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ISSN : 1598-5504(Print)
ISSN : 2383-8272(Online)
Journal of Agriculture & Life Science Vol.54 No.3 pp.9-16

Effect of Woody Biomass based Growing Media on The Physicochemical Properties and Plant Germination in Slope

Jai-Hyun Park, Si-Young Ha, Ji-Young Jung, Jae-Kyung Yang*
Department of Environmental Forest Science, Institute of Agriculture & Life Science, Gyeongsang National University, Jinju, 52828, Republic of Korea
*Corresponding author: Tel: +82-55-772-1862 Fax:
November 30, 2019 ; April 20, 2020 ; May 25, 2020


The road slopes have various problems such as the risk of landslides and soil erosion, and research on stabilizing road slopes using plant greening has attracted the most attention. The overall objective of this research was to evaluate the effects of woody biomass based growing media on plant germination in a slope area. Moreover, we tried to find out what physicochemical properties of growing media affect plant germination on a slope. For experiment, we tested soil, soil mixed with growing media (1:1, w/w), and growing media by itself. Physical and chemical properties were evaluated after a month from the date of treatment application to the experimental slope site. Plant germination of Lespedeza cyrtobotrya was measured for plant growth evaluation. Physicochemical properties were altered by mixing the soil with growing media. Particularly, moisture content, organic matter and C/N ratio were significantly changed in soils mixed with growing media compared to soil alone. We confirmed that plant germination was high when growing media was mixed with the soil. There was a significant linear relationship between particle density and pH of all media tested and plant germination. In addition, in the same trend, the principal component analysis confirmed that the particle density and pH was positive component for plant germination rate, and the C/N ratio was found to be the negative component for plant germination. In conclusion, the particle density, pH and C/N ratio of the soil mixed with growing media was considered effective for plant germination in the experimental slope site, and this wood-based growing media provides a means to improve the harmony between the slope and the surrounding environment.



    In Korea, many road constructions have been carried out with economic development, and as a result, many road slopes have also occurred (You et al., 2009). This problem is appearing not only in Korea but also abroad (Luo et al., 2013, Kateb et al., 2013). These road slopes have various problems such as the risk of landslides and soil erosion (Ni & Zhang, 2007, Jasinki et al., 2005). Hence, several methods of stabilizing road slopes are being studied, and among them, research on stabilizing road slopes using plant greening has attracted the most attention (Li et al., 2019).

    Growing media is materials that help plants grow on behalf of the soil (CEN, 1999) and are one of the materials used to green road slopes (Li et al., 2019). Generally, the materials that make up the growing media are peat, coconut coir, or other organic matter and mixed with inorganic ingredients (CEN, 1999). In recent years, research is being conducted on slopes for greening using growing media with various materials such as solid waste, sewage sludge, pruning waste, and biochar (Ostos et al., 2008, Benito et al., 2005, Headlee et al., 2014). Moffet (1989) reported that when manufacturing growing media, it is necessary to satisfy physical properties such as soil structure for plant growth, to supply nutrients necessary for plant growth, and to consider suitability for the environment to be used. In Europe and China, research is being conducted on the manufacturing, physical and chemical properties of plants and plant growth characteristics using growing media such as spent mushroom substrate, biochar, agriculture waste, pruning waste, sewage sludge and compost (Abad et al., 2001, Benito et al., 2005, Medina et al., 2009, Ostos et al., 2008, Steiner & Harttung, 2014). García-Gómez et al. (2002) reported that growing media using agro-industrial wastes helped plant growth. Growing media using various materials have a positive effect on the growth of plants due to improved physical and chemical properties. Abad et al. (2001) reported that growing media prepared with fertilizers have low water retention and high salt content. Molineux et al. (2009) reported that growing media produced by using recycle waste such as broken bricks and paper ash could be used for plant greening, positively affecting the growth of various species and plants. Hill & Peart (1998) reported that physical properties such as the bulk density and porosity of growing media in slope greening are important factors for soil erosion and early growth of plants.

    As such, studies using various environmentally friendly or recyclable materials for manufacturing growing media used for road slope greening are the directions of recent research. Schmilewski (2008) reported that woody biomass is a renewable material and is suitable for use as a growing media because it can improve porosity. Woody biomass has porosity and elasticity, which allows for low specific gravity and high air porosity (Schmilewski, 2008). Bohne et al. (1998), Brückner (1997) and Lemarie et al. (1989) reported using woody biomass to increase water retention and improve porosity when growing media. However, studies on the application of slopes to growing media using woody biomass are insufficient.

    Therefore, in this study, we tried to confirm the potential as growing media for slope greening by making woody biomass. For the purpose, woody biomass based growing media was applied to the experimental slope, and after a month, the physical and chemical properties and the germination of Lespedeza cyrtobotrya was confirmed. The main components influencing germination among physical and chemical properties were derived through correlation analysis and principle component analysis.

