Do you want to create an amazing science fair project on rice ? You are in the right place. Read the below given article to get a complete idea on rice:- 1. Origin of Rice 2. Distribution of Rice 3. Area and Production of Rice 4. Groups of Rice Culture 5. Rice Yield and Yield Components 6. Requirements for High Yield of Rice 7. Soil and Tillace for Rice 8. Problem Soils and Rice Production and Other Details.
Contents:
- Science Fair Project on the Origin of Rice
- Science Fair Project on the Distribution of Rice
- Science Fair Project on the Area and Production of Rice
- Science Fair Project on the Groups of Rice Culture
- Science Fair Project on Rice Yield and Yield Components
- Science Fair Project on the Requirements for High Yield of Rice
- Science Fair Project on the Soil and Tillace for Rice
- Science Fair Project on Problem Soils and Rice Production
- Science Fair Project on the Characteristics of the Rice Ecotypes
- Science Fair Project on the Nutritional Biofortification of Rice
- Science Fair Project on the Cultivation of Hybrid Rice
- Science Fair Project on the Rice Cropping Seasons in India
- Science Fair Project on Water Requirement for Irrigated Rice Crops
- Science Fair Project on the Effect of Weed on System of Rice Culture
Science Fair Project # 1. Origin of Rice:
It is, generally, agreed that river valleys of Yangtze and Mekon rivers could be the primary centre of origin of O. sativa while delta of Niger river in Africa as the primary centre of origin of O. glaberrima. The foothills of the Himalayas, Chhattisgarh, Jeypore tract of Orissa, northeastern India, northern parts of Myanmar and Thailand, Yunnan province of China etc. are some of the centers of diversity for Asian cultigens.
Rice belongs to the genus Oryza and the tribe Oryzeae of the family Gramineae (Poaceae). The genus Oryza contains 25 recognised species, of which 23 are wild species and two (O. saliva and O. glaberrima) are cultivated.
O. sativa is the most widely grown of the two cultivated species. It is grown worldwide including Asian, North and South American, European Union, Middle Eastern and African countries. O. glaberrima, however, is grown solely in West African countries.
The inner delta of Niger river and some areas around Guinean coast of the Africa are considered to be center of diversity of the African species O. glaberrima. O. Saliva and O. glaberrima are believed to have evolved independently from two different progenitors, O. nivara and O. barthii and they are believed to be domesticated in south or Southeast Asia and tropical West Africa respectively.
The progenitors of O. sativa are considered to be the Asian AA genome diploid species and those of O. glaberrima to be African AA genome diploid species O. barthii and O. longistaminata as indicated in various reviews by Chang (1976) and Wayne Smith (1975).
After being cultivated for perhaps millennia, rice culture was introduced to Japan from about 1000 to 300 BC. Rice cultivation spread westwards across India by 2000 BC and southward into Malaysia, reaching the Philippines by 1400 BC.
Introduction of domesticated rice into Pakistan is thought to have been by the Harappan civilisation of the Indus river valley around 2300 BC. Rice was introduced into the Near East in Hellenistic times 323 to 23 BC, being known to both Greek and Romans.
Science Fair Project # 2. Distribution of Rice:
Unhusked grain (seed), as well as the growing crop, is known as paddy. Husked or hulled rice, usually termed brown rice, is milled to remove the outer layer, including the aleuron layer and the germ, after which it is polished to produce white rice. Rice is concentrated in areas where water management is convenient on flat lands, river basins and delta areas.
Rice will furnish under such widely differing environment that it is difficult to define an ideal environment for its growth and development. Highest yields are usually obtained in countries enjoying a subtropical or warm temperate climate.
Rice is now cultivated as far north as the banks of the Amur river (53° N) on the border between Russia and China and as far south as central Argentina (40° S). It is grown in cool climates in the mountains of Nepal and India and under irrigation in the hoi deserts of Pakistan, Iran and Egypt. It is an upland crop in parts of Asia, Africa and Latin America.
At the other environmental extreme are floating rice, which thrive in seasonally deeply flooded areas such as river deltas – the Mekong in Vietnam, the Chao Phraya in Thailand, the Irrawady in Myanmar and the Ganges- Brahmaputra in Bangladesh and eastern India.
Rice cultivation in the world extends from 39°S latitude (Australia) to 45°N latitude (Japan) and 50°N latitude (China). Most extensive rice growing areas are within 45°N and 40°S latitudes. Highest yields are recorded between 30° and 45°N of the equator. In India, rice is grown from 8° to 34°N latitudes. It is also grown in areas below the sea level as in Kuttanad of Kerala.
It also grows well at altitudes above 1979 m as in parts of Jammu and Kashmir. It is cultivated as rainfed upland crop in West Bengal, Bihar, Assam, Orissa and parts of Uttar Pradesh and Madhya Pradesh. In parts of West Bengal and Bihar, it is grown in shallow and deep waters during rainy season.
One of the main reasons for the wide range of adaptability under which the crop is grown is the great diversity of cultivars. They differ greatly in their tolerance to drought and flooding, some being drought tolerant while others are flood tolerant.
Cultivars are available for cultivation with normal irrigation water and also with brackish water. Varieties are also available for cultivation in cool season. In general, location specific varieties are available to suit the environment in all the rice growing countries.
Science Fair Project # 3. Area and Production of Rice:
Among the rice growing countries, India has the largest area under rice and in case of production it is next to China. However, it stands at 14th position with regard to productivity among the major rice producing countries (Table 1.1).
Many countries with limited rice area figure in the list of high rice productivity. Among the top 10 rice producing countries, China with an area of 29.88 M ha is the highest producer of rice (196.68 M t) in the world. Productivity, among major rice producing countries, is highest (10.00 t ha-1) in Egypt followed by Australia (9.00 t ha-1).
According to area and production, India has the largest area (41.85 M ha) and strands second in production (133.70 M t) in the world (2009). Productivity of rice crop in India (2.19 t ha-1) is much lower than that of Egypt, Japan, China, Vietnam, USA and Indonesia and also the average productivity of the world.
Rice contributes 42 per cent of total food grains production and 45 per cent of the total cereal production in the country. It is grown in all the states and UTs in India. West Bengal ranks first in the area (5.63 M ha) and production (14.34 M t) of rice. Among the states with considerable area under rice cultivation, Punjab has the highest rice productivity (4010 kg ha-1) in the country followed by TN (3070 kg ha-1).
Major rice growing states are WB, UP, AP, Punjab, TN, Orissa, Bihar and Chhattisgarh. These states contribute about 72 per cent of the total area and 76 per cent of the total rice production in the country. Other 25 states and UTs contribute the rest of 28 per cent of the area and 24 per cent of the total rice in the country.
