General Information and Agronomic Aspects
The cultivated rice is an annual grass. Depending on the degree of sensitivity to light its growth duration may range from 60 to more than 200 days. Cultivated rice belongs to two species, Oryza sativa -Asian rice, (which is more widely used) and Oryza glaberrima - African rice. Rice is grown in four ecosystems, which are broadly defined on the basis water regimes. The ecosystems are irrigated, rain-fed lowland and upland, and flood prone.
Rice is cultivated primarily for the grain, which is a main staple food in many countries, especially in Asia. In Kenya it is becoming increasingly popular, especially in urban centres. From 2010 to 2014, Kenya had a yearly production of about 119,000 metric tons (FAOSTAT, 2014). Consumption of wheat has been on a steady increase from 410,000 metric tons in 2010 to 564,000 metric tons in 2014 (Economic Review of Agriculture, 2015). This increase in demand and the development of new upland varieties have created an opportunity for farmers to venture into rice growing.
Rice will give the same or better yield as maize and fetch the double price on the market at harvest time. Grains are quite nutritious when not polished. Common or starchy types are used in various dishes, cakes, soups, pastries, breakfast foods, and starch pastes; glutinous types, containing a sugary material instead of starch, are used in the Orient for special purposes as sweetmeats. Grain is also used to make rice wine, "Saki", much consumed in Japan. Rice hulls are sometimes used in the production of purified alpha cellulose and furfural (an industrial chemical derived from a variety of agricultural by-products, and commonly used as a solvent). Rice straw is used as roofing and packing material, feed, fertiliser, and fuel.
Nutritive Value per 100 g of edible Portion
|Raw or Cooked Rice||Food
(Calories / %Daily Value*)
(g / %DV)
(g / %DV)
(g / %DV)
(mg / %DV)
(mg / %DV)
(mg / %DV)
|Vitamin B 6
|Vitamin B 12
(mg / %DV)
(mg / %DV)
(g / %DV)
|Brown Rice, long-grain, cooked||111 / 6%||23.0 / 8%||0.9 / 1%||2.6 / 5%||10.0 / 1%||83.0 / 8%||0.4 / 2%||43.0 / 1%||0.0 IU / 0%||0.0 / 0%||0.1 / 7%||0.0 / 0%||0.1 / 6%||0.0 / 1%||0.5|
|Brown Rice, medium-grain, cooked||112.0 / 6%||23.5 / 8%||0.8 / 1%||2.3 / 5%||10.0 / 1%||77.0 / 8%||0.5 / 3%||79.0 / 2%||0.0 IU / 0%||0.0 / 0%||0.1 / 7%||0.0 / 0%||0.1 / 7%||0.0 / 1%||0.4|
|White Rice, glutinous, cooked||97.0 / 5%||21.1 / 7%||0.2 / 0%||2.0 / 4%||2.0 / 0%||8.0 / 1%||0.1 / 1%||10.0 / 1%||0.0 IU / 0%||0.0 / 0%||0.0 / 1%||0.0 / 0%||0.0 / 1%||0.0 / 1%||0.1|
|White Rice, long-grain, regular, cooked||130 / 7%||28.2 / 9%||0.3 / 0%||2.7 / 5%||10.0 / 1%||43.0 / 4%||1.2 / 7%||35.0 / 1%||0.0 IU / 0%||0.0 / 0%||0.1 / 5%||0.0 / 0%||0.2 / 11%||0.0 / 1%||0.4|
|White Rice, medium-grain, cooked||130 / 7%||28.6 / 10%||0.2 / 0%||2.4 / 5%||3.0 / 0%||37.0 / 4%||1.5 / 8%||29.0 / 1%||0.0 IU / 0%||0.0 / 0%||0.1 / 3%||0.0 / 0%||0.2 / 11%||0.0 / 0%||0.2|
|White Rice, short-grain, cooked||130 / 7%||28.7 / 10%||0.2 / 0%||2.4 / 5%||1.0 / 0%||33.0 / 3%||26.0 / 1%||1.5 / 8%||0.0 IU / 0%||0.0 / 0%||0.1 / 3%||0.0 / 0%||0.2 / 11%||0.0 / 1%||0.2|
|Rice Bran crude||316.0 / 16%||49.7 / 17%||20.8 / 32%||13.3 / 27%||57.0 / 6%||1677 / 168%||18.5 / 103%||1485 / 42%||0.0 IU / 0%||0.0 / 0%||4.1 / 203%||0.0 / 0%||2.8 / 184%||0.3 / 17%||10.0|
|Brown Rice Flour||363 / 18%||76.5 / 25%||2.8 / 4%||7.2 / 14%||11.0 / 1%||337 / 34%||2.0 / 11%||289.0 / 8%||0 IU / 0%||0.0 / 0%||0.7 / 37%||0.0 / 0%||0.4 / 30%||0.1 / 5%||1.5|
|White Rice Flour||366.0 / 18%||80.1 / 27%||1.4 / 2%||5.9 / 12%||10.0 / 1%||98.0 / 10%||0.4 / 2%||76.0 / 2%||0.0 IU / 0%||0.0 / 0%||0.4 / 22%||0.0 / 0%||0.1 / 9%||0.0 / 1%||0.6|
|Wild Rice cooked||101 / 5%||21.3 / 7%||0.3 / 1%||4.0 / 8%||3.0 / 0%||82.0 / 8%||0.6 / 3%||101 / 3%||3.0 IU / 0%||0.0 / 0%||0.1 / 7%||0.0 / 0%||0.1 / 3%||0.1 / 5%||0.4|
*Percent Daily Values (DV) are based on a 2000 calorie diet. Your daily values may be higher or lower, depending on your calorie needs.
