Pole sitao (Vigna unquiculata subsp. Sesquipedales (L.) Verdc.) has the following names: asparagus bean, garter bean, snake bean, Chinese long bean, Yardlong bean (English); kacang panjang (Indonesian and Malaysian); tao-fak-yao (Thai); dau-dau (Vietnamese); dau-gok (Chinese); lobia (Hindi); and sasage (Japanese). Locally, it is known as sitaw (Tagalog), hantak (Waray), utong (Ilokano), batong (Cebuano) and latuy (Marinduque).
A herbaceous crop, pole sitao has trifoliate leaves. The flowers are in pairs and borne on the axil of the leaf which vary in color depending on the variety. Calyxes are generally green and purple. It is a viny annual crop that produces 30-60 cm long pods which hang in pairs with many seeds. Pods are either green, dark green, light green or purple. They are quick growing and every other day harvesting is often necessary.
Pole sitao is an important crop in Asian countries like Malaysia, Thailand, Indonesia and the Plippines. It is also considered as one of the most important vegetables in certain parts of Taiwan and China.
In the Philippines, pole sitao is the most popularly produced vegetable among edible legumes because the pods, young shoots as well as the beans are available throughout the year. It is grown in home gardens, on dikes around paddy fields, under partially shaded areas as a companion crop or commercial crop.
The succulent young pods of pole sitao are eaten as whole pods and only need very light cooking. It can also be a good supplement to infant food whether cooked singly or mixed with other vegetables. The young leaves, shoots and sprouted seedlings can also be utilized as vegetables. Juices from the leaves are used for some medicinal properties.
Bureau of Agricultural Statistics (BAS), 2010 showed that the total land area planted to pole sitao is 14, 681 hectares with a total volume of production of 119, 453.02 metric tons. Central Luzon has the highest volume of production (32%), followed by Cagayan Valley (15%) and Davao Region (11%).
Pole sitao is a good source of protein, vitamin A, thiamin, riboflavin, iron, phosphorous and potassium. It is also a very good source of vitamin C, folate, magnesium and manganese.
Pole Sitaw Production Guide – Growing Pole Sitaw
In 1975, the Bureau of Plant Industry, Economic Garden, Los Banos, Laguna developed the firs commercial variety of pole sitao known as BPI-Ps 1 and was approved by the Philippine Seedboard. At present, BPI-LBNCRDC has six (6) varieties registered and released by the National Seed Indury Council (NSIC) for commercialization. NSIC Ps 4 (“Hitik”) and NSIC Ps 5 (“Rikit”) are the latest pole sitao varieties approved last 2008. The green podded varieties are BPI-Ps 3, BPI-Ps 4 and NSIC Ps 4 while the light gen podded varieties are PSB-Ps 2 and NSIC Ps 5. Seeds of these five (5) varieties of pole sitao are available at the Center.
A. Soil and Climate Requirements. Pole sitao is well suited in warm climate at a temperature range of 20-35 oC. It can thrive well under full sunlight although it can tolerate partial shading. Higher percentage of pod set can be achieved when planted in May for wet season and in October-November for dry season. Any type of soil is suited to pole sitao production. However, a friable fertile soil is preferred to obtain healthy growth and high quality pods. The soil must have a pH value of 5.5-6.8.
B. Varietal Selection – Planting right varieties adapted to a specific area may increase yield by as much as 20%. In the varietal selection, there are important considerations to look into:
a. Adaptability to soil and climate
d. Disease resistance and insect tolerance
e. Market/consumers demand
C. Land Preparation. Thorough land preparation is important to obtain high yield since operation renders the soil for seed germination. Plow the field twice and harrow after each plowing. For single row trellis, make furrows one (1) meter apart and 0.75 meter for A-type trellis before planting. Apply 2-3 tons dried animal manure per hectare while preparing the field.
D. Planting. The seeding rate for pole sitao requires 10-12 kg/ha. For hill method of planting, after basal fertilization with organic and/or inorganic fertilizers, sow 2-3 seeds per hill with a distance of 30 cm between hills and cover lightly with soil. Allow only 2 plants per hill. For drill method of planting, seeds are planted at a depth of 2-3 cm at a rate of 15-18 seeds per linear meter with 100cm spacing between rows.
E. Mulching. Use rice straw or plastic mulch particularly during dry season. This method helps to suppress weed growth and to conserve soil moisture.
F. Cultivation. Off-baring and hilling-up should be done after 14 days from emergence or before the plants start to cling on.
G. Trellising. In hill and drill methods of planting, provide poles after 14 days from emergence. Vertical trellis is used for single row plot with a distance between rows of one (1) meter. Ipil-ipil, bamboo and kakawate poles are used 3-4 m apart with in the rows and are secured on top with GI wire #16. Tie the top wire to the stakes at the end of e rows to make the poles stable. Plastic straw is used at the bottom portions in every row. Straw lines are tied vertically from top to bottom in every hill. For double row plots, A-type trellis is spaced apart at 0.75 m. Synthetic straw is also used for the pole sitao to cling on for the trellis.