There is a wide variation in the productivity at state level. The states of Andhra Pradesh, Goa, Haryana, Karnataka, Kerala, Punjab, Tamil Nadu, Tripura, West Bengal, A&N Islands, Pondicherry and Delhi have productivity above the national average.
According to the productivity level (2002-03 to 2006-07), the states have been classified into five groups:
In India, the area under rice crop during early fifties was about 30 M ha with an average productivity of 773 kg ha-1. Since then, there was gradual increase in area to 41.92 M ha, production to 89.10 M t and productivity to 2125 kg ha-1 by 2010.
During the period of 60 years from 1950 to 2010, annual rice production, on an average, increased by about 2.2 per cent and the area by around 0.64 per cent. Now the productivity is sharply decreasing and the area reached a saturated point around 42 M ha.
Low and fluctuating yields in eastern India are partly attributed to the high proportion of rainfed area. Rainfed rice is subjected to both drought and flooding besides a host of associated biotic and abiotic constraints. High yielding varieties require greater management than traditionally grown varieties in most aspects of production.
Eastern India fanners lack the resources required to ameliorate some of the potential problems. They instead relay on traditional varieties, which are not as productive but have more stable yields than modern varieties under conditions of uncertain rainfall and low input use.
Science Fair Project # 4. Groups of Rice Culture:
Rice culture, in general, is divided into two broad groups: upland and lowland rice cultures. Upland rice refers to rice grown on both flat and sloping fields that are prepared and seeded under dry-land conditions and depending on rainfall for moisture. This is also known as rainfed rice.
Brazil is the largest producer of upland rice. Flooded rice is grown on flat land with controlled irrigation. It is also known as irrigated rice, lowland rice or waterlogged rice. Lowland rice is commonly flooded when seedlings are 25-30 days old.
A comparison of lowland and upland rice cultures are given below:
Lowland Rice:
1. Cultivated on leveled, bunded, undrained soils.
2. Water supply through rainfall or irrigation.
3. Land submergence during major part of crop, growth.
4. Reduced root zone during major crop growth period.
5. Direct seeding or transplanting.
6. Thin or shallow root system.
7. High tillering.
8. Short and thin leaves.
9. Environmental conditions stable and uniform.
10. Low pest and disease incidence.
11. Weeds are not a serious problem.
12. High input requirement.
13. High cost of production.
14. Stable and high yield.
Upland rice:
1. Cultivated on undulating or leveled, naturally drained soils.
2. Water supply through rainfall only.
3. No land submergence during crop growth.
4. Oxidized root zone during crop growth.
5. Direct seeding.
6. Vigorous deep root system.
7. Relatively low tillering.
8. Long and thick leaves.
9. Environmental conditions unstable and variable.
10. High pest and disease incidence.
11. Weeds are a serious problem.
12. Needs low input.
13. Low cost of production.
14. Unstable and low yield.
Rice is grown in a wide variety of climate-soil hydrology regimes, which are grouped into different rice ecosystems. There has been progress during the past decade in developing rice ecosystems at continental and national scales.
Science Fair Project # 5. Rice Yield and Yield Components:
Rice yield is usually reported as paddy (unhusked seed) at 14 per cent moisture content, except in few countries such as Japan and Korea where the yield is expressed in terms of brown rice (polished rice). A conversion factor 1.25 is usually used when brown rice yield is converted into unhusked rice yield.
A common way of examining grain yield is to measure the total dry weight and dry grain yield and then compute the ratio of these two.
... Dry grain yield = HI x Total dry weight
The grain-straw ratio, similar to the harvest index and extensively used in the past, is a ratio of dry grain yield to dry straw weight.
The grain to straw ratio of rice range from about 0.5 for traditional tall cultivars to about 1.0 for improved short cultivars.
Grain yield of rice is determined by the following four components:
1. Number of panicles m-2
2. Number of grains panicle-1
3. Percentage of ripened grains
4. 1000-grain weight (test weight)
Yield is the product of these four components, which are called yield components. The relationship between yield and yield components can be expressed by the following equation.
Yield ha-1 = No. of panicles m-2
x No. of grains panicle-1
x Per cent of ripened grains
x Wt. of 1000 grains/1000
x 10000
Number of panicles m-2 is the product of the number of an average hill and the number of hills m-2.
In the case of direct sowing, the number of panicles m-2 is obtained by multiplying the number of panicles between 30 cm in the row, where the plant growth is estimated to the average by the figure 10,000 divided by 30 times the width between rows expressed in cm, as shown below:
where,
a = number of panicles between 30 cm in the row
b = seeding width (cm)
c = inter-row space (cm)
d = distance between rows (cm) = b + c
N = number of panicles m-2
On the broadcast field, the number of panicles m-2 is calculated by multiplying the number of panicles in the area of 30 cm by 10, where the plant growth is estimated to the average by 333.
For increasing the yield of grain, values of the above four components must be increased. Weather conditions, cultural management and nutrient supply greatly influence yield components Understanding their interrelationships is a key to improvement in rice yield.
Science Fair Project # 6. Requirements for High Yield of Rice:
Requirements for high yields of rice are indicated below:
a. Variety should have a short, stiff steam.
b. Leaf arrangement should be such that the erect upper leaves graduate down to droopy leaves at low canopy levels.
c. LAI of 5-6 is necessary for achieving maximum photosynthesis during reproductive stage.
d. Maintenance of as many active green leaves as possible until crop maturity.
e. Planting time should be chosen so that the crop is exposed to high solar radiation during reproductive phase.
f. All the essential nutrients must be supplied to meet the crops requirement in time.
g. Nitrogen absorption after heading assumes importance when high yields are expected by increasing the harvest index.
Highest recorded grain yield is 13.2 t ha-1 in Japan, 11.0 t ha-1 in Philippines and 17.8 t ha-1 in India. If these yields are compared with the world average of about 4.16 t ha-1 it is evident that there is lot of potential to improve rice yields.
Among the yield components, spikelets m-2 is usually the most variable yield component, accounting for about 74 per cent of the yield variation. Filled spikelet percentage and grain weight together account for 26 per cent of the yield variation. Panicle number is determined in vegetative stage, grain number per panicle in reproductive stage and grain weight in ripening stage.
Some factors affecting yield components and consequently yield are climatic factors like temperature, solar radiation, water availability and nutrients, especially nitrogen and phosphorus. Reduction division growth stage is very sensitive to extreme temperatures, low solar radiation, drought and nitrogen deficiency.
