Research on growth and development capacity and technical measures to increase productivity and quality of some imported orchid varieties cattleya, dendrobium, oncidium for Northern Vietnam

rotting but poor water retention, roots often dry out [15].

- Fern: This type of substrate is never covered with moss and has good moisture absorption. However, if not mixed with other substrates, the orchid pot can easily become waterlogged, causing the orchid root tip to rot [37].

- Seaweed: Seaweed is used quite commonly in the cultivation of orchids today in the world as well as in Vietnam. Hoang Ngoc Thuan (2000) [37] believes that seaweed has the advantage of retaining moisture very well, being light, soft, convenient for transporting large quantities of orchid pots, especially for industrial orchids such as Phalaenopsis , Cattleya, Oncidium, Rhynchostylis and some newly emerged orchid species .

Orchid growers in the United States have applied the following formulas for mixing substrates for some orchid species (quoted by Cao Thi Cham (2011) [4]):

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Substrate for Cattleya: Medium pine bark 6 parts + Large coconut shell 2 parts + Green stone or porous stone 2 parts + Pumice stone 1 part + Red pine wood ½ part.

Substrate for Dendrobium: Medium pine bark 4 parts + Large coconut shell 2 parts + Green stone or porous stone 4 parts + Red pine wood ½ part.

Substrate for Oncidium: Medium pine bark 6 parts + Large coconut shell 2 parts + Small stick 1 part + Pumice stone 1 part + Red pine wood ½ part.

According to Viet Chuong, Nguyen Viet Thai (2001) [5] and Nguyen Cong Nghiep (2000) [31], charcoal, bricks, coir, coconut fiber, water hyacinth roots, and pine bark can be used to grow orchids. These are materials that are easy to find in Vietnam. One type of substrate or a mixture of the above substrates can be used to grow orchids depending on the specific conditions of each region, each orchid species, and the age of the orchid.

Nguyen Thi Kim Ly (2009) [28] concluded that for Cattleya orchids in the later stages of tissue culture, the most suitable substrate is crushed charcoal and coconut fiber because at this stage the plant has not fully adapted to autotrophic conditions, the roots are still weak, the ability to absorb water and nutrients is poor, so choose light substrates that retain moisture well. For plants 8 months old or older, it is possible to combine several types of substrates in proportions suitable for each growing condition. In the North, under sheltered conditions, 100% poplar roots can be used.

slag, or charcoal, volcanic ash mixed in a 2:1 ratio for planting. In winter and dry season, adding a thin layer of moss on the surface of the pot will help the plant grow better.

Pham Thi Lien (2010) [21] when studying the effect of substrate on the growth and development of Dendrobium orchids concluded that the substrate of charcoal + coconut fiber in a ratio of 1:1 helps the plant grow and develop best.

In 2011, Cao Thi Cham [4] studied the effect of substrate on the growth and development of Cattleya Ronald orchids in the seedling and mature stages. The author confirmed that the most suitable substrate for Cattleya Ronald in vitro is coconut fiber, although the rooting time is slower when using seaweed substrate, the plant grows more stably. The planting substrate also strongly affects the growth, development and flowering of Cattleya Ronald in the mature stage, especially the formation and development of the root system. The suitable substrate for growing Cattleya Ronald in the mature stage is 30% charcoal + 30% fern + 40% coconut fiber. This type of substrate helps drain water well but still ensures the necessary humidity for the plant to grow well.

Researching on growing media for Dendrobium orchids in Thu Duc - Ho Chi Minh City, in 2007, Huynh Thanh Hung [13] showed that the nutritional content in growing media mixed from vermicompost with different materials is higher than using charcoal and is suitable for the growth and development of Dendrobium orchids . Among the mixed growing media, vermicompost mixed with coconut fiber, water hyacinth roots, and coconut husk gives Dendrobium orchids the best growth. When mixing materials together, you should use Gelatin adhesive. Growing Dendrobium orchids can use one of three types of growing media such as: 70% vermicompost + 30% coconut fiber; 70% vermicompost + 30% water hyacinth roots or 70% vermicompost + 30% coconut husk with Gelatin adhesive.

In order to determine the best growing medium for Dendrobium hancockii Rolfe orchid, Vu Ngoc Lan and colleagues (2010) [19] grew the above orchid species in 3 different growing mediums: longan wood, charcoal and coconut fiber. The results showed that longan wood is the most suitable for Dendrobium hancockii Rolfe orchid in the mature stage.