Climate conditions, soil and water management
Rice thrives on land that is water saturated or even submerged during part or all of its growth. Optimal temperatures for rice growing are 20 to 37.7degC, and no growth occurs below 10oC. Optimal pH is between 5 and 7, though rice has been grown in fields with pH between 3 and 10. Rice will grow in altitudes ranging from 0 to 2500 m above sea level, but world wide is mostly grown on the humid coastal lowlands and deltas. Aquatic rice may require a dependable supply of fresh, slowly moving water, at temperature of 21 to 29degC. Rain fed rice requires an average of 800 to 2000 mm of rainfall well distributed over the growing season. If rainfall is less than 1250 mm annually, irrigation is used to make up deficit. The crop is salt tolerant at some stages of growth; during germination but not seedling stages and has even been grown to reclaim salty soils. Terrain should be level enough to permit flooding, yet sloped enough to drain readily. The soils on which rice can grow are as varied as the climatic regime it tolerates, but ideally it prefers a friable loam overlying heavy clay, as in many coastal and delta areas.
Propagation and planting
Seedling production. Steps for producing healthy seedlings:
1. Seed selection. Select plump and healthy seeds.
2. Seed pre treatment. This is practised in order to secure better germination of seeds and better growth of seedlings. It involves:
- Seed disinfection. Hot water treatment is effective in destroying the nematode Aphelenchoides besseyi, which causes the white tip disease. For more information on hot-water treatment click here
- Seed soaking. To supply the required moisture for germination, to shorten germination period and reduce seed rotting. During the soaking period change water to remove poisonous substances and allow entry of fresh air.
- Pre-sprouting. The seeds are drained and covered with grass for 24 to 48 hours. This ensures uniform seed germination, avoids over sprouting and allows air circulation for germination.
- Sowing 80 to 100 g/m2 is normal practice.
- Broadcast seed uniformly.
- Do not submerge the nursery bed after sowing.
- Use a seed rate of about 20 kg/acre (50 kg/ha).
4. Seed bed preparation (nursery):
- Plough at least 2 weeks before sowing and flooding.
- Puddle 1 week before sowing and prepare raised nursery bed
- Drain the nursery bed the day before sowing to stabilise the surface of the soil
- If the soil covering the nursery bed is too soft, sown grains are buried into the soil resulting in poor establishment.
- For 1 ha of transplanted rice, a nursery of about 350 m2 is required
- Irrigate a few days after sowing so that the surface is kept moist, and as the seedlings emerge keep submerged conditions with water controlled at 1 to 3 cm according to growth of seedling.
- Raise the water level to 10 cm one day before uprooting to ease washing off of soil that sticks to roots. This will make transplanting easy.
Main land preparation
a) Under irrigation: Land preparation is carried out by flooding the fields to a depth of 10 cm and then cultivating by use of tractor (40 to 75 hp) equipped with rotavators. Good timing and quality of land preparation will influence the growth of rice. Poor and untimely land preparation will cause serious weed problems and expose plants to harmful substances such as carbon dioxide and butyric acid, released by decaying organic matter in the soil.
It is recommended that land should be tilled and immediately flooded at least 15 days before transplanting or direct sowing. The purposes of this are:
- To save the seedling from the effect of high concentration of harmful substances generated by decomposing organic matter rotated into flooded soils.