    Materials and Methods

    1. Preparation of growing media

    Woody biomass used in this experiment was steam-exploded oak (Yoo-Rim Co., Ltd) and ammonium nitrate was purchased from Sigma-Aldrich Co., Ltd.. The raw materials used in this study included commercial peat, classified as brown peat (pH 3.5-4.5, Satis International Co., Ltd. LA FLORA, Europe), and commercial perlite (particle size 2 mm; Landscape Architecture Co., Ltd., Korea).

    These materials were used to prepare the soilless growing media.

    The growing media was composed of woody biomass, peat moss, ammonium nitrate, and perlite (5.5:3:0.5:1, w/w/w/w). Soil was used as a control. The media used in the experiment are shown in Table 1.

    2. Application of growing media on a small-scale experimental slope

    The small-scale slope experiment was conducted in July at 1056-1, Gajwa-dong, Jinju-si, Gyeongsangnam-do, Republic of Korea. The experiments were carried out on a slope of 40 degrees. The growing media was placed in pots of a length, width, and height of 7.5 × 7.5 × 7.5 cm. Later, 50 seeds of Lespedeza cyrtobotrya were sown in each of the pots. The lowest and highest temperatures in this region were 14.6 ℃ and 33.9 ℃, respectively, with an average precipitation of 221 mm in July.

    3. Characteristics of growing media

    3.1. Determination of physical properties

    The moisture content, bulk density, particle density, and porosity were measured to confirm the physical properties of the media. The moisture content of the medium tested was determined by using the method described by Boodt & Verdonk (1972). The medium was weighed, dried at 105 ± 5 ℃ in an oven dryer and weighed again after drying. The moisture content of the medium was calculated using the following formula.

    Moisture content (%) = W s  - W ds  / W s

    Ws means the weight of sample and Wds means the weight of dried sample.

    The bulk density of the medium was determined using the modified core method developed by Cresswell & Hamilton (2002). A core of 100 cm3 was filled with the dried media, after which the core was pressurized under a weight of 500g for 3 min. After 3 min, the weight of the medium was measured. The bulk density of the medium was calculated using the following formula.

    Bulk density (g/cm 3 ) = M dr  / V cor

    Mdr means the weight of sample and Vcor means the volume of the core.

    The particle density was measured using a modified mass flask method (NIAST, 2000). A 100 mL Erlenmeyer flask was filled with 100 mL of distilled water and the flask was weighed. After weighing, a line was drawn to display the volume of 100 mL. Then, 5 g of the medium was placed in the blank flask and 50 mL of distilled water was poured to it. The flask was then left at room temperature for 6 h, following which, it was again filled with distilled water up to the line and reweighed. The particle density of the medium was calculated using the following formula.

    Particle density (g/cm 3 ) = {W s  / (W s  + W bw  + W bws )} × D w

    Dw represents the density of the water, Ws represents the weight of the dried sample, Wbw represents the weight of the flask with 100 mL distilled water, and Wbws represents the weight of the sample and flask with distilled water poured to the 100 mL graduation mark. Porosity was calculated using the following formula.

    Porosity (%) = {1 - (bulk density / particle density)}× 100

    3.2. Determination of chemical properties

    The electrical conductivity (EC) was analyzed in a water-soluble extract using an EC meter (Orion 3-Star Plus, Thermo Fisher Science, USA). The pH was analyzed in a suspension (1:5, v/v) using a pH meter (European Standard 13038, 1999;European Standard 13037, 1999). The organic matter of the medium was determined using the modified FCQAO method (2006). For this, 2 g of the medium was carbonized in an electrical furnace at 550 ℃, following which, the weight of the ash was measured. The organic matter of the medium was calculated using the following formula.

    Organic matter (%) = 100 - {(M dr  - M ash ) / M dr × 100}

    Mdr represents the sample weight after carbonization and Mash represents the sample weight of after carbonization.

    The media was dried in an oven dryer at 105 ℃ for 24 h to obtain the C/N ratio. After drying, the carbon and nitrogen contents of the medium were analyzed using an elemental analyzer (2400 series 2).

    The available phosphate of the medium was analyzed whilst following the Spanish version of the European standards (AENOR, 2002). The available phosphate in the medium was extracted with distilled water or CaCl2 and measured using a UV–VIS spectrophotometer at 840 nm. The cation exchange capacity (CEC) of the medium was observed using a method modified by Burt (2004) and Hendershot et al. (2008). For this, 5 g of the medium was placed in a 100 mL flask and 1N NH4OAc (50mL) was added. The mixture was allowed to react at room temperature for 30 min. After this, the mixture was filtered through a filter paper (Whatman No. 2) and the pH of the filtrate was measured using a pH meter (HI-8418, HANNA Instrument, USA). The exchangeable cations (K, Mg, and Ca) of the medium were analyzed using the modified Amrhein & Suarez (1990) method. The filtrate, obtained by the same method as used above for the CEC analysis, was analyzed using an ICP spectrometer (OPTIMA 4300DV, Perkin Elmer co., Ltd).

