Effects of Biomaterials Mixed with Artificial Soil on Seedling Quality of Fraxinus Rhynchophylla in a Containerized Production System

Abstract

The composition of artificial soil in a containerized seedling production plays an important role in seedling quality as well as environmental issues. We investigated the effects of different types of biomaterials and mixed ratio with artificial soil on the growth of Fraxinus rhynchophylla seedlings. Soil medium was supplemented with 3 levels (0%, 10%, 20%) of pine bark, mushroom sawdust and rice husk. Root collar diameter (RCD), height growth, and biomass have significantly increased when rice husk was applied. Compared with the control, RCD and height growth showed highest in 20% rice husk treatment with an increase of 5.7% and 17.6%, respectively. In contrast, the treatments of pine bark and mushroom sawdust showed lower results in growth parameters (RCD, height growth, and total biomass) than control. Seedling quality index was also highest at the 20% rice husk treatment, but there was not statistically different among treatments. Our results suggested rice husk can be substituted up to 20% of substrates for containerized F. rhynchophylla seedling production system.

Introduction

Use of containers is one of efficient methods to produce nursery crops (Simmons and Derr 2007). Cultivation by container production has many advantages, including less damage occurring to the root system when transplanted, helping seedlings establish better after transplanting, decreased labor and land acquisition costs for production, increased product availability and longevity (Mathers et al. 2007). A growing media, which is one of the critical influences in a containerized seedling production, can contain two or more materials, rather than a single ingredient. Highly valuable materials such as soil, peat, sand, perlite and vermiculite are generally used as substrates (Tinus and McDonald 1979; Landis et al. 1990). These substrates help to hold on adequate air space and the water-holding ability during plant production so that growing conditions remain advantage for plant growth (Jackson et al. 2009).

The mixed of the materials in artificial soil in a containerized seedling production plays an important role in changing the soil properties as well as economic values. Nowadays, many recycled organic materials used in the greenhouse production are tree barks, composted yard, garbage and animal wastes, rice and peanut husk, mushroom compost, and cotton gin trash (Li et al. 2009). The use of these materials as soil amendments to achieve benefits in terms of plant performance and soil amelioration have been studied in the recent years and good effects have been obtained (Garg et al. 2005). For example, rice husk is the main by-product of agriculture from rice milling industry, covering about one-fifth of the harvested weight of rice crops (Beagle 1978), which improves not only crop performance but also soil physical properties (Anikwe 2000). Similarly, pine bark is a common and popular substrate in container production (Guerrero et al. 2002; Warren and Bilderback 2004), which provides good aeration and has a higher ability to absorb cations than the field soil (Simmons and Derr 2007). Besides, mushroom sawdust has been identified as an alternative to peat to protect environment, conserve natural resources and reduce nutritional requirements of seedlings and containerized plants (Medina et al. 2009; Eudoxie and Alexander 2011).

Some biomaterials, such as bark, rice husk, mushroom sawdust, have been used in agricultural field, but rarely used in forestry nursery. The purpose of this study was to investigate the effects of mixing materials with different ratios on the growth and quality of Fraxinus rhynchophylla in a containerized seedling production system. This research can extend our knowledge on which and how much biomaterial should be applied for F. rhynchophylla to obtain the most effective result in containerized production system.

Materials and Methods

Study site and species

Our study was implemented in a greenhouse with a total area of 728 m2 at Forest Technology and Management Research Center, in Pocheon, Republic of Korea (37°45′N, 127°10′E). This is an automatic greenhouse facilitated with fertilization, irrigation, ventilation and environmental control system. The mean temperature was 13.8°C and the mean relative humidity was 65.5% in 2017.

F. rhynchophylla seeds used in our study were germinated in nursery during early March 2017 and transplanted to the cells of tray in late March 2017.

Experimental design

Seedlings were grown in cells of the tray, which has the size of 32 cm×40 cm with 20 cells. Tray’s cells are cylinder with 6.8 cm in diameter and 15 cm in depth and have a volume of 400 mL.

