – 13 kg·ha-1, and K – 66 kg·ha-1. Phosphorus rate was applied as superphosphate and potassium as potassium chloride every season before the growth renewal. Nitrogen was applied at two equal rates as ammonia nitrate at growth renewal and covering of inter-rows, respectively. In the spring of 2001, some cuttings were planted if plant losses were found.

At the end of November (after foliage falling) in every growing season, plant density was registered (by counting second and third rows of each plot). Then, the height of ten stems and their diameter (50 cm above ground level) on each plot were measured. The number of stems per one stool was also registered. Harvesting of willow stem was performed annually in every by hand engine mower in the first days of January. Right after harvesting, biomass yield was determined. Then, samples were taken to determine water content in willow biomass by drying them at 105°C and the yields of oven dry matter were calculated.

Soil pitches were done and soil samples were taken from both soil profiles, which were analyzed according to standard methods used for analyzing mineral soils [17]. The following analyses were carried out: granulometric composition by the areometric Bouyoucos-Casagrande's method modified by Prószyński and groups were identified according to the Polish standard BN-78/9180-11; content of organic matter by ignition of samples at 550°C; pH in H2O and KCl – by the potentiometric method; content of CaCO3 – by the gasometrical method in Scheibler's apparatus; sum of cations (S) by the Kappen's method; hydrolytical acidity (Hh) in Ca(CH3COO)2 extract of concentration of 1 mol·dm-3; sorption capacity (T) was calculated from the formula T = S + Hh; saturation of sorption complex by cations was calculated as V = (S × 100·T-1); content of organic carbon in potassium dichromate according to the ISO standard 14235; total nitrogen by the Kjeldahl's; content of available phosphorus and potassium was determined in the same extract of calcium lactate [(CH3CHOHCOO)2Ca] by the Egner-Riehm's method and magnesium in CaCl2 extract by the Schachtschabel's method.

Experiments were performed on alluvial soils of the Lower Vistula River Valley typical for Kwidzyn Valley. The soils there show high heterogeneity. According to FAO [6], soils can be classified as Mollic Fluvisols and Eutric Fluvisols. Mollic Fluvisols originated from heavy clay formations and silty loams (Table 1). Content of the finest particles was 62-63%. Eutric Fluvisols showed different granular composition. On the surface, it originated from clayey sand formations and at a relatively shallow depth (38 cm) is underlain by loose sands, which reflects the differences in the shaping of the river bottom. These formations are washed out, which proves an almost complete lack of the finest participles fraction (diameter <0.02 mm). The studied soils showed neutral pH (pHKCl 6.8-7.0). Calcium carbonate (CaCO3) content in the topsoil of Mollic Fluvisols was 0.42%. Content of organic matter in the topsoil of Mollic Fluvisols was 6.43%, which gives the resources of 265.2 Mg ha-1 and indicates its high fertility. Eutric Fluvisols contained 2.5 times less organic matter and its resources amounted to 152.7 Mg ha-1, which affected its agronomical value.

Table 1. Physico-chemical properties and granulometric composition of Eutric Fluvisols and Mollic Fluvisols

Depth cm

pH

CaCO3

Organic matter

C- organic

N- total

S

Hh

T

Granulometric composition

Percent of diameter fraction mm

H2O

KCl

%

Mg·ha-1

%

cmol(+)·kg-1

1.0-0.1

0.1-0.02

<0.02

<0.002

Mollic Fluvisols

0-33

7.7

7.0

0.42

6.43

265.2

2.01

0.260

33.0

2.7

35.7

17

21

62

17

33-66

7.8

6.8

0.0

       

23.8

2.7

26.5

9

28

63

21

66-150

8.0

7.0

0.0

       

15.5

1.4

16.9

74

6

20

7

Eutric Fluvisols

0-38

7.5

6.9

0.0

2.56

152.7

1.01

0.104

8.9

2.1

11.0

71

12

17

5

38-150

7.3

6.9

0.0

       

3.1

1.1

4.4

96

4

0

0

The content of organic carbon in Mollic Fluvisols amounted to 2.01%, which was twice as much as in Eutric Fluvisols; the same relation was found for nitrogen content (Table 1). The capacity of the sorption complex (T) of Mollic Fluvisols was very high not only in topsoil (35.7 cmol(+)·kg-1 of soil), but also in subsoil horizons (Table 1). In the humus horizons of Eutric Fluvisols, lower capacity of sorption complex was found (11.0 cmol(+)·kg-1 of soil), while sandy subsoil was extremely low (4.4 cmol(+)·kg-1 of soil). Both studied soils showed a high content of available phosphorus (131.4-133.5 mg·kg-1). The content of potassium (174.3 mg·kg-1) and magnesium (165.0 mg·kg-1) in Mollic Fluvisols was high, whereas in the Eutric Fluvisols (112.1 and 65.0 mg·kg-1) samples was low and medium, respectively.