* Fertilizer research

Based on the import, testing and evaluation of the varieties, combined with breeding. The Department of Mutation and Hybrid Advantage - Institute of Agricultural Genetics has proposed measures on substrate, fertilization, care techniques... Nguyen Thi Kim Ly (2009) [29] said that orchids should be watered with fertilizer in the early morning or cool afternoon, not at noon. Normally, watering is done once a week, if the orchid garden is cool, the interval is longer, 10 - 15 days/time. On the contrary, orchid gardens with lots of light can be watered twice a week. After watering with fertilizer, the amount of water should be increased the next day to wash away the remaining salt that can have adverse effects on the orchid.

According to Nguyen Xuan Linh (2005) [26], orchids need fertilizer but cannot tolerate high concentrations of nutrients, so fertilizing orchids must be done regularly and it is best to spray fertilizer through leaves. The concentration and dosage depend on the age and development period of the orchid. For orchids under 6 months old, spray N:P:K fertilizer type 30:15:10 at a concentration of 500 ppm (0.5 g/l) every 7 days. For orchids 6 - 12 months old, spray N:P:K fertilizer type 30:15:10 at a concentration of 2000 ppm (2 g/l) every 7 days. For orchids 12 - 18 months old, spray N:P:K fertilizer type 10:30:20 at a concentration of 3000 ppm (3 g/l) every 7 days. When the flower buds appear, spray N:P:K fertilizer type 15:20:25 with a concentration of 2000 ppm, water every 7-10 days. The flowers will be plumper, more durable and have a characteristic color. When the flowers are about to fade and the plant shows signs of weakening, immediately cut the flower branches and water with N:P:K fertilizer (30:10:10) to nourish the plant for the next flowering season.

During the growing period, Oncidium should be fertilized regularly. From spring to early autumn, Oncidium should be fertilized once every 7 days , and from late autumn to winter, fertilized once a month. The fertilization formula must be suitable for the substrate environment. Use Growmore fertilizer for fern, charcoal, coconut fiber substrates and fertilizer with a ratio of N:P:K = 30:10:10 for bark substrates. As with most orchids, Oncidium is very sensitive to fertilizers with high salt concentrations. The plant especially likes organic fertilizers such as fish emulsion or green manure [120].

Nguyen Cong Nghiep (2000) [31] concluded that during the growth season of Cattleya, Dendrobium, Oncidium orchids in particular and orchids in general, synthetic fertilizers with N:P:K ratio of 30:10:10 should not be used. When the flowers begin to bloom, fertilizers with high concentration should be used.

High phosphorus content for characteristic flower color such as N:P:K fertilizer 10:20:20 or 6:30:30. Before the orchid enters the dormant season, use fertilizer with high potassium concentration to increase endurance such as N:P:K fertilizer 10:20:30. Also according to Nguyen Cong Nghiep, fertilizer concentration should not exceed 1 g/liter of water because it will cause the orchid to die or degenerate. Foliar fertilizer in the form of mist spray is very effective.

According to Nguyen Hac Thuy (2001) [38], foliar fertilizers include chemical fertilizers (inorganic), organic fertilizers (animal and plant residues, etc.) and organic fertilizers derived from EDTA and hydrolyzed amino acids from protein-rich organic substances (pomior fertilizer). The author has determined that fertilizers with a high nitrogen ratio (30:10:10) are suitable for seedlings, plants that are sprouting new buds, and plants after cutting flowers. Fertilizers with a high phosphorus ratio (6:30:30) stimulate root and flower growth, make leaves less green, reduce the amount of water in the leaves, and increase the plant's resistance. Fertilizers with a high potassium ratio (10:20:30) help plants stay healthy, resistant to drought, pests, and diseases. Compared to other crops, orchids need a relatively large amount of potassium because the main purpose of orchid cultivation is to enjoy flowers. Potassium helps flowers have beautiful, long-lasting colors, and fertilizers with a potassium ratio are often used when orchids flower.

Viet Chuong and Nguyen Viet Thai (2002) [5] determined the appropriate N:P:K fertilizer ratio for each growth stage of orchids such as N:P:K type 30:10:10 promotes good growth and leaf growth of orchids. Type 10:20:10 is effective for fertilizing orchids to flower. Type 10:10:20 promotes good root growth of orchids. Type 10:20:30 increases the endurance and resistance of orchids.

