The importance of urban greening is rising gradually due to industrialization and urbanization and the demand for landscape plants is increasing amid growing interest in urban greening. Among such landscape plants, landscape trees accounted for 676.9 billion KRW which was approximately 92% of 736 billion KRW for the total production amount of landscape construction materials as of 2015 (KFS, 2016), and the domestic output of landscape plants has increased by approximately 66.5% for the last 10 years from approximately 47.13 million trees in 2005 to approximately 78.46 million trees in 2015 (KFS, 2006; KFS 2016). Due to an increasing demand of landscape trees, the production technology enabling timely mass production and management and the standardization for efficient distribution and field application are required (Kwon et al., 2016).

Meanwhile, trees grown in a container can be planted without damage to the belowground, so it is possible to reduce the defect rate due to less seasonal restrictions, produce standard seedlings (Cho, 2014), and save tree digging costs significantly. For these reasons, this is being researched as an alternative plan for stable supply of landscape trees. For studies regarding the container nursery of landscape tree, Kim and Kim (1999) carried out a study comparing the production cost according to the container production method and openground production method, and Park (1999), Kang (2008), Kim and Kim (2000), Lee (2002) and Yoon and Hong (2002) carried out studies regarding the material or size of container and growth. Cho (2014) also researched differences in the growth according to the nursery methods including the ground surface, aboveground, semiunderground and underground nursery methods. However, domestic studies on container nursery have relatively short history in comparison to the container nursery technologies in advanced countries (Son, 2013), and there is a lack of studies regarding a proper amount of fertilizer for each tree species that can be actually applied in container nursery.

A proper amount of fertilizer directly affects the growth of tree (Kimmins, 1997), and if proper fertilization treatment is not made in case of container nursery, the deterioration of seedling quality due to insufficient amount of fertilizer and environmental pollution problems due to leachate may occur (Hwang et al., 2013). The response to fertilization treatments varies with species, and it is significantly influenced by the level of fertilization treatments (Kwon and Lee, 1994; Hwang et al., 2003; Sung et al., 2011). Studies about the fertilization treatments of trees have been carried out by Kwon et al. (2009), Cho et al. (2011) and Han et al. (2016) but these studies mainly focused on container seedlings based on the container nursery system.

In this experiment, the growth characteristics of Crataegus pinnatifida which was known to have landscape value (Kang et al., 2002) and frequently used for urban greening were investigated with different fertilization level for stable supply of mature landscape trees for urban greening using Multifeed-20 (N:P:K＝20:20:20), one of composite fertilizers. The result of this study can provide information regarding a proper amount of fertilizer required for growing Crataegus pinnatifida in a container including efficient amount of fertilizer for maximum growth, and environmental and economic feasibility of fertilization treatment. It also can be utilized as preliminary data for standardized quality management of landscape tree.

In order to confirm the growth of Crataegus pinnatifida according to the fertilization level, the growth amount was compared and evaluated by measuring the tree height and root collar diameter (Table 2). The tree height and root collar diameter growth amount of Crataegus pinnatifida were significantly different in four different fertilization treatment levels (p<.05). And the fertilization treatments showed approximately 2~3 times larger in tree height and root collar diameter growth amount compared to the control treatment. However, the aspect of growth amount increase varied by the fertilization treatment level, and 0.5 g･L ^-1 and 1.0 g･L ^-1 treatments with less amount of fertilizer showed the largest tree height growth amount than 2.0 g･L ^-1 treatments with the largest amount of fertilizer, and 1.0 g･L ^-1 treatment showed the largest root collar diameter growth.

Similarly, the dry weight of aboveground and belowground was higher in order of 1.0 g･L ^-1 ＞ 0.5 g･L ^-1 ＞ 2.0 g･L ^-1 ＞ the control treatment (p＜0.05). In the result of Duncan’s multiple range test, 1.0 g･L ^-1 treatment showed the highest dry weight. This result is similar to the result of studies conducted by Kwon et al. (2009) and Cho et al. (2011), and excessive amount of fertilizer deteriorated the growth.

There is no significant difference in the H/D ratio between treatment levels (p＞.05), but 1.0 g･L ^-1 treatment and 2.0 g･L ^-1 treatment showed a relatively low H/D ratio. H/D ratio enables the judgment of healthiness of tree (Cho et al., 2011), and it is known that a high H/D ratio means that the seedling is vulnerable to damages by exposure to wind, drought and frost (Roller, 1977). Therefore, 1.0 g･L ^-1 treatment and 2.0 g･L ^-1 treatment with lower H/D ratio were relatively healthier than the control treatment and 0.5 g･L ^-1 treatment.

The T/R ratio calculated based on the dry weight of aboveground and belowground was higher in order of 2.0 g･L ^-1 ＞ 1.0 g･L ^-1 ＞ 0.5 g･L ^-1 ＞ the control treatment, but a quantitative difference was below 1 g, indicating that there was no significant difference (p＞.05).

