INTRODUCTION

Gladiolus (Bhattacharjee and De, 2005), known as the queen of bulb crops, is a non-cold-tolerant genus in the iridaceae family with > 150 species worldwide (Azimi and Banijamali, 2019). The genus is particularly common in South Africa and Central Europe. Approximately 250 original species are distributed across the Mediterranean coastal reg ion, and > 70 % of these species are native to South Africa (Cheong et al., 2000). In 1823, W. Colville crossed G. tristis var. concolor with G. cardinalis to produce the hybrid G. colvillei. Current varieties were formed by hybridization between wild Gladiolus spp., and more than 10,000 varieties have been developed and used for cut flowers and flower beds. Cut gladiolus flowers rank eighth in the global flower market, and the bulb ranks first in South Korea (Pragya et al., 2010). Since 2006, the Tae-an region has adopted domestic gladiolus bulb propagation and cut flower cultivation (Koo et al., 2013), and more than one million bulbs have been harvested. The flower market has remained profitable, and the number of growers has increased. Recently, the domestic production area of bulbs and roots has increased by 218 % (from '20 to '21) (MIFAFF, 2022), and bulbs and cut flowers account for 16 % of the total area and 25 % of the production value. The distribution rate has steadily increased since the establishment of a domestic variety distribution system. In domestic, gladiolus varieties are continuously developed and efforts that being made to commercialize. The Gladiolus ‘White and Cool’ was developed in 2002 and excellent growth as a variety suitable for the domestic environment. It is the most widely distributed among domestic varieties and recognized for its marketability. The gladiolus is produced through asexual propagation and is therefore difficult to cultivate (Moradiashua and Azimi, 2017); moreover, it is a crop that requires a high amount of light and is mainly cultivated in open fields (Sakamoto, 1994). The production and distribution rates are high, but the inflorescences and self-propelled bulbs are harvested manually using aging workforce. Therefore, management costs are high because of excessive labor costs and severe bulb loss. Although there are excellent domestic cultivars, the number of bulb producers is decreasing due to difficulties in cultivation conditions, and most of the bulbs are imported. Therefore, there is an urgent need to improve harvesting techniques to save labor (Lee, 2021). This study compared the conventional soil cultivation with the net cultivation, which involves laying a soothing net on the soil after planting to reduce the labor input, inflorescences, and self-loss rates.

MATERIALS AND METHODS

Plant materials

To investigate the effect of the net cultivation on gladiolus seedling bulb production, the domestic cultivar Gladiolus ‘White and Cool’ was studied at a gladiolus cultivation farm located in Bangok-ri, Taean-eup, Taean-gun, and Chungcheongnam-do.

Cultivation

A planting area of was created in the open field farm Tae-an Chungcheongnam-do, and seedlings for bulb production were planted in each 2,000 m² area using the net and conventional cultivation methods. Flowering bulb as a diameter of 1.5-2 cm were planted at 10 × 10 intervals, and breeding bulbs were planted by stripe seeding 2kg in rows in 1 m². Planting was carried out in mid-March. The cultivation nets were obtained from Daewon Industrial Co., Ltd., located in Goryeong-gun, Gyeongsangbuk-do. A net size of 3 mm × 3 mm was used for an area of 2.4 m wide and 50 m long. To use the net as ground coverage for a 2.4 m wide area, it was folded in half and used at a width of 1.2 m.

In the main field, 1.2 m × 50 m × 23 rows of flat furrows were formed, and cuttings were placed between two layers of netting before being covered with soil (Fig. 1). Next, the relevant parameters were measured once a month for four months from July 9th. The study parameters included the number of leaves, shoot height, bulb height, bulb weight, bulb caliber, number of seedling bulbs, labor input time, and yield (flowering and seedling bulbs).

Statistical processing

Analysis of variance (ANOVA) was performed using Statistical Analysis System (version 9.4; SAS Institute Inc., USA). Significance between each treatment was determined at the 5 % level using Duncan's new multiple range test.