Weather conditions in seasons 2000-2004 were presented according to the Meteorological Station at Bałcyny. Weather conditions during the period of the experiment were presented on the background of reference period 1961-2000 (Figs 1a and b). Mean temperature in the season of planting (2000) was 13.16°C and it was higher by 0.3°C than the in reference period. Also precipitation sum in the season of 2000 was higher than in the reference period by 35.7 mm. In spite of the above, the pattern of the weather conditions in the spring of 2000 was unfavourable for the growth of the planted willow. It resulted in a low rate of established plants. Air temperatures in April and May were higher than in the reference period by 3.9 and 1.0°C, respectively. Relatively higher temperatures were accompanied by lower precipitation compared to the reference period. It affected plant losses in the first three months of willow growth, especially in the conditions of Eutric Fluvisols. Therefore, in the spring of 2001 some cuttings were planted in order to achieve planned plant density on experimental plots. This was not effective in each case. It depended on the genotype and the number of additional cuttings, which resulted in different plant competition on the plots. Moreover, low precipitation in May and June 2001 inhibited the growth rate of those cuttings (Fig. 1 b). In the next growing seasons, mean air temperatures were higher or close to the data from the reference period, while precipitation sums were higher than the appropriate data from the reference period. The only exception was the season of 2003, when during the growing period precipitation sum was lower by 30.6 mm than in the reference period.

Fig. 1. Weather pattern in seasons 2000-2004 according to the Meteorological Station in Bałcyny, Poland

For the statistical analysis of the results, STATISTICA®PL software was used. The Studenta Newmana-Keulsa (SNK) test was applied with α = 0.05. Simple correlation coefficients between the studied traits were determined and multiple regression analysis was performed for the analysis of the yield of oven dry matter.

RESULTS

First growing season
In the first season of growth, plant establishing takes place and intensive growth of the roots is observed but the growth rate of the above ground part is low compared to the next seasons. Therefore, in the work the season of 2000 was treated separately paying attention only to plant losses and the yield of biomass. Then, the results from the seasons 2001-2004 are presented as succeeding productive seasons. In the season of the establishment of the experiment, plant density was 22,684 plants·ha-1, so much as 43.3% planted cuttings were not established (Fig. 2). In Eutric Fluvisols treatment, higher losses were noted than in the willow grown on Mollic Fluvisols, 55.7 and 30.9%, respectively. Such high losses resulted from precipitation shortage, and therefore deficiency of soil water. Because of not satisfactory plant density after the first growing season, replanting was performed in order to obtain the planned density. Willow grown on Eutric Fluvisols showed shorter stems than the one grown on Mollic Fluvisols. Number of stems per one plant noted for willow genotypes in the planting season (2000) was within the range of 1.3 to 1.6 and stem diameter in the range of 5.7 to 10.1 mm.

Fig. 2. Plant losses for seven willow genotypes on Eutric Fluvisols and Mollic Fluvisols in the first growing season (2000)

The yield of oven dry matter in the first season was very low and amounted to 1.70 Mg DM·ha-1 (Fig. 3). Willow grown on Mollic Fluvisols gave a significantly higher yield of oven dry matter than the one grown on Eutric Fluvisols, 2.07 and 1.33 Mg DM·ha-1. Among the studied genotypes, the highest yield was found for Salix viminalis (1059) and the same level was noted for Salix viminalis (1066), and the remaining clones gave a significantly lower yield of oven dry matter.

Fig. 3. Yield of oven dry matter of seven willow genotypes on Eutric Fluvisols and Mollic Fluvisols in the first growing season (2000)

