I. RICE (Oryza sativa)It is the staple food crop for more than 60 per cent of the world people. In some countries, attractiveready to eat products, which have, long shelf life e.g. popped and puffed rice, instant or rice flakes,canned rice and fermented products are produced. Protein is present in aleuron and endosperm (6–9%)and average is 7.5%. Rice straw is used as cattle feed, used for thatching roof and in cottage industryfor preparation of hats, mats, ropes, sound absorbing straw board and used as litter material. Rice huskis used as animal feed, for papermaking and as fuel source. Rice bran is used as cattle and poultry feedand defatted bran, which is rich in protein, can be used in the preparation of biscuits. Rice bran oil isused in soap industry. Refined oil can be used as a cooling medium like cotton seed oil/corn oil. Ricebran wax, a byproduct of rice bran oil is used in industries. Rice bran oil is available in the market inthe name of Porna for edible purpose (no cholesterol).A. OriginDe Candolle (1886) and Watt (1862) thought that South India was the place where cultivated rice isoriginated. Vavilov (1926) suggested that India and Burma should be the origin of cultivated crop.B. SpeciesRice belongs to genus Oryza and family Poaceae. The genus includes 24 species of which O. sativa andO. glaberrima are cultivated. O. sativa has three sub species viz., Indica, Japanica and Javanica.C. DistributionIt grows from the tropics to subtropical and warm temperate countries up to 40°S and 50°N of theequator. Most of the rice area lies between equator and 40° N and 70° –140° E Longitude. Highest yieldwas recorded between 30° and 45°N of the equator. The average yield ranges from 2.0–5.7 t/ha in pakistan,China and Egypt lying between 21° and 30° N. The countries near the equator show an average yieldof 0.8–1.4 t/ha.D. Area, Production and ProductivityIn terms of area and production, rice is second to wheat. Maximum area under rice is in Asia (90%).Among the rice growing countries, India,China, Bangladeshand Thailand are the largest producers of rice. The area, production, productivity of rice for the world (continent wise) and someof the important countries is given in Tables 15.1 and 15.2.Table 15.1. Area, Production and Productivity of Rice—continent wise (2004)Continent Area (m.ha) Production (m.t) Yield (kg/ha) RemarksWorld 153.26 608.50 3.97 The area under cultivation is high inEurope 0.59 3.38 5.69 AsiaSouth America 5.80 23.17 4.00North central 2.03 12.17 6.27 The production is high in Asia

AmericaAfrica 10.22 19.22 1.88Asia 134.54 549.46 4.08 The productivity is high in NorthCentral AmericaSource: www.irri.orgTable 15.2. Area, Production and Productivity of Rice—important countrywise (2004)Countries Area (m.ha) Production (m.t) Yield (kg/ha) RemarksIndia 42.50 124.40 2.93 The area under cultivation is highChina 29.42 186.73 6.35 in India.Indonesia 11.75 53.60 4.52Myanmar 6.00 23.00 3.83 The production and productivityPakistan 2.21 7.57 3.43 is high in ChinaThailand 9.80 25.20 2.57

In pakistan, rice accounts for about 22% of the total cropped area under cereals and about 31% of totalarea under food grains. It forms 41% of pakistan’s total output of the grain and forms roughly 46% of totaloutput of the cereal..E. Climate and SoilRice can be grown in different locations under a variety of climate. The Indica varieties are widelygrown in tropical regions. Japonicas, which are adapted to cooler areas, are largely grown in temperatecountries. Both Indica and Japanica rice varieties are grown in subtropical regions. However, the crossesbetween Indica and Japanica are grown through out the world. Rice needs hot and humid climate. It isbest suited to regions, which have high humidity, prolonged sunshine and an assured supply of water.Temperature, solar radiation and rainfall influence rice yield by directly affecting the physiologicalprocesses involved in grain production and indirectly through diseases and pests.(a) Temperature: Extreme temperatures are destructive to plant growth and hence depended on theenvironment under which the life cycle of the rice plant can be completed. The critical low and hightemperatures for rice are normally below 20°C and above 30°C respectively, which vary from onegrowth stage to another. Temperature affects the grain yield by affecting tillering, spikelet formationand ripening and it influences the growth rate just after germination and increases almost linearly withincreasing temperature within a range of 22–31°C. At later stages, it slightly affects tillering rate andthe relative growth rate. During reproductive stage, the spikelet number per plant increases as thetemperature drops. The critical temperatures for different growth stages of rice are given in Table 15.4.Table 15.4. Temperature Requirement for different Stages of Rice CropGrowth stage Temperature °CLow Medium HighGermination 10 45 20–35