Science Fair Project # 7. Soil and Tillace for Rice:
Major rice growing areas in the country has alluvial soils. In the eastern, northeastern and Peninsular India, besides alluvial soils, coastal and deltaic alluvial soils, red soils, red and yellow soils and laterite soils occupy considerable area under rice. In addition, saline soils occur in the coastal belts of the rice growing region.
Despite wide variations in rice culture, there are two main systems of soil management: dry soil management, in which land is prepared dry and the crop is seeded in the same manner as other cereal crops, referred to as upland rice culture and wet soil management, in which the land is flooded and soil preparation is done in wet or submerged soil, referred to as wetland rice culture.
Upland Soils:
Soil characteristics found in upland rice culture are nonspecific in respect of soil texture, soil reaction, organic matter content, slope and soil fertility variations encompass virtually all possible conditions. Soil texture and topography may be the most important characteristics for upland rice since they profoundly affect the soil moisture status and its tilth for seeding.
A surface soil with medium to fine texture overlying a subsoil of finer texture is considered most desirable for upland rice. Soil reaction for upland rice is most favourable over the pH range of 5.5-6.5, although most upland areas are more acidic.
Upland soils being mostly coarse in texture, their water retentive capacity is very low and hence the crop often suffer due to soil moisture stress with uneven rainfall distribution. Red and laterite soils contain large amounts of free iron oxide, which often leads to crust formation resulting is poor emergence of the seedlings and low crop stand.
These coarse textured soils have low cation exchange capacity and hence nutrient retention capacity is low. This leads to considerable loss of nutrients, particularly nitrogen through deep percolation.
Low Land Soils:
A major portion of the rice in tropical, subtropical and warm temperate parts of the world is grown under conditions where the soil is flooded during greater part of the growing season. Soils of lowland rice are usually on level terrains or on terraces where standing water can be maintained.
By virtue of their physiographic positions often accentuated by inundation and soil management practices for rice, these soils usually have strong hydromorphic characteristics, poor internal drainage but are capable of irrigation and drainage in rice culture management.
The semiaquatic conditions under which lowland rice is grown necessitate a heavy soil through which irrigation water will not easily percolate, for the demands of the plant regarding water are more precise than are its demands on soil conditions.
Most of the extensive areas in Asia are situated in the deltas of great rivers or are spread along their banks. Thus, the situation of lowland rice areas is governed rather by considerations of water supply than by the nature of soil.
The literature, in general, seems to show that high rice yields are usually associated with soils that have a high clay content (40-60 per cent), a 2:1 clay mineral, a medium organic matter content with a high degree of humification and good but not excessive drainage. Soil depth may vary from 18-22 cm. The pH, however, may range from 4.0 to 7.0 without affecting the yields.
Apart from the desirability of growing rice crop on a heavy soil capable of holding water, there appears to be direct evidence that it grows better on heavy clay soil than on lighter soils containing a higher proportion of sand. Provided adequate irrigation water is available, satisfactory yields are obtained on sandy soils when they are given heavy dressings of organic matter and fertilisers.
Heavier soils, especially if they contain a satisfactory level of organic matter are most suited for rice cultivation. Most rice productive areas are found to consists of a soil with high finer particles (clay plus silt around 70 per cent) with CEC not less than 25 meq 100-1 g of the soil.
Chemical analysis of a soil does not appear to provide a very sure guide to its suitability for rice crop. Thus, rice soils are found to be very dissimilar in chemical composition, yet yielding equally good crops.
Problem Soils:
In the rice growing areas of the world, realisation of full yield potential of rice is often limited by soil problems of diverse nature. Problem rice soils include saline and sodic soils, acid sulphate soils and peat soils.
There are about 65 M ha of saline and sodic rice soils in Asia. As a matter of fact, rice is the most ideal crop to be grown on these soils because land submergence leads to lowering of soil pH and salt concentration. Drainage and application of gypsum helps in reclamation of these soils.
Acid sulphate soils are acidic with a pH of 3 to 4 in the upper 50 cm depth. In Asia, about 5 M ha of these soils are found in tidal swamp areas. Iron toxicity is the major problem, which can be corrected by drainage, liming and adding bulky organic manures.
Peat soils having organic matter content of at least 65 per cent in the upper 50 cm soil depth are characterised by high water table. Chemical toxicities including organics such as phenols are common. Sterility of rice is also a serious problem. Copper deficiency or non-availability appears to be responsible for the sterility.
Tillage Practices:
Rice is grown in diverse land and water management systems, unlike many other field crops. Local customs, nature of soil and water supply are among the principal factors for various methods employed in preparing the field for rice crop. The tillage practices for rice differ with the rice ecosystem.
Deep Water and Floating Rice:
It is a traditional method of rice cultivation in India. About 15 per cent of world’s rice area is subjected to annual floods and require deep water and floating rice culture. In this system, tillage and seeding are done in dry soil before the onset of monsoon. Some times, after seeding, the land is repeatedly ploughed to control timing of seedling emergence. Crop establishment and hence the productivity of rice is poor in this system.
Upland Rice:
In areas of scanty rainfall, dry seeding is the common method. The final land preparation is usually completed with harrows. The seed is sown by conventional seeders. In this system, two methods may be distinguished in south India.
One method called malnad cultivation is confined to areas of heavy rainfall, where the crop depends entirely on rainfall and the second is usually followed for the crop, which depends partly on rainfall and partly on irrigation (maidan cultivation).
In the malnad cultivation, the field is ploughed immediately after the harvest of previous rice crop and left until the first rains are received, when the field is worked with blade harrows to break the clods.
A leveling log is then worked to level and to consolidate the field. Seeding is usually with seed drills. Light harrows are worked repeatedly between the rows to control the weeds. After heavy rains, the field becomes flooded until the crop matures.
In the maidan cultivation, the field is ploughed soon after the harvest of the previous crop, if possible or with the early rains or by giving irrigation. The ploughings are repeated up to onset of regular monsoon. With first rain, usually in June, the seed is sown by broadest and harrowed. The crop will grow with rainfall alone up to 8-10 weeks after sowing. Then the crop is treated as lowland rice with irrigation water or impounding rain water in the field till harvest.
Lowland Rice:
The traditional method of preparing land for transplanted lowland rice is puddling (tillage in standing water) the soil. Puddling causes physical destruction of soil aggregation and non-capillary pore space as a result of which the individual soil particles get segregated and dispersed leaving the soil mass into a soft puddle. The soil particles in suspension settle down slowly and form a laminar structure.
The sand particles settle first on subsoil and the finer particles settle on the sand layer, the thickness of which depends on soil clay content. Puddling, therefore, increases soil bulk density from around 1.4 to about 1.8 g cm-3. Increase in bulk density and reduced porosity due to puddling largely reduce the deep percolation of water because of reduction in soil hydraulic conductivity (Table 1.4).
