In India, rice is cultivated mainly on two types of soils i.e., uplands and lowlands. The IS method of cultivation of rice in a particular region depends largely on factors such as situation of land, type of soils, irrigation facilities, availability of labourers, intensity and distribution of rainfalls.
The crop of rice is grown with the following methods:
1. Upland Rice Cultivation:
The upland rice cultivation is mostly adopted in rainfed regions and irrigation facilities are not available. The rainfed uplands are those where aerobic soil environment exists for major period of crop growth and development. There is no water stagnation on the soil surface 48 hours after cessation of rainfall. Due to failure of monsoon, the farmer has to bear a heavy loss.
A vast tract of upland paddy (85%) is located in the states of Assam, Bihar, West Bengal, Orissa, Chhattisgarh, parts of U.P., Tamil Nadu and Andhra Pradesh. The rainfall in these zones varies from 1000 to more than 2000 mm and temperature ranges from 25 to 41°C in July and from 6-25°C in January.
The average yield is less than 1 t/ha due to the following reasons:
i. Moisture stress due to erratic distribution of rains causes drought.
ii. Heavy infestation C4 type of weeds, which are highly competitive with rice crop.
iii. Lack of organic matter, low in N content and low availability of phosphorus, zinc and iron especially in high pH calcareous soils.
iv. Leaching losses of N is more due to light textured soils and soil erosion under un-bonded uplands.
v. Stresses like soil acidity, P deficiency, high P fixation, Al and Mn toxicity in acid soils and Fe deficiency in alkaline soils.
vi. Biotic stresses caused by insect pests and diseases.
vii. Inadequate crop stand caused by traditional method of broadcast seeding coupled with adoption of tall varieties.
viii. Problem in harvesting, threshing and drying in the event of heavy rains during September and October.
In order to meet the growing food demand of the country, there is an urgent need to step up the rice production of this fragile ecosystem. With the adoption of improved production technologies, it becomes possible to increase the productivity of uplands.
Rainfed lowland rice is sown largely by broadcasting in dry or moist fields before or immediately after receiving monsoon showers of south-west monsoon. Uncertainty of the onset of monsoon, need to plant very large area in the shortest span of time and cultural conditions in moist soil types compel the farmers to resort to broadcasting.
On the basis of water regime, rainfed lowlands may be classified into shallow lowland (<30 cm water depth), semi-deep water (30-100 cm water depth) and deep-water (>100 cm water depth) sub- ecologies. In semi-deep and deep-water lowlands, direct seeding behind the country plough is practiced.
Farmers usually grow tall, low productive and lodging-prone rice varieties in uplands. The ideal characters for upland rice varieties are early seedling vigor, medium height, moderate tillering, early maturity (75-105 days), deep roots, drought tolerance, heavy panicles, tolerance to major insect pests and diseases, adequate seed dormancy, acceptable grain quality and responsive to moderate to high management. Many such varieties are available for upland conditions in the country. In rainfed unbunded uplands, where there is a limitation of soil moisture, short duration varieties (70-90 days) are needed.
Proper field preparation and leveling should be followed for achieving adequate crop stand and higher yield. After harvesting of the rabi crops in April-May, the land should be opened with a mould board plough. This prevents the land from getting hard on drying and enables enhanced root growth, conserve moisture at lower depth of soil. Summer ploughing helps in controlling weeds effectively. The field is prepared and bunds are made around the field just after the first shower of monsoon. This will check loss of rain water by run-off.
Optimum time of sowing is one of the important aspects of crop production, especially under rainfed situation. It is governed by the onset of monsoon. The crop must be sown soon after monsoon sets in and 15-20 cm deep soil layer becomes completely wet. Work done by different scientists indicated that mid-June to the end of June is the optimum time for realizing higher yields from rainfed uplands of eastern India.
If the sowing is delayed, crop is adversely affected because of soil and atmospheric drought due to aberrant weather conditions during the grain filling stage. This results in shriveling grains of poor quality. In some rice growing areas, dry seeding a little before onset of monsoon is practiced. The seed remains in the soil, which germinates with the onset of rains. This method is called as khurra sowing in Chhattisgarh.
Select heavy, disease free seed by dipping in 10% salt solution. To treat seed required for one hectare put 1 kg salt in 10 litres of water. Dip 2-3 kg of seed in this solution and remove the empty and unhealthy seeds which float at the surface of the water. Collect heavy seed settled at the bottom and wash it 2-3 times with water.