We used mushroom sawdust, pine bark and rice husk as three biomaterials in the current study. Pine bark was delivered from Wood Distribution Center in Donghae city, Gangwon province; mushroom sawdust was from Forest Mushroom Research Center in Yeoju city, Gyeonggi province; and carbonized rice husk was purchased from the market. The materials were then pulverized using a pulverizer with mesh size of 2 mm in factory of department of Biobased Materials at Chungnam National University, Daejeon, Republic of Korea. The cells were filled with artificial soil, which was mixture of peatmoss, perlite, vermiculite at a ratio of 1:1:1 by volume, following the recommendation for growth of tree seedlings in a containerized seedling production system (Landis et al. 1990). The physical and chemical properties of mixed biomaterials with growing media such as pH, EC and bulk density were shown in Table 1.

Table 1. The physical and chemical properties of three biomaterials after mixing with artificial soil (Aung et al. 2019; Seo et al. 2019)

The 3×3 combined experimental design was applied to test the effects of three different biomaterials and three mixed ratios on growth and quality of F. rhynchophylla seedlings. Soil was supplemented with 0% for the control, 10% and 20% in volume of each biomaterial. The control treatment was set with full artificial soil in volume of 400 mL. The treatments of 10% mixed biomaterial were established by mixing 40 mL of pine bark, mushroom sawdust or rice husk with 360 mL of artificial soil. To get 20% mixed ratio, 80 mL of three biomaterials was incorporated with 320 ml of artificial soil. Each treatment was replicated five times in a completely randomized design. After artificial soil was mixed with different ratios of three biomaterials, F. rhynchophylla seedlings were transplanted into the cells in late March 2017. The trays were then put on a platform, which was elevated 60 cm above the greenhouse floor.

Growth measurements

We measured seedling growth in response to each treatment during August and October 2017. The innermost 6 seedlings were chosen from each tray as samples for growth measurement. Height was measured from the base to the tip of the highest branch of sample seedlings. Digital caliper was used to measure the root collar diameter of the seedlings from 1cm above the ground. Height was measured in cm and root collar diameter in 0.01 mm (Thompson and Schultz 1995). Seedlings were harvested in October and separated to root, stem and leaf. Roots were washed in clean water to remove all soil particles. Then, all parts of seedlings were dried at 65°C for 48 hours to constant weight. After that, aboveground and belowground dry weights were recorded. We used the method suggested by Sestak et al. (1971) to calculate total mass production and ratio of aboveground to belowground biomass.

Quality index calculation

The Dickson quality index−DQI (Dickson et al. 1960) was used as a tool for evaluating seedling quality and calculated as follows:

(D Q I=S D) /(H D+S R)

where SD is seedling’s total dry weight (g), HD is the ratio of seedlings height (cm) to root collar diameter (mm), and SR is the ratio of shoot weight (g) to root dry weight (g) (Deans et al. 1989; Binotto et al. 2010; Cho et al. 2017). 

Statistical analysis

Two-way analysis of variance (ANOVA) with Duncan’s multiple comparison tests was applied to analyze the effects of biomaterials with mixing ratios on seedling height, root collar diameter, total dry weight, and quality index measured in October 2017. All probabilities were tested at a significance level of 0.05.

Results

Seedling height

The seedling height was significantly influenced by biomaterials and mixed ratio (p＜0.05). The height was highest at 20% rice husk followed by control, mushroom sawdust 10%, pine bark 10%, rice husk 10%, mushroom sawdust 20% and lowest at 20% pine bark (Fig. 1).

 

Fig. 1. Height growth of Fraxinus rhynchophylla applied with 3 biomaterials and 3 mixed ratios in a containerized seedling production system.

Root collar diameter

Root collar diameter followed the same trend with seedling height with highest F. rhynchophylla diameter observed in treatment applied with 20% rice husk. The lowest root collar diameter was resulted in 20% mushroom sawdust and 20% pine bark treatments (Fig. 2).

Fig. 2. Root collar diameter growth of Fraxinus rhynchophylla applied with 3 biomaterials and 3 mixed ratios in a containerized seedling production system. Different letters represent significant differences (p ＜ 0.05) between treatments. Vertical bars represent one standard error of the mean (n=5).

Seedling biomass

The amount of leaf, stem, and root dry biomass showed highest at 20% rice husk treatment followed by control treatment with 46.4 and 44.2 g/tree, respectively. Total dry biomass was observed to be lowest at 20% mushroom sawdust treatment. There was no difference showed among other treatments (Fig. 3).

