RICE (Oryza sativa)
Rice is another popular cereal crop grown and consumed by nearly half of the world’s population. It is also a member of the grass family (Gramineae). The seed/fruit of rice is a caryopsis, i.e ., it has its epicarp fused with the mesocarp.
Land Preparation: This is done either manually, using cutlass to clear the bush and remove stump and hoe to make ridges, or mechanically by ploughing, harrowing and ridging.
Varieties or Cultivars: These include the swamp rice (Toma, BG79 and GFB24) and the upland rice (Agbede).
Climatic and Soil Requirement: Rice requires a temperature of over 20°C, 75cm – 120cm of rainfall for upland rice and over 250cm for swamp rice, and light fertile soil.
Method of Propagation: Rice is propagated by seed. Rice can be propagated manually or mechanically.
Seed Rate: 65kg/ha at two to three seeds per hole.
Planting Date: Rice is planted in Southern Nigeria around April and May, and between August and September in the North.
Planting: Rice can be planted by broadcasting, sowing or drilling of the seeds at 2-4cm deep.
Nursery Practices: Swamp rice requires nursery which is done in fertile, water-soaked soil. Seeds are broadcast and germination begins after four to five days and the seedlings are transplanted at between seven to eight weeks of growth to the field. Seeds are sown in nursery around May-June and transplanted in July August to the field.
Spacing: 25cm – 30cm apart, depending on variety.
- Supplying and thinning: These can be done where applicable.
- Fertilizer application: Apply 150kg or three bags of N.P.K fertilizer per hectare at planting by broadcasting.
- Weeding: Weeding is done to ensure rapid growth of rice.
- Pests and diseases: These should be prevented or controlled by spraying with appropriate chemicals.
- Maturity Period: Rice matures in four to seven months depending on variety.
- Harvesting: Red heads of rice are cut off with knife, sickle or combined harvester.
Processing of Rice
- Sundrying: This is done immediately after harvesting for three to four days.
- Threshing: This is the separation of the grains from the stalk by either beating with stick, treading with feet or by the use of mechanical threshers.
- Winnowing: After threshing, the chaff or unwanted dust and remains of stalks are removed by winnowing. This is a fanning operation usually done by throwing the grains in the air to blow away the dust and other residues. After winnowing, the grains of rice remain enclosed by the husk to form what is called paddy.
- Parboiling: This process is used to reduce the breakage of grains during pounding. It also brings some vitamins to the outer layer of the grains and it also reduces the labour required to remove the husks. The paddy rice is heated by putting it into boiling water for about 12-15 hours. The rice swells and the husks are forced apart. The parboiled rice is now sun-dried.
- Hulling: This is the removal of the husks from the grains. The grains are pounded gently to remove the expanded husks. The husks are then separated from the rice by winnowing.
- Polishing: In some cases, the paddy rice is threshed by machine, and polished. Polishing involves the use of specially designed machines to remove the husks and other layers covering the grains. The portion removed is known as rice bran which is very rich in protein and vitamins. Consumption of polished rice may cause vitamin deficiency disease called beri-beri due to the removal of the bran rich in protein.
Rice can be stored as paddy rice or in processed form in silos or jute bags.
Pests of Rice
1) Birds: These pests feed on the grains, leading to low yield of rice.
- Employ children to scare the birds
- Use scare crows.
- Practise early harvesting.
2) Rodents: Cane rat and grasscutter cut the plants and seedlings on the field. leading to great loss.
- Set or use traps.
- Fence the farm round.
3) Rice Weevils: This is a store pest. Adults and larvae bore into the grains and reduce them to powder.
- Fumigate store with phostoxin tablets.
Diseases of Rice
1) Rice Smut: It is caused by a fungus (Tilletia horrida) which is spread by wind. The grains turn into a mass of black spores.
- Use resistant varieties
- Use recommended fungicides to spray the crops.
2) Rice blight: It is caused by a fungus (Piricularia oryzae) spread through the soil. Longitudinal red or yellow spots develop on the leaves, leading to poor yield.
- Avoid the use of heavy nitrogen fertilizer;
- Use resistant varieties
- Use clean seeds.
3) Brown leaf spot: It is caused by a fungus. It causes small narrow brown spots which appear on the leaves.
- Plant resistant varieties.
- Uproot and burn infected plants.