FIG. 2. Distribution of major yam activity sites in Dominica, 1981-1984


I

from 2,500mm to 3,000mm, 27.0C to 31.6C, 16.6C to
22.5C, and 502kg to 846kg, respectively, during the report
period. Well-drained acid soils of clay loam texture predominate.
 Over the report period, either mounds 30cm to 60cm high and
90cm to 150cm apart, or ridges 25cm to 40cm high and 75cm to
150cm apart, were prepared after clean weeding and ploughing.
Prior to planting, all tubers were cut into 100g to 150g portions,
treated with insecticide and fungicide for 15 minutes and air-
dried for 24 hours. Biocides used were benomyl, 1.5g/l, captain
5.5g/l, malathion 3ml/l and sevin 80wp 4g/l, depending on
availability. Prior to all plantings, yam holes were treated with 5g
to 6g of Furadan 10% granules.
 In the first two seasons tubers were divided, allowed to sprout
and then planted; in the latter two seasons, sprouts were remov-
ed, tubers cut and the desprouted setts planted. Yam setts were
planted May to June in all seasons, 70cm apart along the ridges
and 5cm to 10cm beneath the surface, at an angle with the cut
face away from the surface.
 Branched stakes, 1.0m to 2.5m in height, were established
after crop emergence. Yam vines were trained at regular intervals
by loosely tied string. All plots were hand weeded at 6 and 16
weeks after planting. Immediately after the first weeding 60g of
NPK MgO (12:12:17:2) fertilizer was banded 15cm away from
each plant. Total harvest of tubers was conducted after 8-9 mon-

VOL. XX-PROCEEDINGS of the CARIBBEAN FOOD CROPS SOCIETY


ths in all seasons. Total tuber yields were the only data recorded
for the 1981 planting whereas in 1982, time to emergence, an-
thracnose presence (scale 0 5), insect damage (scale 0 5), ap-
parent virus symptoms (scale 0 5), as well as tuber yield were
recorded. For 1983 and 1984 emphasis was placed on multiplica-
tion of planting material and monitoring of anthracnose. Some of
the yams produced in on-station tests were distributed to farmers.
 In support of the above, the station foreman at La Plaine
Agricultural Station was trained in management of virus-tested
yam at the Tissue Culture Facility, CARDI, Barbados. In addi-
tion the Agricultural Assistant/Extension Supervisor and the Ex-
tension Officer for the La Plaine area assisted in observation of
yam cultivation at the Station. Technical support was provided by
the MOA Crop Protection Division.

Distribution and Monitoring
 In 1983, after results of the previous season were assessed, 40
farmers were selected by MOA personnel to whom White Lisbon
clean material would be distributed. At a seminar organized by
MOA, at which CARDI, FTC and MOA Crop Protection were the
resource personnel, each farmer was provided with 3 5kg of
planting material. Preparation of setts for planting was
demonstrated and other production practices were discussed.
Similar exercises, where extension officers played a greater role in
farmer selection, were conducted in 1984 for 30 farmers of Grand
Fond, Riviere Cyrique, Morne Jaune, La Ronde and Boetica in
the South East Extension District and 19 farmers of Trafalgar,
Laudat and Springhill in the Roseau Valley area, (Fig. 2). In all
instances, after harvest, farmers were mandated to return to
MOA the same quantity received for possible redistribution in
the ensuing season. FTC and MOA personnel organized to
monitor a few of these farmers to see how the newly distributed
yams fit into the farming system. In order to provide additional
planting material, yam multiplication centres were also establish-
ed at Portsmouth and Grand Bay Agricultural Stations in the
North West and South Central Districts in the 1983 season.
These locations are similar to La Plaine in edaphic and climatic
parameters except for Portsmouth, where, because of its more
sheltered location, the windrun is less and the temperatures
marginally higher. Portsmouth also differs topographically from
the other locations as the area has less steep slopes.

Discussion
 Results to date are shown in Table 5. Data on time to
emergence was not collected. In 1981, yield data for White
Lisbon, A grade, averaged only 1.6kg of tuber per plant, though
tubers were of good quality.
 In 1982, data was recorded for White Lisbon B and C grades,
 Belep SEA 189, all D. alata, and V 1712, D. cayenensis. Tuber
 yields of White Lisbon were 300% and 175% greater than those
 of 1981 for grades B and C respectively. This could be attributed
 to improved crop management as a result of the Station
 Foreman's training in Barbados. In 1982, White Lisbon also
 yielded more than the other cultivars planted. The lowest yields
 were recorded for cv. V 1712 (0.5kg/plant), and the highest yield
 from White Lisbon B of 4.8kg per plant. There was a small dif-
 ference between Belep and SEA 189; however, both had greater
 yields than V 1712. In addition, White Lisbon B and C differed
 by 2kg per plant. The above yields compare favourably with those
 in the small farm systems in Dominica, where yields range from
 1.8kg to 2.7kg/plant. Furthermore, in the 1982 cultivation, a
 group of 14 plants was inadvertently planted in an area which was
 previously a pen manure patch. Yields ranged from 2.7 to
 15.5kg/plant with a mean of 7.4kg/plant. This, coupled with
 noted interveinal chlorosis symptoms, indicative of nutritional
 disorders in other areas, suggests that further yield improvements


can be achieved by augmenting plant nutrition.


257