Background
Rice is a staple food crop ranked third among the most produced cereal crops worldwide, following corn and wheat. With the increasing population, the number of people facing acute food insecurity has also been increasing.
Poor nutrition and hunger are claiming the lives of 3.1 million children annually, which accounts for nearly half of all deaths in children under the age of 5. These tragic deaths occur because these children lack access to basic nutrients essential for their health and survival.
Furthermore, the majority of crops’ agricultural cycle has been affected by global warming. Increased CO2 concentrations in the atmosphere, decreasing water supplies, and rising temperatures are all predicted to have a negative impact on food production.
To overcome this, standard crop cultivation practices such as land preparation, quality seed selection, good irrigation practice, effective fertilizer application, proper weed management, and integrated insect/pest/disease management should be followed effectively.
Land Preparation
Land preparation practices differ from the method of rice cultivation. Direct-seeded rice (DSR) is a newly emerging practice both for dry and wetland conditions. This method requires minimum tillage, with rice seeds directly sown in the main field without first needing to sprout in a nursery and be transplanted.
- In dryland conditions, the land is tilled using harrows, chisels, or stubble mulch equipment to stir the so This exposes the weeds to the sun to destroy them.
- In the wetland method, the field is ploughed while wet and harrowed crosswise and lengthwise until the soil is puddly or muddy. Puddling minimizes the loss of water and increases nutrient retention and availability.
- In the transplanted method, the land is ploughed during summer to keep it clean and then puddled before transplanting by tractor-drawn case-wheel or rotavator.
Prepare the land 2-3 weeks before seeding and transplanting if the field is very weedy or has plenty of stubble, and help mix in the compost or farmyard manure (FYM).
Laser Levelling
Effective land leveling reduces the work involved in crop establishment and crop management and increases yield and quality. Level land improves water coverage, thereby:
- Reducing the amount of water required for land preparation.
- Improving crop establishment
- Aiding uniform crop maturity
- Decreasing the irrigation time
- Reducing weeds and the subsequent costs of weed control.
Selection of Rice Varieties
Selection of rice varieties is very important. Modern high-yielding varieties (HYV) or hybrids have greater yield potential and are more responsive to inputs (fertilizer, water, pest management) than the more traditional varieties. Medium/short plants (100-120cm) are more responsive to nutrients and water, resistant to lodging and they produce high grain yields.
Farmers’ priorities are always for varieties with the following traits:
- High yield potential
- Resistant to insects and diseases
- A grain quality that is desired by consumers and the market.
- High grain yields
- Wide climate adaptability, including floods, droughts, and changing day-length
- 120-140 days growth duration
- Tolerance to local soil problems: salinity, zinc, phosphorus and iron deficiency, and iron, manganese aluminum toxicity
Rice cultivation Method
Numerous rice cultivation methods are practiced worldwide, including broadcasting, drilling, and transplanting. Farmers employ innovative techniques such as direct seeding of rice and the system of rice intensification (SRI) to enhance yields.
Rice grown using SRI cultivation involves planting young seedlings in a square pattern with larger spacing between them, alternating watering to keep the soil moist, and regular inter-cultivation to aerate the soil.
Farmers generally employ two methods for planting rice: transplanted and direct seeded.
Transplanted Rice
Rice Nursery Management
a) Use improved varieties and quality seeds
- Released varieties for the area and season.
- Seeds procured from authorized seed trad.
- Good quality, well-packed, and well-labeled seed.
b) Seed rate and treatment
- Improved varieties: 45 kg/ha, Hybrid varieties: 15 kg/ha.
- Treat seeds with Bavistin@ 2g/kg seeds before seeding.
c) Nursery size and number: 10x1m2, 15 cm high
- 45 beds/ha.
- Improved varieties: 1kg seeds /10 m2bed.
- Hybrids varieties: 500gm seeds/10 m2bed.
d) Site selection and nursery bed preparation
- The site should be near the homestead, should be fertile and irrigate.
- Accessible for regular supervision.
