These three seasons are named according to the season of harvest of the crop.
Autumn Rice/Pre-Kharif Rice
Summer Rice/Rabi Rice
Winter Rice/Kharif Rice
Most of the rice production (around 56 per cent) is in the autumn season in which the sowing is done between March and August and harvesting is between June and December. This indicates the high dependence of the rice crop on the monsoons, which are concentrated in the months of June to September. The winter crop, whose sowing takes place between June and October and harvesting is between November and April, provides about 33 per cent of the total rice crop. The remaining 11 per cent is sown in the summer season.
Soil
Hence, clay and clay loams are most suited for rice cultivation.It grows nicely in soils having a pH range between 5.5 and 6.5. It can also be grown on alkali soil after treating them with gypsum or pvrite.
Cultivation
The fields are ploughed(tractor) and harrowed in summer for achieving the required-tilth. Farmyard manure is uniformly distributed 2-3 weeks before sowing. The seed is sown directly with the onset of the monsoon showers, either by broadcasting, dibbling behind the __________ plough or by drilling in lines. Line-sowing is preferable, as it ensures an adequate stand establishment and facilitates easy weeding and interculture. The reduced seed-rate requirement is another advantage. The row spacing may be suitably adjusted from 20 to 25 cm. Under the semi-dry system, the rain-water is impounded when the crop is about 1½-2 months old and thereafter it is converted into a wetland crop. By that time, major operations, such as weeding, interculturing and fertilizer application might have been completed.
The latest thinking is to promote line-sowing using a higher seed-rate so as to have a uniformly higher population density for effective competition from weeds and to use effective methods of interculture to solve the weed problem. Wet System: Under this system, the land is ploughed thoroughly and puddled with 3-5 cm of standing water in the field. The optimum depth of puddling is found to be around 10 cm in the clay and clay-loam types of soils. The primary objective is to obtain a soft seedbed for the seedlings to establish themselves faster, to minimize the leaching losses of nutrients and thereby increase the availability of plant nutrients by achieving a reduced soil conditions which facilitates a better availability of nutrient elements, to incorporate the weeds and stubble into the soil and to minimize the weed problem. Puddling can be done with ploughs, tillers or tractors, depending upon their availability and soil conditions. The land is leveled after puddling to facilitate a uniform distribution of water and fertilizers.
Sowing
Seeds may be sown after sprouting them or the seedlings be transplanted under this system. The weed problem is serious under direct-seeded conditions and is difficult to control completely in a broadcast crop. Water management also poses a major problem in unleveled lands and, therefore, transplanting has been generally practiced. Transplanting in a puddled field has the following advantages:
1. A good leveling of the land is ensured.
2. The weeds are buried at the time of puddling and the weed problem is reduced.
3. The population of plants becomes more uniform.
4. The availability of most of the plant nutrients, such as phosphorus, iron and potassium, is increased and nitrogen is conserved better.
5. The seedlings transplanted in a soft puddle are able to establish themselves faster and start early tillering and growth.
6. Nurseries occupy only 10 per cent of the main field area and the cost of maintaining them (irrigation and plant protection) is reduced considerably as compared with a crop sown broadcast.
7. Plant-protection measures can be effectively used in the nursery.
8. Community nurseries facilitate timely transplanting.
9. The treatment of seedlings for nutrient deficiencies and for protection against pests and diseases of facilitated before transplanting.
The seed-rate for direct sowing by broadcasting is 80 to 100 kg/ha and by dibbling it in 60-70 kg/ha. Only well-filled viable seeds should be used for sowing. Lighter seeds that float on a solution of common salt (1.06 specific gravity) should be rejected. The choice of a suitable variety based on topo-sequence, soil type and duration is a prerequisite for obtaining high yield. Seed treatment with Thiram or Ziram or Vitavax at the rate of 100 g per 50 kg of seeds is generally recommended to prevent seed-borne diseases. The untreated seeds of high-yielding varieties should be soaked for 12 hours in a solution of wettable Ceresan or Carbendazim (0.1 per cent, i.e. 1 gm in one litre of water). The seeds should then be thoroughly dried in shade and used for sowing. The nursery area required to provide seedlings for transplanting one hectare is roughly 1/10 of a hectare and the seed-rate is 40-50 kg/ha. To ensure rapid and uniform germination, selected seeds should be soaked for 24 hours in clean water, which should be drained away thereafter and the seeds be incubated in a warm, moist place for 36-48 hours to let them sprout for sowing in the nursery.
