Water Management

• Irrigation requirement of tobacco vary with soil type, climate and type of tobacco grown.
• Tobacco cannot tolerate waterlogging at any stage of growth but at the same time the plants may not withstand drought also.
• Therefore, a compromising situation would be to give light and frequent irrigations to the crop. However, the interval and number of irrigations depends upon soil type, weather, cultivation and type of tobacco to be grown.
• An early drought is often preferred for better establishment and it enables the plant to withstand any moisture stress during the subsequent growth of the plant.
• The bulk of the roots of tobacco plants lie in the top 30 cm of the soil and 2/3 of the water loss is from this layer only.
• The field should be irrigated when the soil moisture falls to about 20 per cent field capacity because higher soil moisture reduced the leaf quality.
• Hard water (saline) from wells must not have more than 50 ppm (50 mg in 1 lit) of chloride, otherwise the leaves will have poor burning quality.

• In alternate / skip furrow method, in the subsequent irrigation avoid first irrigated furrows and irrigate the unirrigated furrows. Follow the same fashion in consecutive irrigations.
• Climatological approach of scheduling irrigation can also be followed if Agro-met observatory is available in the vicinity of the crop area and standardised can evaporimeter is used.

• irrigation through sprinkler system will economise the irrigation water and can be followed if cost is not a limiting factor.

• These tobaccos are generally grown in irrigated conditions.
• About 18-20 irrigations are needed during the crop period at 4-5 days interval.

• They are generally grown as rainfed crops, but under drought conditions, one or two irrigations are desirable for the production of better crop.

• These are generally grown under irrigated conditions and generally 12-15 irrigations are given.

• A light irrigation at transplanting will often improve establishment and early growth in light soils.
• Adequate moisture will promote faster growth and early maturity.
• Irrigation will reduce the amount of scalding of upper leaves and firing of lower leaves during dry weather.
• If tobacco is harvested during hot weather, irrigation might improve curability of the crop.
• If extended rainfall is received after an irrigation, there would be a damage from drowning, leaching of nutrients and lowering of yields under light soils.
• Irrigation water sample is to be analysed for chlorides. Water containing 50 ppm (50 mg in 1 lit) of chlorides and below is to be used for irrigation.
• Irrigation at night is more efficient than during hot day time because of less evaporation.
• Moisture deficiencies are much more during grand growth phase of the crop (i.e) 40 days after planting.
• Soil moisture stress during early stages will improve deeper root development.
• An irrigation immediately after transplanting is most beneficial. a) It helps to settle the soil around the roots b) provides adequate moisture for faster root development and c) cools the soil, increases humidity, reduces transpiration, reduces leaf scalding, parching and transplanting shock. Keeps fertilizer injury to the minimum due to dilution.
• For good yield and quality, tobacco should not be subjected to severe drought conditions. Between establishment stage and knee-high stage of crop, a little moisture stress is not harmful and it may improve yield and quality.
• Low soil moisture at this stage encourages deeper root development which is beneficial during grand growth period.
• Between knee-high stage to early bloom stage (grand growth period), moisture is extremely important. Irrigate often to keep the soil moisture sufficiently high which ensures good leaf spread, rapid growth, high yield and quality.
• During the harvest period, occasionally, it may be desirable to irrigate tobacco. This should be done only during extreme drought.
• A slight moisture stress during harvest period reduces brown spot, slows down harvest rate which helps in improving yield and quality.
• It has been observed that tobacco leaf ripens faster (false ripening) after heavy rains or heavy irrigation. This faster ripening may be due to a) part of leaching of N from root zone, b) excess water damage to the root system by cutting oxygen supply and c) physiological reaction within the leaf due to high moisture.
• If tobacco does not show any signs of wilting before 11.00 am, irrigation is not necessary.
• Changes in physical and chemical properties of leaf of irrigated tobacco is expected to be a) lighter in colour, b) thinner, larger leaves, more leaves with less suckers and c) lower in oil, nicotine and higher in sugars.
• Irrigating the crop with 12 mm of water per irrigation in the establishment phase (planting to 35 days), 36 mm per irrigation during grand growth phase (35 to 80 days) and 27 mm per irrigation during later stages in ridge system of planting was found useful in economising water to the tune of 28 to 32% as compared to flat head system of irrigation.
• At Bhavanisagar (Tamil Nadu) condition, irrigating chewing tobacco at 0.8 IW/CPE (a known amount of irrigation water (IW) is applied when cumulative pan evaporation (CPE) reaches a predetermined level) ratio was optimum for maximum yields.
• In general for a tobacco crop of about 120 days field duration around 20 irrigations are needed at 4-5 days interval.

• As high chlorides in irrigation waters are usually associated with high salinity (total dissolved solids), classification of irrigation water on the basis of chlorides and electrical conductivity is found to serve the purpose adequately.
• Accordingly, a limit of 50 ppm (50 mg in 1 lit) of chlorides in water is suggested for irrigating flue-cured tobacco in light textured soils.
• If irrigation water contains more than 50 ppm (50 mg in 1 lit) chlorides, irrigation with such water adversely affects the quality of leaf produced.

• The water from canals, tanks, wells and deep bore wells can be used but the chloride content should not exceed 50ppm (50 mg in 1 lit). The total irrigation water required including rainfall is 200-250 mm/ha. to be applied in 6-8 irrigations.

• Irrigation through all furrow system consumes more irrigation water and labour.
• The alternate / skip furrow method of irrigation is more economical and checks the wastage of irrigation water, electricity and time. It improves the leaf quality and gives 10-20% higher yield than all furrow irrigation.