    4. Determination of seed germination

    On the small-scale experimental slope, the germination rate of L. cyrtobotrya for each media was measured a month after sowing. The germination rate of .L. cyrtobotrya was calculated as the number of seeds germinated relative to the number of seeds sown, based on when the root length was over 1 mm. The germination rate of the media was calculated using the following formula.

    Germination rate (%) = (N/S) × 100

    N represents the number of seeds germinated and S represents the number of seeds sown.

    5. Statistical analysis

    The values reported in this study are the means of three replicates. Analysis of Duncan's multiple range test (p<0.05) was used to determine the differences in the physical and chemical properties of each media. Pearson correlation analysis and principle component analysis (PCA) were performed through statistical program R (3.2.2 version) to identify the correlations and patterns between physical, chemical and germination of growing media.

    Result and Discussion

    1. Physical properties of growing media on the experimental slope

    Before the growing media containing woody biomass was used for greening road slopes, an experimental slope was formed for the test. Physical properties of the growing media were shown in Table 2. The experimental group using only soil showed the highest bulk density, and when mixing the growing media, it was confirmed that the bulk density was decreased according to the proportion of growing media. As the bulk density increases, the number of pores were decreased and consequently the root growth of the plant is limited (Taylor & Ratliff, 1969). Therefore, when the growing media is mixed with the soil, it is expected to have a positive effect on the growth of plant roots. Stabnikova et al. (2005) reported that the bulk density is related to the moisture, while lower bulk density is associated with higher moisture.

    Similar trends have been observed in our study. Porosity is an index related to the water transport, and is a factor influencing water retention and water permeability (Richard et al., 2001). When growing media was added, the porosity was more than 2 times higher than that of the soil (Table 2). Especially, when soil and growing media were mixed, the highest value was 63.02 %. In Table 2, it was confirmed that the moisture was also increased up to about 8 times higher than that of the existing soil when growing media was added. As a result, it is expected that the use of growing media will increase the growth of plants because it reduces the high bulk density of the existing soil and thereby increases the water retention.

    2. Chemical properties of growing media on the experimental slope

    Tables 3-5 show the chemical properties of soils and growing media on experimental slopes. Organic matter is one of the most important soil factors, because of its capacity to affect plant growth indirectly (as it improves the physical conditions of soil by enhancing aggregation) and directly (by creating a suitable environment for plant root growth) (Senesi & Loffredo, 1999). The organic matter of soil mixed with growing media and growing media were observed 37.6 % and 78.2 %, respectively (Table 3). The organic matter of soil was just 7.0 %, which is considered to be effective for plant growth to use growing media.

    Soluble salt level can be estimated by measuring the electrical conductivity of a saturated soil paste (Noguera et al., 2003). The levels of soluble salts can be determined by electrical conductivity analysis and low soluble salts level (EC < 3500 μS/cm) are preferred for plant growth (Noguera et al., 2003). Low values indicate a lack of available salinity, while high values indicate a large amount of soluble salts that may inhibit biological activity or may be unsuitable for land application if large quantities of the material are used (Moldes et al., 2007). Soil mixed with growing media and growing media have appropriate EC for plant growth (Table 3). Bunt (1988) reported that the optimal pH range of media and mixes for growing plants in containers is 5.2–6.3. The pH of soils and growing media is acidic, and hence the pH of the growing media needs to be adjusted in the future. Our goal was to create a growing media that can be applied directly to the site. As a result of analyzing the soil at the test site, it was confirmed that the existing soil was acidic. In addition, mixing the growing media with the existing soil, it was confirmed that the pH slightly increased (Table 3), and it is thought that the pH should be further improved through further studies.

    The quantity and form of nitrogen present in growing media is important in shaping the quality of the growing media (Moldes et al., 2007). The ratio of C/N is often used to assess the rate of decomposition of the growing media mixture, as it may reflect the maturity of the growing media (Moldes et al., 2007). Ozores- Hampton et al. (1998) suggested a 25:1 ratio or less to consider a growing media to be matured, and Ingelmo et al. (1998) obtained optimal results for the plant growth using different materials as a growing media and with C:N ratios around 25:1. In the present study, the C/N ratio was the highest at 30.0:1 in growing media and the lowest at 0.3:1 in soil (Table 4). Through this, it was confirmed that the growing media increases the C/N ratio, and the growing media was closest to the C/N ratio for plant growth.