Rice Nurseries
The general practice in __________ is to go in for wet nurseries. Another system of nursery-raising, known as the "dapog" method, had been recently suggested for areas where the seedlings are to be obtained within a fortnight for immediate transplanting. Wet nursery: The site selected should be near an assured source of irrigation. The land is ploughed twice in the dry conditions and puddled subsequently by ploughing it in standing water (2-3 cm deep) three or four times, preferably at intervals of 5-6 days. Farmyard manure, greed manure or compost can be applied uniformly @ 5-8 t/h at the time of the first puddling, 3-4 weeks before sowing the nursery. The field is levelled perfectly after the final puddling and made into raised beds, 1-1½ metres in width and of convenient length, leaving 30 cm of channel space in between the beds. Sprouted seeds are broadcast evenly on the soft mud, and only a thin film of water is maintained. The beds are maintained at the saturation level by sprinkling water periodically to maintain only a very thin film of it till such time that the germination is complete and the coleoptile turns green. The level of water is raised gradually and is maintained at a depth of 2-5 cm. In soil poor in natural fertility, it is advisable to fertilize the seedbeds with 0.5 to 1 kg of N, 0.5 kg of P2O5 and 0.5 kg of K2O for every 100 m2 area of the nursery before the final leveling of the nursery-beds. In regions of low temperature, during rabi it is desirable to supply a slightly higher dose of phosphorus to promote root development and to establish a good stand in the nursery. Adequate care should be taken to ward off pests and diseases in the nursery itself by spraying it with insecticides and fungicides periodically. The nursery should also be kept free from weeds; otherwise, they are also carried to the main field at the time of transplanting. When the seedlings are at the 4-5 leaf stage, the nursery is adequately irrigated and the seedlings are removed without causing, as far as possible, any damage to their roots. Young, healthy and vigorous seedlings establish themselves faster and grow better and the major objective of nursery management should be aimed at obtaining such seedlings. Dry nursery. In regions of non-assured water-supply, where wet-bed nurseries cannot be raised, dry nursery-raising is practiced. The field is brought to a very fine tilt by polishing it four or five times at 4-5 day intervals. Ten to fifteen tonnes per hectare of farmyard manure or compost is spread uniformly and incorporated into the soil 2-3 weeks before sowing. Raised beds 1-1½ metros in width, 15 cm in height and of convenient length, are prepared, keeping a 40-50-cm wide channel all around to facilitate drainage, as and when required. The seeds are sown dry, either broadcast or in lines closely, and are covered with a thin layer of soil or compost. The nursery beds are irrigated by sprinkling water on them periodically once in 2-3 days, depending upon the soil and environmental conditions. Light soils may require frequent irrigation. Timely weeding and plant-protection measures are to be adopted. In dry areas and in calcareous and saline-alkaline soils, chlorosis is he major problem is dry nurseries. Seed treatment with FeSO4, the application of iron-chalets or spraying the nurseries with FeSO4 and flooding them gives some relief.
However, in such areas, it is advisable to go in for wet nurseries. The seedlings obtained from the dry nurseries are generally hardy and establish themselves very fast when transplanted. ‘Dapog’ nursery. The ‘dapog’ method of nursery-raising consists in growing seedlings on a concrete floor or on a raised bed of soil covered with polythene sheets. This method is used especially in places where there is assured water-supply and when early transplanting is needed. A small area is required for raising this type of nursery, 30-40 m2 being enough to raise seedlings for transplanting one hectare. The seedlings are ready after 14 days by using this method. The preparation of land, if needed, is done essentially in the same way as in the case of the wet-bed method. Raised seedbeds are prepared after final leveling and are packed, leveled and covered with polythene sheets. Banana leaves, with their midribs removed, can also be used instead of polythene sheets. Pre-germinated seeds should be sown on top of these sheets at the rate of 1 kg of seed per square metre of the nursery. The germinating seeds are sprinkled with water and pressed down gently with hand or with a wooden flat board twice a day for the first 3-6 days. This helps the roots of the seedlings to remain in contact with water retained on the surface and prevents drying. After six days, the seedbed could be irrigated up to a depth of 1-2 cm of water. The seedlings raised by using the ‘dapog’ method are then divided into convenient sizes and rolled like a mat with roots outwards. It is necessary to control the water level in the main field transplanted with ‘dapog’ seedlings, as they are too small and are liable to be damaged very easily by letting in too much of standing water. The leveling of the fields is very essential to avoid the stagnation of water and the mortality of the seedlings. Six to eight seedlings are placed in a hill.
