There are two broad types of rice grown, paddy rice and upland rice. Paddy rice does best in areas where there is rainfall of 2,500mm within 20-24 weeks. Rice can be grown all year round if the water and temperature conditions are right.
Upland or rain fed rice will grow well in areas with 760-1,270mm rainfall per annum
Rice may also be classified according to its grain form either Japonica – short grain or
Indica – long grain
Planting the crop
First the land needs preparing. The land needs clearing and all vegetation burning. The soil needs ploughing to a fine tilth with a depth of 10-20cm . This will help germination and control weeds. The field is then harrowed and levelled as much as possible to promote penetration of water (either rain water or irrigation water). If the rice is going to be grown under irrigation, then ditches, dams and soil erosion measures will need to be taken.
Rice is usually planted at the start of the rains. Chose good quality seeds- there are some well researched varieties available such as NERICA.
The seeds should be pre-germinated first to get the best results. This is done by pouring the seed into cold water and stirring. All light and empty seeds that float to the top are skimmed off. The healthy seeds are placed in jute bags, soaked in running water and then placed in the shade for 24 hours. Cool water is poured in the bags when they begin to dry out. This should induce the seeds to sprout. The sprouted seeds are then drilled in rows at a spacing of 25cm per row with 25cm between stands in a row. Sow 5-7 seeds pre stand and cover with soil. The seeding rate is approximately 44-55 kg ha.
Care of the crop
Rice will grow on poor land, but yields will be better if you add fertilizer. Farmyard manure at 10 tonnes/ha will do the job, although a green manure could be grown and ploughed in to help restore fertility. Getting the soil analyzed by an agronomist will give you the exact requirements to optimize yields.
Rice is easily smothered by weeds so early weeding is essential Early weeding also encourages tillering which increased the yields. Upland rice should be weeded 3 times, 3 weeks apart, starting 3 weeks after planting. Use an inter-row weeder if the rice has been drilled by machine.
Other ways of controlling weeds are by rotating the crop as monoculture results in a build up of the weed population, and by using new varieties which are competitive and can be planted very close, suppressing weeds.
Harvesting and the rice combine harvester
Upland rice usually takes between 18-30 weeks from sowing to harvest. Using a rice combine harvester or a combine harvesting machine with a special rice header will give a quick, reasonably efficient harvest. Rice grains are very hard on the harvesters so expect to replace them more frequently than if they were just harvesting maize, this is a good reason to use a rice combine harvester.
Expect yields of 880 -1,650 kgs/ha although yields of 2,500kg is possible. Some varieties of NERICA have yielded 4 tonnes/ha in trials.
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Written by Fiona Johnson