Importance of water management in coconut plantations

 

Water is the basic need of plants for all metabolic and production processes. A crop is grown in different land situations, soil types, climatic conditions, seasons, and water supply situations. Water management pertains to optimum and efficient use of water for best possible crop production keeping water loss to the minimum. When considering the coconut, the water demand of the coconut palms usually varies from 40 -100 liters/day during the dry period. According to the land suitability assessment of the coconut, suitability classes designed as S3, S4 and S5 have lower storage capacity and poor soil physical conditions. Coconut plantation in such lands are often subject to severe moisture stress during the dry season, lasting more than 3 months. In the absence of irrigation, it is reported that the mortality rate of the seedlings and young palms in the intermediate dry zone can be as high as 70%. Physiological damage to coconut palms due to moisture stress occurs when the rainfall is less than 50mm per month. The effect of drought and extending for a further period of 12 months. The most effective and economical methods of overcoming such a long period be realized 3 -4 years after the commencement of irrigation.  Soil moisture stress caused by drought effects often limits the growth and nut yields of the palm. In the case of coconuts, it is believed that the variations in production due to weather factors are much more pronounced than in other tree crops. This is mainly due to the fact that the reproductive cycle of each coconut crop lasts for about 3i years from the primordial to the maturity stage. Due to the continuous bearing habit of the coconut palm, it usually bears one inflorescence each month which finally develops into a mature bunch over a period of 12 months. The first 3 to 4 months of the 12 months development cycle is considered as the period most sensitive to moisture stress.

 

Image by Quang Nguyen vinh from Pixabay

AVERAGE WATER REQUIREMENT OF COCONUT

 

v  Irrigation Rate depends on soil parameters (water holding capacity/texture/depth /infiltration-lateral and vertical) and the effective root system of the plant.

v  Irrigation frequency depends on the evapotranspiration of the plant/soil system/canopy/root system/atmospheric evaporative demand/relative humidity/temperature/wind/etc

 

The water requirement of the coconut palm varies with different soil types and age of plantation. And as such, it is not possible to generalize the water requirement of coconut palms is different areas. The following average figures have been worked out as a guide.

Ø  Adult palms: 45 litters/palm/day

Ø  Young palms: 5-10 litters/palm/day

Supplementary irrigation coupled with soil water conservation process such as mulching, husk burial reduces the total amount of irrigation water.

·         METHODS OF IRRIGATION

 

Suitability of an irrigation system depends on,

1. Plantation type (large/small, age, mono/intercrop….)
2. Water resources (surface, deep aquifer, quantity, quality…)
3. Soil landscape (topography, soil texture, and depth….)
4. Economics and resources (capital, maintenance, labor, efficiency….)

Methods of irrigation and Efficiency

• Basin irrigation (50-70%)
• Picher irrigation (60-70%)
• Hose irrigation (75-85%)
• Drip irrigation >95%
• Girdle irrigation (75-80%)
• Sprinkler irrigation (60-70%)

1. BASING IRRIGATION

A basin of A shallow depth (about 10 cm) is prepared around the base of the palm, and the basins of adjacent palms are interconnected with furrows. Water is allowed to flow freely from the furrows to the basin. This method is not suitable for undulating lands. Even in flatlands, considerable land preparation is required initially to allow the free flow of water. The water requirement for this method is high as a considerable amount of water is lost due to soil absorption, leaching, and evaporation. This method is particularly not suitable for sandy soils due to heavy losses of water by percolation. Furthermore, it is difficult to apply a fixed volume of water to a palm by this method. The initial cost is Rs 9500-11000 per acre.

2.DRIP IRRIGATION

Drip the irrigation system is feasible in coconut lands. Drip irrigation involves the wetting of a smaller soil volume in the root zone to provide the water requirement of the plant. The advantages of this system are as follows.

• It requires relatively less water as the system can be designed for the efficient use of water.
• Water usage can be regulated.
• Fertilizer could be added to the irrigation water, thereby saving cost of fertilizer application.
• Intercrops also could be irrigated with a simple modification to the system.

The high capital investment and maintenance problems are the disadvantages of this system. Installation cost is Rs 30000-45000 per acre.

Installation of an irrigation system is expensive and requires some scientific knowledge. It is essential to have a continuous supply of irrigation water even during the drought (adequate under groundwater, aquifer, and river). Further, the irrigation should be implemented as a complete package including relevant fertilizer/agronomic/management practices.

3. HORSE IRRIGATION

An underground PVC pipes network to supply water to outlets is more suitable for coconut plantation. One-inch diameter and 100 ft long rubber hoses are used to irrigate 16 palms within one outlet. This would facilitate other practices in the estate such as weeding, picking, and transport of nuts. Also, it facilitates irrigating intercrops and maintenance is very easy and profitable. The pipe system consists of mainline sub mainline and risers. At the end of each riser, 1” ball valves are installed to deliver water to palms. The hose irrigation system could be done at a cost of Rs: 20000-25000 per acre.

 4. PITCHER IRRIGATION

  This method is useful to protect seedlings in the dry and dry intermediate zones where the mortality rate is high. Following are the steps in pitcher irrigation. Take two unglazed clay pots having capacity of 15-20 liters and make a hole at the bottom of each pot and insert a 2feets long rope. Paint one side of the pot so that water will not seep through. Bury the clay pot up to the neck at 0.7 m distance to the plant with a painted surface away from the plant placing the rope in the direction of the plant. Fill the pot with water, keep the mouth of the pot closed and top up regularly. Generally, during the dry weather, it may necessary to fill it in twice a week. Although the water is used efficiently in this method, the rate of water flow to the plant is very slow. Therefore, the method is not very suitable for adult palms. The cost is Rs 250 per plant

REFERENCES

1.Articles of CCD (Coconut Cultivation Board)

2. M. D.S. LIYANAGE, COCONUT RESEARCH INSTITUTE, LUNUWILA.

3. A GUIDE TO SCIENTIFIC CULTIVATION AND MANAGEMENT OF COCONUT, M. D.S. LIYANAGE.