The constraints faced in the production of vegetables can be broadly classified as climatological, technological and others including socio-economic limitations.
Other than the Northern region and parts of the Northeast, the rest of Thailand is hot and humid with little differences in day and night temperature and some seasonal variation in temperatures between summer and winter months. The Central and Southern parts of the country remain hot and wet throughout the year. The South in particular receives the benefit of the Northeast and Southwest monsoons. The conditions for growing most commercial vegetables are not suitable. Consequently, the South produces the least amount of vegetables. Depending on the monsoons is risky, however, as uncertainties in weather shifts, can cause problems with food production. The Central and Northeastern regions have facilities that can assist farmers to produce regular crops. The distribution of rainfall is satisfactory in the North and the cooler climate permits the production of a large number of vegetables. In the South and Central regions, unpredictable monsoons can bring about a high incidence of diseases and pests. Under these adverse conditions, vegetable production in summer is uncertain. During the winter months, many crops can be grown with the result that frequent surpluses occur during this period, while a shortage may occur in the summer months. The range of crops grown during summer is also limited. Those who subsist on vegetable diets have to depend more on leafy vegetables during warmer months. There is however a moderately well organized distribution and supply system within the country, but prices may go beyond the reach of the low-income groups for some vegetables.
There are practical difficulties in collecting accurate statistics on the status of the vegetable sector. Using surveys from markets and major production areas, it is possible to get estimates of production but the veritable millions of homestead gardens which also contribute substantially to the food budget of so many homes could never be accurately estimated. Data collection on vegetables is highly inadequate as fewer personnel are deployed when compared to other major food and industrial crops. Although Thailand is better equipped than most countries in the region for gathering information in vegetables, more investments are needed to upgrade information gathering systems.
The fact that most vegetable crops have shown insignificant increases in productivity clearly indicates the low coverage of new improved varieties across the country. The number of improved varieties available to farmers is also limited in that some crops and imported varieties do not always perform well under local conditions. Although floating kangkong is very popular in several regions, there are no developed varieties and growers depend on unselected local germplasm that grows in an almost semi-arid state. For popular vegetables such as Chinese kale, pak choi and chili, varieties are limited in number and local hybrid material is not available. The same is true for garlic and shallots, which are important vegetables in Thailand. The climatic conditions are not favorable for garlic seed production and farmers have to depend on unselected planting material. Some attempts have been made to produce a true botanical seed source for such crops.
The indigenous vegetable seed sector is mainly dependent on farmer saved seed than the formal seed sector. Only semi-commercial and commercial farmers have access to good seed from public and private sectors. The rest of the farmers in rural areas have only their traditional varieties to depend upon. In 1994, Thailand produced 3.2 million tons of vegetables with an average yield of 8.6 t/ha. In 1997 the country produced 5.1 million tons of vegetables with an average yield of over 10.7 t/ha. Whilst these figures show some progress, the country is far behind performances recorded by the Republic of Korea, North Korea, Taiwan, China and Japan. Since 1994, the area under hybrid vegetables has shown an increase from about 300 000 ha covered for the major crops such as cabbage, Chinese cabbage, radish, cucumber, bitter gourd, luffa, cauliflower, water melon and melon. Although many private seed companies are active in this field, unless a greater percentage of area is covered, a quantum leap in vegetable production to meet the challenges of the coming years will not be easily achievable.
Vegetable varieties have to be developed by seed companies to cater to the climatic and soil needs of different agro-ecologies. The most vital input in vegetable production is a quality seed. Whilst it is nearly impossible for the extension services to provide superior seed to the entire farming community, small farmers who are the most disadvantaged need to be assisted in procuring seed from reliable sources. The ultimate success of production programmes will depend to a large measure on the availability of many varieties that can help year round culture of more important vegetables. Good seed ensures high yields and, consequently, better returns to farmers. If production targets are to be reached, hybrid seed should be made available even to small farmers at reasonable prices. Some effort should also be made to produce hybrids using indigenous germplasm which has better resistance to biotic stresses than imported hybrids.