Puddling, a traditional method of tillage for lowland rice, is still the major method due to the following associated advantages in rice cultivation:
a. Puddling makes seedling transplantation easier with least injury.
b. It is an effective method of weed management due to associated land submergence.
c. Reduced losses of water through deep percolation minimises irrigation needs.
d. Reduced soil conditions due to standing water increase the availability of nutrients especially P, Fe and Mn.
Since puddling and land submergence go hand in hand, it is difficult to separate the effect of the two on soil, crop and weeds. Intensive puddling, starting 15 days ahead of transplantation increased the rice yield with lesser irrigation water. Increased yield was largely due to minimum weed growth with intensive puddling. Soil compaction was also effective in reducing weed growth, minimising irrigation needs and improving the rice productivity.
Soil compaction by rollers has been reported to be equally effective as that of puddling for lowland rice. Compaction increases the soil bulk density, reduces the hydraulic conductivity and deep percolation losses of water. However, transplanting is difficult in compacted soil.
Shallow ploughing up to 5.0 cm depth of compacted soil was as ideal as puddled soil for transplanting the rice seedlings, retaining the advantages of compaction for higher productivity.
Tillage for Rice Based Cropping Systems:
In rice based cropping systems of Asia, stand establishment of upland crops after lowland rice is problematic, especially, in soils with high montmorillonitic clay. High soil strength in seed and root zone, rapid drying of the seed zone, poor aeration and waterlogging due to heavy rain after seeding upland crops are the major limitations for their productivity.
Tillage is difficult on heavy soils as they are hard when dry and sticky when wet. When the soil is wet, minimum or no tillage for upland crops after lowland rice is recommended. However, without tillage, moisture sensitive upland crops may suffer from aerobic conditions. As such, shallow tillage is the only option.
When cotton is raised after rice as in south India, cotton seed is normally sown in moist soil in a hole mode with a sharp stick and the hole closed. If necessary, pot watering is done to establish adequate crop stand. In intensive cropping systems such as cotton-sorghum-groundnut, a minimal tillage system involving ploughing the land only for the first crop can be recommended with herbicides for weed control.
In relay cropping systems, pulse crops are broadcasted in standing rice crop around a week before rice harvest. Absolutely there is no tillage for the pulse crop. Any tillage after rice leads to rapid soil moisture loss resulting in no scope for any crop after rice, since the crops are grown on store soil moisture without any irrigation.
In irrigated rice-wheat and rice-maize systems of north India, wheat or maize after rice is a problem due to undesirable physical properties of the lowland rice soils. Intensive efforts have been made to address this problem, however, without much practical success. Mishra (1989) evaluated different combinations of tillage implements for wheat crop after rice.
Two passes of rotavator with a roller for clod breaking gave overall best performance in terms of yield, time and energy saving. However, conventional tillage (3-4 ploughings) after rice for wheat was ideal compared to minimum tillage. In general, zero or minimum tillage is not favourable for many crops after rice under different rice ecosystems.
Energy Efficient Tillage Systems:
Conventional tillage by bullock drawn plough is highly energy inefficient. Almost 30-40 per cent energy can be saved if bullock drawn disc harrow is used after one MB ploughing. Similarly, by using bullock drawn disc puddler after one MB ploughing, 40-50 per cent energy can be saved compared with conventional puddling by country plough. Tractor drawn disc puddler is most energy efficient. It consumes 1223 MJ ha-1 (137.4 HP hr-1) energy. Puddling by power tiller operated rotavator requires 1338 MJ ha-1.
Tractor drawn cultivator has been found to be most energy efficient for good field preparation for direct seeding of rice. Two passes followed by three disc harrowings results in an ideal field condition for direct seeding. Field preparation by rotavator is good for sowing by seed drills.
Studies on field preparation involving one MB ploughing and with two passes of cultivator, one MB ploughing and two passes of disc harrow, two passes of cultivator and two passes of disc harrow along with one pass of rotavator indicated that all the methods tested were equally effective for direct seeding of rice. However, the energy requirement was significantly less due to two passes of cultivator followed by two passes of disc harrow.
Science Fair Project # 8. Problem Soils and Rice Production:
Problem soils are those requiring special management practices to overcome the inherent soil constraints limiting the productivity of crops. Crop production on these problem soils may not be remunerative without adoption of specific management practices to alleviate the soil constraints, besides selection of crops and varieties best suited for the situation.
India accounts for about 47 per cent of saline, 20 per cent of sodic (alkali) and 7 per cent of acid sulphate soils of tropical Asia. These soils suffer from multiple constraints and need different and often elaborate management practices as compared to normal soils for successful crop production.
Sodic Soils:
These soils cover about 2.5 M ha and primarily concentrated in Indo-Gangetic plains of Punjab, Haryana, Uttar Pradesh, Bihar and Rajasthan. They contain sufficient amount of exchangeable sodium to interfere with the growth of most crops and do not contain appreciable quantity of soluble salts.
The exchangeable sodium percentage (ESP) is more than 15 Cml (P+) kg-1 of soil and the electrical conductivity of the saturation extract (EC) is less than 4 dS m-1. The pH, generally, range between 8.5 and 10.5.
Management Practices:
Adequate care should be taken to minimise the effect of alkalinity on rice growth and development.
The following practices are found effective in managing the alkali soils for rice production:
1. Select tolerant/resistant varieties: IR 8, Ratna, Kalarata, CSR 23 and 30, Damodar, Kalinga III, Vytilla 4, Vikas.
2. Puddling is not beneficial during initial period of reclamation. Shallow tillage at optimum soil moisture is deal.
3. Use seedlings of 5-6 weeks age for planting at the earliest convenience in July.
4. At initial reclamation process, plant 4-5 seedlings per hill at 15 x 15 cm spacing.
5. Nitrogen should be applied through ammonium sulphate, calcium ammonium nitrate or urea in 3-4 splits at 150 kg ha-1 (25% higher than normal recommendation).
6. If necessary, apply P and K at planting along with 25 kg ha-1 of zinc sulphate.
7. Land should not be kept fallow for long during reclamation process. Rice in wet season followed by berseem, wheat or barley in dry season is an ideal cropping system in north India. Fingermillet, sunflower or a pulse crop in dry season is ideal in south India.
Saline Soils:
These soils contain sufficient soluble salts to interfere with growth of most crops. The pH is usually lower than 8.5 with EC more than 4 dSm-1 and ESP less than 15 Cmol (P+) kg-1.