Rice Transplanting
The seedlings are ready for transplanting in kharif within 20 to 25 days (4-5-leaf stage), where as in rabi it may take 30 to 40 days. Two to three seedlings are planted at 20 X 10 cm or 20 X 15 cm spacing in leveled fields. In regions of low fertility, and for late planting, closer planting is advocated.
Weed Control
In line-planted or drilled rice, weeding can be done with a hand-hoe or with rotary weeders. In a broadcast-sown crop, weeds pose a major problem and hand-weeding is still practiced. The best time to weed the crop is three weeks after sowing or planting. Herbicides, such as Butachlor, 2,4 D and Propanil, give a satisfactory weed control in rice and can be used as a tool for controlling weeds, when used at the recommended doses and at the right time. Irrespective of the method of weeding, it is ideal to maintain a weed-free condition up to 40-45 days after sowing.
Water management
The water requirement of rice is higher than that of other cereal crops of similar duration. Figures ranging from 37 to 75 acre-inches of water have been reported from various locations in India as the water requirement of rice, and this variation is primarily due to different soil and environmental conditions obtaining in different parts of the country. Losses due to percolation are more in submerged rice lands. In lighter soils, such losses amount to about 60 per cent of the total water requirement. Soil compaction and puddling help to reduce percolation losses. Losses due to transpiration account for about 40 per cent. Losses due to evaporation depend upon the climatic factors and range from 20 to 40 per cent. Considerable saving (30-40 per cent) in water is possible
What you need to know about land preparation
There are five parts in understanding good land preparation.
These components are an understanding of the:
1.
role of tillage and land leveling in land preparation
2.
reasons why good land preparation is important
3.
different systems and equipment that are used for tillage
4.
power requirements for tillage of different soil types using different equipment
5.
basic setting up and operating equipment
After any study of land preparation you should understand the different tillage systems, tillage patterns and equipment used for land preparation. You should be able to select the most appropriate tillage system, tillage pattern and equipment for your situation.
The components of land preparation
The aim of land preparation is two-fold:
*
to place the soil in the best physical condition for crop growth
*
to ensure that the soil surface is left level
Land preparation is a combination of tillage practices that places the soil in the best physical condition for plant establishment and crop growth. To attain this condition:
*
soil must be tilled to a depth so plants can develop a root system which will physically support the plant and also allow the extraction of sufficient moisture and nutrients so yield potentials can be realized
*
soil disturbance should be sufficient to control weeds
*
tillage must leave the soil surface level. Level fields improve water use efficiency and help control in crop weeds. The field also needs a drainage system that will allow the rapid removal of excess water.
An overview of tillage
Land preparation covers a range of soil disturbances from zero-tillage, which minimizes soil disturbance through to a totally ‘puddled’ soil, which actually destroys soil structure. When considering the choice of tillage system, it is very important to have clearly defined short and long-term objectives. These objectives may be to:
*
decrease ped or clod size
*
remove, incorporate or modify plant residue
*
manage soil water (both wetting and drying)
*
control weeds
*
mix and incorporate soil amendments such as lime and basal fertilizer
*
control or destroy insects, their eggs, larvae and breeding places
*
reduce wind and water erosion by leaving a rough surface.
Because the soil is a complex biophysical medium, having both living and non-living components, any tillage operation has more than one effect. For example, if soil is tilled to control weeds soil ped sizes will be decreased; soil moisture will be lost and crop residues will be incorporated. It is important then to determine the primary objective of each operation and also any subsequent effects that may result from that operation.
Dry tillage
Wet tillage
The tillage requirements will vary according to cropping system to be used. What may be desirable for one may be totally inappropriate for another. A good example is the contrast between lowland and upland systems. Typically for lowland rice, fields are puddled in part to destroy structure and develop a hard pan to reduce water loss through deep percolation. Such a loss of structure and the formation of a physical barrier are totally undesirable in an upland situation.
Primary Tillage
Primary tillage is the first working after the last harvest and normally the most aggressive tillage operation. It is normally undertaken when the soil is wet enough to allow the field to be ploughed and strong enough to give reasonable levels of traction. This can be immediately after the crop harvest or at the beginning of the next wet season. When there is sufficient power available some soil types are ploughed dry.
The objectives of primary tillage are:
*
till the soil to attain a reasonable depth (10-15cm ) with varying clod sizes.
*
kill weeds by burying or cutting and exposing the roots
*
soil aeration and water accumulation. Depending on the soil type and the plough the soil will normally be inverted aerating the deep layers and trapping water during a rainfall event
*
chop and incorporate crop residues.