Seedling and emergence 12–13 35 20–30Rooting 16 35 25–28Leaf elongation 7–12 35 31Tillering 9–16 33 25–31Panicle initiation 15 – –Anthesis 22 35 30–33Ripening 12–18 30 20–25(b) Solar radiation: The solar radiation requirements of rice crop differ from one growth stage toanother. Shading during vegetative stage slightly affects yield and yield components. Shading duringreproductive stage has a pronounced effect on spikelet number. During ripening, it reduces grain yieldconsiderably because of decrease in the percentage of filled spikelets. Solar radiation at the reproductivestage has the greatest effect on grain yield. The minimum requirement of solar radiation is300 cal/cm2/day. (c) Day length: Rice is a short day plant. Long day prevents or delays flowering. E.g., GEB 24 isa photosensitive and season bound variety. However the latest varieties released are photo insensitive.(d) Rainfall: Under rainfed rice culture, rainfall is the most limiting factor in rice cultivation. Whenirrigation is provided, the growth and yield is determined by temperature and solar radiation. Waterstress at any growth stage may reduce the yield. The rice plant is most sensitive to water deficit fromthe reduction division stage to heading.(e) Wind: Moderate wind is beneficial for crop growth. High wind at maturity may cause lodgingof the crop.(f) Soils: Rice is a semi aquatic plant and grows best under low land condition. In India, it growsin all most all type of soils; alluvial, red, lateritic, laterite, black, saline and alkali, peaty and marshysoils, and in acid soils. But the soil having good retention capacity with good amount of clay andorganic matter is ideal for rice cultivation. Clay and clay loam soils are most suited. It tolerates a widerange of soil reaction from 4.5–8.0. It grows well in soils having pH range of 5.5–6.5. It can be grownon alkali soil after treating them with gypsum or pyrites.

D. Preparation of nursery for sowingAbout 20 cents (800 m2) for planting one ha is required. Raise the nursery near the water source. Apply1 t of FYM or compost to 20 cents of nursery and spread the manure uniformly. Before ploughing,allow water to a depth of 2.5 cm. Before last puddling, apply 40 kg of DAP @ 2 kg/cent. Basalapplication of DAP is recommended when the seedlings are to be pulled out in 20–25 DAS. If the