Management Practices:
Young seedlings up to four weeks age are sensitive to salinity. Damage to seedlings at transplanting increases its sensitivity to salinity. The crop is tolerant to salinity at tillering. However, it becomes sensitive during anthesis and grain filling.
Crop management practices include:
a. Selection of salt tolerant varieties: SR 26B, CSR 5, CSR 10, CSR 23, Vytilla 3, Vytilla 4, Vikas, Narendra Usardhan 2, CSR 27, CSR 30, CSR 36.
b. Deep ploughing (30-45 cm) before onset of monsoon followed by 2-3 harrowings.
c. Division of field into subplots connected to a central drain for draining surplus water.
d. Preplanting irrigation with good quality water to leach down the accumulated salts from root zone. Transplanting should be only after leaching salts from upper 8-10 cm soil either with rains or good quality water.
e. A spacing of 15 x 15 cm with 4-5 seedlings per hill is essential to compensate crop stand due to seedling mortality.
f. Maintain deep submergence (6-8 cm) during seedling establishment, flowering and grain filling to minimise the salt effect.
g. Flow irrigation from field to field is better than stagnant water for long time.
h. Replace the stagnated water in the field once in a week.
i. Integrated nutrient management with organics and inorganics is ideal for improving the fertiliser use efficiency.
j. The field should not be kept fallow during dry season. If not a rice crop, a salt tolerant crop may be grown to minimise salt accumulation in surface layers.
Saline-Sodic Soils:
These soils contain high amounts of exchangeable sodium and soluble salts sufficient to interfere with crop growth. The EC is more than 4 dS m-1, ESP more than 15 Cmol (P+) kg-1 and pH, generally, more than 8.5.
These soils occur in low lying pockets with obstruction to drainage and occasional waterlogging for a short period. In these soils, the problem is twofold: high salt content and poor internal drainage due to hard clay pan formed by dispersed sodium clay.
Management practices include:
a. Application of gypsum at 5-71 ha-1 with or without mechanical stirring followed by leaching with good quality irrigation water.
b. Application of pyrite (amendment) considerably improve the quality of saline-alkali soil.
c. Post-transplanting leaching under intermittent submergence progressively decrease the salinity and sodicity for safe rice cultivation.
d. Cultural practices for rice on saline-sodic soils are almost same for those indicated for saline or alkali soils.
Acid, Red and Lateritic Soils:
These are shallow to medium porous soils dominated by Fe and Al. They are low in organic matter and nitrogen with high phosphorus fixing capacity.
Management Practices:
1. Selection of varieties: Bala, Narsing, DR 91, Cauvery, Ratna, Jaya.
2. Soil compaction to minimise leaching losses of nutrients through deep percolation.
3. Lime application to correct soil acidity and iron toxicity. Basic slang and press mud from paper mills are economical.
4. Addition of any organic material along with fertilisers (60+40+20 NPK kg ha-1).
5. Application of powdered rock phosphate or acidulated rock phosphate is better than water soluble sources of phosphorus.
6. Transplanting rice seedling three weeks after flooding.
7. Provision of adequate drainage.
Acid Sulphate Soils:
The soils are usually around 50 cm deep, poorly drained and nearly neutral or slightly acidic in reaction. They become acid sulphate soils if pyrite oxadizes after drainage. These are difficult to manage because drainage of these soils results in more oxidation leading to further soil degradation. Hence, these soils are to the managed in waterlogged condition for lowland rice.
Management practices include:
1. Selection of varieties: RD 15, RD 19, SR 26B, Mali, Vyttila 3.
2. Flushing the soil to make it free from excess salts.
3. Application of lime or basic carriers to correct soil acidity.
4. Application of NO3 or MnO2 to keep the system in a fairly oxadised condition.
5. Application of recommended nitrogen fertilisers (80 kg ha-1) in splits.
6. Soil or foliar application of zinc.
Science Fair Project # 9. Characteristics of the Rice Ecotypes:
Cultivars of O.sativa are grouped into three ecotypes: Indicas, Japonicas and Javanicas. Indicas are grown through the tropics and subtropics. These are characterised by tall stature, weak stem, droopy leaves, profuse tillering and do not adequately respond to fertilisers. Japonicas are limited to temperate and subtropical zones.
Due to their short stature, sturdy stem, narrow, erect and dark green leaves, this group responds well to fertilisers. Javanicas are mainly grown in parts of Indonesia. They have fewer tillers, tall stature with sturdy stem, long panicles and long bold grains. Most accepted or common characters used to classify the three rice ecotypes are grain length and lodging potential. The other criteria used to differentiate the three are indicated in Table 1.5.
Varietal Improvement:
Rice breeding programme in India was started by Dr. GP Hector, the then Economic Botanist during 1911 at Dacca (now in Bangladesh). Subsequently, in 1912, a crop specialist was appointed exclusively for rice in Madras Province.
Subsequent progress in rice varietal improvement with special reference to India can be summarized as indicated below:
1. Establishment of the Central Rice Research Institute (CRRI) at Cuttack in 1946 for improving the rice productivity and production in the country.
2. The ICAR initiated rice research projects in 14 states of the country and released around 500 pure line selections by 1950.
3. Initiation of interracial hybridisation programme between Japonicas and Indicas by FAO during 1952.
4. In 1960, the CRRI, Cuttack initiated hybridisation programme between Japonicas and Indicas in 11 states to evolve high yielding fertiliser responsive varieties, which was a remarkable success in the development of Japonica x Indica varieties.
5. The International Rice Research Institute (IRRI), established in Philippines in 1960 with the concept of improving the plant type in Indica rices based on the use of a gene from semi- dwarf Chinese varieties, developed dwarf high yielding miracle rice IR 8 in 1966.
6. Launching of the All India Coordinated Rice Improvement Project (AICRIP), now Directorate of Rice Research (DRR), by the ICAR in 1965 helped in coordination of interdisciplinary and inter-institutional research results on the country basis for improving the production, productivity and profitability of rice in India.
7. The ICAR initiated hybrid rice research programme in December 1989, which was further strengthened by technical support from IRRI and FAO since 1991. Twenty seven hybrids have been released by 2006.
8. Invention of recombinant DNA technology in the seventies and transgenic technology in the eighties has now culminated into a promising role for biotechnologies in the future rice improvement. Development of new rice varieties having multiple genes for resistance to different pests and diseases and pro-vitamin-A rich ‘Golden Rice’ (nutritional biofortication of rice) are the examples of success in this direction.
Popular Varieties/Hybrids:
During the period of interracial hybridisation between semi dwarf Taiwanese types/derivatives and Indicia, which was started during 1965, the most significant achievement was the prolific release of high yielding varieties. In fact, 123 varieties were released during this period in 12 years as compared to 51 high yielding varieties released during the four decades prior to 1965.