- Seedbed methods: Dry beds and wet beds.
f) Fertilisers and manures
- Compost: 100kg/10m2bed
- Urea: 200g/10m2bed
- Mix these at land preparation
g) Seeding in the beds
- Dry beds: Broadcast/line showing at 10cm, with 2-3cm deep furrows and cover with so
- Wet beds: Puddled seeds beds are prepared (10x1m2), with 30cm space between b
- Seeds should be soaked for 24 hours in clean water, incubated for 24-48 hours for sprouting, and seeded on the beds, just mo Occasionally, seeds are seeded without making beds.
h) Management of the nursery beds
- Irrigation and weeding as needed to keep beds moist (2-3cm water) and clean.
- Urea top dress @ 20g/bed or urea spray @5g/liter water if N-deficiency is seen.
- Blast: Hexaconazol @ 1ml/litre water spray.
- Insects/pests: Multineem @ 2 ml/liter water.
- Zn deficiency: Zinc formulation spray (10g ZnSo4 + 5g lime in 20-liter water), two times at a ten-day interval.
Rice transplanting
After 20 to 25 days of seeding in the nursery, the seedlings are prepared for transplanting into the field. The two most common methods for transplanting are the straight-row approach (improved practice) and the random method (farmer’s practice). One can manually perform straight-row transplanting or use a transplanter. In the rice field, this transplanting technique makes weed control easier.
Planting is done with two to three seedlings per hill, at 20 to 25 cm apart. Plant spacing is primarily determined by the cultivar. Whatever the season, rice types that are tall, leafy, heavy-tillering, and prone to lodging should be spaced 25–30 cm apart as opposed to varieties that are short, resistant to lodging, and photoperiod-insensitive (20–25 cm). In rich soil, space the seedlings wider apart; in low soil, space them closer.
Direct Seeded Rice
Direct-seeded rice has gained popularity due to labor shortages and high transplanting costs. It’s planted in two ways: dry beds for dry regions, and wet/puddled beds where irrigation or early rainfall is feasible.
Dry-Direct Seeding Rice (Dry-DSR)
Seed drills have many different types of furrow openers, which are designed for different soil types and crop residues. A smooth, level seedbed is necessary to ensure that seeds are not planted at depths greater than 10 to 15mm. Covering harrows are drawn behind the combine. Sowing is made at the correct depth (2-3cm). A good plant stand has 35 – 40 established plants per meter of drill row.
The benefit of drill seeding is that fertilizer can be applied at the same time as the seed. Manual weeding is much easier in machine-drilled crops than in broadcast crops. In the dry bed system, the land is well prepared, and the seeds are shown broadcast or in furrows and covered with planks. Another technique is drilling by hand on prepared furrows, or by seed drillers. The soil must have enough moisture to help germination. Around 60-80kg/ha seeds are used in this DSR system.
Wet-Direct Seeding Rice (Wet-DSR)
In the case of the wet bed method, the soil is puddled, and sprouted seeds are seeded by random or by drum seeder in rows 25cm apart. The seeds are soaked for 24 hrs and incubated for 24-48 hrs before planting. The land must be well-leveled and drained at seeding. Irrigation should be given only after 5 days when the seedlings have established.
The drum seeder operates best on a seedbed that is well-leveled, smooth, and wet. A trained operator and good-quality sprouted seeds are needed for a good plant stand. Also, timely water management is important for weed control.
Weed Management
Increasing temperatures increase the weed infestation in the rice field. Weeds compete for water, nutrients, sunlight, air, and space with crop plants and reduce crop yields and the quality of grains. Fertiliser application may not increase yields in weedy fields because weeds absorb nitrogen more effectively than rice plants. Weeds are also harmful because they may host important pests and diseases of rice. They may also provide shelter for rats. Hence, timely and effective weed control is essential. Various types of weeds can be found in the rice field. They include:
Grasses
- Long narrow leaves and parallel veins.
- Round hollow stem.
- Leaves are aligned up and down in two rows.
Sedges
- Leaves are aligned up and down the stem in three rows.
- Stems are usually solid and triangular.
Broadleaf weeds
- Leaves may have various shapes and arrangements of veins.
- Leaves are usually wider than those of grasses and sedges.
The Time and Methods of Weed Control
Weeds must be controlled within 2-3 weeks of crop establishment before they compete with the crops and cause significant damage. In a wet system of rice, pre-emergence herbicide and hand weeding are advised thirty days after transplanting.