Primary Tillage Implements
The implements used for primary tillage are the moldboard, one-way disc, tine and offset disc ploughs.
Moldboard plough
The moldboard plough is most commonly used in animal and 2-wheel powered systems in Asia. Moldboards are still commonly used in the USA and Europe in upland farming systems. The number and size of moldboard shares (bottoms) vary according to the power source. Animals normally pull I plough share, 2-wheel tractors 1or 2 and 4-wheel tractors will pull 3-4 ploughshares. In Asia all systems are mounted on the tractor.
Moldboard plough for hand tractor
The moldboard plough causes total inversion of the soil sod and relies on the digging point for penetration. This plough cause the least damage to soil structure, works well in very hard soil conditions but does not have in built stump or obstacle protection mechanisms. They have very heavy power requirements and kill weeds through inversion and pulverization of the soil sod. The moldboard normally throws the soil in one direction but reversible models are available for larger 4-wheel tractors.
Soil inversion using moldboard plough
One-way disc
The one way disc plough is used in 2-wheel and 4-wheel tractor powered systems in Asia. The number and size of disc shares vary according to the power source. 2-wheel tractors will use 2 or 3 disc ploughs, while a 4-wheel tractor will pull 3,4 or 7 disc versions. In Asia all systems are mounted on the tractor.
Disc plough used in with 4-wheel tractor
The disc plough causes total inversion of the soil sod and relies on the ploughs in built weight for penetration. This plough works well in hard soil and heavy trash conditions and can ride over stumps or obstacle in the soil. The power requirement for the disc plough is less than a moldboard plough but it will ride out of the ground if soil conditions are very hard. The disc plough throws the soil in one direction and kills weeds through cutting, inversion and pulverization of the soil sod.
Offset disc
As the name suggests this is a disc plough that is capable of operating offset from the tractor. The plough is made up of between four and twenty-four discs mounted in two gangs. Each gang has a common center bolt and throws the soil in different direction. These ploughs are only used on 4-wheel tractors and are very versatile. An offset plough can be operated in any ploughing pattern. The offset plough can be either 3-point linkage mounted or a trailing version.
Offset disc for 4-wheel tractor
The very aggressive action of the plough gives good weed control and cuts and buries crop residues. This plough is also widely used in upland situations.
Offset disc for 4-wheel tractor
Tined plough
Tined ploughs are the most versatile primary tillage implement as they can be also used secondary tillage and modified to be used as a seed drill. Tine implements are used only in dry working situations as they cut the soil rather than invert the soil and kill weeds by cutting and lifting the weeds to the surface. Different size ploughshares or sweeps can be fitted to the tines. Sweeps range from 50mm to 500mm in width. These ploughs are widely used where residues need to be left on the surface. Tine ploughs have lower power requirements than disc and moldboard ploughs and are used with animals and 4-wheel tractors. These ploughs can be configured as 3-point linkage mounted or as trailing versions.
Trailing tine plough in operation
Primary tillage implements may be used for subsequent tillage operations; that is, for secondary tillage. Offset disc and tined ploughs are often used between primary tillage and planting.
Summary of tillage equipment performance
Moldboard One way Disc Offset disc Tine Implement
System Animal,2-wheel, 4-wheel tractor 2-wheel, 4-wheel tractor 4-wheel tractor Animal, 2-wheel, 4-wheel tractor
Width 1-3 shares 2-4 disc 9-21 discs 1-15 tine
Soil disturbance High Medium -high High Low
Plough action Total inversion Inversion Inversion /cutting Cutting
Soil Penetration Share design Machine weight Machine weight Weight/design
Weed control Bury Bury Cut/bury Cut
Handle obstacles Poor Good Good Medium -good
Power requirement Heavy Medium-heavy Medium-heavy Low-medium
Secondary Tillage
Secondary tillage is any working completed after primary tillage and is undertaken for
*
reducing ped size,
*
weed control,
*
incorporation of fertilizers,
*
puddling and
*
leveling soil surface.
Secondary workings are usually shallower and less aggressive than primary tillage. In the animal powered system, the second working is normally undertaken with the moldboard plough when the field is fully saturated. The final workings are then completed using peg tooth harrows to puddle the soil and leave the surface level and ready for planting.
Harrowing operation
Harrowing operation
In 2-wheel tractor systems, the moldboard, the disc and the rotovator are used for second working. In some instances peg tooth harrows are also used if rotovators are not available. Cage wheels on the tractor are needed for traction in all soil types and these also help puddle the soil.