The semi dwarf varieties have been superior in efficiency of grain production, relative to the tall traditional varieties. As in 2006, around 800 rice varieties/hybrids have been released in India to meet the needs of rice producers in different agro-ecosystems of the country. Relatively popular rice cultivars across states in India are given in Table 1.6 and for Andhra Pradesh in Table 1.7.
Science Fair Project # 10. Nutritional Biofortification of Rice:
According to WHO estimates, around 5 M children in south and south-east Asia suffer from vitamin-A deficiency syndrome (VAD) and majority of them are becoming either partly or totally blind due to deficiency of this vitamin.
Since, rice happens to be the most consumed food in India, any genetic modification to enrich it with nutrients such as Vitamin-A or other basic minerals like iron and zinc can significantly overcome this deficiency. Development of ‘Golden Rice’ is an example of success in this direction.
Prof Ingo Potrykus of the Swiss Federal Institute of Technology, Zurich and Prof Peter Beyer of the University of Freiburg, Germany are responsible for this wonder product called Golden Rice that is fast becoming a poster crop for what is good about biotechnology, in the face of all the bad press the technology has been receiving. The feat was accomplished by following the steps indicated in Fig 1.3.
In all, three organisms unrelated to rice were involved in creating the new rice: Daffodils and the bacterium Erwinia uredovora provided the genes that encode β-carotene, while the crown gall bacterium Agrobacterium tumifaciens provided the plasmids that served as gene couriers into rice tissue.
The US Food and Drug Administration has classified provitamin-A or β-carotene as generally acceptable as safe. It is gratifying that the architects of the Golden Rice have left the technology in the public domain enabling the nutritionally under-nourished millions in the developing world to enjoy the fruits of science with no strings attached to it.
In India, a network programme funded by Humanitarian Board and the Department of Biotechnology is underway to bring in provitamin-A, iron and zinc in the grains of popular rice varieties using transgenic Golden Rice lines SGR 1 and SGR 2 mode available through Humanitarian Board. Nutritional bio-fortification of rice to provide nutritional security and help eradicate hidden hunger.
Science Fair Project # 11. Cultivation of Hybrid Rice:
Research programme initiated during 1970 to develop hybrid rice cultivars in the country was not successful during the subsequent two decades as the cytoplasmic male sterile (CMS) lines used for development of hybrid rice in China could not be used in tropical country like India because of their susceptibility to pests and diseases, poor adaptability and poor grain quality.
New CMS lines were bread at IRRI and by intensive national programmes from 1989 with a mission mode project. A remarkable success was achieved within a short span of 5 years and half a dozen rice hybrid rice cultivars were developed from public and private sectors. The first four hybrid rice cultivars were released in the country during 1994.
A total of 26 rice hybrids were released up to 2006 for commercial cultivation (Table 1.10). Among these, 22 were developed by the public sector and remaining five (PHB 71, 6201, 6444, RH 204 and Suruchi) by the private sector.
In continuation of the 26 rice hybrids listed in Table 1.10, another twenty one rice hybrids, making a total of 47, were released for cultivation during the period from 2006 to 2010, (Table 1.11).
Hybrid Rice Seed Production:
Hybrid rice seed production is a two-step process:
(1) Maintenance of A line, and
(2) Production of hybrid seed from A x R lines.
Production of A line seed is relatively easy as both A and B lines are genetically same except the cytoplasm. They have similar growth behaviour and flower almost at the same time. Adequate care is necessary for proper isolation, rouging in both lines and enhancing the panicle exsersion by spraying GA3.
A and R lines are genetically different. There may be 10-15 days difference in their flowering time. As such, staggered sowing of A and R lines is necessary. In the presently available CMS lines, one-fourth of the panicle remains within the leaf sheath.
Application of 60-80 g of GA3 ha-1 at 5 per cent panicle appearance on two consecutive days not only helps in proper exersion of the panicle but height of the R lines increases, flowers remain open for a longer period and stigma protrudes outside for higher out crossing.
As for as possible, hybrid seed should be produced in areas where they are recommended. About 25 g m-2 seed in nursery results in healthy nursery. In addition to timely weeding, application of fertiliser and irrigation water is necessary. Male to female row ratio of 2:8 has been observed to be most appropriate. For supplementing pollination, rope pulling and planting across in wind direction is desirable.
In two line hybrids, the A, B and R system is a bit cumbersome. Under Indian conditions, where temperature is not a limiting factor, only TGMS is adequate in the breeding programme. A single recessive gene controls the TGMS. Rice varieties carrying this gene remain sterile above 25°C during pollen primordial formation stage. Three TGMS genes have been identified and transferred to high yielding background.
Package for Hybrid Rice Seed Production:
Constraints to Hybrid Rice:
1. Limited yield heterosis (10-15 per cent) in commercial rice hybrids relative to that in millets.
2. Early duration, making them not ideally suited to kharif
3. Commercially usable and locally adaptable CMS lines are not readily available at present.
4. In most rice hybrids released in India, grain quality is not acceptable.
5. Hybrids released up to now do not possess resistance to major pests and diseases as desired by fanners.
6. Inadequate supply of pure breeder seed of commercial cytoplasmic male sterile and restorer lines.
7. Lack of free exchange of promising germplasm between public institutions and private seed sector.
8. GA3 is a costly input, alternate cheaper sources should be looked into.
Science Fair Project # 12. Rice Cropping Seasons in India:
Rice crop has very wide range of seasons to such an extent that it may not be unusual to see the rice crop in all the stages of growth at the same time and at the same area provided water is not the limiting factor. Broadly, however, there are two main seasons for the rice crop in India, though three crops are taken in Andhra Pradesh, Tamil Nadu, Karnataka and Kerala.
The kharif (west season) is characterised by a gradual fall in temperature, more number of cloudy days, low light intensity, gradual shortening of photoperiod, high relative humidity and cyclonic weather. During rabi (dry season), there is a gradual rise in temperature, bright sunshine, near absence of cloudy days, gradual lengthening of the photoperiod and lower relative humidity. There is no rabi crop in the northern states due to low temperatures from December to March.
Rice is essentially a short-day plant. A combination of temperature, photoperiod and light intensity determines the growing period, crop performance and productivity. Yields, in general, are higher in rabi than in kharif.
Highest yields are reported from summer crop. By and large, long and medium duration varieties are confined to kharif and short duration varieties to rabi, where the source of irrigation water is wells or monsoon rainfed tanks. Rice cropping seasons in India are given in Table 1.12.
