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

the maha season. Yala season is characterized by low rainfall, high temperatures, and strong,
dry winds.
In general, maize is not grown in the dry zone during the yala season. Results of an
experiment carried out to study the performance of six varieties of maize grown under irrigation
during yala 1976 are shown in Table 3. For the purpose of comparison, the same varieties grown
under rainfed conditions during the previous maha season (1975/76) are also included in the same
Table. There were differences in yield, plant height, and days to silk for all varieties during
the two seasons. Mean grain yield of the varieties was reduced by 2~ and plant height by 3~
during the yala season as compared to the maha season. The varieties silked and matured earlier
during the yala season. The reasons for these growth differences may be associated with high
temperature during the yala season.
The maize stem borer Chi 70 parte77us SWinhoe, is the most damaging single pest of maize.
OCcurrence of this pest is one of the major constraints in maize production during yala.
Continuous data collected by the Entomological Division of the Agric. Res. Center, Maha Illuppallama
shows a minimum population of stem borer during September to November and rising to a peak
during February to Apri 1·.
Chemical control experiments reveal that a single application of granular carbofuran or
diazinon, or two sprays of these chemicals gave satisfactory control of C. parte77us. The
application of granules into the whorl of the plant appears to be more effective and residual
than spray applications. At present chemicals offer the only means of control. Unfortunately,
these are very expensive. If maize is considered as a crop for the yala season it may be
necessary to develop varieties more tolerant or resistant to stem-borer and adverse weather
conditions.
Table 3. Variation in agronomic characters of six maize varieties grown in maha 1975/76 and yala
1976, at Maha Illuppallama.
Days to Plant height Grain yield
Varieties 5~ silking (cm) (kg/ha)
Maha Yala Maha Yala Maha Yala
Thai Comp. 63 58 223 138 3165 2549
Cupurico x Flint Comp. 63 61 240 143 3165 2813
Salvador 8 x V250C A6, A21, 64 62 232 149 3213 2535
PD (MS)6
Tuxpeno P.B. 64 62 212 142 3330 2296
Thai Opaque 2 Comp. 63 56 220 148 3213 2003
T 48 (check) 63 56 232 161 3008 2003
LSD (P = 0.05) 349 658
CV (~;) 8.3 17.2
Studies on water requirement and irrigation have revealed that a 115 day maize crop needs
to be supplied with 615 mm of water when it grows under irrigation during the drier period of the
year. Furthermore, 112 kg N/ha appears to be the best level of N for the yala season.
Intercropping studies.
Though it is possible to grow maize under irrigation during yala season, it may not be
competitive in terms of returns with other crops such as chilli and other vegetables that compete
for the same resources. Table 4 provides a summary of selected yala season crops with their net
returns. At today's prices, maize is at about the level of soybean and cowpea in terms of total
costs and gross returns per hectare.
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