 

Fig. 3. Total dry weight of Fraxinus rhynchophylla applied with 3 biomaterials and 3 mixed ratios in a containerized seedling production system. Different letters represent significant differences (p ＜ 0.05) between treatments. Vertical bars represent one standard error of the mean (n=5).

The highest proportion in the root biomass was shown at 20% rice husk treatment with an increase of 10.6% compared with control indicating that root system was developed well in this treatment (Table 2).

Table 2. Leaf, stem, root dry weight and biomass allocation of Fraxinus rhynchophylla applied with 3 biomaterials and 3 mixed ratios in a containerized seedling production system. Parentheses represent one standard error of the mean (n=5)

^aR/S ratio: Root to shoot ratio; ^bL/A ratio: Leaf to aboveground ratio.

Seedling quality index

Quality index of F. rhynchophylla was ranged from 9.1 to 11.2. The highest one was shown at 20% rice husk, followed by 20% pine bark and lowest at 20% mushroom sawdust, but there were no statistical differences among treatments (Fig. 4)

 

Fig. 4. Seedling quality index of Fraxinus rhynchophylla applied with 3 biomaterials and 3 mixed ratios in a containerized seedling production system. Different letters represent significant differences (p ＜ 0.05) between treatments. Vertical bars represent one standard error of the mean (n=5).

Discussion

In our study, treatments of biomaterials and mixed ratio are significant for most measured parameters on F. rhynchophylla seedlings (Figs. 1-4). All the measured parameters (height, root collar diameter, total biomass, and seedling quality index) consistently showed the highest results in 20% rice husk treatment. Our findings are in agreement with Mori (1994), who reported that charcoaled rice husks could induce the growth of Scleroderma sp. seedlings substantially in the nursery.

It was reported that transplant shock in spruce plantations can be equal to 1 or 2 years of growth loss in planted spruce seedlings (Vyse 1981), so reduction of transplant shock is necessary for better survival and growth of seedlings. Jacobs et al. (2005) reported positive relationships between seedling root biomass and field performance. In our study, we observed highest root biomass (16.7 g/tree) in 20% rice husk treatment, which can be expected best field performance. Evans and Gachukia (2007) verified that fresh rice hulls could be used to provide drainage and air-filled pore space which can lead to better root growth. Sambo et al. (2008) indicated that all of the ground rice hulls had a higher air-filled pore space than peat from 10% to 20% (Bunt 1988; Jenkins and Jarrell 1989) or at least 45% (Boertje 1984). Rose et al. (1991) reported same results with our finding that seedlings with larger root-volume category (＞13 cm3 ) resulted significantly greater height growth than those with smaller category (＜9 cm3 ) in a study using Douglas-fir (Pseudotsuga menziesii).

Mattsson (1997) signified that there are two types of seedling quality assessment: morphological and physiological, in which morphological quality is based on height, stem diameter, root mass, shoot mass, and shoot: root ratio, whereas physiological quality is based on the internal functions of seedling (for example: water potential, mineral nutrition). Growing plant in containers can change growth, function and morphology of root systems (Mathers et al. 2007). Even though seedlings’ height and root collar diameter are commonly evaluated features in seedling quality, aboveground morphology is not always an exact predictor of performance after out-planting (Chavasse 1977). Belowground parts can usually be assessed as more accurate indicator for seedling quality (Davis and Jacobs 2005). Our study resulted highest in both above and belowground biomass in 20% rice husk treatment, and consequently, quality index too. Better growth of belowground parts (root system) could adapt well in new environment, leading to successful establishment of forest plantations. To adapt and establish well in initial year of planting is the most important factor for survival of seedlings in the field. Lordan et al. (2013) stated soil amendment with rice husk substrate enhanced soil conditions, supporting a better soil environment for root activity and thereby resulted in better plant performance. Our study can conclude that 20% rice husk treatment to be the best for out-planting of F. rhynchophylla seedlings.

Conclusion

We suggest to apply 20% rice husk to growing media for F. rhynchophylla in order to improve seedling quality, which can translate better survival and performance of transplants for successful forest restoration. Further research for mixing biomaterials to growing media should concentrate on using 20% rice husk mixed ratio to different tree species other than F. rhynchophylla, because interesting outcomes could be resulted due to different nature of tree species.