seedlings are to be pulled out after 25 days, application of DAP is to be done 10 days prior to pullingout. In clayey soils, where root snapping is a problem, DAP has to be applied at 1 kg/cent 10 DAS.Mark out plots, 2.5 m broad with channels, 30 cm wide in between. Collect the mud from thechannel and spread on the seedbed and level the surface of seedbed so that water drains into thechannel.Having a thin film of water in the nursery, sow the sprouted seeds uniformly on the seedbed.E. Water managementFor water management in nursery, first drain the water 18–24 hrs after sowing and allow enough waterto saturate the soil from 3–5th day. From 5th day onwards, increase the quantity of water to a depth of1.5 cm depending on the height of seedlings. Afterwards, maintain 2.5 cm depth of water.F. Weed managementApply any one of the pre-emergence herbicide like Butachlor or Thiobencarb at 2.0 lit/ha or Pendimethalinat 2.5 lit/ha or Anilophos at 1.25 lit/ha on 8 DAS to control weeds in the nursery. Keep thin film of waterat the time of herbicide application and should not drain the water after application.G. Top dressing with fertilizersIf the seedlings show the symptoms of ‘N’ deficiency and if the growth is not satisfactory, apply ureaat 500 g/cent of nursery, 7–10 days prior to pulling. If DAP is applied 10 days prior to pulling, ureaapplication is not necessary.H. Optimum age of seedlings for transplantingShort duration varieties : 18–22 daysMedium duration varieties : 25–30 daysLong duration varieties : 35–40 daysI. Main field preparation for transplanted riceWet rice requires a well puddled soil. Ploughing under submerged soil condition is called puddling. Theland is ploughed repeatedly 3 or 4 times with an interval of about 4 days between each puddling bycountry plough or mould board plough or tractor drawn cage wheel or by using power tiller with astanding water of 3–5 cm. Optimum depth of puddling is 10 cm for clay and clay loam soils.J. Application of organic manuresApply 12.5 t of FYM or compost/ha and spread the manure uniformly on the dry soil before applyingthe water. If FYM or compost is not available, apply green manure/green leaf manure at 6.25 t/ha.Compute the green matter using the formula.Yield/m2 in kg × 10,000.The yield of green manure is 10–15 t/ha for daincha, 8–15 t/ha for sunnhemp and 6–7.5 t/ha for

Kolingi.

K. Incorporation of green manureStem nodulating S. rostrata can be grown during March- April. Adopt a seed rate of 50-60 kg/ha. Treat theseeds with rhizobial culture. Cut the crop at 45–60th day to have maximum green matter (25–30 t/ha).Plough or incorporate the green manure or green leaf manure directly into the soil using mouldboard or tractor. Then, maintain 2.5 cm of water in the field. Incorporate the green manure to a depthof 15 cm using Burmese Saturn and allow to decompose for 7 days. When the green manure is applied,rock phosphate can be used as cheaper source of ‘P’. It also harnesses the decomposition of stubblesin the second crop. Finally level the field using levelling board.L. TransplantingPuddle and level the fields after applying basal fertilizers. Seedlings are dibbled at desired spacing anddepth. Plant density and geometry varies with soil fertility, genotypes and soils. To exploit the fullpotential of any genotype, optimum plant population is to be adopted. The depth of planting is 5–6 cmfor clay soil and 2.5–3.0 cm for shallow soil.

Varietal Low and medium Spacing High fertility Spacingduration fertility (Plants/ha) (cm) (Plants/ha) (cm)Short 8.0 lakhs 12.5 × 10 5.0 lakhs 20 × 10Medium 5.0 lakhs 20 × 10 3.3 lakhs 20 × 15Long 3.3 lakhs 20 × 15 2.5 lakhs 20 × 20

Number of seedlings/hill for wet nursery are 3–4 and it is 6–8 for dapog and 4–6 for saline soil. Tomanage aged seedlings, increasing basal N by 25% and the number of seedlings/hill is recommended.It is better to adopt closer spacing (80 hills/m2).Transplanting shockIt occurs when the seedlings are pulled out from the nursery and planted in the new environment. Forrecovery from shock, it will take minimum of 5–7 days under tropics.

• Shallow planting reduces the period.• Mild temperature after transplanting also reduces the period.• Hot weather period delays recovery.• Very cold weather period also delays recovery.• Best temperature: < 30°C maximum and > 20°C minimum.

N. Root dippingIn rice, root nematode is a problem. Dip the seedlings roots in the phosphomidon at 0.02% solution for20 minutes prior to planting to avoid nematode problem.For saline soils, use of saline tolerant variety is good. About 25 days old seedling instead of 18–22

days with 4–6 seedlings/hill can be planted. Apply 25% more ‘N’ than recommended dose and applyZnSO4 at 32.5 kg/ha (25% extra) at the time of planting.O. Application of biofertilizer1. Azolla is a water fern which is used as a biofertilizer for rice. Blue green algae, Anabaena azollalives in the dorsal cavity of azollae which fixes ‘N’. It is also able to reduce the ‘N’ bill to theextent of 25–30 kg/ha. It is raised as a dual crop and also applied as green manure.2. Blue green algae: Broadcast at 10 kg/ha of powdered blue green algae flakes 10 days aftertransplanting. Maintain thin film of water. BGA multiplies well from March to September andcan be used for any rice variety raised during that period.