There is an important category of under-utilized vegetables grown by rural communities across the country that needs improvement. These are currently produced largely from traditional varieties and they provide a large volume of food to low income communities. Any varietal improvement in this area will be beneficial to the rural farming sector since their food and nutritional value is well known. The seed production of several OP varieties could also help if appropriate community based seed programmers are organized to encourage lateral spread of such seed between farmer and producer groups in areas where seed is currently not available. The fact that some regions such as the South and Central are unable to produce sufficient vegetables is ample evidence that the seed supply of appropriate varieties is not adequate. This problem needs to be addressed through the dissemination of suitable varieties to such constrained environments.
The vegetable sector is plagued with pest and disease problems. Very few varieties are locally available that are tolerant or resistant to biotic stresses. In the summer season, production is seriously affected by these problems as waves of pests attack the crops. When farmers have to depend on seed imported from the temperate zones, their crops become highly susceptible to tropical pests and diseases or to unfamiliarly high temperature regimes. In earlier times, many hybrid sweet corn varieties were introduced from the United States and other countries which did not adapt well to the climatic conditions in Thailand. These varieties produced kernels of poor quality and succumbed to corn leaf blight caused by Helminthosporium maydis. Solanaceous crops like potato and tomato were susceptible to bacterial wilt, late blight and high temperatures. Unfavourable weather conditions also affected the lettuce varieties introduced from the west which often suffered from leaf tip burn. Several cruciferous vegetables were affected by soft rot caused by Erwinia corotovora.
Specific constraints due to non-availability of good varieties and seed for major vegetable crops are briefly summarized below:
Vegetable production is a risky business in Thailand as most currently available varieties are unable to survive repeated attacks by pests and diseases. For example:
In tomato, the absence of heat tolerant, bacterial wilt resistant, late blight resistant and leaf curl virus resistant varieties.
In Chinese cabbage, heat tolerant and soft rot resistant varieties.
In leaf mustard, lack of heat tolerant varieties.
In cauliflower, lack of heat tolerant varieties.
In all cruciferous vegetables, lack of diamond back moth resistant varieties.
In lettuce, non availability of tip-burn resistant to late blight.
In cucumber, lack of resistance to downy mildew disease.
Since farmers have to depend on seed supplied by private seed companies, commercial high quality hybrids and OP varieties seldom have the resistance to local biotic stresses. As a result farmers are compelled to use heavy doses of pesticides to produce crops from these imported varieties. It is however gratifying to note that the Horticulture Research Institute has launched a programme to develop indigenous vegetables which have built-in resistance to most pests and diseases, and which will minimize the use of harmful pesticides. Over one hundred species have been identified and collected for further development.
In the production and distribution of quality seed, the specific limitations are:
The limited research investment into development of new varieties/hybrids and production of hybrid seeds, as national institutions have hardly embarked on any programme to utilize local germplasm.
The inability of the public sector agencies to produce, process, and distribute seed of improved open pollinated varieties of vegetable crops.
The lack of decentralized seed increase programmes using the informal seed sector.
The unsatisfactory pricing structure for vegetable seed.
The lack of seed certification service to ensure seed quality standards.
The non availability of participatory seed programmes at farmer-level.
In Thailand about 75 percent of the vegetable seeds of both open pollinated varieties and hybrids is supplied by 50 companies (multinational and local) operating in the country. Approximately 5 percent is supplied by government agencies, and the remaining 20 percent comes from seeds saved by farmers themselves. Cost of imported or locally developed hybrid seed, and even some OP varieties, is too high and resource poor farmers are seldom given the incentive to use quality assured seed by providing a subsidized price structure. Most hybrid seed costs are beyond the reach of the resource poor farmers, whereas, commercial growers can easily afford these high costs as seed costs amount to only about six percent of their total production costs. One of the major constraints in this field is the lack of sufficient trained manpower to handle seed programmes. In recent years, however, there has been synergism in the formal seed sector where private companies have seemed to actively supplement and support government efforts to improve the seed sector.
The development of appropriate technology packages is the collective responsibility of farmers, researchers and extension personnel. Such participatory programmes are not well organized to achieve high outputs. The traditional knowledge of farmers and the incorpo-ration of their techniques into newly developed technologies would assure high adoption rates. This incorporation should encompass appropriate varieties, seed and seedling management, fertilizer use, water and pest management, and pre and post-harvest technologies. Such packages are needed for each ecological and socio-economic setting such as rainfed, irrigated, low input, high input and for homestead, market gardens, semi-commercial and large-scale production systems. Both research and extension need to take a holistic view to integrate all components of a production system. Due to the lack of a precise technology for each of the above situations, productivity has suffered, and gaps remain between potential and actual yields.
