Scientific Name : Oryza sativa
Family : Poaceae
Origin : Indo Burma region(South East Asia)
Rice is a staple food crop of more than 60% of the world population and most of the people of South east Asia.
It is a crop of wet tropical climate and also grown in humid regions of subtropics.
In India rice occupies the first position among the cereals in respect of both area and production.
Rice contains less protein 6-7 % in white rice and 7.9% in brown rice and contains 2-2.5% fat which is lost durin milling.
Rice grain is relatively rich in lysine which is 4% of total protein fraction.
West Bengal is the top rice producing state in India. Apart from this Rice can be cultivated in Uttar Pradesh, Punjab, Bihar, Andra Pradesh, Odisha, Chattisgarh etc.
Classification
Oryza have 24 cultivated species out of which 2 are cultivated.
- Oryza Sativa is diploid(2n=24), It has three main geographic races.
Indica : Grown in tropical and subtropical regions of India.
Japanica : Grown in temperate and subtropical regions of Japan.
Javonica : Grown in Indonesia
- Oryza glaberrima is grown in West Africa only.
Climate
It is a short day plant and requires hot and humid climate.
Soil
Clay and clay loam soils are best suited for rice cultivation.
Acidic soils are most suitable and requires a pH of 4 to 6.
Seasons
Aus/summer : Sowing time April-may
Aman/Kharif : Sowing time June-July
Boro/Rabi : Sowing time November-December
Varieties and Hybrids
Tn-1, Jaya, IR-8, Malinga, Mahsuri, Bala, Cauvery, TKM-6, Lunishree, Norin-8, IR-20, pankaj, CORH-1 etc.
Rice can be grown in 2 methods
Lowland/Transplanted rice cultivation(With Puddling)
Upland rice cultivation(Without puddling)
LOW LAND RICE CULTIVATION
Nursery management
Wet nursery area
Select 20 cents (800 m2) of land area for raising seedlings for one hectare.
Seed rate
30 kg-long duration
40 kg-medium duration
60 kg-short duration varieties and
20 kg-hybrids
Seed treatment
Treat the seeds with Carbendazim at 2 g/l of water for 1 kg of seeds. Soak the seeds in water for 10 hrs and remove excess water.
This wet seed treatment gives protection to the seedlings up to 40 days from seedling disease such as blast and this method is better than dry seed treatment.
If the seeds are required for sowing immediately, keep the soaked seed in gunny in dark and cover with extra gunny bags and leave for 24hrs for sprouting.
Seed treatment can be done by using Pseudomonas fluorescens(10g/ha) or Azospirullum of 600g/ha(3 packets) and leave it for 24 hours and use it for sowing.
Seedbed Formation
Mark plots of 2.5m breadth with channels 30cm wide all around the seedbeds.
Collect the puddled soil from the channel and spread on the seedbeds or drag a heavy stone along the channel to lower it, so that the seed bed is at a higher level.
Level the surface of the seedbed, so that the water drains into the channel.
Sowing
Sow the sprouted seeds uniformly on the seedbed, having thin film of water in the nursery.
Irrigation
Leave the water 18 to 24hrs after sowing.
Allow enough water to saturate the soil from 3rd to 5th day.
From 5th day onwards, increase the water depth to 1.5cm depending on the height of the seedlings.
Thereafter maintain 2.5cm depth of water.
There should not be water stagnation.
Weed Management
Apply pre-emergence herbicides on 3rd or 4th day after sowing to control weeds in the lowland nursery. Keep a thin film of water and allow it to disappear.
Avoid drainage of water which will control germinating weeds.
Manures and Fertilizers
Apply 1t of fully decomposed FYM or compost to nursery and spread the manure uniformly on dry soil.
Basal application of DAP is recommended when the seedlings are to be pulled out in 20-25 days after sowing in less fertile nursery soils.
For that situation, before the last puddling, apply 40kg of DAP and if not readily available, apply straight fertilizers 16kg of urea and 120kg of SSP.
If seedlings are to be pulled out after 25 days, application of DAP is to be done 10 days prior to pulling out.
- Dry nursery area
Dry ploughed field with fine tilth is required.