- To prevent loss of nitrogen released by decomposing organic matter through denitrification. The ammonia released during decomposing of organic matter is conserved because ammonia is not converted to nitrate due to the absence of oxygen in the soil. This ammonia is later utilised by the rice plant.
b) Under rainfed situation: Land should be ploughed twice and harrowed once.
It is important to transplant from the nursery as soon as the seedlings are big enough. Seedlings are said to be ready for transplanting after a period of between 3 to 4 weeks depending on daylight, temperatures and the variety. "Basmati 217" will be ready for transplanting 25 days after sowing (4.5 to 5 leaf stage); "BW 196" and others at 28 to 30 days after sowing (5 to 5.5 leaf number).
Seedlings are spaced according to the tillering ability of a variety. "Basmati 217" should be planted at 20 cm x 10 cm, "BW 196" and others at 20 x 20 cm.
Seedling number per hill: Two to three for "Basmati" and other low tillering varieties. For "BW 196" one to two seedlings per hill are more suitable for good rooting and tillering. Higher seedling rates increase competition for the available nutrients, hence should be discouraged.
Practise shallow planting of about three cm depth for vigorous initial growth and will result in good rooting and tillering. Deep transplanting delays and reduces tillering resulting in a non-uniform crop growth and ripening, consequently resulting in yield losses. Seedlings should be transplanted in an upright position to allow correct tillering and rooting.
Direct sowing method: Trials have been done on direct sowing and have showed that the same level of yields performance as those of transplanting system can be obtained. This method saves substantially on labour input. However it has some disadvantages such as uneven germination rate and more weeding work in the paddy field.
Planting under rainfed conditions:
Planting should be done before the onset of the long rains. Farmers are advised to use certified seed and appropriate variety for the region. Drill seed in rows at the rate of 50 kg/ha with a spacing of 25 cm for short varieties and 35 cm for tall varieties. In case of broadcasting, 75 kg/ha is often used.
Main field water management
Water is applied to the rice field for the use of the rice plant and also for suppressing weed growth. For this reason, it is important to practise appropriate water management throughout the growing period of a rice crop.
In lowland rice fields, water comes from rainfall and irrigation. Water is lost by transpiration, evaporation, seepage and percolation. Prevent water loss by:
- Repairing levees to minimise seepage.
- Removal of weeds to avoid competition with rice plants for water.
- Increasing the height of levees to prevent surface run-off water.
Critical stages when water is required in large quantities are:
- For a period of 3 to 7 days after transplanting cover the crop up to 80% of its height. This reduces transpiration and gives the plants a chance to re-establish their roots to be able to take up enough water from the soil
- From the stage of booting to 14 days after heading, more water is required because the shedding of pollen and the process of fertilsation requires very high moisture content in the air. Low moisture content in the air leads to sterile spikelets.
Seven to 10 days before harvesting, drain the field to harden the soil for good harvesting and also to hasten the drying and ripening of the rice grains.
Varieties in Kenya
"Sindano", highly susceptible to Rice Yellow Mottle Virus (RYMV) and "Basmati 217" highly susceptible to blast have been grown since the 1960s. Since then alternative varieties of both irrigated rice and rain fed rice have been identified.
Varieties of irrigated rice and their characteristics:
|Variety||Height in cm||Maturity days||Yield t/ha||Cooking quality||RYMW||Blast|
|"Basmati 217"||118||122||4.6||Very good||Resistant||Susceptible|
|"Basmati 370"||118||122||5.3||Very good||Resistant||Susceptible|
|"IR 2035-25-2"||86.2||128||5.5||Good||Moderately susceptible||Moderately resistant|
|"BW 96"||68||135||9.0||Fair||Susceptible||Moderately resistant|
|"UP 254"||84.2||124||6.4||Good||Moderately susceptible||Moderately resistant|
|"AD 9246"||78.2||128||5.1||Good||Moderately resistant||Moderately susceptible|
|"IR 19090"||96.6||122||5.8||Good||Moderately susceptible||Moderately resistant|
|Varieties for lowland (swampy) zones||Varieties for upland (dry land) zones|
|"Ci cong Ai"||"Dourado Precose"|
|"TGR 78"||"2051 A 233/79"|
|"IR 2793-80-1"||"TGR 94"|
|"BW 196"||"WAB 181-18"|
|"WaBis 675"||"Nam ROO"|
|"NERICA 1", "NERICA 4", "NERICA 10", "NERICA 11"|
The upland "NERICA" rice varieties were developed at the Africa Rice Center (AfricaRice) ex-WARDA. They are resistant to blast, RYMV stemborers and leafminers and are high yielding and doing well from West Africa to Uganda. They are now also being promoted by NIB (National Irrigation Board), Kenya, KALRO and JICA. In Kenya they have great potential for medium altitudes with high rainfall or possibility for irrigation. "NERICA" can be planted as other small grains, but do need irrigation especially during flowering, and fertilisation.