Moreover, for optimal weed management in a dry system, first-hand weeding should be done 15 to 21 days after planting, and second-hand weeding should be done 35 to 40 days after the first-hand weeding. Weed control methods include Crop management, Direct (short-term) methods, Indirect (fallow and rotation) methods, and the use of herbicides.
- Crop management includes Land preparation, land leveling, good seed, clean nurseries, and seedlings, appropriate variety selection, clean bunds and canals, closer spacing and crop establishment methods, water management, nutrient management, rogue weeds, and clean equipment.
- Direct methods include hand weeding, mechanized weeding, and biological control 2-3 hand weeding or mechanical weeding is necessary depending upon the weeds, at 20-50 days after seeding/transplanting.
- Herbicides to control weeds: In integrated weed management, chemical weed control is one option. This refers to the combined application of mechanical, cultural, manual, and/or chemical control techniques. Herbicides are sold in formulations as granules, liquids, and wettable powders. Before and after emergence, they are used. Herbicides have two types of actions: selective and non-selective, and contact and systemic.
- Indirect methods include Fallow management and crop rotation.
Herbicides Use
– To prevent crop loss, weeds must be controlled during the first 20 to 40 days.
– Farmers can save money by using 1 kg/ha of pendimethalin 5-8 days after sowing in a dry system.
– Verify that the product is appropriate for the kind of crop and its stage of emergence (pre/post).
– Apply product uniformly throughout the field by keeping a constant walking pace, constant pressure, and consistent spraying.
Reduce the amount of product that is moved to non-target areas by applying at low pressures, avoiding applications in extremely windy conditions, and managing water runoff from fields to nearby properties.
– To lessen weeds, use well-leveled terrain and standing water.
Water Management
Water management in transplanted rice
Because of the flooded nature of lowland rice, its water balance and water productivity are different from those of other cereals such as wheat and maize. Water inputs to lowland rice fields are needed to match the outflows by seepage, percolation, evaporation, and transpiration.
- Typical combined values for seepage and percolation vary from 1-5mm/day in heavy clay soils to 25-30mm/day in sandy and sandy loam soils. Outflows of water by seepage and percolation account for around 25-50% of all water inputs in heavy soils with shallow water tables (20-50cm depth), and around 50-85% in coarse-textured soils with deep water tables (150cm depth or more).
- Evaporation occurs from the ponded water layer, while transpiration is water loss from the leaves of the plants. The typical combined evapotranspiration rates of rice fields are 4-5mm/day in the wet season and 6-7mm/day in the dry season, but they can reach 10-11mm/day in subtropical regions before the onset of the monsoon.
- The total seasonal water input to rice fields (rainfall plus irrigation) varies from as little as 400mm in heavy clay soils with shallow groundwater tables, to more than 2000mm in coarse-textured (sandy or loamy) soils with deep groundwater tables. Around 1300-1500mm is a typical value for irrigated rice in Asia to get a high yield.
- Land preparation lays the foundation for the whole cropping season and it is important in any situation to “get the basics right” for good water management afterward. Field channels, land leveling, and tillage operations (puddling, bund preparation, and maintenance) are especially important for good water management.
Water management in direct-seeded rice
In the case of DSR crops established after applying pre-sowing irrigation:
- The first irrigation can be applied 7-10 days after sowing, depending on the soil type. When the DSR crop is established in dry conditions followed by irrigation, additional 1-2 irrigations are required at intervals of 3-5 days during the crop establishment phase.
- Subsequent irrigations at intervals of 5-7 days must be applied to DSR crops. During the active tillering phase (30-45 DAS) and reproductive phase (from panicle emergence to the grain filling stage), maintaining optimum moisture levels (irrigation at 2–3-day intervals) is required to harvest enhanced yields from DSR crops.
- Avoiding water stress at flowering is recommended: this being one of the most sensitive stages of rice to water stress, frequent irrigations should be given one week before and one week after flowering to harvest bountiful rice grain.
Water management in DSR-Wet Bed System
Pre-germinated seeds are sown on the puddled soil a few days after puddling and leveling. With direct seeding, the crop starts to grow and use water from the moment of establishment onwards.