RESULT AND DISCUSSION

Comparison of growth under net cultivation and conventional cultivation

The above-ground growth of the gladioli was slightly higher with net cultivation than with conventional cultivation during the early period. Similar observations were made during the third survey period (Fig. 2_A). Plant growth rate was slightly higher during net cultivation from the beginning to the third survey period; however, there was no significant difference (Fig. 2_B). Leaf width and stem thickness did not differ significantly at any growth stage (Fig. 2_C and D). There were no significant differences in leaf number, shoot length, leaf width, or stem thickness, regardless of the growth period. There were no differences in the growth rates of the aboveground parts between the two cultivation methods. However, in both the control and treatment groups, growth was poor because of drought and inadequate nutrient supply to the above-ground parts (summer stress). To reduce stress on the above-ground parts, different strategies, such as shading treatments (Lee et al., 2001), have been adopted. This is thought to be related to the failure to maintain soil moisture owing to the shallow planting depth (Choi et al., 1997). The soil cover cultivation method, which is mainly used to maintain soil humidity and control the temperature, is known to be effective in increasing yield; however, growth characteristics reportedly differ depending on the characteristics of the covering materials and crop varieties (Kim et al., 1996). In this study, the covering cultivation method was conducted using a netting material that maintained air permeability, unlike P.E. There was no difference between the general open-field cultivation method and the amount of growth. This showed the potential of the use net cultivation as an efficient cultivation method that can maintain existing growth and save labor during harvest.

There were no significant differences between conventional and net cultivation in terms of the number of seedling bulbs, bulb diameter, bulb height, and bulb weight; however, below-ground root development was low under the net cultivation owing to the influence of the net. The number of seedling bulbs was higher under conventional cultivation than under net cultivation, and the population was slightly higher under net cultivation (Fig. 3 and 4). Because there was no difference in the growth of the above-ground parts in the previous results, it is possible to harvest even small bulbs during net cultivation, thus reducing the rate of bulb loss. Labor input costs may be decreased through time reduction.

Comparison of yield between net cultivation and conventional cultivation

To compare the yields between net cultivation and conventional cultivation, the labor input time, flowering bulb yield, and seedling bulb yield were determined (Fig. 5). Seedling bulbs were measured based on the criterion for a flowering sphere, which is a circumference of 6 cm. The results of the survey showed that the labor input time per unit area under conventional cultivation was 2.5 fold higher than that under net cultivation. Moreover, under net cultivation, the yield per unit area was 2.5 % and 27 % higher for flowering bulbs and seedling bulbs, respectively, than that under conventional cultivation (Table 1). Based on the harvest of the 2,000 m² area, the total labor input time per person was 414 h for conventional cultivation and 161 h for net cultivation, indicating a 2.57-fold reduction under net cultivation. The yields in the flowering zones for net and conventional cultivation were 1,587 kg and 1,541 kg, respectively, indicating a 3 % increase under net cultivation. The yield of seedling bulbs increased by 28 % to 943 kg during net cultivation and was 736 kg during conventional cultivation (Fig. 6).

Studies have been conducted on bulb cultivation, planting density (Ko et al., 2011), planting period (Yoo and Roh, 2014), seedling size, and planting distance (Yoo at al., 2009;Song et al., 2014). The results of these studies have led to an increase in the production of bulbs; however, as the production volume increased, more traditional manpower was required, resulting in an increase in management costs and severe bulb loss due to excessive labor costs. Therefore, improvement in harvesting work became essential. A study on a cultivation method using a net confirmed that the harvest time can be reduced while increasing the yield and not affecting the growth.

Matters to be considered when cultivating under nets in the future include finding or manufacturing and using dedicated nets to replace poor nets that prevent root development. In addition, early rooting of the children's spheres should be induced by removing the space between the net and the soil by compacting and irrigating the area after the installation is completed.

적 요

글라디올러스의 노지재배 시 수확량을 증대시키고 노동투입 시간을 줄이기 위해 기존 토경 재배와 그물망 재배를 통한 효 과를 비교하고자 국내 육성 품종 ‘화이트앤쿨’을 대상으로 태 안에 위치한 재배 농가에서 실험을 실시하였다.

주요어: 국산품종, 노지재배, 무성번식, 생산량, 자구 수확량