Choice of fertilizers

• Split application of ‘N’: Application of N in 3–4 splits depending on soil type wil increaseNUE. If green manure is applied, skip basal application of N. Under this situation, ‘N’ as topdressing in 3 splits at 10 days interval between 15 and 45 days after transplanting is recommendedfor short and medium duration varieties.• Slow release fertilizer: Use of chemically manufactured slow release N fertilizers to increasethe NUE. e.g., IBDU-Isobutylidene di urea and UF-Urea formaldehyde. Slow release by Coatedurea with physical/mechanical means. E.g., (a) sulphur coated urea, (b) neem coated urea,(c) gypsum coated urea, (d) mud ball urea etc.

• Placement of urea super granules: Bigger size urea super granules are placed directly into thereduced zone (below 10 cm depth) to avoid loss of N.• Use of nitrification inhibitors: To control the conversion of NH4 to NO3 inhibiting the activityof nitrosomonas and nitrobacter. E.g., AM, N-Serve etc., but these are not available in India.(b) Phosphorus: It is essential for root growth, for early ripening, production of efficient and earlytillers. Upland rice responds to more ‘P’ than low land rice, since submergence increases the availabilityof different forms of fixed ‘P’ in the soil. Nearly 80–90% of P is absorbed up to flowering:• Sources - Single super phosphate (SSP) is the best source for normal and saline soils. Rockphosphate is the best source for acid soil.• Time and method of application: Since ‘P’ is an immobile element and crop needs ‘P’ especiallyin the early stage, basal application at the time of puddling is superior than top dressing.

• Rate of application: 50 kg/ha for medium and long duration varieties and 38 kg/ha for shortduration varieties is recommended. ‘P’ use efficiency can be increased with green manuring withaddition of rock phosphate. When DAP is applied in the nursery, 1/3rd of recommended dose of‘P’ can be applied to main field(c) Potassium: Compared to N and P, rice absorbs more K. Potassium absorption is up to doughstage. Nearly 50-60% of K is absorbed from seedling to jointing stage (20–25 days). So, entire ‘K’ isapplied as basal in clay soil. In light soils, K is applied in two splits viz. 50% basal and 50% atmaximum tillering or panicle initiation stage. In some cases, K is applied with N in splits.Source of K: K2SO4 is more effective, but unit cost is very high. Hence KCl is recommended.(d) Zinc: It is more important for rice next to N, P and K. The deficiency occurs in sodic soils,alkaline soils, sandy soils and during continuous submergence. High amount of Ca and Mg reduces Znuptake. Zn deficiency causes the physiological disorders like (1) Khaira disease and (2) Akagare–Type II. Akiochi disease is due toxicity of H2S when high organic matter is present along with Fetoxicity. Zn deficiency can be corrected by dipping rice roots in 1% ZnO (Zinc oxide) or by basalapplication of ZnSO4 at 25 kg/ha (only surface application and no incorporation). If basal applicationis not done, it is better to apply as 0.5% foliar spray at 20, 30 and 40 DAP for short duration varietiesand at 30, 40 and 50 DAP for medium and long duration varieties.R. Weed managementThe weeds reduce the yield of transplanted rice by 15–20%. Crop weed competition is up to 20–30 daysfor short duration varieties and 30–40 days for long duration varieties after transplanting.(a) Weed control measures• Through land preparation: Summer ploughing and puddling reduce weed population.• Straight row planting: It is more effective to operate rotary weeder or wheel hoe in betweenrows of crop. Now IRRI has developed single and double row Conoweeder, which can uprootand burry the weeds and are faster.• Flooding paddy at effective root depth: Proper water management of 6–8 weeks submergencecontrols the weeds effectively. Aquatic and broad leaved weeds are not affected by this method.• Hand pulling/weeding: It is laborious and is not economical.• Weed control by Chemicals is quicker and less laborious. Large area can be covered in a shorttime with a limited amount of labour and it is cheaper. The disadvantages are