Nursery area with sand and loamy soil status is more suitable for this type of nursery.
Area 20cents.
Plots of 1 to 1.5 m width of beds and channels may be formed. Length may be according to the slope and soil. Raised beds are more ideal if the soil is clayey in nature.
Seed rate and seed treatment as that of wet nursery.
Sowing may be dry seeding. Seeds may be covered with sand and finely powdered well decomposed farm yard manure.
Irrigation may be done to wet the soil to saturation.
Optimum age for transplanting – 4th leaf stage
This type of nursery is handy in times of delayed receipt of canal water.
Land preparation
Plough the land during summer to maintain the water requirement for preparation of land.
Flood the field 1 or 2 days before ploughing and allow water to soak in. Keep the surface of the field covered with water.
Keep water to a depth of 2.5cm at the time of puddling.
Keep water to a depth of 2.5cm at the time of puddling
Fertilizers and Manures
Apply Urea of 100kg/ha, DAP of 60kg/ha and SSP of 60kg/ha.
25 kg of ZnSo4 is also recommended for rice cultivation.
Along with this apply 12.5t of FYM or compost or green leaf manure of 6.25t/ha.
Pulling out of seedlings
Pull out the seedlings at the appropriate time (4th leaf stage).
Pulling at 3rd leaf stage is also possible. These seedlings can produce more tillers, provided enough care taken during the establishment phase through thin film of water management and perfect leveling of main field.
Transplanting after 5th and higher order leaf numbers will affect the performance of the crop and grain yield. Then they are called as ‘aged seedlings’. Special package is needed to minimize the grain yield loss while planting those aged seedlings.
Weed management
Use of rotary weeder from 15 DAT at 10 days interval. It saves labour for weeding, aerates the soil and root zone, prolongs the root activity, and improves the grain filling though efficient translocation and ultimately the grain yield.
Cultural practices like dual cropping of rice-azolla, and rice-green manure (described in wet seeded rice section 2.5 & 2.6 of this chapter) reduces the weed infestation to a greater extent.
Summer ploughing and cultivation of irrigated dry crops during post-rainy periods reduces the weed infestation.
Pre-emergence herbicides
Use Butachlor 1.25kg/ha as pre-emergence application. Alternatively, pre-emergence application of herbicide mixture like Butachlor 0.6kg + 2,4 D 0.75kg/ha followed by one hand weeding on 30 – 35 DAT will have a broad spectrum of weed control.
Post – emergence herbicides
If pre-emergence herbicide application is not done, hand weeding has to be done on 15th DAT.
2,4-D sodium salt @ 1.25 kg/ha dissolved in 625 litres with a high volume sprayer, three weeks after transplanting or when the weeds are in 3 – 4 leaf stage.
Irrigation
Puddling and leveling minimizes the water requirement
Plough with tractor drawn cage wheel to reduce percolation losses and to save water requirement up to 20%.
At the time of transplanting, a shallow depth of 2cm of water is adequate since high depth of water will lead to deep planting resulting in reduction of tillering.
Maintain 2 cm of water up to seven days of transplanting.
Critical stages
Moisture stress due to inadequate water at rooting and tillering stage causes poor root growth leading to reduction in tillering, poor stand and low yield.
Critical stages of water requirement in rice are a) panicle initiation, b) booting, c) heading and d) flowering. During these stages, the irrigation interval should not exceed the stipulated time so as to cause the depletion of moisture below the saturation level.
Provide adequate drainage facilities to drain excess water or strictly follow irrigation schedule of one day after disappearance of ponded water. Last irrigation may be 15 days ahead of harvest.
Harvesting and Yield
Taking the average duration of the crop as an indication, drain the water from the field 7 to 10 days before the expected harvest date as draining hastens maturity and improves harvesting conditions.
When 80% of the panicles turn straw colour, the crop is ready for harvest. Even at this stage, the leaves of some of the varieties may remain green.
Confirm maturity by selecting the most mature tiller and dehusk a few grains. If the rice is clear and firm, it is in hard dough stage.
When most of the grains at the base of the panicle in the selected tiller are in a hard dough stage, the crop is ready for harvest. At this stage harvest the crop, thresh and winnow the grains.
