Rice: An Introduction
Rice is a cereal crop that belongs to the grass family Graminae. Rice plant can grow to 2 to 6 feet tall with a round jointed stem, long pointed leaves and edible seeds borne in the dense head on separate stalks.
Rice is one of the major crop cultivated in India, other parts of the Asia and rest part of the world. Methods of cultivation of rice can differ from place to place.
Rice is mainly cultivated because of its nutrition value and health benefits.
Rice is a cholesterol free food and is a good source of energy. It helps in blood pressure management, cancer prevention, prevent skin problems, supports cardiovascular health and is a rich source of Carbohydrates, protein and healthy fats. It also contain Vitamin-B6, Calcium, Magnesium and Iron.
- Botanical Name: Oryza sativa
- Family: Poaceae or Gramineae
- Order: Cyperales
- Class: Liliopsida / Monocotyledons
- Division: Magnoliophyta
- Chromosome Number: 24
Origin and Geographical Distribution
Origin of Rice: Yangtze River valley in China.
Rice is the world’s leading food crop, cultivated over an area of about 165 million hectares. It provides about 22 percent of the world’s supply of calories and 17% of the proteins.
The average yield per hectare is found to be highest in Punjab(3346 kg/ha).
Climate and Temperature
Ideal climate to grow rice is hot and humid climate but this paddy crop can be cultivated in wide varying condition of climate and altitude. Ideal temperature to grow rice varies from 20 to 40 degrees Celsius.
In India, rice is cultivated mainly on two types of soil, uplands and lowlands.
A. Upland rice cultivation (Rain fed rice)
(c) System of rice intensification (SRI)
Upland Rice Cultivation
The upland rice cultivation is mostly adopted in areas which receive an annual rainfall of 800-1000 mm and irrigation facilities are not available. In this system of cultivation, farmer has to depend upon rain water. Due to failure of monsoon, the farmer has to bear a heavy loss.
After harvesting the rabi crops in April-May, the field should be ploughed with soil turning plough. The field should be prepared and bunds should be made around the field just after the first shower of monsoon. This will check loss of rain water by run-off.
Sowing of Seeds and Seed Rate
The ideal time in north India is between end of June and first week of July. If the sowing is delayed, crop is adversely affected because of soil and atmospheric drought due to aberrant weather conditions during the grain filling stage.
In some rice growing areas, dry seeding a little before onset of monsoon is practised. The seed remains in the soil, which germinates with the onset of rains.
Under upland conditions, drilling or line sowing is always better than broadcast because line sowing facilitates the cultural operations and enables to identify the weeds even at the early stage for weeding purpose.
Usually sprouted seed should be sown in rows 30 cm apart at a depth not more than 5cm. The moisture stress condition may result in poor germination, therefore, about 25% higher seed rate than the recommended rate(100-120 kg/ha) should be used.
For obtaining an uniform plant population and higher crop yields, it is advisable to thin out the excess plants or re sowing in gaps in the rows after about 2-3 weeks of sowing.
Irrigated or Low land Rice Cultivation
This system of rice cultivation is practiced in areas having an assured and adequate supply of water. In this system, sprouted seeds may be directly sown in puddled field or the crop may be transplanted with seedlings raised in a nursery.
Manures and Fertlizers
In upland rice, organic manures(FYM or compost) @10-15 tonnes/ha should be incorporated 4-6 weeks before sowing.
Rice requires 5000 litres of water to produce a kg of grain. The high water requirement of rice is mainly due to percolation losses.
The water requirement of rice varies from 2,500 mm depending upon growing season, soil type, crop duration and management practices, etc.
Transplanted rice, in general, requires about 40-60, 200-300 and 800-1000 mm of water, respectively for nursery raising, puddling and crop raising in main field from transplanting to physiological maturity.
Infestation of weeds in rice fields may reduce the grain yield by 50-90% in upland, 30-35% in drilled irrigated and 15-20% in transplanted crop.
Rice varieties take 100-150 days to mature. The proper stage for harvesting is when about 80% spikelets in 80% panicles show ripening. Timely harvesting ensures quality and consumer acceptance. The plant should be cut close to the ground and left in the field for a few days to dry.
A well managed crop of mid-late duration(135-150 days) varieties like IR8, IR20, Jaya, etc. and hybrids yield about 6.0-7.0 tonnes grain/ha, whereas short duration cultivars yield about 4.5-5.5 tonnes grain/ha.