Water Management

• Sugarcane being a long duration crop producing huge amount of biomass, requires large quantity of water. It is mostly grown as an irrigated crop.
• The water requirement of sugarcane has been estimated to vary from 2000 to 3000 mm per annum per hectare.
• Deficit or excess moisture affects cane yield and juice quality and thus sugar output, besides predisposing the crop to attack of several pests .

• Irrigation once in 9 days at germination phase, 10 days at tillering and growth phases and at 13 days during maturity phase is found to be ideal for sugarcane.

• The degree of water use efficiency (WUE) is influenced by various factors such as length and gradient of the furrow, water flow rate, soil texture and structure, age of the crop, cross sectional area of the furrow.
• In this method, ridges and furrows are formed and sugarcane is planted in the furrows. Irrigation is given in the furrows. Length of the furrow depends upon the soil type and the gradient.
• A gentle slope is desirable to achieve good water flow and distribution of water along the soil profile. On a well levelled land the furrow length can vary from 70 to 100 m.
• Low irrigation efficiency, which ranges from 30 to 40 percent, uneven distribution of water, about 10 to 15% loss of land area for irrigation channels and undesirable weed growth are some of the important disadvantages.

• Water is a very precious input in sugarcane production. There are many other crops which compete with sugarcane for water. Many of the competing crops are highly remunerative. Also, depletion of ground water and droughts are becoming common. Therefore using irrigation water as economically as possible without affecting sugarcane production and productivity is highly important. Adopting micro irrigation systems in future will become a necessity.
• The drip system of irrigation also known as ‘trickle irrigation’ was developed by an Israeli Engineer, Symcha Blass. In this system, water is carried in small pipes, usually made of PVC, and delivered in drops or trickles near the root zone in such a way that only required quantity is supplied avoiding almost all kinds of losses.
• The technique involves laying plastic tubes of small diameter near the root zone and delivering water through emitters. The water is usually carried at a particular level of pressure.
• There are essentially two types of drip irrigation systems, viz, surface drip system and sub-surface drip system.
• In the surface drip system, the water carrying lateral pipes are placed on the soil surface close to the plant and the emitters fixed at regular intervals discharge water at required rates.
• Water gets into the soil and wets the root zone to the required depth. The quantity of water could be easily regulated. There is no wastage of water through percolation and wetting of areas away from the root zone.
• There is small amount of water loss through evaporation as water trickles on the ground. The evaporative loss of water will be slightly more during hot weather period.
• In the sub surface system, the water carrying lateral pipes are buried in the soil, in the root zone and water is delivered in trickles.

• The main advantages include
• Saving in water upto 40%
• Better distribution of fertilizers
• Possibility of using saline water for irrigation (as the quantity of water applied is less, the salt problem is less)
• Possibility of increased yields of around 10-30 percent

• To practice the drip system of irrigation, certain changes in the cultivation practices may be required.
• To economise the quantity of lateral pipes required, it is necessary to adopt paired row system of planting in which the lateral pipe would run between the paired rows, leaving the wide gap dry.
• Weed control measures would be specifically required near the cane row, as more moisture is present there.
• Basal fertlizer may be placed below the setts in the furrows. Top dressing may be given near the cane rows on either side, very close to the rows, after opening small slits or furrows, by appropriate hand tools.
• While harvesting, care is required to safeguard the lateral pipes. Also considerable care is required while carrying out ratooning operations.

• The water requirement per year is around 20,000 to 30,000 cubic meters to raise a good crop. This is equal to 2000 to 3000 mm.
• The total water required depends on various factors such as soil type, climatic conditions like rainfall, temperature, wind etc. the cultivation practices, water application efficiency and crop duration.
• Approximate water requirement of a 12 month sugarcane at each growth phase is indicated below:

1. a. Germination (0 – 45 days) : 300mm
2. b. Tillering phase (45 – 120 days):550mm
3. c. Grand growth phase (120 – 270 days): 1000mm
4. d. Ripening phase (270 – 360 days):650mm

• During the germination phase, the general principle of irrigation is "light irrigation given at frequent intervals", so that the soil is kept just moist, not dry or over moist. When the soil is dry due to under irrigation, the buds dry leading to a lower and delayed germination. Higher amount of water application leads to bud rotting due to fungal attack, lack of aeration, and soil dampness.

• The tillering phase is crucial and therefore needs optimum supply of water. Any shortage would reduce tillering, increase tiller mortality and thus ultimately the stalk population.

• Shortage of water in the grand growth phase leads to shortening of internodes and thus cane length, and reduced cane weight.
• The tillering and grand growth phases mostly coincide with hot weather period and atmospheric demand for water is greater.

• The ripening phase requires a mild moisture stress for sugar accumulation. Plentiful supply of water leads to continued vegetative growth thus hampering sugar accumulation.
• The soil should not be allowed to crack, as the minute cracks would damage the root system. If the old crop is not given required water and is subjected to stress, there could be serious cane weight loss, cane breakage, pith formation, increase in fibre percent and deterioration in juice quality.

• Soil type profoundly influences the water requirement as it determines water holding capacity, infiltration rate and permeability. Available moisture holding capacity increases with increase in the fineness of the soil texture. Coarse textured soils hold about 6-10 cm of water per metre depth, while medium textured soils hold 12-19 cm/m and fine textured soils 13-20 cm/m. Irrigation intervals should be narrower in coarse textured soils and should be increased in fine textured soils. Sandy and sandy loam soils need frequent irrigation while clay soils do not.