Repeat the process for required quantity of seeds. Washing is done to remove the adhered salt which may otherwise reduce the germ inability of the seed. Heavy seed selected by this method ensures healthy, sturdy and uniform seedlings which result into uniform crop growth in the field.
i. Treat the seeds with Carbendazim or Tricyclozole solution at 2 g/l of water for 1 kg of seeds. Soak the seeds in water for 10 hrs and drain 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 bags in dark place and cover with extra gunnies and leave for 24 hrs for sprouting.
ii. Treat the seeds with talc based formulation of Pseudomonas fluorescence 10g/kg of seed and soak in 1 liter of water overnight. Drain the excess water and allow the seeds to sprout for 24 hrs and then sowing may be performed.
iii. Three packets (600 g/ha) of Azospirillum and 3 packets (600g/ha) of Phosphobacteria or 6 packets (1200gAia) of Azophos. In bio-inoculants mixed with sufficient water wherein the seeds are soaked overnight before sowing in the nursery bed (The bacterial suspension after decanting may be poured over the nursery area itself). Bio-control agents are compatible with biofertilizers. Biofertilizers and bio-control agents can be mixed together for seed soaking. However, fungicides and biocontrol agents are incompatible.
Plant population is the basic prerequisite and key factor in determining the quantum of yield. Inadequate crop stand could lead to ineffective utilization of costly inputs. The seed rate naturally influences the growth of the seedlings. Thin sowing gives strong and tiller seedlings, whereas thick sowing provides thin and tall seedlings without tillers.
Under upland conditions, drilling or line sowing is always better than broadcast because line sowing facilitates the cultural operations and enables to identify the weeds even at the early stage for weeding purpose. Usually sprouted seed should be sown in rows 30 cm apart at a depth not more than 5 cm. The moisture stress condition may result in poor germination, therefore about 25% higher seed rate than the recommended rate (100-120 kg/ha) should be used.
Drill the seeds with seed drill or behind the plough with the help of funnel in rows after applying fertilizer. The row to row distance should be 20 cm. About 60-80 kg seed/ha is recommended. Bullock-drawn seed drills of 3 rows and tractor-drawn seed drills of 9 rows can cover 0.4 and 2 ha/day, respectively. For obtaining uniform plant population and higher crop yields, it is advisable to thin out the excess plants or reshowing in gaps in the rows after about 2-3 weeks of sowing.
Adequate supply of essential plant nutrients in balance quantity is necessary for getting good yield of rice. Most of the uplands are poor in fertility status. Due to higher elevation and light textured soils, percolation losses may result in low availability of N due to excessive leaching.
Crop response to application of manures universally accepted under upland conditions, hence FYM or compost @ 10-15 tonnes/ha should be incorporated 4-6 weeks before sowing. The recovery of N is low (20-30 %) because of moisture stress and weed growth in uplands. Deficiency of phosphorus is common in red and lateritic soils, hence its application is essential. Similarly, potassium also helps in improving the WUE and yield.
In case of rainfed upland ecologies, 45-60 kg N/ha is recommended in 3 equal split doses. The first split dose of N (15-20 kg/ha) is given basal before last harrowing. If native N available in soil is not too low, the first application should be delayed till the first weeding (20 days after germination).
The second dose of nitrogen should be applied as top-dress after 40 days from germination and the third dose a week before panicle initiation. Adequate soil moisture is essential for top-dressing N fertilizer. Application of phosphorus (30-35 kg P2O5/ ha) and potassium (20-30 kg K2O/ha) is also required to be applied on the basis of soil test results.
In case of rainfed lowlands, 60 kg N/ha is applied in three split doses with one-half (30- 40 kg) as basal dose at the time of final land preparation and one-fourth (15-20 kg) as top dress each at early tillering stage and a week before panicle initiation. Water should be drained out before top-dressing and let in 24 hour later.
In areas, where first top dressing is not possible due to excess standing water, it is added to the basal dose itself in the form of either neem-cake or coulter-coated urea, which release N slowly. About 40-45 kg P2O5 and 30 kg K2O/ha should be applied basal depending on soil-test value.
Beushaning (Biasi):
This method of sowing is followed in direct-seeded lowland rice in Chhattisgarh, Orissa, Madhya Pradesh, Bihar and to some extent in West Bengal, Assam and U.P. to control weeds, optimize crop stand and provide soil aeration. The method involves direct seeding of rice during the onset of first pre-monsoon showers followed by cross ploughing the young crop 30-40 days after sowing with a light country plough in 5-10 cm standing water once or twice depending on the density of weeds and crop stand.