Water management in DSR-Dry Bed System
Farmers can reduce water use by shifting from puddled to non-puddled land preparation in a direct dry-seeded system. Dry land preparation does not involve land soaking so do not require large amounts of irrigation water. With direct seeding, the crop starts growing and using water from the moment of establishment onwards.
Dry seeding can also increase the effective use of rainfall through early crop establishment and hence reduce irrigation needs. However, dry seeding with subsequent flooding is only possible in soils that are heavy (clay), and which have low permeability and poor internal drainage.
Water at Critical Growth Stages
- Early vegetative stage
After crop establishment, continuous ponding of water generally provides the best growth environment for rice and will result in high yields. Flooding also helps suppress weed growth, improves the efficiency of nitrogen use and, in some environments, helps protect the crop from fluctuations in temperatures. After transplanting, water levels should be around 3cm initially, and gradually increase to 5-10 cm as the plant height increases.
With direct wet seeding, the soil should be kept just at saturation from sowing until around 10 days after emergence, and then the depth of ponded water should be increased gradually as the plant height increases. After sowing, apply irrigation if there is no rainfall to wet the soil. Saturate the soil once the plants have developed three leaves, and gradually increase the depth of the ponded water as the plant height increases.
- Reproductive stage
Rice crops are extremely sensitive to water shortage at the flowering stage (from flowering to grain filling), and if soil water contents drop below saturation, then effects akin to drought can be seen. Drought at the flowering stage results in an increase in spikelet sterility and a decreased percentage in filled spikelets, and in turn a decreased number of grains per panicle and decreased yields. Maintain the water level in the fields at 5-10cm at all times during this stage to boost rice production.
- Maturity stage
This period does not necessarily require flooding. Soil that is 80–90% saturated is sufficient. Drain the fields 10-15 days before the expected harvest date to hasten the maturity and ripening of the grain, prevent excessive nitrogen uptake, and render the land more accessible for harvest operations.
Nutrient Management
Use these fertilizers in the main field to help you to increase rice yield.
Organic fertilizers
Apply the mentioned fertilizers as basal dose.
- Apply Farmyard Manure (FYM) @ 12.5 tonnes/ha.
- Apply Green Manure @ 6.25 tonnes/ha.
- Apply Azospirrilum (Nitrogen fixing bacteria) @ 2 kg/ha mixing with 25 kg FYM and 25 kg soil and broadcast the mixture uniformly in the main field.
- Apply Phosphorus Solubilizing bacteria @ 2 kg/ha mixing with 25 kg FYM and 25 kg soil and broadcast the mixture uniformly in the main field.
- Apply pseudomonas fluorescence @ 2.5 kg/ha mixed with 50 kg FYM and 25 kg of soil and broadcast the mixture uniformly.
- Apply fresh Azolla by 10 tonnes/ha.
Chemical fertilizer
Application of NPK @120:40:40 kg/ha for improved varieties and NPK @ 150:50:40 kg/ha for hybrid varieties is recommended. About 25% of recommended N and K can be applied before transplanting and all the recommended P may be applied as basal or incorporated in soil. In zinc-deficient soil, the application of 25 kg zinc sulfate with 50 kg sand just before transplanting is recommended to overcome deficiency.
Table showing NPK dose and time of application for both improved and hybrid rice varieties.
| Time of application | Improved Variety (NPK; kg/ha) | Hybrid Variety (NPK; kg/ha) | Remark |
| Basal application | 30:40:10 | 37.5:50:10 | Apply 25% of N, K, and a whole dose of P. |
| 1st top dress | 30:0:10 | 37.5:0:10 | Apply 20 days after transplanting during the active tillering stage. |
| 2nd top dress | 30:0:10 | 37.5:0:10 | Apply at 40 days after transplanting. |
| 3rd top dress | 30:0:10 | 37.5:0:10 | Apply at 60 days after transplanting. |
| Total | 120:40:40 | 150:50:40 |
During 3rd top dress, it is also recommended to use Boron @ 2kg /ha. Boron application increases the production of pollen grain as well as helps in pollination.