Farmers are usually unaware of the correct pre-harvest practices required for each crop. For instance, withdrawal of irrigation two weeks before harvest of a potato or onion crop hardens the crop, which facilitates curing and long-term storage and reduces post-harvest losses. Harvesting of fruit vegetables with high moisture content should be done in low ambient temperatures and away from direct sunlight to reduce perishability and ensure better keeping quality. In Thailand, fruit flies attack every cucurbit crop unless the farmer has protected the crop by covering, as spraying with pesticides has no guarantee of success and is expensive and risky.
Most vegetables are bulky and perish within a short time if not carefully handled. Poor handling conditions account for over 30 percent of losses in vegetables. Unless leafy vegetables and some fruit vegetables are harvested at the right stage of maturity and carefully packed, losses between 10–30 percent can occur at the consumer level.
Unless a disposal system works with the least possible delay from the time of harvest and the time of disposal at retail outlets, losses are bound to happen. Having temporary storage facilities, preferably with temperature control, can reduce the losses. For more durable vegetables, such as potatoes, conditioned long-term storage is necessary.
Packaging of perishables is somewhat critical under local conditions. High ambient temperatures prevailing almost throughout the year make it essential to ensure adequate ventilation and moisture control on packages. Transporters may also pack vegetables very tightly resulting in high losses.
Most local markets have poor infrastructures to facilitate the efficient handling of perishable goods. Vegetables that come badly packed are stacked in open exposed areas, un-protected, and without adequate temperature control.
Except for the contract farmers and those who are financed by middlemen, there are no production contracts with buyers for the majority of vegetable farmers. Crops are produced without any knowledge of the market demand; consequently, farmers are then at the mercy of middlemen who offer low prices. It is reported that the DOAE has recently launched a programme of organizing farmers into production groups who can negotiate prices. However, the production sector is so widely scattered, it will take much more personnel and effort to create a significant impact.
Low prices for the produce may also be due to the poor planning of a cropping calendar. Growers do not have a planned programme targeting market demand. Any crop grown a few weeks ahead of the main season will attract better prices. For example, advancing a tomato crop by two weeks earlier than the main season by raising seedlings well in advance, will help the farmer to get the first harvest earlier than others and obtain premium prices. Also, by choosing early varieties he/she could achieve the same result. Any crop slightly out of season, either early or late, means better profits.
It is often seen that the grower is not in tune with market intelligence. They are not aware of the specific needs of consumers. Consumer preferences can vary with different classes of consumers and if this information is known, production can be geared to cater to special consumer groups who are very quality conscious.
Many vegetable growers are ignorant about off-season production of vegetables. They are unaware of varieties to be grown, cultural practices to be followed, and the production systems necessary to raise successful off-season crops. Most farmers are unaware of the availability of different maturity groups of vegetable crops. The economic advantages in terms of saving on production costs by the choice of early, mid-season or late varieties needs to be explained.
The bulk of the vegetable produce is marketed through informal channels from growers to consumers in the absence of producer groups. The system operates with some success among the contract farming groups, which currently number about 131, and involve 500 000 farming families. These farmers grow crops under contract to supply exporters. Similar arrangements are only beginning to be established elsewhere.
Most collection centres in the growing areas are ill-equipped to handle large consignments of vegetables, especially during the peak vegetable season. Facilities for cleaning, trimming, grading and packaging are virtually absent. These centres only act as transporting outlets and do not provide any other assistance and services to farmers. No value addition to the vegetable produce is done here. However, the centres at the Royal Projects in Kanchanaburi and Chiang Rai are equipped with facilities to ensure proper handling of produce. The vegetable sector gets marginal support from governmental marketing agencies, and the entire industry is primarily a private sector operation.
As mentioned earlier, high seed prices discourage farmers from using quality seed. Other than the semi-commercial and commercial farmers, high quality hybrid seeds are beyond the reach of an average small farmer. In cases where a middleman markets an expensive seed, small farmers neither have the purchasing ability nor the access to credit. Although farmers are trained to use good seed, it is not practiced due to several reasons. Farmer's training programmes seem to be somewhat ineffective as growers continue to use highly toxic chemicals. Either the extension messages are not reaching small farmers at the field level, or the farmers disregard the advisory services and pay more attention to representatives of chemical companies that operate at the field level.
