Rice

Rice belongs to the tribe Oryzeae, sub-family Poacoideae in the grass family Poaceae (syn. Gramineae). The genus Oryza is said to contain six species of which Orysa sativa Linn is commercially the most important and Oryza glaberrima Steud is the red-skinned species indigenous to West Africa and widely cultivated in these parts. Cultivated rice is a near semi-aquatic annual grass, although it can survive as a perennial grass in the tropics, producing new tillers.

  • Uses of Rice
  1. Food
  2. Starch
  3. Beverages
  4. Briquettes from Husk
  5. Livestock feed from Husk
  6. Alcoholic beverages
  7. Ceramics from Husk
  8. Fiberboard from Husk
  9. Composting from Straw
  10. Roofing material from Straw
  • Soil and Climatic Conditions Required for Production

The type of soil suitable for rice cultivation depends more on the conditions under which the plant is grown than the nature of the plant. For example, under upland condition, the main production determinant is the nature of the rainfall. Though total effective rainfall is important, rainfall distribution is even more important. Generally, the soil requirement depends on the adequacy and regularity of rainfall. If these climatic conditions are adequate, the range of soils in which upland rice can be cultivated is fairly wide. However, if the rainfall cannot be relied upon, it would be necessary to choose a soil which has high water holding capacity, a medium textured soil, deep and at the foot of the slope. On the other hand, for the semi aquatic conditions under which irrigated and rainfed lowland rice is grown, a heavy soil which will not allow easy percolation of irrigation or rain water, because the demand of the crop for water is more precise than its demand on soil conditions. Besides the desirability to grow the crop on a heavy soil capable of holding water on the land, there appears to be a direct evidence that the crop performs better on heavy clay soil than upon lighter soils containing a high proportion of sand. Thus, clay soils derived from basic rocks like basalts and amphiboles have been found superior to those from more coarse loam.

  • Planting Materials

Early work on varietal improvement focussed on the introduction of elite varieties from Asia 0r other African countries and on genetic improvement through hybridization. These activities gave rise to early varieties, which were mostly tall and photoperiod sensitive adapted to deep water and flooded ecologies. These varieties were released as FAROs 1 to 10.

Most of these varieties were introductions that were tested and found suitable for Nigerian rice growing environment. FAROs 1, 2, 8, 9 and 10 were identified and released for the shallow swamps of rainfed ecologies of the inland valleys, while FAROs 4, 6 and 7 were released for deep­water flood plain ecologies. The only upland variety was FARO 3 (Agbede) and was the only locally identified cultivar from a collection of complex upland cultivars earlier introduced by the First World War veterans. At this time too, Oryza glaberimma cultivars showed superiority over the improved and introduced cultivars such as FARO 6 and 7. These were Baidande and Jatau, but were never given varietal numbers.

Though the objective of rice breeding in Nigeria was to change in favour of semi-dwarf cultivars, other varieties identified or improved and released immediately after this period were still tall and photoperiod – sensitive varieties. These were FAROs 11, 12, 13, 14, 15, 16 and 17. FAROs 11, 12 and 13 were introductions, while FAROs 14, 15, 16 and 17 were locally improved varieties through hybridization and selection, for the shallow swamps. FARO 14, however, was adapted for deep water ecology. Following the development of semi-dwarf cultivars at the International Rice Research Institute (IRRI), Philippines, FAROs 18 and 24 were introduced, evaluated and released in Nigeria in 1974. Between 1966 and 1974 only two upland cultivars were released. These were FAROs 11 and 25. FARO 25 was a local breed of a cross of Jete and Tjina (FAROX 56/30). This showed that emphasis was placed more on lowland rice research and production than the others.

Between 1982 and 1986, 14 varieties were locally developed and released in Nigeria. Nine of these were developed by the national programme of NCRI (FAROs 26 to 34) and released for shallow swamp or irrigated ecologies. Another two cultivars, FAROs 35 and 37 developed by the International Institute for Tropical Agriculture (IITA) were also released for irrigated ecology. IITA also developed one upland cultivar (ITA 128) released as FARO 43. Another national research Institute, Institute of Agricultural Research and Training (IAR&T) developed ART 12, which was released as FARO 42. It can be seen that a lot of attention was devoted to the development of upland rice varieties at this time. In fact, three upland cultivars were adopted from IRAT, Cote d’Ivoire and released as FAROs 38, 39 and 41.

From 1992 till date, eight other cultivars were released (FAROs 44 to 57). FAROs 44 and 51 are Productions from Taiwan and Indonesia, respectively and were identified through the International Rice Testing Programme for Africa (INGERAfrica), while FAROs 45, 46, 47, 48, 49 and 50 were varieties developed by IITA rice programme. FAROs 55 and 56 are NERICA 1 and NERICA 2 respectively (NERICA = New Rice For Africa). These are recent introductions from WARDA.

  • Rice Processing:

Rice processing usually involves parboiling and milling. There are two major types of milling-

  1. Milling of paddy rice to produce the rice grains
  2. Milling of rice grains into flour.

Paddy Rice Processing:
In this process, paddy rice (harvested rice with its husk) is given hydrothermal treatment (parboiled) to meet certain consumer preferences before milling. There are three major steps in preparing paddy rice before milling. These include; soaking/steeping, steaming/parboiling and drying. These steps bring about certain changes in the physical, chemical and aesthetic qualities of milled rice.

  1. Soaking/Steeping:
    The main objective of this process is to achieve quick and uniform water absorption. The rice paddy is soaked in hot water at about 70°C for 5 – 6 hours. The grain absorbs moisture and reaches a moisture content of 30 – 36% in 2 to 4 hours.
  2. Steaming/Parboiling:
    This is the heat treatment of soaked paddy to complete the physical and chemical changes in the rice grain. During steaming, the moisture content of the paddy increases to about 38%. Water is boiled to a temperature of 100°C and the soaked paddy lowered into it for about 15 – 20 minutes during which time the husks split. The cracking of 50% of the paddy rice indicates the end of steaming.
  3. Drying:
    Parboiled rice should be dried to a moisture content of 14% for safe storage or milling. The manner in which moisture content is attained is of very great importance. If drying is done too fast, internal stresses develop in the grain and cause breakage during milling. If the moisture is removed at a very slow rate, microorganisms will grow and partially or fully spoil the parboiled rice. After drying is completed, the paddy should be allowed to stand for at least 1 or 2 days before it is milled to permit internal moisture differences and stresses to equalize.

Milling:
Milling can be carried out by traditional or by mechanized means. In traditional milling, parboiled or raw paddy is pounded in a mortar with pestle after drying. The husk is then blown off by the air or wind. Optionally, the dehusked or brown rice is pounded lightly to remove the bran before consumption or marketing. Two models of mechanized mills are available. The small capacity single mills usually operated at the village level. Their capacities range from 45- 270 kg of paddy/hour. They are powered by electric motors, diesel engines or tractors. Such mills combine the dehusking and polishing process into one operation. The other is the larger capacity multi-purpose machines, which use a different machine for each processing step. Bucket elevators are used to move the grain from one machine to the next. The capacity of a standard size is 2 to 4 t/hr.

Direct Milling into Flour:
Both parboiled and non-parboiled paddy rice can be processed to produce milled rice that would be milled to rice flour. However, the commonest raw material for rice flour production is broken, non-parboiled rice. Rice flour is mainly used for the extraction of starch used in other industries such : pharmaceutical, food and beverages, textile etc.

fc for paddy rice and flour production.

 

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