In 4-wheel tractor systems, seven-disc ploughs, offset disc ploughs and rotovators are the most commonly used equipment for second workings. In this system, fields are either mechanically puddled with tractors using a rotovator and leveling board or by tractors fitted with large cage wheels and harrows.
Rotary tilling using rotovator
It is common in many countries for the first two workings to be undertaken using tractors and the final working done by animals and harrows.
Problems of flotation and traction are a major concern in most soil types after the second working and during land leveling. In clay soils traction is improved if there is free water on the surface to clean the tires. In some of the sandy soils, flotation is a problem when excessive wheel slip causes the tires to break through the firmer surface layers and the tractor sinks.
Secondary Tillage Implements
The implements used for secondary tillage are the peg tooth harrow, disc harrow, tined cultivator, rotary tiller, and inter row cultivators.
Peg tooth harrow
Peg tooth harrows are widely used in animal and 2-wheel tractor powered systems for second workings, soil puddling and land leveling. The width of harrow depends on the number of animals and size of tractor engine but range in size from 1-2m depending on soil conditions. The teeth or pegs in the harrow can be made from wood but more modern versions use steel. The degree of aggression is determined by the angle of operation. The more upright the harrow the more aggressive is the action.
Spike tooth harrow for hand tractor
Disc cultivator
Disc cultivators are used with 4-wheel tractors and are made up of either 2 or 4 gangs of discs. The discs are smaller than on a one-way or offset plough and the machine is much lighter. The degree of aggression is determined by the gang angle relative to the forward travel. These implements are normally used in dry fields. The disc cultivator can be either 3-point linkage mounted or a trailing version.
The very aggressive action of the plough gives good weed control and cuts and buries crop residues. This plough is also widely used in upland situations.
Three-point linkage mounted
Three-point linkage mounted
Tined cultivator
Tined cultivators are very versatile implements as they can be used for secondary tillage and modified to be used as a seed drill. Tine cultivator are used only in dry working situations as they cut the soil rather than invert the soil and kill weeds by cutting and lifting the weeds to the surface. Sweeps range from 50mm to 200mm in width. These cultivators are used where residues need to be left on the surface. Tine cultivators have lower power requirements than disc cultivators and used with animals and 4-wheel tractors. These ploughs can be configured as 3-point linkage mounted or as trailing versions.
Tine Cultivator
Rotovator
Rotovators are commonly used for secondary workings and especially seedbed preparation. They are used with 2-wheel and 4-wheel tractors in both upland and flooded fields. Rotovators have a very aggressive action, which pulverizes the soil and buries weeds and crop residues. In some flooded situations rotovators are used for primary tillage.
Rotary tiller - rotavator
Upland Tillage
Upland tillage is undertaken in locations where crops are grown in aerobic soil conditions. This means that the soils are non-puddled soils and there is no freestanding water in the fields. Soil moisture levels are critical when ploughing in an upland-farming situation. If the soil is too dry it will not till easily, the power requirement will increase and in clay soils large clods may be formed. In clay soils these large clods may cause problems when trying to decrease ped size to create a seedbed. If the soil is ploughed very wet, near soil saturation, smearing and soil sealing can become problems during seedbed preparation.
Animal powered systems use a moldboard plough, while 2-wheel and 4-wheel tractor powered systems use one-way disc, offset disc and tined implements. These systems often require more tillage operations to control weeds. In low land systems weeds are often controlled by incorporation while in upland systems weeds are best cut and left on the surface to die.
Upland tillage
In these systems water erosion can be a problem and ploughing on the contour is recommended.
Tillage Patterns
An optimal tillage pattern reduces the time spent in non-productive work. One of the most important objectives of a tillage pattern is to minimize the number of turns and maximize the length of the tillage runs. There are several patterns that can be used when tilling a field. These are circuitous, up and back or headland and working in lands.
Circuitous pattern
In a circuitous pattern the machine begins working along a boundary. It continues along the other boundaries of the land, returning to its starting point. This pattern works from the outside to the center of the field and is the most commonly used system for ploughing in Asia. It is commonly used with moldboards, discs and offset discs. This is the system that most animals are accustomed to working and it also requires less spatial judgment by the operator than working in a land type system. The major disadvantage of this system is that the field ends up with a large cut out furrow in the center. Over time the field ends up having an oblong saucer shaped depression in the center that is hard to drain and makes it difficult to get an even depth of cultivation, good weed and water control. A solution to this problem is ploughing out from the middle or working the field in lands
Up and back or headland pattern
The field is ploughed in runs parallel to each other. It starts at one boundary of the field and ends at the opposite with turns being made on the headlands. This system can only be used for tined implements, rotovators, harrows and reversible ploughs. It is usually the most field efficient system and if equipment is correctly set up and operated should not leave furrows in the field.