Science Fair Project # 13. Water Requirement for Irrigated Rice Crops:
Lowland (irrigated) rice is an inefficient user of irrigation water. It requires more water than other crops of similar duration due to huge water needs for puddling and subsequent land submergence. Based on the environment in which it is grown, 50-70 per cent of the applied water is lost through deep percolation. The amount of water used at field level is 20,000 m3t-1 with poor water management and as low as 3,000 m3 t-1 with good management.
It has been reported that bout 5000 1 of water is required to produce 1.0 kg rice. Average production of grain (kg ha-1 mm-1 of water) is 3.7 for rice, as against 13.4 for fingermillet, 12.6 for wheat, 9.0 for sorghum, 9.2 for maize and 8.0 for pearlmillet. It is often said and agreed that seasonal water requirement for rice vary from 750 to 1500 mm with the average being 1200 mm.
If irrigation period is assumed to be 120 days, the average requirement will be 10 mm day-1, which appears to be reasonable on condition that land submergence is the usual practice with a minimum of 2 mm day-1 percolation and seepage losses.
Water is lost from irrigated rice field during the season through ET. percolation and seepage. The total water loss ranges from 5.6 to 20.4 mm day-1 but most observed values for total water loss range from 6 to 10 mm day-1. Thus, on an average, about 180-300 mm water per month is needed to produce a reasonably good crop of rice. In field operation, a total of 1, 240 mm is an average water requirement for rice crop (Table 1.22).
Decrease in yield due to partial submergence of the crop could be attributed to impaired tillering and decreased photosynthetic area of leaf surface. To overcome the problem, varieties with intermediate plant height (110-130 cm taller than semidwarf and shorter than traditional varieties) are replacing semidwarf varieties in shallow water areas that are subjected to occasional floods.
Water Management Practices:
Rice plants grow well in shallow ponded water, as they are able to effectively transport oxygen from shoot to the root system for respiration. However, it is often misinterpreted as if rice crop could be grown under any ponded condition and drainage is not a necessity.
Continuous Submergence:
Continuous land submergence for rice is, usually, practiced due to the associated major advantages of increase in availability of nutrients and less weed management problems. Results of experiments at various locations in India and other countries reveal that shallow submergence of not more than 5 cm depth throughout the crop period is optimum for high yield. Differences in yield due to varying submergence levels up to 12 cm were marginal, however, with large differences in the quantity of water needed with increasing depth of land submergence.
During kharif, when the atmospheric evaporative demand is low, continuous saturation could be as good as shallow land submergence. However, weed management will be a practical problem. Since, availability of irrigation water is not a problem during wet season, continuous shallow land submergence is preferred to maintenance of soil saturation. High evaporative demand during dry season necessitates continuous shallow depth of submergence (5.0 cm).
Intermittent Submergence:
Continuous land submergence requires huge quantity of water for rice production. In order to minimise the irrigation requirement, the approach of intermittent submergence has been studied all over the country under the All India Coordinated Research Project on Water Management.
Review of results of these studies has shown that in wet season rice, intermittent submergence saves substantial amount of irrigation water without compromising the yield. Intermittent period (number of days after the disappearance of water) varied from one to nine days depending on rainfall pattern, depth of water table and soil texture.
In areas of medium textured soil, optimum period for delaying irrigation water is 3 days. For light soils as in Punjab, it is one day, while for conditions like Modipuram (Bihar), it is as high as 9 days. Saving in irrigation water ranged from 21 to 68 per cent over the practice of continuous land submergence.
Land submergence up to 5 cm during moisture sensitive stages and maintenance of soil saturation during other period (phasic submergence) can give comparable yields under conditions of low atmospheric evaporative demand (wet season).
Irrigation needs can be brought down by about 25 per cent without affecting the yield. However, this practice leads to considerable loss in nitrogen. During dry season, however, continuous shallow submergence (5.0 cm) appears to be ideal for higher yield.
Continuous Flowing Irrigation:
Standing water in lowland rice minimise the irrigation needs leading to high water use efficiency compared with continuous flowing irrigation water from field to field. Flowing water from field to field increase grain yield of rice by preventing accumulation of harmful salts in the soil. However, nitrogen losses will be higher with continuous flowing irrigation water. Flowing irrigation water is ideal for problem soils.
Rotational Irrigation:
Required quantity of irrigation water is applied at regular intervals, such that there may not be any standing water in the field between two irrigations. Irrigation interval is adjusted in such a way that the crop will not experience water deficits at any period. It is usually followed at time of deficit water supplies. It ensures better equity among water users in command area.
This method, however, leads to leaching loss of nitrogen, besides heavy weed infestation. In practice, there may not be much saving in irrigation water as huge amounts are necessary to bring the soil to saturation at each irrigation. However, standing rice crop can be saved from terminal soil moisture stress at times of irrigation water scarcity.
Recommended Irrigation Practices:
Based on the results of experiments conducted under different rice ecosystems, the following water management practices appear to be ideal for high water use efficiency and grain yield for irrigated low-laud rice:
1. Intensive puddling to minimise deep percolation of water
2. Maintenance of 2 cm depth of water at planting, 5 cm up to 3 days after planting, 2 cm up to panicle primordial initiation and 5 cm upto 21 days after heading followed by gradual withholding of irrigations
3. Mid-season drainage at late tillering for 2-3 days in fertile heavy soils
4. Draining the field before top dressing nitrogen fertilisers and allowing water after a day or two
5. Maintenance of deep submergence at seedling and flowering periods and changing water periodically to dilute salt concentration in saline soils.
There may not be much scope for practicing the above recommended schedule in the absence of adequate control over irrigation water. However, there is immense scope for the recommended practices when the source of irrigation water is wells, leading to optimum rice yields with high water use efficiency.
Science Fair Project # 14. Effect of Weed on System of Rice Culture:
Yield losses due to weeds vary with many factors such as system of rice culture, variety, plant population, fertilisers applied, duration and time of infestation, weed species, amount of wed growth, season, ecological and climatic conditions. While there are numerous reports of yield losses due to uncontrolled weed growth in research station experiments, few attempts have been made to determine the nature and damage of yield loss due to weeds in farmers fields.
Losses in the absence of any weed control are unrealistic because most farmers follow some weed control. Therefore, a comparison between weeded and un-weeded plots over states the additional benefits of weed control. A more realistic approach is to compare the added benefits from additional weeding compared with farmers weed control method.
Limited available data show that production losses can reach 30-40 per cent for fields that are poorly weeded. In Philippines, yield increases averaging 15.7 per cent for irrigated transplanted rice, 40.8 per cent for rainfed transplanted rice and 62.2 per cent for upland rice due to additional weeding in farmer’s fields have been reported. Competition from weeds is greater when rice is seeded into dry soil than when it is wet seeded or transplanted.
