Báo cáo Nghiên cứu khoa học The technical procedures for growing and caring of citrus in Vietnam

Ministry of Agriculture and Rural development THE SOUTHERN FRUIT RESEARCH INSTITUTE -------------- --------------- THE TECHNICAL PROCEDURES FOR GROWING AND CARING OF CITRUS IN VIETNAM VO HUU THOAI I. SITE SELECTION Establishment of an orchard is a long term investment and hence needs the complete planning. Any mistake committed during selection of site, plant density, choice of varieties, quality of seedling… reflects greatly on the orchard performance. For got management and sustained yields, it is very important to select a good site for orchard. Climate: Temperature: It should be remembered that the optimum temperature range for tropical trees is between 23-30oC, if temperature is low at 10oC can damage tropical trees. Rainfall: In general, a climate with low rainfall and plenty sunshine in good for tropical trees. High rainfall areas are less suitable for fruit trees because of pressures of pests and diseases, lower yield and poor fruit quality. Soil: Fruit trees can grow and produce well in a wide variety of soil types, except very light, sandy soils and heavy clay soils. In general, most fruit trees prefer the soil pH between 5.5 and 6.5. The water table should be no higher than one meter below the soil surface. Other important factors Day length, the amount of sunshine, the level of relative humidity, latitude, altitude and slope of land may all affect fruit tree growth, fruit yield and quality. Selected site for citrus planting, , it is isolated from HLB disease areas. II. ESTABLISHMENT OF ORCHARD Aspect for planting Being evergreen, fruit tree perfom best in site that are warm and sunny. The mounding is at right angles to the sunrise is recommended. Each tree on the mounding will receive more sunlight from sun. Windbreak Windbrerak should be estalished before planting commance, the benefits of windbreak include reduction in wind damage to trees and fruit, reduction in evaporative stress to trees and an improved microclimate for crop pollination in Mekong delta, Hibiscus plant is recommanded and Cusuarina for highland. To establish the wind- break in order to prevent flower and fruit falling from storm The layout of orchard There are 2 popular planting systems are being practiced, theye are: Square system: Is simplest and ubiquitous system of planting adopted for a number of fruit crops, as it provides ease in cultivation and irrigation. The trees are planted in 4 corners of the square in straight lines. (suitable for the southeast areas). Quincunx system: it is similar to square system except that a fifth plant is located at the centre of each square (suitable for mekong delta with high density). * * * * * * * * * * * * * * * * * * * The disease - free seedlings should be planted in selected orchard Planting density and distance(spacing) Planting density depending on factors such as the species of tree, cultivar, the type of rootstock, the environment and planting zone. Table: Commonly planting distance in citrus crops Crops Mekong delta South –East Kinh mandarin Tieu manarin Pummmelo Lemon 2 x 3m 4 x 5m 4 x 5m 3 x 4m 3 x 4m 4 x 5m 5 x 6m 4 x 5m Mounding The depth of topsoil can be increased, which is rich in nutrient and oganic matter, by moving topsoil from between the rows into the tree lines. Mounding can help overcome site limitations such as shallow topsoil, poor drainage and have beneficial effects by increasing the nutrient supply under the tree line and improving aeration in the root zone. Irrigation systems recommanded to install on the moundings. Mekong delta: usually have got acid sulfat soil layer under topsoil, high water table level and shallow topsoil. Therefore mouding is recommanded in this soil type. For fruit tree cultivation in the Mekong Delta, land is specially made into alternative canal-beds in order to increase the deepth of topsoil. Then fruit trees planted on small mounds of the bed. The mound size is about 50-60cm height and 80-100cm in diameter. South-East : The mounding is suitable with upland (highland) of the eastern part of south Vietnam. If growers are unable to carry out the mounding for the whole site, similar mound in Mekong Delta are recommended with 30-40cm height and 60-80cm in diameter. Prepare for planting holes Planting holes of 60cm x 100cm x 100cm are dug and allowed to weather for about two weeks prior to planting. Then, organic manure, lime and phosphate fertilizer can be mixed with topsoil and subsoil (incorporated) to be used to fill the planting holes. The time of planting The optimum time for planting fruit trees varies according to the species, water sources. It is best planted at the beginning of the raining. Growers should avoid transplanting seedling during hot summer weather . Irrigation system There are three main source of irrigation water for orchards: Well, river, stream, and ponds. Irrigation system should be established when the orchard is being laid out. In the Mekong delta is furrow irrigation or over canopy can be used because of abundant water. Drip irrigation can be used if water is limited such as highland area. Ground cover and mulching The use of grass cover and plant residue is recommended to reduce water loss from the soil and increase