Text and Photos by Henrylito D. Tacio
Ubi or yam (scientific name: Dioscorea alata) is the most expensive root or tuber crop in the country today, a fact that should encourage Filipino farmers to grow it. Its selling price is much higher than cassava, potato, sweet potato, and taro.
Another thing, there is a ready market for the crop. Here and abroad, yam is being marketed in the forms of puree, powder, dried chips, cubes in syrup, ice cream, jam, halaya, and many others. The puree is used as food flavoring or coloring for ice cream, for bakery products such as cakes, pies, donuts, hopia, and also in pastries and candied products.
A report from the Bureau of Agricultural Research (BAR) states that the demand for yam has increased to 10 to 20 percent annually. Yam processors in the country demand as much as 49,000 tons a year, from which 13,000 tons of this is exported abroad.
The report added that most of the demands for processed yam products abroad come mostly from the United States, Canada, Australia, Japan, Taiwan, and other the Middle East and European countries.
Locally, there is a huge demand for purple yam, which many foreigners find exotic. Overseas Filipino workers who come home usually bring ubi as pasalubong to their kababayans when they go back to their different destinations.
The increased awareness of Filipinos in different parts of the world of the availability of high-quality ubi powder will boost exportation and will surely make a niche in the international market.
But still, the supply could hardly keep up with the demand for this dollar earner. According to experts, the reasons why the supply of yam in the country cannot meet the demand are: farmers still follow the traditional method of growing ubi, and there is a perennial scarcity of planting materials or setts (the upper part of the root nearest the stem).
Although yam production is fast becoming popular among farmers in recent years, production still lags. The Bureau of Agricultural Statistics said that it took ten years for the yam industry to double its production area. Although there is a growing demand for purple yam, cultivation and production remain to be the biggest threat to the industry.
Here is some information from the Department of Agriculture on how to grow ubi:
Yam thrives anywhere in the Philippines and a wide range of soil types and elevation because it can tolerate adverse conditions such as droughts and pest infestations. However, it thrives best in sandy loam or silt loam fertile, well-drained soil and temperature ranging from 25°C to 30°C. Ubi needs ample moisture throughout the growing season.
The crop can be cultivated at any time of the year, but for best results, planting should be done at the beginning or just after the rainy season when it can obtain all the moisture it needs for growth. Traditionally, it is planted in March and June and harvested from December to February.
Yam can be grown in crop rotation with short-season crops. In some parts of the country, it is often planted during the first season after land clearing. The bush fallow system of cropping involves both rotation and intercropping.
Generally, yam is planted in crop rotation with cassava and intercropped with melon, corn, or okra. Suitable alternate crops with yam are peanut, cowpea, and other legumes, which improve the soil.
Two deep plowings and two harrowings are usually enough for yam for a field that has been previously cultivated. Yam needs deep loose soil. To pulverize the soil, the length field is harrowed along and across.
Yam is planted on flat or ridged seedbeds. If flatbeds are used, planting is done after the last harrowing. On sloping or rolling fields, the ridges are contoured to minimize soil erosion.
About 20,000 to 27,778 setts (obtained from healthy tubers of healthy plants) are needed for a hectare of land. There are four types of setts: head, middle, tail, and whole. The first three are prepared by cutting large tubers into pieces. The fourth type refers to the whole small tuber.
Large tubers are sliced into setts weighing from 60-250 grams. Tubers weighing less than 60 grams should not be sliced. Each set must have enough skin area. The cut sides of setts are treated with ash or fungicide. The setts are air- or sun-dried until cuts are dry. After drying, setts maybe pre-sprouted or planted directly.
Sprouts emerge from setts about 2-3 weeks after planting. Pre-sprouting the setts before planting is recommended to minimize weeding expenses before sprout emergence.
The setts cut from large tubers have planted either skin up or skin sideways. Whole tubers were measuring 60-250 grams; either crown up or crown sideways should be planted. The setts are then covered with a thin layer of soil. The pre-sprouting bed is watered at least once a week until most of the setts have sprouted. With pre-sprouted setts, planting may either be staggered or done at one time.
In staggered planting, the following activities must be performed in all batches of planting: (1) Remove from pre-sprouting bed setts that have emerged to prevent sprouts from growing too long. (2) Place the sprouted setts on a platform in a shady area. (3) Repeat the process every week or every two weeks until the desired number of sprouted setts for one batch of planting is obtained. Plant before the sprouts become too long to transport or before sprouts start wilting.
In one-time planting, the procedure of sett preparation is essentially the same as that for staggered planting. One-time planting is done only after most of the viable setts have produced sprouts. At this time, sprouts of some setts are already very long. The sprouts are cut along before transporting setts to the field for planting.
For non-sprouted setts, these are planted in the seedbed at a distance of 1 meter by 50 centimeters or 60 centimeters by 60 centimeters. The setts are planted 10 centimeters deep during the rainy season and 15 centimeters during the dry season. Setts can be planted in any position.
For pre-sprouted setts, these are planted at the start of rain if it is possible to irrigate or mulch the field. The setts are planted in the seedbed at a depth of 10 centimeters and a distance of 1 meter by 50centimeters or 60 centimeters by 60 centimeters. It is recommended that the sprouts are planted in an upward position.
The field is mulched to reduce soil temperature, conserve soil moisture, increase organic matter content of the soil and suppress weed growth. Dry coconut fronds, corn stalks, rice straw, and other similar materials can be used in mulching. Mulching is done just after planting.
With non-sprouted setts and without mulching, 3-5 weedings are needed. With pre-sprouted setts and with mulching, only two weedings at 2-month intervals are needed.
A stake is placed for each plant before vines start crawling on the ground. Stakes should be 1-2 meters long. Bamboo, wood, cassava stalks, talahib stalks, or any similar materials can support the ubi vines, which can be used as stakes for at least seven months. If cassava stalk is used, it should be set up in an inverted position (young end down) to prevent the stalk from producing new shoots.
Yam vines twine to the right. When vines start trailing on the ground, these should be trained to climb their respective stakes. The vines are trained again when branches start crossing the rows, especially when weeding and hilling-up operations by using animal-drawn implements.
A hectare of yam can remove about 128 kilograms of nitrogen, 17 kilograms of phosphorus, and 162 kilograms of potassium from the soil. Soil samples are collected from the field and submitted for a soil analysis to the Bureau of Soils and Water Management.
In inorganic fertilization, the recommended amount of fertilizer should be split into two, one half to be applied about one month after emergence (or one month after planting of pre-sprouted setts) and the other half about two months after the first application. The fertilizer is applied following the band method with the fertilizer placed about 10 centimeters away from the plants.
For organic fertilization, compost with a mixture of decayed organic matter from plant parts and animal manure is recommended. The compost is mixed with the soil during land preparation or maybe placed just below the setts during the planting.
Yam is ready for harvest when its foliage is already yellowing or drying up. For most varieties, the drying up period of the foliage starts in late November and lasts until January the following year. Tubers intended for sett production are harvested at the later part of the drying up period. However, tubers for consumption or for selling in the market are harvested earlier, even before foliage dries up.