The first weeding, 3-4 weeks after planting needs 25-35 labourers ha-1 (not experimental farm labour), depending on weed density. The second weeding, generally, 15-30 days after the first usually requires 15-25 labourers ha-1.
The cost of direct methods of weed control as percentage of total cost of production has been reported as 6.3 per cent in transplanted rice in Japan, 11.1 per cent in transplanted rice in Indonesia, 13.0 per cent in dry seed rice in Bangladesh and only 2.0 per cent for transplanted rice in Philippines. As a general rule, higher the wage rate or more severe the weed infestation, more likely that herbicide will be economical.
Rice crop is grown by direct seeding and transplanting. Direct seeded rice is grown both under rainfed (upland) and flooded (lowland) conditions, whereas transplanting is preferred under flooded conditions. Weed competition in direct seeded rice is maximal during the first 3 weeks period with yield reduction ranging from 40-65 per cent.
Most critical period when crop losses due to weed competition could be most severe ranges from 10-20 days after emergence. In general, a 30 days weed free period appears to be ideal to minimise loss in grain yield.
In direct seeded rainfed (upland) rice, weeds emerge simultaneously with crop leading to early competition. In transplanted rice, flooding and puddling destroy existing weeds before transplanting and new flush of weeds establish after 2-3 weeks of planting, thus enabling rice seedlings to establish well and withstand subsequent weed competition. Thus, the weed problem is more under upland rice conditions than in flooded lowland rice.
Weed flora of rice fields depends on the rice ecosystem and the management practices.
Major weeds that normally infest rice crop are given bellow:
In general, grosses and sedges dominate weed spectrum in rice. Echinochloa crusgalli and Cyperus rotundus are the most competitive weeds in both direct seeded and transplanted rice.
Cultural Management:
Manual weeding is the most widely used method of weed control in rice which is, however, difficult, time consuming and often costly. Similarity between grassy weeds and rice crop, especially during early stages poses problem for manual weeding. Intercultivation between two rows of crop by a rotary weeder is useful, time saving and more economical than manual weeding.
Preparatory tillage is an effective means of destroying the existing weed growth. Flooding and puddling is an added advantage in lowland rice weed management. Intensive puddling starting 15-20 days ahead of transplanting and continuous land submergence eliminated the need for any weed control method in lowland rice.
Soil compaction to a bulk density around 1.8 g cc-1 was very effective for minimising weed infestation in direct seeded lowland rice. However, the final yield was not comparable with that of direct seeded puddled rice due to stunted rice growth with soil compaction. When labour is scarce and expensive, herbicides may be cheaper and effective.
Use of Herbicides:
Time of herbicide application depends on the stage of weed growth at which they are very effective in suppressing their growth and relative susceptibility of the rice crop to the herbicide used.
Different times and methods of applications are:
i. Preplanting (PPL),
ii. Preplant incorporation (PPI),
iii. Preplant surface (PPS),
iv. Preemergence (PRE),
v. Late preemergence (L-PRE),
vi. Postemergence (POST),
vii. Early postemergence (E-POST)
viii. Late postemergence (L-POST).
Herbicide rate (dose) is mentioned as kilogram active ingredient ha-1 (kg ai ha-1), unless otherwise specified, for all the crops in the text.
Recommended herbicides are given below:
Rice Nursery:
Anilophos (0.25 – 0.5) 4 – 7 DAS
Butachlor (0.75 – 1.) 3 – 6 DAS
Oxadiazon (0.5 – 0.75) 4 – 6 DAS
DCPA (0.75 – 1.0) 3 – 6 DAS
Pendimethalin (1.0 – 2.0) 3 – 6 DAS
Pyrazosulfuron (0.015) 1 – 2 DAS
Quinclorac (0.25 – 0.40) 6- 12 DAS (weeds 2 – 3leaf stage)
Thiobencarb (1.5 – 3.0) 6 – 10 DAS (weeds 1 – 2 leaf stage)
Upland Drilled/Broadcast Rice:
Anilophos (0.4 – 0.5) 6 – 7 DAS
Bensulfuron (0.03 – 0.05) 3 -5 DAS
Butachlor (1.5 – 2.0) 3-6 DAS
Dinitramine (1.0 – 2.0) 3 – 5 DAS
Chlorimuron + metsulfuron mix (4 g ha-1) 20 DAS
Ethoxysulfuron (18 g ha-1) 20 DAS
Oxadiazon (0.5 – 0.75) 2-8 DAS
Pendimethalin (1.0 – 2.0) 3-5 DAS
Quinclorac (0.25 – 0.4) 3-5 DAS
Butachlor (1.0) + 2,4 -DEE (0.5) 6-8 DAS by sand mix
Lowland Transplanted Rice:
Almix (0.003 – 0.005) 5-7 DAT
Anilophos (0.5 – 0.75) 4-7 DAT
Butachlor (1.5 – 2.0) 4-7 DAT
Chlorimuron-ethyl (0.01) 5 – 7 DAS
Cinosulfuron (0.025 – 0.0035) 5 -7 DAT
Clonozone (0.2 – 0.25) 5 – 7 DAS
Ethoxysulforon (0.01 – 0.15) 15 – 20 DAS
Flufenact (0.10 – 0.12) 7 – 10 DAT
Oryzalin (1.0 – 1.5) 4 – 7 DAT
Gzadiargyl (0.07 – 0.125) 7 – 10 DAS
Pendimethalin (1.0 – 1.5) 4 – 7 DAT
Pendimethalin (1.0 – 2.0) 4-6 DAT
Pretilachlor (0.75 – 1.0) 3 – 5 DAT
Propanil (4.0 – 6.0) weeds 2-3 leaf stage
Pyrazosulfuron – ethyl (0.02 – 0.03) 3 – 6 DAT
Triazolopyramidine (0.015 – 0.25) 5 – 7 DAS
Butachlor (1.0) + 2,4 -DEE (1.0 + 0.5) 21 – 27 DAT
Fluchloralin (1.0 + 2,4 -DEE (0.5) 21 – 27 DAT
Almix (0.004) + Butachlor (1.0) 21-27 DAT
Herbicides like Oxadiargy and mixed chemicals like Pretlachlor + 2,4-DEE, Anilophos + Trichlopyr, Anilophos + Ethoxysulforon, Almix + Anilophps and Cinmethylin + 2,4-DEE are found, in the recent past, performing better under transplanted conditions. Anilophos + Trichlopyr, Anilophos + Ethoxysulforon appears to be effective in direct seeded rice.
Herbicides can be applied mixed with sand or as spry fluid. Sand mixing is convenient under field conditions.