Section 3 (Crop Management)

Boonpradub and Kraokaw
Cultivars
Kernel yields in all twenty-one maize genotypes when grown under irrigated conditions were
significantly different (Table 2). Pioneer 3012, Cargill 727 and Pacific 700 provided an average of 15 to
26 % increase in kernel yields over NS 72 (check). This was probably due to greater kernels per ear as
compared to other genotypes. Boonpradub and Senthong (2001) also evaluated the thirty-one maize
genotypes including hybrid and open-pollinated varieties under different moisture regimes using a line
source sprinkler irrigation system. They found that Pioneer 3012 showed significantly the highest kernel
yield under well-watered condition.
Planting time
When maize grown under post-rice condition, planting time significantly showed different in kernel
yield as shown in Table 3. Results found that mid-November to mid- December was found best for
planting this crop in post-rice condition. There was probably due to maize obtaining better kernel number
and kernel weight. To delay planting of maize thereafter, its yield was generally low. The reduction was
24 and 36 % when grown in January and February, respectively. Yield loss due to delay planting was
high temperature during flowering date (data not shown). Furthermore, ear number was not affected by
planting time.
Plant density
The results as shown in Table 4 indicated that maize grown under plant density at 66,666 plants ha -1
gave significantly 18% higher kernel yield than those at 53,333 plants ha -1 resulting in more ear number
per ha. However, plant height and yield components; namely ear width, ear length and kernel weight,
were not affected by plant density. Boonpradub et al. (1998) had been studied on maize grown after rice
under different plant densities found that mean yield increased consistently with increase in plant density
from 53,333 plants ha -1 to 80,000 plants ha -1
Fertilization
The nitrogen fertilizer was needed to be applied in order to increase maize yield when grown under
post-rice condition as shown in Table 5. The kernel yield of maize with 187.5 kg N ha -1 application was
not significantly superior to that of 125 kg N ha -1 . However, it was significantly different when compared
with 62.5 kg ha -1 as a results of higher kernel number. A greater reduction in kernel number as affected by
nitrogen stress was probably due to delayed silking resulting in an increase in the length of the anthesis -
silking interval (ASI) as the results of nitrogen deficiencies (Girardin et al., 1987). The application of
nitrogen fertilizer as a basal fertilizer followed by a top-dressing fertilizer at 1 month should be
recommended. Similar result was also displayed when its trial was done under farmers’ fields (Table 6).
The recommended N fertilizer showed higher kernel yield and better economic return as compared to
farmers’ practices.
Conclusion
It can be concluded that maize has become a newly upland crop for growing under the post-rice
condition in Thailand. This is probably due to its providing better income and profit for the farmers as
compared to the second rice. In addition, it is helpful to reduce water consumption during dry season and
break the population dynamic of pest. However, besides major on soil and environmental constraints, the
suitable maize cultivars, appropriate cultural practices and more seed available also need to be further
developed.
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