Climatic conditions for rice cultivation

Climatic conditions for rice cultivation

1. AGR 301 PRACTICAL CROP PRODUCTION-1 (Kharif crops) CLIMATIC REQUIREMENT FOR RICE CULTIVATION

2. INTRODUCTION Rice fields cover around 160 million hectares Rice can be grown in different locations under a variety of climates. The indica are widely grown in tropical regions . The japonicas are adapted to cooler areas, are largely grown in temperate countries . Both indica and japonica rices are grown in subtropical regions . Rice needs hot and humid climate.

3. (Temperature, solar radiation and rainfall) influences rice yield by directly affecting the physiological process involved in grain production and indirectly through diseases and pest

4. CLIMATIC REQUIRMENTS Altitude & Latitude Humidity Temperature Range Rainfall Day length Wind velocity Photoperiodicity

5. Altitude & latitude Grown from  8° to 35° N latitude  and from  sea level to 3000 meters . Best latitude : It is grown in a wide range of climatic conditions spanning from  44 ° N latitude in North Korea to 35 ° S latitude in Australia. Best altitude : It is cultivated from 6 ft below sea level ( such as in Kerala , India) to 2700 ft above sea level .

6. Temperature Range : General Growth:  21°C to 37°C. the best temperature for rice is between 70°F and 99°F   Soil temperatures   above 99 degrees Fahrenheit ( 37 degrees Celsius ) have a harmful effect on crop . Ideal condition Rice needs a long, warm growing season , so a climate with nighttime lows staying at 60°F (15°C) or higher for a minimum of three months annually is ideal.

7. Tilling Phase : Requires higher temperatures. Optimum temperature D ay temperature of   25°to 33°C Night temperature of 15° to 20°C   is considered optimum for the development and growth of rice. Low temperature affects the rate of tillering either in the day and night time. Ambient temperature with in the range of 30-32 °C

8. Blooming : Optimal at  26.5°C to 29.5°C . Ripening : Ideal temperatures between  20°C to 25°C . 16°C to 20°C at flowering and fertilization , and 18°C to 32°C at ripening. Temperature higher than 35°c affects grain filling. the rice yield declined 10% by every 1°C increase in minimum night temperature . Photoperiodicity : Primarily a  short-day plant , though some varieties are non-sensitive to photoperiods.

9. SI NO GROWTH STAGES LOW HIGH OPTIMUM 1 Germination 16-19 45 18-40 2 Seedling emergence and establishment 12-15 35 25-30 3 Rooting 16 35 25-28 4 Leaf elongation 7-12 45 31 5 Tillering 9-16 33 25-31 6 Panicle initiation 15 - 7 Initiatial flowering 15-20 30 18-28 8 Anthesis 22 35-36 30-33 9 Ripening 12-18 30 20-29

10. SOLAR RADIATION : Solar energy is the most important climatic factor in rice cultivation in temperate climates. The plant’s most critical period of solar energy requirement is from Panicle Initiation to until about 10 days before maturity which is important for the accumulation of dry matter. The yield of rice during monsoon (kharif) season is lower than that in the dry (summer) season. Because of the lower 5 levels of solar radiation received during the crop’s grain filling and ripening stages .

11. The light compensation = 15000 lux (solar energy/cm) 10.764 feet candles Photosynthesis = Respiration Light saturation = 45000 lux The rice yield is significantly affected by the solar radiation predominantly the last 35–45 days of ripening period . The minimum requirement of SR is 300 cal /cm2/day .