Role of Major Nutrients
- Nitrogen
Rice plants require N at early and mid-tillering stages to ensure a sufficient number of panicles (grain bunches). Nitrogen absorbed at the panicle initiation stage increases spikelet (flower) numbers per panicle. Nitrogen absorbed during the ripening phase, in the presence of adequate solar radiation, enhances the grain-filling process. For best results, farmers should apply N fertilizer several times during the growing season to ensure that the N supply matches the crop’s needs at the critical growth stages of tillering, panicle initiation, and grain filling, and to minimize losses.
- Phosphorus
Phosphorus is particularly important in the early growth stages. It promotes root development, tillering, and early flowering.
- Potassium
Potassium strengthens plant cell walls and contributes to a greater canopy for maximum photosynthesis and crop growth. It does not have a pronounced effect on tillering, but it can increase the number of spikelets per panicle (flowers per grain bunch) and the percentage of filled grain.
Pest and Disease Management
The development and spread of diseases and pests are influenced by temperature, humidity, and patterns of precipitation. An estimated 37% of crops are damaged annually by pests and diseases.
The following methods are generally used to control the pests and diseases in rice crops.
Chemical Control
The application of pesticides is one of the quickest and, sometimes, the only solution for the sudden outbreak of pests, especially insect pests. Their application enables the farmer to take quick and direct action. However, their prophylactic usage is neither economically nor environmentally sound.
| S.N. | Major Pests | Damage | Control |
| 1 | Field cricket | Cut the seedlings and feed on roots and underground parts.
| Chloropyriphus 20 EC @ 2ml/L spray |
| 2 | Stem borer
| · Cause dead hearts and white heads. · yellowing of leaf sheaths; presence of entrance or exit holes on the stem.
| · Use a resistant variety of rice. · Cultural practices. · Biological controls like, Trichograma @ 50,000-1,00,000 /ha. · Apply Bt @ 3g/L. · Insecticide (chlorophyriphus 50% + Cypermethrin 5%), spray @ 2ml / litre water. |
| 3 | Rice hispa
| The adults scrape chlorophyll from the leaf while the grubs produce mines between the upper and lower epidermis, seen as narrow, white, parallel long lines on the leaves, and the plants become stunted.
| · Spray NPV 2ml/L. · Spray cypermethrin @ 2 ml / L. |
| 4 | Leaf hoppers Brown planthopper | Suck the sap and blockage of vascular bundles by feeding sheaths cause the plant to wilt and die, also known as hopper-burn. Brown plant hopper transmits both rice grassy stunt and rice ragged stunt virus.
| · Follow field sanitation. · Spray Metasystox @ 2ml / L or Imidacloprid 17.8% @ 0.25 ml / L water. |
| 5 | Rice bug
| Rice bugs feed at the milking stage on grains, causing empty grain while feeding at the dough stage, and giving rise to broken/chaffy grains. | · Spray Cypermethrin@ 2 ml/L. |
| 6 | Leaf roller
| The maggots feed on the tip of the leaf sheath. The affected leaf sheath is then converted to a gall known as ‘silver shoot’.
| · Spray NPV@2 ml/L. · Spray insecticide Cypermethrin@ 2 ml/L |
| 7 | Mealy bug
| The nymphs and the adult females suck the plant sap from the plant base. Their feeding causes abnormal tillering, production of smaller leaves, and failure of the panicle to emerge. Dried plants occur in patches in the field.
| · Flooding the field. · Use Fipronil @ 30 kg/ha |
| S.N. | Major Diseases | Damage | Control |
| 1 | Blast
| With leaf blast, the lesions are elliptical, or spindle-shaped with brown borders and grey centers. It also affects the collar and neck areas.
| · Use resistant variety. · Seed treatment with carbendazim @ 2g / kg. · Spray hexaconazole 5% EC @ 2g / L. |
| 2 | Bacterial leaf blight | Water-soaked stripes that later cover a large area of the leaf blade; lesions are greyish-white with a wavy light-brown margin.
| · Use resistant variety. · Seed treatment with Agrimycin @ 0.25 g / L dipped in solution for 30 minutes. |
| 3 | Brown leaf spot | Small, circular, brown lesions, may girdle the coleoptile and distort the primary and secondary leaves, circular to oval brown lesions on leaves and grains.
