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Moisture Stress Management in Sugarcane
- The common stress situations faced in sugarcane cultivation are moisture stress, excess moisture, problem soils and water.
- Moisture stress is one of the most important and widespread limiting factors for successful sugarcane cultivation.
- Important causes for moisture stress are:Limited availability of water for irrigation in lift irrigated areas, Canal closure during summer in many of the canal irrigated tracts and Droughts which occur in a cyclic manner.
- The extent of damage to sugarcane yield and quality depends upon the crop stage and duration of stress.
- In most of the areas, the crop experiences moisture stress during the formative phase of growth, affecting germination and tillering, thus leading to reduced stalk population.
- In the early planted cane, moisture stress coincides with the grand growth phase of the crop, thus affecting stalk elongation and stalk growth. In the case of late planted crops, moisture stress affects the formative phase as well as the maturity and ripening phases.
- Moisture stress also aggravates certain pest and disease problem.e.g. shoot borer .Under sever stress, yield loss could be as high as 60-70 percent.
Management practices
- Planting sugarcane early in the season helps cane to grow up sufficiently before the moisture stress sets in
- A higher seed rate is usually helpful under moisture stress. Higher seed rate achieved through closer row spacing is better than putting more setts per row.
- Sugarcane trash mulching is a highly useful technique to conserve soil moisture and reduce the impact of moisture stress and atmospheric drought.
- Under moisture stress, basal manuring of phosphorus followed by an early N and K top dressing is desirable. During the moisture stress period lasting for about 3 months, foliar nutrition may be resorted to.
- Urea is the most common and useful fertilizer which can be fed through foliage at 25g / litre. Along with urea, muriate of potash (KCI) at 25g /litre concentration has been found highly effective under moisture stress.
- Protective irrigations by means of alternate or skip furrow combined with trash mulching is yet another technique to sustain yields with limited available irrigation water.
- 'Kaolin' acts as a reflectant and reduces evapo-transpiration. It could be sprayed at 60 g/ litre.
- For drought management mulching the ridges with cane trash on 7th month followed with kaolin spray at 120 days (12.5 kg/ha) at 2 per cent ensures higher cane yield.
- Using a drought or moisture stress tolerant variety is one of the most important means to combat moisture stress.
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Salt Accumulation in Soil
- Salt accumulation in the sugarcane soils occurs due to weathering of parent material, high temperature, low rainfall, continuous use of bad quality ground water, excess irrigation in the canal irrigated tracts, poor drainage, and improper land use.
- In coastal areas, sea water intrusion causes salinity. There are three types of salt affected soils, viz., saline soil,saline-alkali soil and alkali soil.
- The saline soils have pH less than 8.5, with the electrical conductivity (EC) of more than 4.0 mmhos/cm and an exchangeable sodium percentage (ESP) of less than 15.
- In the saline-alkali soils, the pH seldom exceeds 8.5, but EC is more than 4 mmhos/cm and the ESP is more than 15.
- Alkali soils have a pH more than 8.5, but the EC will be less than 4 mmhos and ESP is more than 15.
Effects of salt accumulation
- Salt problem in the soil leads to unfavourable soil physical, chemical and biological properties. Due to excess salts in the soil solution plants have to exert more energy to absorb water. Due to increased osmotic potential, water uptake is affected and physiological water stress is caused.
- Germination failures, reduced germination and delayed germination
- Reduced crop growth, poor tillering, leaf burning and curling, reduced internode length, poor root growth and pithiness in the cane
- Cane yield reductions even upto 50% or sometines more
- Poor juice quality - soluble salts accumulate in juice, reduce sugar content and thus lower recovery. Milling problems (scaling in the evaporators)
- Ratoon failures - due to poor sprouting and subsequent growth
Reclamation methods
- Important reclamation methods are :
- Physical amelioration,
- Chemical amelioration,
- Biological amelioration and
- Agronomic practices
Physical amelioration
- Deep ploughing,
- Sub soiling,
- Application of sand and
- Profile inversion.
Chemical amelioration
- The objective is to change the soil chemical nature by adding suitable amendments to replace sodium with calcium, and remove carbonates and bicarbonate with sulphate.
- The chemical amendments are used to reclaim saline-alkali and alkali soils.
- Gypsum is the most important amendment used. The gypsum application rate is decided by soil analysis and calculation. However, based on soil pH also gypsum applications may be done at doses ranging from 2.5 to 12.5 t/ha.
Biological amelioration
- It involves use of organic matter, vegetation and waste products. Organic manures, green manuring etc., will improve soil structure and internal drainage. Vegetative cover reduces evaporation from the soil surface and thus minimises salt accumulation.
- Agricultural waste products like groundnut hull, coir pith waste, etc., can be added to the soil to improve soil texture and internal drainage.
Agronomic practices
- Agronomic practices like higher seed rate to ensure adequate initial population, trench planting and additional nutrition and its proper method of application help to improve crop performance.
- Salt tolerant varieties, Co 85004, Co 85007, CoC 671, Co 86032 and CoSi 96071 are more suited under salt affected soils.
- Additional nitrogen (25% extra) is useful in salt affect soils. Foliar nutition of N is a useful practice under saline conditions. In the alkaline soils, heavy amounts of green manure or farm yard manure or pressmud should be applied.
- Zinc sulphate at 25 kg/ha may be applied to the soil.
- The drip system of irrigation is useful under saline soil conditions so that the root zone is kept free of salts.
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Excess Moisture/Water Logging
- Waterlogging is associated with high rainfall, river floods and improper management of irrigation water. In most of the areas itis preceded by severe moisture stress during summer.
- Thus the crop undergoes moisture stress in its formative or grand growth phase followed by waterlogging during grand growth phase or maturity phase.
- In most of the canal irrigated tracts excess irrigation coupled with lack of proper drainage leads to excess moisture and waterlogged situtations.
- Excess moisture or waterlogging causes changes in the soil physical, chemical and biological properties which are usually adverse, and thus affect sugarcane yield and quality.
- Water logging or excess moisture during germination stage affects germination. During tillering, there is greater tiller mortality. At later stages, water logging reduces stalk population by causing stalk mortality.
- Yield losses occur due to stalk mortality, reduced crop growth due to lack of nutrition and water uptake, lodging, cane breakage, etc., About 5-30% loss in yield have been reported for 15 to 60 days of waterlogged condition.
- Water logged conditions hasten maturity. Juice quality becomes poor with reduced sucrose level, high amount of invert sugars, gums, non-proteinous nitrogen content in juice. The recovery will be drastically affected.
Management practices
- It is desirable to bring the saturated soil to field capacity as quickly as possible through proper drainage. The simplest method of draining excess water is to dig open channels deeper than the irrigation channels in the field to draw out excess water. These channels can be opened at regular intervals, to a depth of 60 cm. These drains are closed while giving irrigation and after irrigation they are opened.
- Early planting is helpful to reduce the impact of excess moisture. The early planted crops which put up more growth by the time waterlogging occurs will tolerate waterlogging condition better.
- Higher earthing up helps in better root development and provides good support to the plant.
- There are a number of sugarcane varieties which can withstand waterlogging/excess water conditions. Some of the recent varieties which can be grown under waterlogged conditions are Co 8231, Co8232, Co8245,CoSi 86071, CoSi 776, Co 8371.
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