Land system
This system requires ploughing to begin in the center of the field and works out to the edges. It requires some measurement of the field to establish the center point and if done correctly leaves a level field with drainage channels on the edges. This system can be used with all types of ploughs. In very large fields, a number of lands may be ploughed
Creating a 'Hard Pan'
In some soil types it is desirable to develop a ‘hard pan’ or impermeable layer to stop deep percolation of water below the root zone of the crop. This hard layer is best achieved by using an implement that actually smears the soil during its normal mode of action. The rotovator is the best implement for this operation. High levels of wheelslip from tractors fitted with cage wheels will also give a similar effect. Similarly disc ploughs, offset or tandem discs working in very wet soils can attain a similar effect.
Compaction rating Implement/operation
Worst Rotovator 1
Moist plough
Wet disk harrow 1.5
Caribou/oxen 1.75
Moldboard plough 2
Human footprint 2
Tractor (low tire pressure) 4
Least Bulldozer 7
Creating a hard pan using a rotovator
Power Requirements
The power requirements for any tillage implement will depend on the depth of working, the soil moisture content and the soil texture. While speed of operation will have an effect on power requirements the actual range of working speeds for each operation are relatively constant and, therefore, the speed effect minimal.
Implements Approximate power requirement(Engine kW/m at 7.2 Km/hr using a Front wheel assisted Tractor)
Soil Types Clay Loam Sand
Primary Tillage Implements
Moldboard Plough 26 22 18
Disc Plough 25 21 18
Tine Plough 20 16 14
Offset disc Plough 24 20 16
Implements Approximate power requirement(Engine kW/m at 7.2 Km/hr using a Front wheel assisted Tractor)
Soil Types Clay Loam Sand Wet
Secondary Tillage Implements
Tined Cultivator 14 11 9
Inter-row cultivator 8 6 4
Disc cultivator 18 16 14
Rotovator 35 30 20 25-35
Puddler 7
Setting up an implement for use
To maximize the efficiency of the tillage operation, all implements must be safely attached to the tractor and leveled correctly before use.
The key points when using an implement are:
*
all nuts retaining the discs, ploughshares and sweeps should be checked and tightened before use.
*
3-point linkage stabilizer chains should be attached relatively loose, but not so loose that the implement will hit the tractor tires.
*
PTO shafts should be connected and secured correctly with all safety shields in place
*
use depth control wheels or slides to set the operating depth or height on all implements
*
implements should be level in two planes: front to back as well as side-to-side.
*
depth of cut should be uniform across the furrows and the field should be left as level as possible after ploughing
*
if the tractor is “pulling” to one side, then the plough is not correctly adjusted.
*
the speed of operation will depend on the implement and the terrain. The range for most implements will be between 4-7 km/hr.
These three seasons are named according to the season of harvest of the crop.
Autumn Rice/Pre-Kharif Rice
Summer Rice/Rabi Rice
Winter Rice/Kharif Rice
Most of the rice production (around 56 per cent) is in the autumn season in which the sowing is done between March and August and harvesting is between June and December. This indicates the high dependence of the rice crop on the monsoons, which are concentrated in the months of June to September. The winter crop, whose sowing takes place between June and October and harvesting is between November and April, provides about 33 per cent of the total rice crop. The remaining 11 per cent is sown in the summer season.
Soil
Hence, clay and clay loams are most suited for rice cultivation.It grows nicely in soils having a pH range between 5.5 and 6.5. It can also be grown on alkali soil after treating them with gypsum or pvrite.
Cultivation
The fields are ploughed(tractor) and harrowed in summer for achieving the required-tilth. Farmyard manure is uniformly distributed 2-3 weeks before sowing. The seed is sown directly with the onset of the monsoon showers, either by broadcasting, dibbling behind the __________ plough or by drilling in lines. Line-sowing is preferable, as it ensures an adequate stand establishment and facilitates easy weeding and interculture. The reduced seed-rate requirement is another advantage. The row spacing may be suitably adjusted from 20 to 25 cm. Under the semi-dry system, the rain-water is impounded when the crop is about 1½-2 months old and thereafter it is converted into a wetland crop. By that time, major operations, such as weeding, interculturing and fertilizer application might have been completed.
