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

names of Muthu and Aruna, respectively. Characteristics of the maize varieties developed at Sri
Lanka are described in Table 2.
Fertilizer studies.
Several fertilizer experiments were conducted to determine the optimum rates. Results of
these experiments are reported elsewhere (Hindagala, et a7., 1971; Nagarajah, et a7., 1972).
Fertilizer rates of 67-45-28 kg NPK/ha were found to be adequate for the main maize growing under
rainfed conditions.
Various experiments have shown that highest yields could be obtained when nitrogen is
applied in two splits at different growth stages. Application of 1/4th of the recommended rate
of nitrogen (17 kg/ha) as basal and the balance at 4-5 weeks after seeding appears to be better
than other split combinations.
weed management.
Competition from weeds such as Cyanodon dacti70n can reduce yield by about 30-~. To a
certain extent, farmers control weeds by hand weedings, but this is not done at appropriate
times. Experiments on the number of weeding required for maize in Sri Lanka indicate that more
than one weeding is required for good growth and high yields. It also appears that weeding has
to be done 2 weeks after planting followed by another weeding at 4 weeks after planting which can
be coupled with top dressing of fertilizer.
Table 2.
Characteristics of varieties.
Ruwan Muthu Aruna Bhadra-1
Grain type Flint to semi flint Semi-dent Semi-fl int Fl int
Grain colour Orange White Orange to yellow Orange
PH. hgt. (em) 185-195 167-175 130-140 180-200
Ear hgt. (cm) 95-100 80-90 50-55 100-120
Days to 50% sil k 58-60 58-60 48-50 58-60
Days to maturity 110-115 110-115 90-100 110-115
Lodging Good resistance to Good resistance Good resistance Moderately
root and sta"1 k
susceptible
Yield (kg/ha) 4282 5366 4401 4280
Plant density.
Plant density is an important factor affecting yield. Plant density studies have shown
that with adequate fertilizer and moisture, maize grown at a density of 50,000-60,000
plants/ha will produced optimum yields. The yield response to an increase in density is dependent
on the fertility level of the soil, particularly nitrogen, as deficiency of this nutrient is
common in tropical soils.
An experiment was carried out at the Regional Agric. Res. Center, Maha 11 1uppal lama, to
study the effect of plant density and nitrog~n levels on the yield of maize. Based on these
investigations, it was concluded that with adequate moisture and fertilizer a plant density of
about 50,000-60,000 plants/ha would be best during the maha season. However, in dry areas where
maize is grown at low fertility levels, it would be desirable to reduce the plant density in
order to prevent barren plants and poor ear development. Traditional tall leafy varieties should
also be grown at lower densities of approximately 37 000 plants/ha.
Agronomic investigations during yala season.
The climatic conditions in the dry zone during the yala season are different from those of
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