12. DAY LENGTH Rice is a short day plant and sensitive to photoperiods . Long days can prevent or delay flowering. But photo insensitive varieties enable the farmer in tropics and subtropics to grow rice at any time of the year without great changes in growth duration. examples: A58 Nipponbare

13. Example for photosensitive variety GEB 24( kichili samba ) Nonabokkra CRS27 IR64( semi dwarf variety )

14. HUMIDITY : The RH effects in tropics are generally confused with the effects of solar energy and temperature. The average RH before harvest follows a trend opposite to that of the solar radiation values for the same period. Therefore, no importance is attributed to the – ve effect of RH on grain yield of rice. A relative humidity of  85-90 per cent  at the heading stage 

15. Germination & Seedling : 70%–90% Vegetative (tillering): 60%–80% Reproductive (Panicle Initiation to Flowering) : 60%–70% Grain Filling : 50%–70% Ripening : 50%–60%

16. WIND VELOCITY : A gentle wind during the growing period of the rice plant is known to improve the turbulence in the canopy. The air blown around the plants replenishes the Co2 supply to the plant. Strong winds are detrimental especially at heading . They cause severe lodging and shattering in some rice varieties. WV of 0.75-2.25 cm/sec Is not conductive for photosynthesis.

17. RAINFALL : Rainfall variability is more critical for upland rice than for lowland rice. Moisture stress can damage or even kill the plants in an area that receives as much as 200 mm of rainfall in a day and then receives no rainfall for the next 20 days. An evenly distributed rainfall of 100 mm per month is preferable to 200 mm per month that falls in 2 & 3 days.

18. Rice is grown in rainfed conditions with rainfall of 1000-1500 mm/annum , if distributed over 3-3 ½ months . The water requirement of rice is 1200 mm. The best growing condition can be found in areas where yearly rainfall is between 69 and 118 inches(175 and 300cm)

19. AEROBIC RICE TEMPERATURE: Optimal range : 25°C to 30°C during the growing season . Minimum temperature : The crop requires a temperature of at least 20°C for germination. Maximum temperature : Aerobic rice can tolerate temperatures up to 35°C , but higher temperatures may affect yield and grain quality .

20. RAINFALL : Annual rainfall : 500 to 800 mm is usually sufficient for aerobic rice , as it relies more on rainfall compared to traditional flooded rice. It can be grown in regions with rainfall less than 1,000 mm annually , provided rain is well-distributed during critical growth stages. Waterlogging : Aerobic rice does not tolerate waterlogging . Therefore, well-drained soils and regions with moderate rainfall are more suitable

21. HUMIDITY Moderate humidity (50%–70%) is ideal. High humidity levels combined with waterlogged conditions can lead to diseases and pest infestations .

22. ALTITUDE : Low to mid-altitudes : Aerobic rice is typically grown in lowland areas but can also be cultivated at altitudes up to 1,000 meters above sea level, provided other climatic factors are favorable. Drought Tolerance Aerobic rice varieties are more drought-tolerant than traditional rice, and they can withstand moderate water stress, particularly during the vegetative stage. However, prolonged drought during critical stages such as flowering and grain filling can reduce yields.

23. DEEP WATER RICE TEMPERATURE : Optimal range : 25°C to 30°C during the growing season. Minimum temperature : Deepwater rice requires a minimum temperature of around 20°C for germination and early growth. Maximum temperature : The crop can tolerate temperatures up to 35°C , but prolonged exposure to temperatures above 35°C, especially during flowering, can reduce yields due to spikelet sterility . Night temperatures : Deepwater rice can tolerate moderate night temperatures around 20°C to 25°C . However, night temperatures below 15°C can negatively affect grain filling and overall productivity.

24. HUMIDITY : Optimal humidity : 60%–80% is ideal during most growth stages. Higher humidity levels (above 80%) may increase the risk of fungal diseases such as rice blast, sheath blight, Waterborne diseases, especially in combination with warm temperatures.

25. Humidity during grain filling : Moderate humidity levels (50%–70%) are preferable during the grain filling stage to avoid diseases like grain discoloration fungal infections . High humidity combined with warm temperatures can also affect grain quality.

