Proceedings of the Fifth Asian Regional Maize Workshop - Search ...

to rice in order to reach
self-sufficiency in food production.
6. Constraints.
A. SOCio-economic constraints
The main socio-economic constraints for the development of the maize-based production
systems are:
1. Diversity in socio-economic conditions of maize growers.
2. Insufficient access to credit for intensive cropping.
3. Insufficient support services: research and extension.
4. Great ethnic diversity among maize growers.
5. Difficult access to many regions where farmers grow maize.
B. Agroecological and technical constraints
The main agroecological and technical constraints for he development of maize production are
the following:
1. Inbreeding depression in local varieties due to a small population size of each different and
isolated type.
2. High incidence of the downy mildew disease in lowlands.
3. High weed infestation in fields of the Vientiane plain.
4. Wide range of agroecological environments with various types of maize cropping systems.
5. Low fertility of upland soils.
7. Acqui red knowl edge.
Most research activities have been conducted under on-station conditions at Hat Dok Keo,
Naphok, and to some extent at Pakcheng and Nabong. Emphasis has been on improved varieties of
feed maize. The major achievements are the following:
a. Varietal selection and improvement: The variety HDK 4 has been created and promoted for the
lowland farmers of the Vientiane plain for animal feed production. several other varieties or
populations from the international variety trials were identified as promising: Suwan-1, Pop.28,
etc. "rhese varieties were identified for high to medium input environments and according to
their resistance to the downy mildew disease. Mass selection is being applied on HDK 4 to
maintain a certain level of purity since it appeared to become less productive than Suwan-1.
b. Improve.ent of cultural practices: The cultural practices for HDK 4 and similar varieties are
well known for the Vientiane plain and for both rainfed and irrigated conditions. Plant density
is estimated to be optimum with 53,000 plants/ha. Planting is made by dibbling 3 seeds every 42
em along rows spaced 90 em apart and thinning at 2 plants per hole. Fertilizer rates for soils
similar to Naphok's acrisols are 45/45-50-20 (NPK) kg/ha. several fertilizer trials have been
conducted on maize at Naphok showing important deficiencies in nitrogen and phosphorus in the
soils of the Vientiane plain. Irrigation techniques have been developed for dry season irrigated
maize.
c. Improvement of plant protection: Varietal resistance has been promoted against the downy
mildew disease. Varieties are systematically evaluated and screened for their resistance to the
downy mildew disease. The variety Suwan-1 has shown the best resistance to downy mildew,
followed by HDK 4. Pesticide treatments have been developed for protection against the most
common insect pests.
d. Post-harvest technology: Techniques for seed storage have been developed, but some aspects
related to seed quality control can still be improved.
Some preliminary observations have been collected also on sweet corn varieties at Naphok and
at Hat Dok Keo. Hat Dok Keo has set up a gene bank collection for maize. Naphok has developed
the artificial hand pollination method for maintaining the purity of the selected varieties.
In summary, past research activities have placed emphasis on improvement of feed maize
varieties grown with a high level of inputs. On-farm trials were never conducted on maize, and
there were no research activities in the major maize producing areas (northern provinces).
Research on maize used as human food was recently initiated in a small-scale manner.
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