Biomass yield in 2001-2004
Willow coppice grown on Mollic Fluvisols gave a significantly higher yield than the one grown on Eutric Fluvisols, 13.22 and 6.96 Mg·ha-1, respectively (Figs 4a, b). Among the tested genotypes, the significantly highest yield was noted for Salix viminalis 1061 and 1059. The other genotypes gave lower yield. The lowest mean yielding ability was shown by the genotype Salix americana (5.64 Mg DM·ha-1). The highest productivity the willow showed in 2003, i.e. in the third season after planting on Mollic Fluvisols, and it amounted to 16.51 Mg DM·ha-1. In other growing seasons, the willow gave a lower yield. The lowest yield was noted in 2001, which can be explained by high plant losses in the first season. Despite the fact that replanting was performed in the spring of 2001, satisfactory results were not obtained. In the season of 2002, the yield of oven dry matter increased. The mean productivity of the tested clones ranged from 4.52 Mg DM·ha-1 for the genotype Salix viminalis (1061) grown on Eutric Fluvisols to 19.68 Mg DM·ha-1 for the same genotype grown on Mollic Fluvisols. The highest productivity during the trial was found for the genotype Salix viminalis (1061) grown on Mollic Fluvisols and it amounted to 27.13 Mg DM·ha-1. Correlation coefficient values showed that the yield of oven dry matter was positively correlated to stem diameter (r = 0.57), plant density (r = 0.46), and plant height (r = 0.31) (Table 2). Below multiple regression equations for the yield of oven dry matter of willow coppice grown on Eutric Fluvisols (a) and Mollic Fluvisols (b) are presented.

(a)      y = -13.2739+0.0002x1+0.4753x2+3.7155x3+0.3902x4
R2 = 0.5981

(b)      y = -29.0521+0.0002x1+0.9088x2+9.8981x3+0.0842x4
R2 = 0.6541

where:
y – yield of oven dry matter,
1 – density of plants per 1 ha,
x2 – number of stems per stool,
x3 – plant height,
x4 – stem diameter.

Fig. 4. Yield of oven dry matter of seven willow genotypes harvested in annual cutting cycles in years 2001-2004

Table 2. Values of coefficients of simple correlation for the studied willow traits in annual cutting cycles in 2001-2004

Item

Density of plants

Number of stems per stool

Height

Stem diameter

Yield

Density of plants

1.00

       

Number of steams per stool

-0.42*

1.00

     

Height

0.01

0.55*

1.00

   

Stem diameter

0.33*

-0.28*

-0.01

1.00

 

Yield

0.46*

0.05

0.31*

0.57*

1.00

* significant value at α = 0.05

From this equation it can be concluded that the yield of oven dry matter is determined in 60% on Eutric Fluvisols and in 65% on Mollic Fluvisols by plant density, number of stems per stool, plant height, and stem diameter.

Plant losses and morphological features of willow plants in years 2001-2004
Plant losses in Mollic Fluvisols treatment were significantly lower compared to Eutric Fluvisols (Figs 5a, b). Among the studied genotypes, the mean highest density (32,899 plants·ha-1) – with the lowest losses ratio 17.7% was found for Salix viminalis (1059). Despite the fact that new cuttings were planted in the season of 2001, their establishment ratio was very low because of competition from the already established willow plants. This was also due to unfavourable weather conditions. Extremely low precipitation in the period of January – June resulted in soil drought, which caused high plant losses in 2001 again – 35.6% on average. This value increased gradually to 37.0; 40.3; and 42.1% for 2002, 2003, and 2004 growing seasons, respectively.

Fig. 5. Plant losses for seven willow genotypes in annual cutting cycles in years 2001-2004

Willow grown on Eutric Fluvisols showed a higher number of stems compared to the one grown on Mollic Fluvisols (Figs 6a and b). It can be concluded that willow grown in less favourable habitats tends to produce more stems compared to the one grown on better soils. More numerous stems are usually shorter and thinner. The highest number of stems on one stool was found for Salix americana and a similar value was noted for Salix viminalis (1089), whereas other studied genotypes showed a significantly lower number of stems per plant. In 2003, the highest number of stems was noted. In the other seasons of the experiment, the value of this feature was lower and ranged between 5.0 and 7.9. The number of stems per plant was negatively correlated with plant density per 1 ha (r = -0.42) (Table 2).

Fig. 6. Number of stems per stool of seven willow genotypes in annual cutting cycles in years 2001-2004

Willow grown on Mollic Fluvisols was significantly higher than the one grown on Eutric Fluvisols – 2.96 and 2.23 m, respectively (Figs 7a and b). Salix viminalis (1066) plants were significantly higher than the other genotypes (mean 2.81 m). The highest stems were noted in growing season 2002. During the whole time of the duration of the experiment, the height of stems ranged from 1.46 m for Salix americana grown on Eutric Fluvisols in 2001 to 3.72 m for Salix viminalis (1061) grown on Mollic Fluvisols in 2002.