The fertilization treatments showed the higher seedling quality index (SQI) of Crataegus pinnatifida seedling compared to the control treatment (p＜.05), and as the result of Duncan’s multiple range test, 1.0 g･L ^-1 showed the best traits, which was approximately 4~9 times higher in comparison to other treatments. This shows a similar trend with the result of growth characteristics such as growth amount and dry weight, and the seedling quality index was high due to low H/D ratio and high dry weight (Bayala et al., 2009).

The growth of trees according to the nutrition composition in soil affects various physiological responses as well as the growth amount and biomass of seedling, but it also affects photosynthesis, which is the final metabolite eventually (Lee et al., 2006). Meanwhile, chlorophyll content which is closely related to the rate of photosynthesis is also related to nitrogen content, so SPAD value which indicates nitrogen content indirectly is also presented as chlorophyll content (Loh et al., 2002; Yoon et al., 2005; Lee, 2007). In this experiment, the trend of chlorophyll content which was closely related to the rate of photosynthesis was measured at intervals of 30 days by the fertilization level for each period including early stage, middle stage and late stage (Table 3). As the experiment result, a statistically significant difference was shown in the SPAD value according to 4 fertilization treatment levels for all periods (p＜.05), and as a result of Duncan’s multiple range test, 2.0 g･L ^-1 treatment showd the highest SPAD value (Fig. 2). This shows a similar trend with the result of study carried out by Kang et al. (2010), and as the amount of nitrogen fertilizer increased, the SPAD value which indicates the ratio of nitrogen content indirectly also has increased. However, when comparing the SPAD value measured from the fertilization treatments in this experiment with the SPAD value measured by Kang (2003) and Kang et al. (2010), it is considered that the SPAD value of all fertilization treatments except for the control treatment is relatively high. And, a difference in the SPAD value between fertilization treatments in the late stage was approximately below 2~4, indicating that the actual effect on the rate of photosynthesis would be insignificant. Also, Piekielek et al. (1995) and Kim et al. (2005) reported that the SPAD value could be utilized as an indicator for nitrogen content rather than the relevance with growth characteristics. The reason that 2.0 g･L ^-1 treatment with the largest amount of nitrogen fertilizer showed a higher SPAD value but relatively lower growth, seedling healthiness and quality index than 1.0 g･L ^-1 treatment with a half the amount of fertilizer would be deteriorated growth due to excessive nitrogen. A proper amount of nitrogen can promote the growth of tree but an excessive amount of nitrogen may cause deteriorated growth, environmental pollution, disease and insect damage and storm and flood damage (Kim et al., 2006).

In summary, the treatment showing the maximum growth effect in comparison to the minimum amount of fertilizer for the growth of Crataegus pinnatifida in a container is 1.0 g･L ^-1 , and this is a proper amount of fertilizer by considering the environment and economic feasibility. In this way, the fertilization level is not always proportional to the growth, and the management and field application for mass production of landscape trees require a proper fertilization treatment for each type of tree. In addition, a study regarding proper container nursery system for landscape trees including proper soil, watering system and container is also required.

A proper nursery system for each tree such as soil, nutrition and watering system is required for efficient production of landscape trees growing in a container used for urban greening and gardening. In this experiment, the growth characteristics of Crataegus pinnatifida including growth amount, biomass, seedling healthiness (H/D ratio), T/R ratio, seedling quality index (SQI) and chlorophyll content (SPAD Value) with four fertilization treatment levels (0, 0.5, 1.0, 2.0 g/L) was investigated and analyzed to find the economical, eco-friendly and proper amount of fertilizer that could show the maximum growth effect in comparison to the minimum amount of fertilizer.

There were significant differences in the tree height and root collar diameter growth amount, dry weight of aboveground and belowground of Crataegus pinnatifida according to the fertilization treatment level. 1.0 g･L ^-1 treatment showed an excellent result. In the case of height/root collar diameter (H/D) ratio and top/root (T/R) ratio, there were no significant differences between the treatments.

The SQI of Crataegus pinnatifida was significantly different in four different fertilization treatment levels, and 1.0 g･L ^-1 treatment showed approximately 4~9 times better traits than other treatments. The SPAD value was measured for each period including early stage, middle stage and late stage, and there was a significant difference in the SPAD value in all periods according to the fertilization level. 2.0 g･L ^-1 treatment showed the highest SPAD value. However, 2.0 g･L ^-1 treatment showed more poor tree growth and seedling quality index than 1.0 g･L ^-1 treatment, which contained a half the amount of fertilizer, indicating that excessive amount of nitrogen fertilizer was supplied, deteriorating the growth of trees.

To sum up the result of this experiment, a difference in the growth according to the fertilization level was confirmed from growing Crataegus pinnatifida in a container, and 1.0 g･L ^-1 treatment showed the best growth in comparison to the treatment with the largest amount of fertilizer. Therefore, 1.0 g･L ^-1 treatment showed the maximum growth effect in comparison to the minimum amount of fertilizer, and this is a proper amount of fertilizer by considering the environment and economic feasibility.