Some characteristics of the NERICA varieties (KEPHIS)
|Variety||Optimal production altitude (masl)||Maturity in days||Gain yield (t/ha)||Special attributes|
|"NERICA 1"||1500-1700||90-100||2.5-55||Aromatic, blast tolerant, long grains|
|"NERICA 4"||1500-1700||90-112||3.2-6.5||Blast tolerant, long grains|
|"NERICA 10"||1500-1700||86-93||3.5-6.7||Blast tolerant, long grains|
|"NERICA 11"||1500-1700||90-105||3.5||High rationing, tolerant to blast and drought, long grains|
|NIBAM 110||1500-1700||110-120||3.0-5.0||Blast tolerant, RYMV tolerant, long grains, no anthocyanin|
|IR_05N221||Irrigated and rain-fed lowland||75-90||4.0-6.7||Tolerant to some blast and RYMV strains, good cooking qualities, good milling quality|
Varieties in Tanzania
- "Supa". Optimal production altitutde: 0-400 m; grain yield: 1.5-3.5 t/ha; moderately resistant to RYMV and sheath rot.
- "IR 54". Optimal production altitude: 400-600 m; grain yield: 4.0-7.0 t/ha; moderately resistant to bacterial blight and sheath rot
- "IR 22". Optimal production altitude: 400-1000 m; grain yield: 6.6-8.0 t/ha; days to maturity: 120-13"5; resistant to bacterial blight.
- "Katrin". Optimal production altitude: 400-1000 m; grain yield: 6.6-8.0 t/ha; very low panicle shattering.
- "Dakawa". Optimal production altitude: 400-1000 m; grain yield: 3.5-5.2 t/ha; none-photoperiod sensitive; resistant to lodging except under high N levels; easy to thresh.
- "TXD 85". Optimal production altitude: 0-400 m; grain yield: 4.8-7.0 t/ha; moderately resistant to sheath rot, blast and RYMV.
- "TXD 88". Optimal production altitude: 0-400 m; grain yield: 2.8-6.5 t/ha; moderately resistant to sheath rot, blast and RYMV.
- "SARO 5". Optimal production altitude: 0-600 m; grain yield: 4.0-6.5 t/ha; susceptible to RYMV and sheath rot. Adapted to rain-fed lowlands and irrigated ecosystems.
- "Kalalu". Grain yield: 2-3 t/ha; resistant to RYMV and blast.
- "Mwangaza". Grain yield: 2-3 t/ha; resistant to RYMV and blast.
Continuous rice monoculture systems result in decline in soil fertility due to over dependence on chemical fertiliser, and deterioration in physical properties of the soil like texture and microbial existence.
To improve the situation, trials have been carried out on many potential rotation systems. Soybeans and green grams have shown a lot of potential in alleviating the problem. Such legumes can be cultivated during off-season at the time the land used to lie fallow. Crop rotation with bananas or sugarcane is another possibility.
Natural fertilisers commonly used in rice production are rice straw, rice ash, stable manure, buffalo dung, green manure, natural manure, rock phosphate, gypsum etc. The need of nitrogen varies with varieties. In Kenya, commonly about 80kg N/ha is recommended, along with 58 kg P2O5 (Mwea irrigation scheme). However, the National Irrigation Board (NIB) has found that planting soybean or green gram in the fallow season can halve the need for nitrogen. They further recommend composting of rice straw and manure to further cut down on chemical fertilisers. In organic growing, phosphorous can be applied as rock phosphate, and nitrogen through green manure legumes, which fix the nitrogen from the atmosphere.
See also Mwea Rice Production Manual available from NIB.
Time from planting to harvesting varies between 4 to 6 months. Rice is cut, swathed and threshed from windrow. In the tropics it is essential to harvest the crop on time, otherwise grain losses may result from feeding by rats, birds, insects and from shattering and lodging. The crop should be ready to harvest when 80% of the panicles are straw dust coloured and the grain in the lower portion are in the hard dough stage. In a well-grown crop the grain matures evenly and can be harvested in one operation. Cutting can be done with a sickle. The cut stems are bundled for transport to the threshing place, where final drying to around 12% moisture takes place before threshing and storage.