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

3. Making single cnosses:
Plant the selected inbreds which are pest resistant and have a high combining ability in
paired rows, making all possible crosses between them during anthesis. Between 450 and 500
crosses can be developed each season.
4. Local yield trial:
Plant the new crosses in four replications. Every cross is planted in one 9 m row per
replication, spacing of 75 em between rows and 25 cm between hills within rows. At harvest, the
top 5% high yielding and pest resistant crosses are selected.
5. Evaluation of resistance to root lodging:
The 5% of crosses which have the best yields and pest resistance are planted, with two
replications (in Taiwan, this is done in a coastal town with a prevailing seasonal wind). Every
cross is planted in a plot with four 9 m rows in each replication, 75 cm between rows and 25 cm
between hills within rows. At the milking stage, the crosses are rated into five classes
according to the degree to which plants in the whole-plot are lodged. The following five-class
rating scale is used (Thompson, 1972, 1982).
Class 1. No lodged plants. 0
Class 2. Half the plants in the plot lodged at 228'
Class 3. Half the plants in the plot lodged at 458'
Class 4. Half the plants in the plot lodged at 700.
Class 5. At least half the plants in the plot have fallen on the ground.
At harvest, the five crosses which have the highest yields and the best resistance to
pests and lodging are selected.
6. Evaluation of tolerance to high soil moisture.
The 5% of best high-yielding and pest resistant crosses are planted in paddy fields, with
two replications. Each cross is planted in a plot with four 9 m rows in each replication, 75 cm
between rows 25 cm between hills per row. When plants reach the 5th leaf stage, the plots are
flooded with water for three days (Wenkert, et aT., 1981). At harvest, 5% of the crosses with
the best yields, resistance to pests and tolerance of soil moisture are selected.
7. Regional yield trials:
The three crosses with the best performance as described above are then recommended for
yield trials, to be planted in all major corn production areas throughout Taiwan (i.e. Miaoli,
Taichung, Yunlin, Chiayi, Tainan, Kaohsiung, Taitung and Hualin counties) over two years. At the
end of the two year yield trial, the cross with the best performance is recommended to the
committee organized by the Department of Agriculture and Forestry of the Taiwan Provincial
Government, for examination.
Agnonomic production research:
As previously mentioned, the cultivation environment in Taiwan is not ideal for corn
production. Also the arable land is limited and there is a shortage of laborers in the rural
areas. In order to increase corn yields, these problems have to be solved. To cope with them,
apart from varietal improvement, there should be an adoption of cultural practices which can
lessen the losses caused by flooding, lodging, insect pests or reduce the production costs.
In this part of the paper, the cultural practices which have been developed for preventing
the losses from unfavorable climatic conditions and increasing profits will be discussed.
1. Ridged culture:
To decrease the damage caused by flooding, ridged culture is usually adopted by the
farmers in southern Taiwan. In this practice, two rows are planted on each ridge. The distance
between rows is 70 cm, and between ridges is 150 cm (Fig. 2). The excessive standing water is
drained out through the furrow between the ridges. By adopting this cultural method in the
spring crop, 50-70% of the plants are saved-from being damaged by flooding.
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