Monday, December 10, 2012
Rice --Introduction, Cultivation
RICE(Oryza sativa)
It is the staple food crop for more than 60 per cent of the world
people. In some countries, attractive ready to eat products, which have, long
shelf life e.g.popped and puffed rice, instant or rice flakes, canned rice and
fermented products are produced. Protein is present in aleuron and endosperm
(6–9%) and average is 7.5%. Rice straw is used as cattle feed, used for
thatching roof and in cottage industry for preparation of hats, mats, ropes,
sound absorbing straw board and used as litter material. Rice husk is used as
animal feed, for papermaking and as fuel source. Rice bran is used as cattle
and poultry feed and defatted bran, which is rich in protein,can be used in the
preparation of biscuits. Rice bran oil is used in soap industry. Refined oil
can be used as a cooling medium like cotton seed oil/corn oil. Rice bran wax, a
byproduct of rice bran oil is used in industries. Rice bran oil is available in
the market in the name of Porna for edible purpose (no cholesterol).
Origin:
De Candolle (1886) and Watt (1862) thought that South India was the
place where cultivated rice is originated. Vavilov (1926) suggested that India
and Burma should be the origin of cultivated crop.
Species
Rice belongs to genus Oryza and family Poaceae. The genus includes 24
species of which O. sativa and O. glaberrima
are cultivated. O. sativa has
three sub species viz., Indica, Japanica
and Javanica.
1. Indica:
Indigenous to India. It is adapted to subtropical-tropical regions. In India,
the varieties are very tall, photosensitive, lodging, poor fertilizer
responsive, moderate filling and late matur-ing. The morphological differences
between the varieties are very wide and awnless.
2. Japanica:It is
confined to subtropical temperate regions (Japan, China, and Korea). Varieties
are very dwarf, erect, non-lodging, photo insensitive, early maturing, high
yielding and fertilizerresponsive. The morphological difference between the
varieties is very narrow and awnless. Hence, crosses were made between Indica
and Japanica—first cross was ADT 27 during 1964.
3. Javanica:It
is a wild form of rice and is cultivated in some parts of Indonesia. Varieties
are the tallest, erect, poor filling and awned.
Distribution
It grows from the tropics to subtropical and warm temperate countries
up to 40°S and 50°N of the equator. Most of the rice area lies between equator
and 40° N and 70° –140° E Longitude. Highest yield was recorded between 30° and
45°N of the equator. The average yield ranges from 2.0–5.7 t/ha in India, China
and Egypt lying between 21° and 30° N. The countries near the equator show an
average yield of 0.8–1.4 t/ha.
Area, Production and Productivity
In terms of area and production, rice is second to wheat. Maximum area
under rice is in Asia (90%). Among the rice growing countries, India has the
largest area (42.5 m.ha) followed by China, Bangla-desh and Thailand. The area,
production, productivity of rice for the world (continent wise) and some of the
important countries is given in Tables 1 and 2.
Climate and Soil
Rice can be grown in different locations under a variety of climate.
The Indica varieties are widely grown in tropical regions. Japonicas, which are
adapted to cooler areas, are largely grown in temperate countries. Both Indica
and Japanica rice varieties are grown in subtropical regions. However, the
crosses between Indica and Japanica are grown through out the world. Rice needs
hot and humid climate. It is best suited to regions, which have high humidity,
prolonged sunshine and an assured supply of water. Temperature, solar radiation
and rainfall influence rice yield by directly affecting the physiological
processes involved in grain production and indirectly through diseases and
pests.
(a) Temperature: Extreme temperatures are destructive to plant growth
and hence depended on the environment under which the life cycle of the rice plant
can be completed. The critical low and high temperatures for rice are normally
below 20°C and above 30°C respectively, which vary from one growth stage to
another. Temperature affects the grain yield by affecting tillering, spikelet
formation and ripening and it influences the growth rate just after germination
and increases almost linearly with increasing temperature within a range of
22–31°C. At later stages, it slightly affects tillering rate and the relative
growth rate. During reproductive stage, the spikelet number per plant increases
as the temperature drops. The critical temperatures for different growth stages
of rice are given in Table 3.
(b) Solar radiation: The solar radiation requirements of rice crop
differ from one growth stage to another. Shading during vegetative stage
slightly affects yield and yield components. Shading during reproductive stage
has a pronounced effect on spikelet number. During ripening, it reduces grain
yield considerably because of decrease in the percentage of filled spikelets.
Solar radiation at the reproduc-tive stage has the greatest effect on grain
yield. The minimum requirement of solar radiation is 300 cal/cm 2/day.
(c) Day length: Rice is a short day plant. Long day prevents or delays
flowering. E.g.,GEB 24 is a photosensitive and season bound variety. However
the latest varieties released are photo insensitive.
(d)Rainfall: Under rainfed rice culture, rainfall is the most limiting
factor in rice cultivation. When irrigation is provided, the growth and yield
is determined by temperature and solar radiation. Water stress at any growth
stage may reduce the yield. The rice plant is most sensitive to water deficit
from the reduction division stage to heading.
(e) Wind: Moderate wind is beneficial for crop growth. High wind at
maturity may cause lodging of the crop.