The latest thinking is to promote line-sowing using a higher seed-rate so as to have a uniformly higher population density for effective competition from weeds and to use effective methods of interculture to solve the weed problem. Wet System: Under this system, the land is ploughed thoroughly and puddled with 3-5 cm of standing water in the field. The optimum depth of puddling is found to be around 10 cm in the clay and clay-loam types of soils. The primary objective is to obtain a soft seedbed for the seedlings to establish themselves faster, to minimize the leaching losses of nutrients and thereby increase the availability of plant nutrients by achieving a reduced soil conditions which facilitates a better availability of nutrient elements, to incorporate the weeds and stubble into the soil and to minimize the weed problem. Puddling can be done with ploughs, tillers or tractors, depending upon their availability and soil conditions. The land is leveled after puddling to facilitate a uniform distribution of water and fertilizers.
Sowing
Seeds may be sown after sprouting them or the seedlings be transplanted under this system. The weed problem is serious under direct-seeded conditions and is difficult to control completely in a broadcast crop. Water management also poses a major problem in unleveled lands and, therefore, transplanting has been generally practiced. Transplanting in a puddled field has the following advantages:
1. A good leveling of the land is ensured.
2. The weeds are buried at the time of puddling and the weed problem is reduced.
3. The population of plants becomes more uniform.
4. The availability of most of the plant nutrients, such as phosphorus, iron and potassium, is increased and nitrogen is conserved better.
5. The seedlings transplanted in a soft puddle are able to establish themselves faster and start early tillering and growth.
6. Nurseries occupy only 10 per cent of the main field area and the cost of maintaining them (irrigation and plant protection) is reduced considerably as compared with a crop sown broadcast.
7. Plant-protection measures can be effectively used in the nursery.
8. Community nurseries facilitate timely transplanting.
9. The treatment of seedlings for nutrient deficiencies and for protection against pests and diseases of facilitated before transplanting.
The seed-rate for direct sowing by broadcasting is 80 to 100 kg/ha and by dibbling it in 60-70 kg/ha. Only well-filled viable seeds should be used for sowing. Lighter seeds that float on a solution of common salt (1.06 specific gravity) should be rejected. The choice of a suitable variety based on topo-sequence, soil type and duration is a prerequisite for obtaining high yield. Seed treatment with Thiram or Ziram or Vitavax at the rate of 100 g per 50 kg of seeds is generally recommended to prevent seed-borne diseases. The untreated seeds of high-yielding varieties should be soaked for 12 hours in a solution of wettable Ceresan or Carbendazim (0.1 per cent, i.e. 1 gm in one litre of water). The seeds should then be thoroughly dried in shade and used for sowing. The nursery area required to provide seedlings for transplanting one hectare is roughly 1/10 of a hectare and the seed-rate is 40-50 kg/ha. To ensure rapid and uniform germination, selected seeds should be soaked for 24 hours in clean water, which should be drained away thereafter and the seeds be incubated in a warm, moist place for 36-48 hours to let them sprout for sowing in the nursery.
Rice Nurseries
The general practice in __________ is to go in for wet nurseries. Another system of nursery-raising, known as the "dapog" method, had been recently suggested for areas where the seedlings are to be obtained within a fortnight for immediate transplanting. Wet nursery: The site selected should be near an assured source of irrigation. The land is ploughed twice in the dry conditions and puddled subsequently by ploughing it in standing water (2-3 cm deep) three or four times, preferably at intervals of 5-6 days. Farmyard manure, greed manure or compost can be applied uniformly @ 5-8 t/h at the time of the first puddling, 3-4 weeks before sowing the nursery. The field is levelled perfectly after the final puddling and made into raised beds, 1-1½ metres in width and of convenient length, leaving 30 cm of channel space in between the beds. Sprouted seeds are broadcast evenly on the soft mud, and only a thin film of water is maintained. The beds are maintained at the saturation level by sprinkling water periodically to maintain only a very thin film of it till such time that the germination is complete and the coleoptile turns green. The level of water is raised gradually and is maintained at a depth of 2-5 cm. In soil poor in natural fertility, it is advisable to fertilize the seedbeds with 0.5 to 1 kg of N, 0.5 kg of P2O5 and 0.5 kg of K2O for every 100 m2 area of the nursery before the final leveling of the nursery-beds. In regions of low temperature, during rabi it is desirable to supply a slightly higher dose of phosphorus to promote root development and to establish a good stand in the nursery. Adequate care should be taken to ward off pests and diseases in the nursery itself by spraying it with insecticides and fungicides