Dry the grains to 12% moisture level for storage. Grain yield in rice is estimated only at 14% moisture for any comparison.
Maturity may be hastened by 3-4 days by spraying 20% NaCl a week before harvest to escape monsoon rains.
It yields upto 6t/ha during summer and 5.4t/ha during winter.
RAINFED UN-PUDDLED LOWLAND RICE CULTIVATION
The whole growth of the crop depends on the rainfall received in the place and is called Rainfed rice
It is mainly grown in coastal districts of Tamil Nadu like Kanchipuram, Tiruvallur, Pudukottai, Ramanathapuram, Virudhunagar, Sivagangai and Kanyakumari.
Season
June – July – (Coastal northern districts)
September – October (Coastal southern districts
Land preparation
Plough the land to get fine tilth taking advantage of rains and soil moisture availability.
Perfect land leveling should be there for efficient weed and water management.
Provides shallow trenches (15 cm width) at an interval of 3m all along the field to facilitate draining excess water at the early growth stage.
Sowing
Seed rate of 75kg/ha dry seed
Seed hardening with 1% KCl for 16 hours (seed and KCl solution 1:1) and shade dried to bring to storable moisture. This will enable the crop to withstand early moisture stress.
On the day of sowing, treat the hardened seeds first with Pseudomonas fluorescens 10g/kg of seed and then with Azospirillum and Phosphobacteria @ 600g each per ha seed, whichever is available.
Drill sow with 20 cm inter row spacing using seed drill.
The seeds can also be sown behind the country plough
Depth of sowing should be 3 – 5 cm and the top soil can be made compact with leveling board.
Manures and fertilizer application
Apply 50kg/ha urea, 25kg/ha of SSP and 25kg/ha of MOP
Apply a basal dose of 750 kg of FYM
Apply Urea of 25 kg/ha and MOP of 12.5kg/ha in two equal splits at 20 – 25 and 40 – 45 days after germination.
If the moisture availability from the tillering phase is substantial, three splits (25 kg N and 12.5 kg K at 20-25, 40-45 and 60-65 DAG) can be adopted.
Basal application of FeSO4 at 50 kg/ha is desirable for iron deficient soil.
Weed management
First weeding can be done between 15 and 21 days after germination.
Second weeding may be done 30 – 45 days after first weeding.
Apply pendimethalin 1.0kg/ha on 5 days after sowing on the day of receipt of soaking rain followed by one hand weeding on 30 to 35 days after sowing.
UPLAND RICE CULTIVATION
Nutrient may be split applied depending up on the growth.
Use of PPFM-Pink Pigmented Facultative Microbes (seed treatment @ 0.2 kg / 5 kg seeds, soil application basal @ 2.0 kg/ha and foliar spray@ 500 ml/ha at PI & flag leaf stages)for mitigation of terminal drought is recommended.
Intercropping
Use Blackgram for every four rows of rice.
Grain Yield
Grain yield depends up on the moisture availability and nutrient status.
SRI (System of Rice Intensification)
This methodology was developed by Henri de Laulanie in Medagaskar in 1980.
It is an agro ecological approach for increasing the productivity of irrigated rice by changing the management of plants, soil, water and nutrients and cultivating the rice with as much organic manure as possible.
Basic principles in SRI are significantly reducing plant population, irrigation quantities and improving soil conditions by using less or no herbicides/chemicals.
Benefits include 20-100% or more increased yields upto 90% reduction in required seeds and upto 50% water saving.
SRI mainly adopted for irrigated upland or rainfed rice as well as other crops such as wheat, sugarcane, millets, mustard etc.
It is a practice where rice fields are kept wet not flooded with water.
In Andra Pradesh, SRI was demonstrated in all the districts during kharif, 2003.
In SRI, Wide spacing planting 25*25cm are adopted
Transplanting of young seedlings at 2 leaf stage (8-12 days old)
Nursery area of 100m2 is required
Seed rate is 2-5kg/ha
With SRI, Avg yields of rice are 6-7 tons/ha compared to conventional method(2-3 tons/ha).