    The cation exchange capacity of a growing media indicates the capability of a growing media to absorb or exchange soluble cation (Ehrlich, 1990). The soil showed the lowest cation exchange capacity at 0.59 cmolc/kg, while the growing media showed the highest cation exchange capacity at 5.94 cmolc/kg. Phosphorus is one of the major essential macronutrients for biological growth and development (Ehrlich, 1990). Available phosphate was determined as 0.1, 0.6, 2.4 mg/kg in soil, soil mixed with growing media and growing media, respectively (Table 4). Table 4 shows in C/N ratio, available phosphate and cation exchange capacity increased when growing media was used on experimental slope. Therefore, growing media containing woody biomass is considered to be effective in promoting the chemical environment suitable for plant growth.

    Out of all the mineral nutrients, potassium (K) plays a particularly critical role in plant growth and metabolism, and it contributes greatly to the survival of plants that are under various biotic and abiotic stresses (Wang et al., 2013). Magnesium is pivotal for activating a large number of enzymes for plant growth. Hence, magnesium plays an important role in numerous physiological and biochemical processes affecting plant growth and development (Bose et al., 2011). Calcium is required for cell elongation in both shoots and roots growth and development (Burstrom, 1968). The soil K, Mg and Ca were 2.3, 12.3 and 20.6 cmolc/kg, respectively, which were lower than 8.6, 18.1 and 65.8 cmolc/kg of growing media (Table 5). Then, those were found to be K of 5.7, Mg of 16.0 and Ca of 46.3 cmolc/kg in soil mixed with growing media. Hence, growing media is considered to have an effect of increasing exchangeable cation.

    3. Seed germination in growing media on the experimental slope

    Fig 1 show the rate of germination of soil and growing media on the slopes of the 40°. Germination rates of soil, soil mixed with growing media and growing media showed significant, and the highest germination rate was 13.5 % when soil mixed with growing media was used. The germination rate of soil and growing media was low, and it is expected that the pH of the soil and growing media will have an impact. Roem & Berendse (2000) reported that soil acidity is likely to be an important cause of the decline in plant growth. However, the soil mixed growing media was slightly improved in pH and other physical and chemical factors were expected that to have contributed to plant growth.

    4. Pearson correlation analysis and principle component analysis of media

    We conducted a Pearson correlation analysis to determine the correlation between each of the two variables between four physical properties, nine chemical properties, and germination rates (Table 6). Among the results, the factors affecting the germination were noted, and the factors affecting the germination were found to be particle density and pH. When particle density decreases, the number of larger pores is reduced, and the forces of the roots necessary for deformation and displacement of substrate particles readily become limiting, and root elongation rates decrease (Taylor & Ratliff, 1969). The low pH of growing media is generally associated with a low indigenous microbial population (Roem & Berendse, 2000). Therefore, particle density and pH are expected to have a positive effect on germination. In Fig. 2, principle component analysis (PCA) analyzes for each treatment were conducted to determine cluster patterns of the physical, chemical and germination of the growing media.

    As a result, the factors influencing germination were confirmed by particle density and pH, which shows the same tendency as pearson correlation. This is thought to be necessary to increase the particle density and pH in order to increase the germination of plants. In addition, the C/N ratio was confirmed to be the strongest negative correlation with the germination, it is expected that the increase of nitrogen content will be effective to increase the germination. Therefore, a process has been necessity which converts into highly effective growing media by application of lime (to add lime and increase pH) and ammonium nitrate (to add N).

    This study was conducted for pre-testing before using the growing media using wood biomass on the road slope. The germination rate was 13.5%, which was the highest when mixing soil and growing media. Correlation analysis confirmed that the positive factor affecting germination was particle density, which was improved over soil when growing media were used. As a result of identifying the patterns of growing media properties through principle component analysis (PCA), the clusters between physical and chemical characteristics were confirmed, and the germination was found to be positively affected by particle density and pH. This is the same trend as the correlation analysis, and it is expected that the particle density and pH of soil mixed with growing media had a positive effect on the germination of slope. In conclusion, soil mixed with growing media could be used for road slope greening.


    This study was carried out with the support of ´R&D Program for Forest Science Technology (Project No. "FTIS 2017091C10 1919AB01)´ provided by Korea Forest Service (Korea Forestry Promotion Institute).



    Germination of growing media on the experimental slope. Soil 100% used control, soil 50% + growing media 50% (w/w), growing media 100%. Statistically significant differences (p<0.05) are indicated with different letters above the bars.


    Principle component analysis of physical and chemical properties and germination of the media.


    Media component of soil and growing media

    Physical properties of growing media on the experimental slope

    pH, electrical conductivity and organic matter of growing media on the experimental slope

    C/N ratio, available phosphate and cation exchange capacity of growing media on the experimental slope

    Exchangeable cation of growing media on the experimental slope

    Pearson correlation analysis of physical and chemical properties and germination of the media


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