H. Vine Training. As vines develop, train the crop to cling to the trellis by spreading them evenly across the trellis until they reach the top.
I. Soil Nutrition. The general fertilizer recommendation for pole sitao is 135 kg/ha N, 135 kg/ha P205, and 112 kg/ha K20. However, fertilization should be based on soil analysis. Before first plowing, apply 3 tons of well decomposed manure per hectare. Before planting, apply 3 bags/ha of 14-14-14 as basal fertilizer and sidedress wi1-2 bags of urea (46-0-0) at 1 month after planting. Muriate of potash (0-0-60) should be applied at the rate of 1-2 bags during flowering stage. Foliar fertilizers should also be
applied weekly starting at flowering stage.
J. Organic fertilizer: Fertilizer should be bio-degradable materials of microbial, plant or animal origins produced on organic farms such as vermicompost and processed chicken manure. Basal applications organic compost of 5-10 tons/ha are needed for vegetable legume crops. Supplementary application of Fermented Plant Juice (FPJ) or Fermented Fruit Juice (FFJ) should also be applied twice a week up to fruiting stage.
K. Irrigation. Pole sitao has a relatively deep root system which enables it to tolerate drought. Application of water the critical growing period of the crop particularly during dry season is required to increase yield. Adequate supply of water is necessary to increase flowering and pod setting. Too much water can result in flower drop and ca cause root rot. During wet season, irrigate only when necessary.
L. Weed Management. Weeds may cause considerable yield loss if not controlled early in the season. Hand weeding should be done as often as necessary even after flowering. Perform spot hand weeding.
M. Crop Protection. Insect control for pole sitao depends greatly on the use of chemicals especially during seedling stage. Though there are attempts to practice integrated pest control especially through cultural management practices.
N. Pest and Disease Management
For effective control, use resistant varieties and other measures like crop rotation, rouging and pruning of infected plant parts and planting of repellant and companion crops. Organic pesticides such as citronella extract, guyabano seed extract, luyang dilaw and perla soap can also be utilized to control and minimize pests for vegetable legume, and if needed, the use of chemicals/fungicides will be the last resort in controlling pests and diseases of pole sitao.
O. Harvesting. The young and tender pods of pole sitao are ready for harvest 7-10 days after flowering. Harvesting should be done at 2-3 days interval to prolong the productive life of the plants. Harvesting is done manually. Harvest the pod by holding the stem end before twisting it free. To avoid weight loss, harvesting should be done early in the morning or during the cooler times of the day. The pods should be kept in a shaded area after harvest. To prolong the shelf-life, dip the harvested pods in coconut water for 1 minute. In the Philippines, no attempt has been made to mechanize harvesting.
P. Post Harvest Handling. Separate the marketable and non-marketable pods. Marketable pods are
tender, straight, long and unblemished. Non-marketable pods are short, curved, damaged by insects or diseases.; and past the picking stage but can still be utilized as vegetable. Pack the harvested pods in plastic sacks, thick lined bamboo baskets, polyethylene bags or wrap with fresh banana leaves. If pole sitao pods cannot be sold used for 1-3 days, store small quantities in moistened clay jars. Store pods at 12-15 oC for not more than 2 weeks at 90% relative humidity if cold storage facilities is available. Keep the pods away from ripening fruits during transport and storage.
Except for isolation and rouging, the cultural management techniques in seed production are similar to fresh pods production.
A. Isolation. The isolation distance depends on the nature of pollination of the crop, whether self or cross pollinated. The isolation distance of pole sitao is 10-50 meters.
B. Field Inspection. It involves identification of a variety and removal of undesirable plants from the main crop through a process termed rouging. The undesirable plants may be weeds, plant of other crop species, plants of another cultivar of the same species, diseased plants and other off-type plants. Rouging should be done at least three times: first at pre-flowering stage; second at flowering; and third at pod formation.
C. Harvesting. Select plants that are vigorous and free from pests and diseases. Harvest pods when physiologically mature or when pods have turned brown and begin to dry. Harvested pods at 20 days after pollination will give the best quality seeds. It may be necessary to harvest 3 times a week at peak harvest. Dry pods should not be allowed to remain in the field to prevent shattering during sunny days rotting or sprouting of seeds within the pods during the rainy days. When dry pods remain longer in the field, these are also being exposed to insect pests.
Place the harvested pods under the sun for 2-4 days until brittle. Threshing is carried on by beating pods enclosed in net bags or sacks and manually beat with a stick. Separation of seeds from the threshed pods is done by winnowing. Sort out small, wrinkled and seeds damaged by insect. Sun dry the seeds for 4-5 days. Before packaging and storage, seeds must have 10% moisture content (MC). Seeds must be packed in thick plastic, containers or aluminum foil, label with the name of the variety and date of planting then keep in a cool or storage area. In the absence of cold storage, seeds can also be stored in the refrigerator. If properly stored, viability of the seeds becomes longer.
source: Bureau of Plant Industry