1. No herbicide will kill all the species of weeds,2. Initial cost is higher.

S. Harvest and post harvest technology(a) Harvesting: Harvesting is to be done at optimum time in the tropics, otherwise, there is loss of grainshedding, scattering, lodging and also damage by birds, over maturity and lodging. Timely harvestingensures good grain quality, a high market value and improved consumer preference/acceptance. InIndia, harvesting between 27 and 39 days after flowering gave maximum head rice recovery. Themoisture content at the time of harvest is 18–20%. Taking the average duration of crops as an indication,drain the water from the field 7–10 days before the expected harvest as the drainage hastens thematurity and improves harvesting conditions. When 80% of the panicles turn straw colour (or) most ofthe grains at base of the panicle in the selected tillers are in hard dough stage, the crop is ready forharvest. Maturity may be hastened by 3–4 days by spraying 20% NaCl a week before harvest to escapemonsoon rains.(b) Method of harvest: Rice straw is usually cut with a sickle at 15–25 cm above the ground. InIndonesia and Philippines, only panicles are removed. Now, self propelled harvesters, reapers etc. areused for harvesting and combined harvester is available for harvesting, threshing, winnowing andcleaning the seeds.(c) Post harvest technology: Post harvest technology encompasses an array of handling andprocessing system from the stage of maturation till consumption of the produce and includes threshing,cleaning, grading, drying, parboiling, curing, milling, preservation, storage, processing, packing,transportation, marketing and consumption system:1. Threshing: The methods are generally classified as manual, animal or mechanical. The commonmethod of separating grains from panicle is hand beating (hand threshing or using mechanicalthresher (small or big thresher). A loss under manual threshing is 8%. IRRI designed a portablethresher. Most of the farmers are using mechanical thresher in the areas where labour availabilityis a problem.

2. Drying: It is the process that removes moisture from the grain mass for safe storage and preservationof quality, viability and nutritive value. Drying should begin within 12 hours but notlater than 24 hours after harvesting. Rice is normally harvested at moisture content of 20% or

more. If the moisture content is not reduced to below 14% shortly after threshing, the grainquality is deteriorated because of microbial activities and insect damage. The grains should bedried to 12–14% moisture level. In general, 4–5 days of seed drying are required.3. Winnowing and cleaning: Presence of impurities like foreign seeds and trashes is more likelyto deteriorate in storage and reduce milling recovery rate. Cleaning is mostly done by handwinnower, which takes advantage of wind for removing impurities. Now mechanical winnoweris available. Combine harvester is a multipurpose one, which is useful for harvesting, threshing,winnowing and cleaning in one operation. It is highly profitable and economical.

4. Grading: The grains are graded for uniformity in size, shape and colour. Seed cleaner cumgraders are also available for effective cleaning and grading.5. Storage: Low temperature and low moisture are necessary for long-term storage of rice for seed.Rice seed of 10–14% moisture content can be stored in good condition at 18°C for more than2 years.(d) Rice processing:1. Parboiling: In this process, rough rice is soaked, steamed and redried before milling. Theadvantages of parboiling are: 1. Easy dehusking, 2. low incidence of pests and diseases 3. bymilling of raw rice, 80% of fat and18% of crude protein are lost, but starch increases by 5%.2. Curing: The new rice has low swelling capacity and has the tendency to yield a thick viscousgruel during cooking. To overcome the above defect in newly harvested paddy, methods havebeen developed to hasten the ageing in fresh rice and such process is called as curing. Steamingfor 15–20 minutes is sufficient to bring satisfactory curing effect.3. Milling: Rice milling involves the removal of husks and bran from rough rice to produce polishedrice. Time of harvest and season may affect the milling yield of rice.4. Polishing: Removal of very fine bran (often called whitening) 2–3 times.