If weed population is more, ploughing is followed by planking. This practice is called biasi in Chhattisgarh and beushen in Orissa. After this operation, the crop is weeded, thinned and the gaps are filled with the uprooted seedlings. This operation is called chalai or khelua. In some areas, khelua is done a week or 10 days after beushaning. It has been observed that beushening reduce the straw yield and increase the grain yield by controlling vegetative growth. Improved beushaning involves sowing of rice in lines and interculturing with a country plough in between the inter-row spaces.
Interculturing with cono-weeder also results in similar yield advantages as with beushaning. It is also feasible to grow rice and dhaincha (Sesbania aculeata) simultaneously and incorporating the latter at an appropriate stage after accumulation of water in the field during the beushaning operation. This way N requirement of rice is also met partially, equivalent to 30-40 kg N/ha of urea fertilizer. However, this practice is possible only under excess water situations.
2. Wet or Lowland Rice Cultivation:
This system of rice cultivation is practiced in areas having an assured and adequate supply of water. In this system, the field is brought to a soil puddle by repeated ploughing with 5-7 cm standing water. After obtaining requisite puddle condition, sprouted seeds may be directly sown or the rice seedlings raised in the nursery are transplanted. It is also called as medium land rice for those areas, which receive an annual rainfall of 1,000-1,500 mm.
Selection of site for transplanting in kharif, nursery may be raised on upland area where there is no standing rainwater. For rabi and summer nurseries lowland area can be chosen. However, nursery should be grown on loam or sandy loam soil because on such soils, uprooting of the seedlings is easy. Follow the procedure for the selection of seed and their treatment.
In India one, two and three crops of rice is grown in a year. However, majority of rice is grown in rainy (kharif) season. In north-western and central India only kharif crop of rice is grown, in eastern India, kharif, boro (Rabi) and summer three crops are grown and in south, 3-4 crops are grown in a year.
There are 3 methods of raising seedlings as detailed below:
(A) Wet Nursery:
Wet nurseries are preferred under assured supply of irrigation. Select field for raising nursery near to water source. To provide seedlings for one hectare, the nursery area should be 1/10th of a hectare (1000 m2).The soil is puddled by 2-3 runs of puddlers or 3-4 ploughings with country plough. After 2 days of puddling, divide the nursery area into narrow beds of 1.25 m width and of convenient length. Prepare the drainage channel 30 cm wide in between the beds. Apply 225 g urea and 500 g single superphosphate per 10 m2 area.
A seed rate of 30 kg for long duration, 40 kg for medium duration and 60 kg per hectare is sufficient for short duration varieties. For hybrids of rice 20 kg seed is optimum for transplanting in one hectare. Thin sowing in nurseries is always better and it will produce strong and sturdy seedlings, which can withstand adverse climatic conditions better and produce better yields. Therefore, 40 to 60 grams of seed per square metre should be sown in the nursery beds.
Uniformly broadcast about 2-3 handfuls of desired seed on a square meter of seed bed, having thin film of water in the nursery. Drain the water 18-24 hrs after sowing. Care must be taken to avoid stagnation of water in any part of the seedbed. Allow enough water to saturate the soil from 3rd to 5th day. From 5th day onwards increase the water depth to 1.5 cm depending on the height of the seedlings. Thereafter maintain 2.5 cm depth of water in the nursery.
Apply any one of the pre-emergence herbicides viz., Pretilachlor + safener 0.3kg/ha, on 3rd or 4th day after sowing to control weeds in the lowland nursery. Adopt suitable control measures for insect-pests and diseases. Drain the excess water at the time of heavy rainfall. An application of 50 g urea/m2 may be applied as top dressing in case of N deficiency symptoms. Seedlings would be ready for transplanting within 20-25 days after sowing.
(B) Dry Nursery:
This method is adopted in areas, where water is not sufficient to grow seedlings in wet nurseries. Plough the field till the soil is thoroughly pulverized (fine tilth). Raised beds are more ideal if the soil is clayey in nature. Prepare beds of the same size as in wet nurseries, but 15 cm high with channels (30 cm wide) between them. Sow the seeds in rows 10 cm apart in dry or moist condition of the soil.