Fig. 7. Height of plants of seven willow genotypes in annual cutting cycles in years 2001-2004

Fig. 8. Stem diameter of seven willow genotypes in annual cutting cycles in years 2001-2004

Willow grown on Eutric Fluvisols had significantly thinner stems compared to the willow from Mollic Fluvisols (Figs 8a, b). Salix viminalis clone (1061) grown on Mollic Fluvisols was characterized by the thickest stems with the diameter of 13.2 mm, which was a significantly higher value in relation to the other studied genotypes. In the 2002 growing season, stems were thicker compared to the other growing seasons –13.5 mm on average.

DISCUSSION

In the results of the studies it was shown that proper selection of field for energy plantation is of key importance for crop productivity. Willow grown on better soil (Mollic Fluvisols) gave better yield than the ones grown on less fertile soil (Eutric Fluvisols). It was found that clones of the species Salix viminalis gave a higher yield than the hybrid Salix viminalis × Salix purpurea and the species  Salix americana. Similar results were obtained by Labrecque and Teodorescu [15]. The cited authors studied productivity of two willow species (Salix viminalis and S. discolor) grown on sandy or clay soil with and without fertilization in two triennial cutting cycles. The highest productivity (70,36 Mg DM·ha-1) was found for Salix viminalis in the second triennial cutting cycle on clay soil with fertilization. When willow of the same clone was grown on sandy soil without fertilization, the yield of 28.73 Mg DM·ha-1 was obtained. The respective values calculated on an annual basis amounted to 2.45 and 9.58 Mg DM·ha-1. The performed experiments implied a considerable influence of soil conditions on the productivity of Salix spp. plants. A high yield level was noted for S. discolor (24.97 Mg DM·ha-1). The same two species grown on the second habitat (poorly drained; heavy clay) gave a lower yield: 19.94 and 17.89 Mg DM·ha-1 for S. discolor and Salix viminalis, respectively. The species S. petiolaris gave a lower yield on both soils irrespective of the level of nutrients application.

In the previous studies, the productivity of willow coppice in five succeeding annual cutting cycles amounted to 15.4 Mg DM·ha-1 [31]. The most productive genotype appeared to be Salix viminalis × Salix viminalis lanceolata, giving the yield of 18.0 Mg DM·ha-1, and the lowest yield level was noted for Salix alba (9.5 Mg DM·ha-1). The highest productivity the willow showed in the fourth season after planting – on average 16.5 Mg DM·ha-1. In other studies [26], the yield of willow oven dry biomass in an annual cutting cycle amounted on average to 13.69 Mg·ha-1. The clone Salix viminalis × Salix viminalis lanceolata gave a yield of 18.22 Mg·ha-1, while the clone Salix triandra gave a biomass yield of 9.87 Mg·ha-1. Szczukowski et al. [29] reported that the productivity of Salix viminalis grown in an annual cutting cycle ranged between 11.00 and 18.19 Mg DM·ha-1.

In other studies, Labrecque et al. [16] reported that on a well-drained site on sandy load at the rate of the applied sludge of the rate of 22.5 Mg DM·ha-1, the best yield was found for Salix viminalis (30.17 Mg DM·ha-1) in the second growing season. Bullard et al. [3] studied the performance of two genotypes: Salix viminalis cv. Joruun and the clone of species S. dasyclados on two soils. A significant variation in relation to soil habitat was noted. Biomass yield obtained on mineral soil was higher by 1 tone than the one from peat-mineral soil.

In the experiment, the initial plant density amounted to 40,000 plants per 1 ha. As a result of unfavourable weather pattern, when the precipitation sum in April, May and June 2000 was lower than in the reference period, considerable losses of plants took place. Despite replanting in 2001, satisfactory plant density was not reached because five years after planting on Mollic Fluvisols losses amounted to 31%, and on Eutric Fluvisols to 46%. The obtained yield of willow biomass was positively correlated with plant density r = 0.46. Therefore, it can be concluded that in the described trial the optimal yield was not reached because of high plant losses.

Adegbidi et al. [1] studied the effect of planting density (15,000; 37,000; and 107,600 cuttings·ha-1). Willow was grown in three cutting cycles: annual, biennial and triennial, also irrigation and fertilization were applied. The average annual production of biomass in relation to clone, irrigation and fertilization ranged from 2.5 to 21.5 Mg DM·ha-1·year -1. It was found that the highest yield (not proven) was obtained at the planting density of 37,000 cuttings·ha-1. Christersson [4] reported that the annual yield of biomass oven dry matter in the case of Salix viminalis ranged from 12 to 18 Mg DM·ha-1.