periodically. The nursery should also be kept free from weeds; otherwise, they are also carried to the main field at the time of transplanting. When the seedlings are at the 4-5 leaf stage, the nursery is adequately irrigated and the seedlings are removed without causing, as far as possible, any damage to their roots. Young, healthy and vigorous seedlings establish themselves faster and grow better and the major objective of nursery management should be aimed at obtaining such seedlings. Dry nursery. In regions of non-assured water-supply, where wet-bed nurseries cannot be raised, dry nursery-raising is practiced. The field is brought to a very fine tilt by polishing it four or five times at 4-5 day intervals. Ten to fifteen tonnes per hectare of farmyard manure or compost is spread uniformly and incorporated into the soil 2-3 weeks before sowing. Raised beds 1-1½ metros in width, 15 cm in height and of convenient length, are prepared, keeping a 40-50-cm wide channel all around to facilitate drainage, as and when required. The seeds are sown dry, either broadcast or in lines closely, and are covered with a thin layer of soil or compost. The nursery beds are irrigated by sprinkling water on them periodically once in 2-3 days, depending upon the soil and environmental conditions. Light soils may require frequent irrigation. Timely weeding and plant-protection measures are to be adopted. In dry areas and in calcareous and saline-alkaline soils, chlorosis is he major problem is dry nurseries. Seed treatment with FeSO4, the application of iron-chalets or spraying the nurseries with FeSO4 and flooding them gives some relief.
However, in such areas, it is advisable to go in for wet nurseries. The seedlings obtained from the dry nurseries are generally hardy and establish themselves very fast when transplanted. ‘Dapog’ nursery. The ‘dapog’ method of nursery-raising consists in growing seedlings on a concrete floor or on a raised bed of soil covered with polythene sheets. This method is used especially in places where there is assured water-supply and when early transplanting is needed. A small area is required for raising this type of nursery, 30-40 m2 being enough to raise seedlings for transplanting one hectare. The seedlings are ready after 14 days by using this method. The preparation of land, if needed, is done essentially in the same way as in the case of the wet-bed method. Raised seedbeds are prepared after final leveling and are packed, leveled and covered with polythene sheets. Banana leaves, with their midribs removed, can also be used instead of polythene sheets. Pre-germinated seeds should be sown on top of these sheets at the rate of 1 kg of seed per square metre of the nursery. The germinating seeds are sprinkled with water and pressed down gently with hand or with a wooden flat board twice a day for the first 3-6 days. This helps the roots of the seedlings to remain in contact with water retained on the surface and prevents drying. After six days, the seedbed could be irrigated up to a depth of 1-2 cm of water. The seedlings raised by using the ‘dapog’ method are then divided into convenient sizes and rolled like a mat with roots outwards. It is necessary to control the water level in the main field transplanted with ‘dapog’ seedlings, as they are too small and are liable to be damaged very easily by letting in too much of standing water. The leveling of the fields is very essential to avoid the stagnation of water and the mortality of the seedlings. Six to eight seedlings are placed in a hill.
Rice Transplanting
The seedlings are ready for transplanting in kharif within 20 to 25 days (4-5-leaf stage), where as in rabi it may take 30 to 40 days. Two to three seedlings are planted at 20 X 10 cm or 20 X 15 cm spacing in leveled fields. In regions of low fertility, and for late planting, closer planting is advocated.
Weed Control
In line-planted or drilled rice, weeding can be done with a hand-hoe or with rotary weeders. In a broadcast-sown crop, weeds pose a major problem and hand-weeding is still practiced. The best time to weed the crop is three weeks after sowing or planting. Herbicides, such as Butachlor, 2,4 D and Propanil, give a satisfactory weed control in rice and can be used as a tool for controlling weeds, when used at the recommended doses and at the right time. Irrespective of the method of weeding, it is ideal to maintain a weed-free condition up to 40-45 days after sowing.
Water management
The water requirement of rice is higher than that of other cereal crops of similar duration. Figures ranging from 37 to 75 acre-inches of water have been reported from various locations in India as the water requirement of rice, and this variation is primarily due to different soil and environmental conditions obtaining in different parts of the country. Losses due to percolation are more in submerged rice lands. In lighter soils, such losses amount to about 60 per cent of the total water requirement. Soil compaction and puddling help to reduce percolation losses. Losses due to transpiration account for about 40 per cent. Losses due to evaporation depend upon the climatic factors and range from 20 to 40 per cent. Considerable saving (30-40 per cent) in water is possible