The seeds should be covered immediately with a layer of soil or with finely powdered well decomposed farm yard manure. Use the same seed rate and fertilizer as in wet nurseries. Allow the water to run in channels first and then raise the level of water slowly to saturate the soil. Keep the seed bed saturated with water, but do not flood water in beds. Follow all the operations as described for wet nurseries. Fourth leaf stage is the optimum stage of seedlings for transplantation.
(C) Dapog Method:
This method of raising nursery has been introduced in India from Philippines. The method is used especially in places where supply of water in the seed-bed is dependable. It saves almost half of the time in raising seedling. Only 25-30 m2 area is enough to grow seedlings for transplanting one ha.
In this method, beds of about 1.5 m width are prepared on slightly raised (4-5 cm) soil-bed covered with polyethylene sheets or on a concrete floor. About 1 m2 of seed bed is required for every 3 kg of seed. Cover the soil surface of the seed bed uniformly with banana leaves (protruding midribs removed) or plastic sheets. Cement or fertilizer bags could also be used for this purpose.
Covering is necessary to prevent roots of the seedlings from coming in contact with the soil, thus facilitating the separation of seedlings during transplanting’s during transplanting. Pre-germinated seeds should be sown broadcast on the top of the cover @ 1.5 kg/m2 area or 50 times of the test weight/m2 of the variety used.
The beds are kept moist constantly and pressed slightly 2-3 times a day with a smooth wooden flat board for the first 3 days, so that root remains in constant touch with water. When the seedlings attain 2 cm height, a constant film of water (1-2 cm) should be maintained. In about 12 days roots are well developed and are entangled with one another.
In the dapog method, fertilization of nursery is not necessary. Dapog seedlings should not be pulled. The nursery can be cut (divided) into strips of convenient size and rolled like a mat with roots outward and then transferred to the planting site. Seedlings of 1 m2 area can be transplanted in 200 m2 area.
The seedlings raised by this method are established immediately. The crop comes to flower 4 days earlier than the normal transplanted crop. At the event of drought or failure of irrigation system when transplanting of over-aged seedlings cannot be done, this system offers a good scope to get another lot of fresh seedling within 12 days.
Dapog nursery method does not require seed-bed preparation, fertilizer or other chemicals use for raising the seedlings. The labour cost in seedling uprooting is saved as the whole mat of seedlings over polythene is lifted, rooted and straight way transferred to transplanting site.
Seed rate is exceptionally high (2.5 times more than other methods). Seedlings being very small cannot be transplanted in presence of even slight water in the field, which sometimes becomes unavoidable. Instead of two three 3-4 seedlings are to be transplanted per hill.
The field should be ploughed once followed by harrowing and planking soon after first rain. Summer deep ploughing is also beneficial as it exposes the eggs of harmful insect-pests and rhizomes of weeds. All the weeds and stubbles of the previous crop should be removed from the field. Puddling (tillage in standing water) is the traditional method of land preparation for transplanted lowland rice. The field should be flooded or saturated with water (2.5 cm depth) for 15 days before planting.
This helps in decomposition of stubbles of previous crop. Before puddling, an earthen bund of about 30 cm high should be made around the field. Puddling is very important operation in transplanted rice. It helps to kill the weeds and buries them in puddle layer. It helps to create beneficial physical, biological and chemical conditions for plant growth of rice. Puddling increases soil bulk density from around 1.4 to about 1.8 g cm3.
Increase in bulk density and reduced porosity due to puddling largely reduce the deep percolation of water because of reduction in soil hydraulic conductivity. A well leveled field is important for uniform fertilizer distribution, water control and weed control. To achieve a good puddle and leveled field mould board plough, puddler and plank/ladder should be used.
The power tiller operated rotavator, tractor with single cage wheel and cultivator and tractor with double cage wheels should be used to achieve a very good puddle condition in all types of soils. Puddle the field by 3-4 runs of puddler in standing water. Apply uniformly ½ of N and total quantities of P, K and Zn on drained surface at the time of last puddling and incorporate in the top 10-15 cm deep soil.
Puddling, a traditional method of tillage for lowland rice offers the following advantages:
i. Puddling (soft mud) makes seedling transplantation easier with minimum plant injury.
ii. All weeds are killed and buried, which increased the organic matter in the soil.
iii. Reduce water losses through infiltration and deep percolation, thus water retaining capacity of soil is increased.
iv. Provides reduced soil conditions due to standing water, thus increase the availability of many plant nutrients such as P, Fe, Mn etc.