26. ALTITUDE : Lowland areas : Deepwater rice is cultivated in low-lying areas such as river basins, floodplains, or deltas. It is typically grown at altitudes near sea level or up to 200 meters above sea level, where flooding naturally occurs during the monsoon or rainy season. Flood duration : Deepwater rice is well-adapted to areas where floodwaters remain for 3 to 7 months Sunlight : Full sunlight with long daylight hours

27. SYSTEMATIC RICE INTENSIFICATION HUMIDITY Optimal humidity : 50%–70% is generally favorable for SRI rice, particularly during the reproductive and grain-filling stages. Moderate humidity helps prevent water stress and promotes healthy plant development.

28. Excessive humidity (>80%) : High humidity can increase the risk of fungal diseases such as rice blast and sheath blight , particularly if combined with over-irrigation or poor drainage. Low humidity (<50%) : In low-humidity conditions, water management must be more closely monitored to ensure the plants receive sufficient moisture without causing drought stress.

29. SUNLIGHT : Full sunlight : SRI rice requires 8 to 10 hours of full sunlight per day for optimal photosynthesis, particularly during the vegetative growth stage . Ample sunlight also promotes the robust development of tillers (shoots) and root systems. Shading : Excessive shading from nearby vegetation or cloud cover can reduce the growth and yield potential of SRI rice.

30. Altitude : Suitable for low to mid-altitude regions, up to 1,500 meters Wind : Moderate winds are tolerable , but avoid heavy wind during reproductive stages Soil : Well-drained Loamy soils with good water retention and aeration, organic matter-rich

31. ALTERNATING WETTING AND DRYING SYSTEM Temperature : 25°C to 35°C Rainfall : 800 mm to 1,200 mm annually (with irrigation support if needed) Humidity : 50%–70% Soil type : Well-drained soils, loamy soils with good water retention Sunlight : 8–10 hours of full sunlight per day

32. Raised Bed- Saturated Soil Culture (RB-SSC): Temperature : 25°C to 35°C (minimum: 20°C, maximum: 35°C for optimal growth) Rainfall : 1,000 mm to 1,500 mm annually , with controlled irrigation for soil saturation Water management : Saturated soil (not flooded ), with regular irrigation to maintain moisture levels in raised beds Humidity : 50%–70%, avoid high humidity to reduce disease risks

33. Sunlight : 8 to 10 hours of full sunlight per day Soil : Well-drained, loamy or clay-loam soils, rich in organic matter Wind : Tolerates moderate winds , but windbreaks may be needed in strong wind-prone areas

34. Effect of increasing temp on rice production Every increase in 1°C temperature reduced during dry season 5–7% or about 10% grain yield. According to the Asian Development Bank’s report , a 4°C increase in temperature could decrease 75% rice yield in the Philippines. Additionally, the exposure of more than 35 °C for a short time (few hours) decrease pollen viability and increased spikelet sterility in rice plant

35. EFFECT OF GREEN HOUSE GAS Methane (CH4) emitted from paddy fields accounts for 17.9% of the total CH4 emissions which is responsible for climatic change in the world It is also observed that CH4 emission at its peak in tillering and heading stage of the rice crop. Every increase of 75 ppm atmospheric CO2 concentration, the increase of 0.5 t h−1 rice yields occurs

36. Factors responsible for CH4 emission from rice field High Use of Inorganic Fertilizer Water Management Soil Types CH4 Emission and Rice Cultivars CH4 Emission and Temperature Soil Tillage and CH4 Emission

37. AUTHOURS JUSTIFICATION ( Porter et al. 2014 ). When temperature increases, the rice crop maturity, and yield reduce up to 8% and 12%. ( Mumtaz et al. 2007 ). in India, the rice production would be reduced by 4.5% to 9% because of climate change by 2050. ( Peng et al. 2004 ). In Philippine, every year rice yield reduced by 15% per 1 °C increase in global temperature ( IPCC 2013 )Agriculture is one of the principal sources of GHG emission contributing 10–12% of the total GHG emissions.

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