Herein, biomass yield obtained in annual cutting cycles was increased to the fourth growing season. In Sweden, nine genotypes were studied planted at the density of 10,000 cuttings·ha-1. The highest potential was found in the fourth season of growth [34]. Kopp et al. [13] reported that the annual production of biomass obtained from irrigated plots increased during the first four seasons of growing and maximal yield was obtained in the fifth season. In this trial, the highest productivity was found for the fertilized clone SV1 of Salix dasyclados (16.3 Mg DM·ha-1). The genotypes SA2 – Salix alba and SH3 – Salix purpurea gave yields in the range of 13-14 Mg DM·ha-1. Results of the studies cited above indicate that the productivity of willow clones can remain on relatively the same level during ten seasons in annual cutting cycles if proper clone choice is done and maintenance of the plantations is adequate.

It should be stated that plant losses in the described trial can be estimated as very high. It resulted from unfavourable weather conditions at the time of planting and plantation establishing. It was determined that favourable weather conditions at the time of the establishment of a willow coppice plantation are a key factor determining the number of the established cuttings. In the other experiment performed during six years at our Department, the losses among 40,000 cuttings amounted to 10.8%. Losses noted for the hybrid Salix viminalis × Salix purpurea amounted to 6.5% and for the clone Salix cordata to 17% [31]. Bullard et al. [2] showed that among 111,000 cuttings planted on 1 ha, 95,000 survived and the losses amounted to 15%. Kopp et al. [12] studied the survival of the clone SV1 of the species Salix dasyclados. After five growing seasons, 75% of the planted willow survived. The above mentioned authors stated significant differences of survival rates for the following density treatments: 15,000; 37,000; and 111,000 cutting·ha-1 88, 80, and 57%, respectively. In other experiments it was shown that the losses of Salix viminalis plants in relation to the number of planted plants at annual cutting frequency amounted to 18.02%, whereas for biennial and triennial cutting cycles to 18.08 and 19.65%, respectively [21].

CONCLUSIONS

  1. It should be stressed that crop productivity is affected by the quality of the soil, as well as by willow species and cutting frequency. Limiting factor in willow plants establishment is water availability.

  2. Willow plants grown on Mollic Fluvisols showed taller and thicker stems compared to those which were harvested in Eutric Fluvisols habitats. Plants grown on Eutric Fluvisols tended to develop a higher number of branches per stool.

  3. The best suitability for the production of a high biomass yield was found for Salix viminalis plants marked in our collection as 1061 and 1059 grown on Mollic Fluvisols.

  4. In the conducted studies, the productivity of willow in relation to the above mentioned factors ranged from just a few to 27 Mg·ha-1 of oven dry matter annually.

  5. Willow grown on Mollic Fluvisols gave a significantly higher yield of oven dry matter (on average by 48%) than the one grown on Eutric Fluvisols.


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    2. Bullard M.J., Mustil S.J., McMilan S.D., Carver P., Nixon P.M.I., 2002. Yield improvements through modification of planting density and harvest frequency in short rotation coppice Salix spp. 2. Resource capture and use in two morphological diverse varieties. Biomass and Bioenergy 22, 27-39.

    3. Bullard M.J., Mustil S.J., McMilan S.D., Nixon P.M.I, Carver P., Britt C.P., 2002. Yield improvements through modification of planting density and harvest frequency in short rotation coppice Salix spp. 1. Yield response in two morphologically diverse varieties. Biomass and Bioenergy 22, 15-25.

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    Accepted for print: 26.02.2009


    Mariusz Stolarski
    Department of Plant Breeding and Seed Production,
    University of Warmia and Mazury in Olsztyn, Poland
    pl. Łódzki 3, 10-724 Olsztyn-Kortowo, Poland
    email: mariusz.stolarski@uwm.edu.pl

    Stefan Szczukowski
    Department of Plant Breeding and Seed Production,
    University of Warmia and Mazury in Olsztyn, Poland
    pl. Łódzki 3, 10-724 Olsztyn-Kortowo, Poland
    email: stefan.szczukowski@uwm.edu.pl

    Józef Tworkowski
    Department of Plant Breeding and Seed Production,
    University of Warmia and Mazury in Olsztyn, Poland
    pl. Łódzki 3, 10-724 Olsztyn-Kortowo, Poland
    email: jozef.tworkowski@uwm.edu.pl

    Arkadiusz Bieniek
    Department of Soil Science and Soil Protection,
    University of Warmia and Mazury in Olsztyn, Poland
    pl. Łódzki 3, 10-724 Olsztyn-Kortowo, Poland
    email: arek.bieniek@uwm.edu.pl

    Responses to this article, comments are invited and should be submitted within three months of the publication of the article. If accepted for publication, they will be published in the chapter headed 'Discussions' and hyperlinked to the article.