Time of planting is the most important factor affecting the growth and yield of rice crop. Performance of a variety/hybrids is entirely depends on the time of its planting. In general, transplanting in the first fortnight of July gives higher yield in kharif. Delay in planting by 10-20 days from 15th July reduced the yield. Transplanting of short duration dwarf varieties from 15th June to end of July and those of medium duration varieties from 15th June to first fortnight of July is reported to be the best.
Pulling Out (Uprooting) the Seedlings:
Optimum age of the seedlings is 18-22 days for short, 25-30 days for medium and 35- 40 days for long duration varieties. The nursery should be watered a day prior to the uprooting of the seedlings. Pull out the seedlings gently at the appropriate time (4th leaf stage. Pulling at 3rd leaf stage is also possible. Two or three seedlings are handled at a time in between the thumb and forefingers. To remove mud, wash the seedlings gently in water.
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. The seedlings are protected from drying by keeping them in irrigation channel. 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’. Sometimes situations may arise to use the aged seedlings for planting especially under delayed rains or water release conditions. For this, special management practices are required to be followed for maximum yields.
Root Dipping:
Prepare the slurry with 5 packets (1000 g)/ha of Azospirillum and 5 packets (1000g/ha) of Phosphobacteria or 10 packets of (2000 g/ha) of Azophos inoculants in 40 lit. of water and dip the root portion of the seedlings for 15 – 30 minutes in bacterial suspension and transplant.
The most ideal seedling for transplanting should have 4 leaves. They may have 3 leaves, but under no circumstances, the seedling should have more than 5 leaves. Usually 2-3 healthy seedlings of 20-30 days per hill should be planted at 20 cm x 15 cm apart during kharif, and 30-35 days at 15 cm x 15 cm during rabi season. However, the general recommendation is to use 21-25 days old seedlings.
Erect, upright and shallow (2-3 cm) transplanting of seedlings ensures quick establishment of roots in the soil and results in vigorous tillering. Deep planting (>5 cm) leads to delayed establishment and reduced number of tillers. If the basal node is planted deep in the mud, tillering is delayed as tiller will start only after leaves originate at higher nodes.
Planting in line (at a minimum row spacing of 20 cm) permits rotary weeding and associated benefits. Planting rice in double rows in sunrise and sunset direction helps in better transmission of sunlight, better movement of carbon-dioxide (CO2) in the rice field. Early planting in the beginning of July for kharif crop gives higher yield.
If old seedlings of more than 25 days age are to be planted, the number of seedling/hill should be increased (3-4/hill), besides use of higher dose of N at the time of sowing and reduced spacing. This would help in maintaining required plant population, as older seedlings usually produce less tillers/plant.
In BPH endemic areas an alley of 30 cm may be left at the end of every 1.5 m to facilitate spraying against the pest even though it may result in slight reduction of yield or else wider spacing of 20 cm x 10 cm is recommended to give 50-55 hills/m-2 instead of 70 hills m-2.
Transplanting enables the farmers to have optimum plant population at desired spacing in the field. It also provides scope for land preparation, which aids in keeping down the weeds. Since the nurseries occupy a small area of the field, the control of insect-pest and diseases and irrigation and manuring of young crop is easier and cheaper than direct sown crop.
In order to achieve maximum yield an optimum plant population of 60-80 hills and 50 hills per m2 is required for short and medium duration varieties, respectively. Therefore, gaps if any are filled within 7 to 10 days after transplanting.
In some of the lowland areas the rice fields get inundated early in the season due to heavy rains or overflow of nalas/river. Water stagnates to a depth of 40-70 cm and such situation continues during the later period of growth. The rice crop transplanted in said situation gets severely damaged. In such areas having 40-50 cm of standing water a technique known as ‘double transplanting’ or clonal propagation has been found to improve yield of transplanted crop to a great extent.
The clonal tillers are taller with more dry weight than the traditional nursery seedlings of similar age. Thus, the clonally-transplanted crop establishes well and acclimatizes sooner in the similar flooded environment compared with nursery seedlings which did not establish properly as they have been previously growing in an aerobic upland environment. Therefore, the grain yield of the crop transplanted with clonal tillers is significantly higher than that planted with traditional nursery seedlings.
Broadcast Sprouted Seeds in Puddle Soils:
This method is adopted in areas, where there is a shortage of manpower for transplanting. In this method the field is prepared and puddle in the same way as in case of transplanted rice. About 100 kg seed/ha is required. Seeds are soaked in water for germination before broadcast. Seeds with radical length of 1-2 mm are uniformly broadcast by hand.