According to Pham Thi Lien (2002) [20], fertilization often focuses on the three main elements N, P, K with many ratios depending on the purpose of use, orchid species, and orchid growth period. In addition, trace elements such as copper (Cu), iron (Fe), zinc (Zn) ... and some other necessary vitamins can also be combined. However, in water orchids, approximately 90%, only 2% are mineral elements, so if too much fertilizer is applied, it will inhibit the growth of the plant, burn the roots, so fertilization is very flexible, depending on the weather, on each stage of growth of the plant.

In 2008, Duong Hoa Xo and Nguyen Dang Nghia [51] studied the application of some new technical measures to develop a production model for orchid groups.

Mokara and Dendrobium . In which, the author has built a fertilization process for orchids.

Dendrobium has high productivity and quality:

- Process of using 100% organic fertilizer:

K-Humate Vitamax-B1 Seaweed

- Fertilizer usage process 50% inorganic + 50% organic: 30:10:10 Vitamax-B1

Seaweed KNO 3

According to Bui Thi Thu Hien (2009) [9], Pomior P399 fertilizer should be used without the need to supplement Mg ++ and Ca ++ at a concentration of 0.3% for the process of stem and leaf development, and a concentration of 0.4% for the process of flower bud differentiation to harvest for the white-purple hybrid orchid ( Dendrobium sonia 18 ).

Pham Thi Lien (2010) [21] when studying the effect of fertilizer on the flowering ability of Dendrobium orchids concluded that in the summer, fertilizers with high P, K ratios clearly affected the flowering rate but had little effect on flower quality. In the winter, fertilizers with high P, K ratios increased both the flowering rate and flower quality.

According to Tran Manh (2010) [30], Cattleya is an epiphyte, so fertilizing orchids by misting is more effective than watering directly into the substrate in the pot. The fertilizer used is foliar fertilizer with an N:P:K ratio of 30:10:10, sprayed at the recommended concentration twice a week. When the pseudobulbs begin to bud, use 10:20:20 fertilizer and to stimulate Cattleya orchids to bloom early, use 6:30:30 fertilizer. In addition, when growing Cattleya orchids , you can fertilize with mixed inorganic fertilizers with diluted organic fertilizers or foliar fertilizers of biological origin such as seaweed, fish essence, agostim.... Vitamin B1 at a concentration of 0.01% sprayed once a week also has the effect of promoting the growth of Cattleya orchids. Before the dormant season, fertilize Cattleya with 10:20:30 fertilizer to strengthen the plant during the dormant season and when the plant enters the dormant season, watering should be stopped completely.

In parallel with the study of the influence of substrate on the growth and development of Cattleya Ronald orchids, in 2011, Cao Thi Cham [4] studied the influence of substrate on the growth and development of Cattleya Ronald orchids.

The effect of foliar fertilizer on the growth of Cattleya Ronald orchids in the seedling and adult stages. According to the author, the optimal foliar fertilizer for Cattleya Ronald in the seedling stage is Orchid 1 (30:10:10) and HPV2 fertilizer (10:20:10) is the most suitable fertilizer to use for spraying Cattleya Ronald orchids in the adult stage. Before fertilizing, water the plant thoroughly and then spray the fertilizer on the entire stem, leaves, and roots of the plant, periodically once a week.

* Research on irrigation methods

According to Nguyen Xuan Linh (1998) [23], watering orchids at the seedling stage must be done carefully, watering gently with a fine mist sprayer, watering 3-4 times/day if too dry. For mature orchids, depending on the season, orchid species, growth period, and growing medium, the number of waterings and the appropriate amount of water must be decided.

According to Nguyen Quang Thach et al (2005) [35], young orchids do not need to be watered immediately after planting 1 - 2 days because the growing medium has just been washed and soaked and still retains high humidity. Young orchids that have just been taken out of the bottle for a few days often have wilted leaves and must be watered gently with a fine mist sprayer, watering regularly 3 - 4 times a day if it is too dry. When the orchid roots emerge, start fertilizing and increase the amount of water. If mature orchids are watered insufficiently, they will gradually wither and die, but over-watering will make the orchid roots wet, lack oxygen, unable to absorb nutrients, the roots will rot and die. Watering must be in harmony with temperature, humidity and light. Therefore, there is no single formula that specifies how many times a day to water and how much water to water each time.

