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

also revealed the authenticity of economic viability of our present fertilizer recommendation
40:20 N:P 2 0 5 for sole maize cropping.
of
Study on Mize weed control.
"rhe weeding operation has been the most expensive operation in maize husbandry practices.
This is mainly because 90" of the maize is grown in rainfed dry1ands. Most of the important
weeds encountered are broad leaf perennials. The major among them are Fagopyrum dibotrys,
Persicaria runeinata, CCtmtelina maeu7ata, Galinsoga parvif1ora, and the grass weed Digitaria
eiTiaris. Although farmers have been able to control these weeds, research on manual weeding is
needed. Therefore, attempts have been made to study the efficacy of manual weeding emphasizing
two of its important functional components viz. time and number of weedings. The research
results indicate that the most crucial time for crop x weed competition occurs at 25-30 days
after crop emergence and continues until 50-55 days.
The avoidance of crop x weed competition after 60 days of crop emergence shows little or no
effect on yield.
Therefore, to harvest a normal yield, farmers should keep their maize crop free of weeds at
least for a period of 23-50 days and up to 50-55 days after crop emergence. This can be achieved
by two hand weedings given at one month intervals. If farmers can do only one weeding, they
should do it 25-30 days after crop emergence.
Maize density x fertility study :
In spite of the high seeding rate used by farmers, the final plant stand at harvest time is
always about 25,000 to 30,000 plants/ha. The lesser number of plants at harvest" is mainly
attributed to the following factors:
1• CUtworm damage at seed1i ng stage.
2. Mechanical injury at time of weeding.
3. Damage by stray cattle and wild animals.
4. Smothering by aggressive weeds.
Efforts have been made to study the effect of plant population on yield at different levels
of soil fertility. The main aim is to determine the ideal plant population to suit the fertility
levels.
Results have indicated that both density and fertility seem to affect the final crop yield,
although the effect of density seemed more significant than fertility.
At the lowest fertility level (10 t/ha farm yard manure), there was a 21X increase in yield
when doubling density from 25,000 to 50,000 plants/ha. At the higher density of 75,000
p1ants/ha the increase in yield from doubling the plant density was only 5X, and the crop growth
and development were poor. At moderate fertil ity levels (40:20 N P z
05 kg/ha) an increase in
yield of 43X was obtained by doubling density from 25,000 to 50,000 p1ants/ha. With a population
of 75,000 plants there was a 40X increase in yield, and again the plant growth and development
observed were comparatively poor. Crop responses observed at high fertility level (80:40 N
P 2 05 kg/ha) were similar except that the plant growth at this fertility level was normal at all
the density levels. The yield increased 24X at double density and 19% in triple density.
HYBRID MAIZE IN EHlTAN
Hybrid maize was introduced in Bhutan in the early 1980's. The parental seeds of the
varieties Pioneer 410 and 440 were acquired from Hyderabad Pioneer Seed CO. (India). The F1 seed
was produced in Tashiyangtsi, Bhutan, to be later sold to farmers.
COst of certified seed was US$ 0.7/kg.
Yield 3-4 t/ha at farmers condition.
IllPllCt of hybrid seed progr-.e.
Since the Bhutanese farming is basically for subsistence the hybrid seed programme failed to
make any impact among the Bhutanese farming community. The main reasons for this failure were:
1. COst of parental seed increased year after year until it was nearly US$ 4O/kg.
2. Lack of skilled technical manpower in seed production.
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