(f)Soils: Rice is a semi aquatic plant and grows best under low land
condition. In India, it grows in all most all type of soils; alluvial, red,
lateritic, laterite, black, saline and alkali, peaty and marshy soils, and in
acid soils. But the soil having good retention capacity with good amount of
clay and organic matter is ideal for rice cultivation. Clay and clay loam soils
are most suited. It tolerates a wide range of soil reaction from 4.5–8.0. It
grows well in soils having pH range of 5.5–6.5. It can be grown on alkali soil
after treating them with gypsum or pyrites.
Transplanted rice
Wet nursery: The seed rate of 60 kg/ha is recommended for short
duration, 40 kg/ha for medium duration and 30 kg/ha for long duration
varieties.
A. Pre-treatment of seeds (before sowing)
(a) Dry seed treatment: Mix any one the fungicide at 2 g/kg of seed
(Thiram, Captan, Carboxin or Carbendazim). Treat the seeds at least 24 hrs
prior to soaking for sprouting. The seeds can be stored for 30 days without any
loss in viability.
B. Treatment of seeds at the time of soaking the seeds for sprouting
(a) Wet seed treatment: Treat the seeds in Carbendazim or Pyroquilon
or Tricyclozole solution at 2g/lit of water for 1 kg of seed. Soak the seeds in
the solution for 2 hrs. Drain the solution, sprout the seeds and sow in the
nursery bed. It gives protection to the seedlings up to 40 days from seedlings
disease such as blast and it is better than dry seed treatment.
(b) Seed treatment with Azospirillum: Three packets (600 g/ha) of
Azospirillum culture are to the mixed with sufficient water wherein seeds are
soaked over night before sowing in the nursery bed. The bacterial suspension
after decanting may be poured over the nursery area itself.
(c) Seed treatment with Pseudomonas fluorescence: Three packets (600
g/ha) of Pseudomonas culture should be added in water wherein seeds are soaked
over night before sowing in the nursery bed. It can be mixed with Azospirillum
culture, as it is not inhibitory to Azospirillum.
C. Soaking and sprouting the seeds
The seeds are soaked for 10 hrs. Drain the excess water. The seeds
should not be soaked in running water, which removes the minerals and
nutrients. Keep the soaked seeds in gunny bag in dark room and cover with extra
gunnies for 24 hrs for sprouting. The seeds should not be covered with thick
material, which develops heat and reduces the aeration.
D. Preparation of nursery for sowing
About 20 cents (800 m2) for planting one ha is required. Raise the
nursery near the water source. Apply 1 t of FYM or compost to 20 cents of
nursery and spread the manure uniformly. Before ploughing, allow water to a
depth of 2.5 cm. Before last puddling, apply 40 kg of DAP @ 2 kg/cent. Basal
application of DAP is recommended when the seedlings are to be pulled out in
20–25 DAS. If the seedlings are to be pulled out after 25 days, application of
DAP is to be done 10 days prior to pulling out. In clayey soils, where root
snapping is a problem, DAP has to be applied at 1 kg/cent 10 DAS.
Mark out plots, 2.5 m broad with channels, 30 cm wide in between.
Collect the mud from the channel and spread on the seedbed and level the
surface of seedbed so that water drains into the channel. Having a thin film of
water in the nursery, sow the sprouted seeds uniformly on the seedbed.
E. Water management
For water management in nursery, first drain the water 18–24 hrs after
sowing and allow enough water to saturate the soil from 3–5th day. From 5th day
onwards, increase the quantity of water to a depth of 1.5 cm depending on the
height of seedlings. Afterwards, maintain 2.5 cm depth of water.
F. Weed management
Apply any one of the pre-emergence herbicide like Butachlor or
Thiobencarb at 2.0 lit/ha or Pendimethalin at 2.5 lit/ha or Anilophos at 1.25
lit/ha on 8 DAS to control weeds in the nursery. Keep thin film of water at the
time of herbicide application and should not drain the water after application.
G. Top dressing with fertilizers
If the seedlings show the symptoms of ‘N’ deficiency and if the growth
is not satisfactory, apply urea at 500 g/cent of nursery, 7–10 days prior to
pulling. If DAP is applied 10 days prior to pulling, urea application is not
necessary.
H. Optimum age of seedlings for
transplanting
Short duration varieties : 18–22 days, Medium duration varieties :
25–30 days, Long duration varieties : 35–40 days
I. Main field preparation for
transplanted rice
Wet rice requires a well puddled soil. Ploughing under submerged soil
condition is called puddling. The land is ploughed repeatedly 3 or 4 times with
aninterval of about 4 days between each puddling by country plough or mould
board plough or tractor drawn cage wheel or by using power tiller with a standing
water of 3–5 cm. Optimum depth of puddling is 10 cm for clay and clay loam
soils.
J. Application of organic manures
Apply 12.5 t of FYM or compost/ha and spread the manure uniformly on
the dry soil before applying the water. If FYM or compost is not available,
apply green manure/green leaf manure at 6.25 t/ha. Compute the green matter
using the formula. Yield/m2 in kg ×
10,000.
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