According to Minh Tri, Xuan Giao (2010) [40], in Ho Chi Minh City, watering Cattleya is very necessary, however, with 50% shading, if watered too much, it will create a low temperature below 25 o C, making it difficult for the plant to root. Therefore, Cattleya needs a dry period between waterings to stimulate root growth. In Da Lat, there is frequent fog and high humidity, so watering is only done once a week during the dry season and not during the rainy season. The northern provinces have a short dry season, while the

The dry season in the provinces from Thua Thien Hue to Binh Thuan is very long, so irrigation must be applied specifically for each region.

* Studies on technical measures to control flowering

Trinh Cam Tu, Bui Trang Viet (2006) [42], [43], [44] when studying the role of growth regulators in the development of Dendrobium Sonia flower branches showed that IAA 0.5 mg/liter helps form a vascular system below the inflorescence meristem, BA 5 mg/liter helps the terminal flower buds to wither slowly and GA3 1 mg/liter helps to lengthen the internodes of the flower branch axis. When studying and using growth regulators to increase the number of buds and quality of Dendrobium sp. orchids, it was shown that the mixture of IAA 2 mg/liter, BA 5 mg/liter, GA3 10 mg/liter combined with CoCl 2 0.25% when sprayed directly on the flower branches has the effect of prolonging the life of the inflorescence meristem, increasing the number of buds on the flower branches.

Pham Thi Lien (2010) [21] when studying the effects of lighting time and light intensity on the growth and development of Dendrobium orchids concluded that the additional lighting time of 5 hours/night with a 55w Compax bulb in winter conditions is suitable for the development of stems and leaves. The additional light intensity at night of 210 lux/4m2, 5 hours/night in winter conditions increases the flowering rate and flower quality of Dendrobium mee white orchids.

In 2011, Nguyen Thi Ngoc Lan studied the control of flowering for Dendrobium orchids . According to the author, Dendrobium orchids grown with a substrate of 50% charcoal + 50% coconut fiber until the stage of stem and leaf growth cessation (18 months old), stop watering for 3 - 5 days and spray additional fertilizer Growmore 10:30:10 or 10:10:30 (1 - 1.5 g/liter) every 7 days to increase the flowering rate, concentrated flowering, increase productivity and flower quality. In the Winter-Spring crop, supplementing light with a Compax lamp with an intensity of 75 lux for 4 hours results in a higher flowering rate and increased flower quality. However, this method applied in the Summer-Autumn crop has no positive effect [18].

Phan Van Truong (2008) collaborated with the Institute of Agricultural Biology - Hanoi University of Agriculture to research and develop a process to control the flowering of Oncidium orchids. This treatment process can give a flowering rate of 75 - 80% [41].

Oncidium orchid (mature stage) has pseudobulb diameter >4cm

Dry shock 10 days

Grow in light conditions of 15,000 - 20,000 lux

Treatment with growth inhibitor (Gibberellin resistance) (7 g/liter) once

Flower buds appear

Fertilize flowers with 20:20:20 fertilizer (7 g/liter) twice a week

Pham Thi Lien (2010) [21] said that the dry shock method by stopping watering for 3 - 5 days helps Dendrobium orchids bloom concentratedly and increase flower quality in both summer and winter.

The topic has absorbed the research results on technical measures to control flowering of orchids belonging to the genera Cattleya, Dendrobium, Oncidium . However, the authors have only stopped at some technical measures such as using growth regulators, the influence of photoperiod, the influence of substrate or the influence of dry shock on the flowering ability of some orchids belonging to these 3 genera. The topic has inherited and continued to focus on the research direction of some technical measures to control flowering for imported hybrid orchids to increase the flowering ability of these orchids.

* Research on pests and diseases

When investigating pests and diseases on orchids, the authors of the Ornamental Plants Center, Agricultural Genetics Institute proposed preventive measures and identified 10 diseases on orchids, including 8 fungal diseases and 2 bacterial diseases. Diseases caused by fungi include black stem of seedlings, leaf spots, anthracnose, rot, petal ring spots, petal rust spots, and black tip rot. Of which, leaf spot disease causes significant damage.