The overuse of agro-chemicals poses a serious health hazard to consumers as well as affecting the export of fresh vegetables. Other than the professional growers who produce crops under contract for export projects, most farmers are still ignorant of modern production technologies. Sometimes, for economic reasons, the level of input used is far below recommended levels and hence productivity suffers. Actual yields obtained are far below potential yields for most crops. Knowledge on the use of fertilizers, pesticides, weedicides and on irrigation frequencies and levels needs to be improved.
After harvest, most farmers are not aware of methods to prepare the produce in a presentable manner for better consumer appeal. Cleaning, grading, trimming etc. are not carried out systematically. Farmers lack knowledge on the use of growth regulators to increase yields, enhance quality of produce, hasten maturity, and harden produce for better shelf life.
Poor nursery management technologies result in production of low quality seedlings, which affects the performance of the crop in the field. Very few farmers have knowledge of protected cropping to produce crops free of agro-chemicals or raise off-season crops of high value vegetables. Most farmers lack knowledge of IPM technology and organic farming methods except in areas where pilot projects have been carried out.
The field staff are mostly general purpose extension officers who, in addition to other crops, are expected to oversee the extension work for vegetables. Therefore, it is difficult to develop competence on such a large number of crops when an officer is expected to transfer technology on over 20 vegetable crops. Extension officers are also expected to have sufficient exposure to various disciplines including crop varieties, cultural practices to be followed, plant physiology, pre and post-harvest technology, processing, marketing etc. Unless more staff are deployed specifically for these major disciplines, it becomes impossible for a single officer to develop even a low level of competence to handle technology transfer programmes.
There are wide gaps between demonstration plots and on-farm yields in almost every crop which may be due to weak linkages among research, extension and farmers. Since there are a large number of vegetables produced, there is a justification to have a separate cadre of vegetable extension officers at field level.
Contract farmers carry out vegetable production on a highly professional basis. Their inputs match the modern technologies they practice. Credit is an essential ingredient in developing such high levels of production. In some parts of the country credit is offered by middlemen, who also purchase the crops at prices decided by them. In most instances these traders exploit farmers. Since small farmers cannot offer security they are unable to obtain credit from agricultural banks. Group formation may help in obtaining such credit if some assistance is provided by the government.
Large areas of marginal land could be considered for development if irrigation facilities are available, in order to spread vegetable production into new areas. Marginal rice lands are not being considered for diversification into vegetable growing. While improvements in productivity can be brought about by the use of appropriate hybrid technology, some increase in cultivable area will be needed to raise production levels in order to meet future needs. Rainfall is a limiting factor in some parts of the country. Conservation techniques such as water harvesting and the use of other agronomic options to raise short-season crops in such constrained environments may be needed. Rehabilitation programmes to utilize problem soils for certain hardy vegetables would help to expand production further. Thailand has experience in land reclamation, especially conversion of submerged soils using the ditch and dyke system. Diversification and inter-cropping of such lands with vegetable crops could be considered to help alleviate hunger.
The problem of water quality has posed limitations in coastal and inland areas where salinity and alkalinity occur. Development of suitable crops for such environments is another area for exploration.
In peri-urban areas, the issues of water and atmospheric pollution are important. The use of water polluted with city and industrial wastes for vegetable growing poses a serious health hazard as vegetables are mostly consumed fresh. As urban population increases, peri-urban vegetable production should receive due recognition.
Vegetables are an essential component of the Thai diet, and in recent years per capita consumption has gone up steadily. However, certain sections of the population still consume vegetables in amounts less than the recommended per capita intake of 73 kg per year. As indicated earlier, the present per capita availability of vegetables is only 60 kg. Nutrition intervention programmes to reduce Vitamin A and iron deficiencies in school children need intensification to cover the deficient areas of the country.
Farmers are either ignorant of technologies or disregard advice against the use of dangerous pesticides and fungicides for which a nationwide mass media programme to educate people is required. The pesticide companies should also be urged to cooperate with the government in the education programme.