soil organic matter and structure. During 4-6 months of dry season the tree basins are mulched with weed residue, banana leaves, coconut fiber, straw… Between the row of tree, grass is recommended to sow such as Commelina diffusa(rau trai),Setaria palmifolia(cỏ lá tre), Kradun thong... Keeping grass in the orchards in order to avoid soil erosion and retain humidity ; It is good condition for beneficial in sects to live Fertilizers for fruit trees Young trees: The plants have become established, monthly applications of DAP: 18%N – 46% P2O5 (Diammonium phosphate), at a rate of 40g/10 liters of water/tree, will encourage rapid vegetative growth. Besides, we also applied regular dressings of organic manures. The rate of fertilizer application should be increased as trees become older. Bearing trees: fertilizers is recommended to be applied three times during the crop cycle: Fertilizers for fruit trees Young trees: The plants have become established, monthly applications of DAP: 18%N – 46% P2O5 (Diammonium phosphate), at a rate of 40g/10 liters of water/tree, will encourage rapid vegetative growth. Besides, we also applied regular dressings of organic manures. The rate of fertilizer application should be increased as trees become older. Bearing trees: fertilizers is recommended to be applied three times during the crop cycle: 1. 1. After reaping: SSupply with NPK in from 15-15-15 ar 20-20-20 and oranic fertilizer will help develop new roots and leaves, improve soil structure. 2. 2. Before blooming: FFertilizer used during this time must be low in N content while high in P and K content. Such as NPK fertilizer in from 8-24-24. CKNO3 should be sprayed on the plant canopy to help increase maturity of leaves. 3. 3. After fruit setting and fruit development. FFertilizer containing high nitrogen and phosphorus are applied at this stage. CCaNO3 is also prefered during this stage as calcium help to increase fruit quality (at tractive color, firmer flesh and prolong self life of fruit in postharvert stage). In this stage, the amount of fertilizer should be divided into from 2 to 3 time for application. Nutrient component of manures (%) /100gr. ( Lê Văn Căn, 1982) Components Manures H2O N P2O5 K2O CaO MgO Poultry manure(pig) Castle manures Chicken manure 82 83,1 56 0,60 0,29 1,63 0,41 0,17 0,54 0,26 1,0 0,85 0,09 0,35 2,40 0,10 0,13 0,74 To apply organic fertilizers such as:Green manure, Castle manure and chicken manure Table: Recommandation of fertilizers based on yield of tree( kg /tree) dose (gr/tree/year) Kind of fertilizer The yield of tree Urea Super Phosphate KCl 20kg/tree/year 650 900 370 40kg/tree/year 1080 1500 620 60kg/tree/year 1300 1800 700 90kg/tree/year 1750 2400 1000 120kg/tree/year 2170 3030 1250 150kg/tree/year 2600 3640 1500 The method of fertilizer application: The fertilizer should be placed in a circular band around the periphery of the plant canopy, then cover with soil and water. Training and pruning There are three main objectives for training and pruning, sush as: + The first is to increase the total effective leaf area and promote photosynthesis. + Secondly, easily manage orchard and increase the vigor of the tree, maintain the most efficient balance between vegetative growth and fruiting. + Thirdly, removing diseased or infected branches. Training: First year of planting: after planting, when seedling grows to a height of 70-80cm, It back cut to height of 30-40cm the ground in order to promote the lateral shoot growth. Second year: keep branches No. 1,2 and 3. Which will grow into scaffold branches. Pinch the end of branches No. 4,5 and 6, which should be cut off in the next two years. Third year and fourth year: remove branches No. 6,5 and 4. scaffold branches 35-40o 30-35o scaffold branches scaffold branches After training Pruning: The fruits should be removed while they are small and green during second year of tree. Never to remove more than 15% of the total shoots. Removing diseased or infected brancher, water sucker, undesirable branch and shoots (wrong position, wrong direction). Control of pest and diseases On fruit crops, pests and diseases caused much damages and the farmers normally use pestisides for controlling them, which lead to residue on fruits. However, for controlling of pests, the best way is using IPM, which use less toxicity chemicals, combines with cultural practices, biological agents, and organic fertilizers. Green ants (Oecophylla smaragdina) are being used as the biology control Only use bio or natural products to spray or apply as basal. Such as: seaweed, copper… in order to control pest and diseases. Bio- products could be used as Bacillus thuringiensis (BT). fruit bagging by net bag, black papers for preventing pests and disease and improve color of skin. Protect fruits from sunburn and fruitfly To use yellow traps to attract insects. It will be died by petroleum jelly on yellow traps. To plant Murraya paniculata in oder to attract the coming citrus psylla. Psylla are considered as vector to transmit the HLB diseases. Murraya is host plant for citrus psylla and may be immune to HLB disease. Therefore, Murraya may become trap of psylla. To use the water pipe with high pressure to irrigation for trees and by the way to reduce the density of mites. THANK YOU FOR YOUR ATTENTION!