| · Grow resistant variety. · Spray Dithane M-45 @ 3gm /L at 15 days interval. |
| 4 | Footrot
| Initially, the disease appears as a small, blackish, irregular lesion on the outer leaf sheath near the water line and penetrates the inner leaf sheaths. | · Seed treatment with carbendazim @ 2g / kg seed. · Spray hexaconazole @ 2ml / L. |
| 5 | Sheath blight.
| The initial lesions are small, ellipsoid, or ovoid, and greenish-grey and usually develop near the water line in lowland fields.
| · Seed treatment with Carbendazim @ 2g / kg seed. · Spray Dithane M 45 @ 2g/ L at 15 days interval; 2-3 spray. |
| 6 | Khaira/Zinc Deficiency | In the seedlings, leaves develop brown blotches and streaks that may fuse to cover older leaves entirely; plants remain stunted and in severe cases may die, while those that recover will show substantial delay in maturity and loss in yield.
| · ZnSo4@ 25 kg/ha as basal application or spray 20g Zinc+ 12g lime in 50 liters of water: two sprays at a10 day interval. |
Integrated Pest Management (IPM)
IPM concepts are the selection, integration, and implementation of methods of pest and disease control that are ecologically sound, economically viable, and socially acceptable.
Use of resistant varieties
This is the easiest, most effective, compatible, economical, and practical method among all the pest management practices. Several resistant varieties, with single or multiple resistances to insect pests and diseases, are commercially available. These varieties have high yield potential and possess desired agronomical characteristics. Use only varieties that are officially released for a particular domain and season. Cultivation of unreleased or unregistered varieties may lead to crop failure due to pest/disease hazards and/or adaptation problems.
Cultural control method
These refer to good agronomic practices that enhance crop productivity and suppress the pest population. The cultural practices that are commonly used for rice are:
- Proper sanitation – Timely removal of weeds to reduce the pest survival rate and to reduce the potential of any carryover of the pest.
- Proper water management – Timely irrigation and a good drainage system are required to control plant hoppers.
- Proper spacing – Provision of alley ways of 30cm and width of 2-3m, otherwise bed planting is helpful, particularly in areas prone to the White-backed plant hopper and Brown plant hopper.
- Timely planting – Timely and synchronous planting can reduce the occurrence of insect pests like yellow stem borer, Gall midge, Brown plant hopper, White-backed plant hopper, and green leaf hopper.
- Balanced fertilizer – Well-planned, optimum doses of nitrogen and other fertilizers based on soil testing are essential. Splitting the dosage of nitrogen can also reduce the risk of Gall midge, Leaf hopper, Brown plant hopper, White-backed plant hopper, and green leaf hopper.
Mechanical Control Method
This involves (a) Removal of affected plant parts; (b) Use of light trap, pheromone trap, sticky trap, and suction devices; (c) Use of poisoned bait; (d) Hand collection of egg mass and larvae and destroying them; (e) Use of hand net for mass catching of adult pests and destroying them.
Biological Control Method
Biological agents like predators, parasites, and pathogens which decrease the pest population in the rice ecosystem. It is very important to conserve the natural enemies of pests in the field. Avoid the use of broad-spectrum pesticides when natural enemies are abundant.
However, the inundated release of the egg parasite, Trichogramma japonicum, T. chilonis is a highly effective means to decrease the incidence of yellow stem borer or Leaf folder. A very high count of Trichoderma viridae and a few bacterial antagonists are also effective against fungal pests.
Harvesting
Rice should be harvested when 80% of the panicle turns yellow, and moisture content is around 20-25%. Grain losses may occur from late harvest due to rats, birds, crop lodging, insects, and shattering. The most common method for harvesting rice is the manual system. The crop is cut with simple hand tools, including sickles for cutting 15-20cm above ground level. The manual harvesting system is very effective in lodged crop conditions but is labor-intensive. Manual harvesting requires 40 to 80 man-hours/ha. Cutting can also be done mechanically with a reaper, although using reapers for rice is not widespread in Nepal. A reaper with a cutting width of 1.5m can operate at a rate of 2 to 4 ha per day. Due to labor scarcity, rented combine harvesters are also becoming popular among large production areas.
