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A solution for drought affected coconut plantation

by D. Medagedara

Out of the total area under coconut cultivation in Sri Lanka about 80 per cent of the coconut land falls within dry and intermediate zone. The balance 20 per cent of the coconut lands are to be found in the wet zone along the coastal belt. The total production of coconut is determined on the yields from rain-fed wet and intermediate zones.

Rain is the main factor that determines the yield of coconut in the zone. It appears that coconut lands in dry zone and Mahaweli area have contributed a considerable share for the total coconut production of this country. The coconut cultivation in the dry zone could be done successfully if adequate supply of water could be made available to the coconut lands.

Coconut seedling grown  under drip irrigation

According to the reports of the Coconut Research Institute the daily requirement of water for an adult coconut palm is 40 to 100 litres and for young coconut plants 20-50 litres. About 90 per cent of coconut lands in Sri Lanka have to experience dry spells varying from 2 to 9 months almost every year.

The effects of drought on coconut land would vary according to the type of soil, soil moisture, availability of underground water and maintenance. The intensive effects of drought could be overcome successfully by conservation at soil moisture through water management. Drip irrigation is an effective way of providing water for drought affected coconut palms.

Effects of the weather

The total area under coconut cultivation in Sri Lanka is about 0.5 million hectares and 29 per cent at this area falls within the dry zone. The average rainfall in the dry zone is about 1000 mm. The cultivation of coconut could be done successively under irrigation. 51 per cent of coconut lands in the Sri Lanka falls within the intermediate zone and the annual rainfall in this area is 1000-1500 mm. All coconut plantations in the country irrespective of difference in zone experience the ill-effects of dry spells varying from 2-9 months in almost every year. Even then successful yields could be obtained by providing a subsidiary water supply and its proper management.

20 per cent of coconut plantations are in Sri Lanka falls within the wet zone along the coastal belt and this area too experiences dry spells not less than two months in almost every year. If the coconut cultivation in the wet zone gets necessary attention in the way of conservation of soil, supply of water and proper water management, successful results could be achieved.

In case of intermediate zone there is a reasonable rainfall but as there are seasonal fluctuations of rainfall there is the necessity to augment the water supply by other means and also to conserve the soil and water to achieve a successful yield. The rainfall is the main factors that determine the coconut yield the rainfall and its pattern of spreading during the previous subsequent year.

Effects of drought

A coconut seedling takes 3-4 years to grow before bearing. Drought can affect at any stage of a coconut palm and thereby reduced the production of nuts. Some of the reasons for reduced coconut production are delay inflorescence, absence of inflorescence, fall of buttons and immature nuts reduced the number of nuts but their size, and even death at coconut palms.

The dry spells affect the coconut palms on the higher level of coconut lands before it affects coconut palms on the lower levels. Therefore water must be provided from the higher levels to the lower levels of the plantation. The higher level of the lands with slopes are normally consisted of stones and gravel mixed with the soil and as a result there is the tendency to dry up such areas quietly. The lower area normally has a soil with a mixture of sandy loam and as such the tendency to getting this area drying up is comparatively less.

For successful cultivation of coconut a rainfall at the rate of 3.2 mm per day is required for a coconut palm. At that rate if an annual rainfall of 1168 mm is received the production could be increased by 30 per cent and the weight of copra could be increased by 54 per cent.

The dry and intermediate zones which get an annual rainfall of less than 1168 mm irrigation facilities have to be provided. The drip irrigation system could provide 85 per cent - 95 per cent efficiency than other irrigation systems for coconut cultivation. Drip irrigation unlike other modes of irrigation system can be provided from low sources of water. By drip irrigation ill- effects of drought for coconut cultivation could be reduced and by maintaining uniformity in the growth of the young coconut palms the productive lifespan of the palm also could be extended.

As the coconut palms start bearing within 3 to 4 years a successful yield of coconuts could be obtained in a short time. When you get an undisturbed annual yield of coconuts it would be economically advantageous. If inter-cropping is resorted according to the available demand in the markets the profitability could be increased still further and as a result values of the land also increases.

The expenditure needed for labour, for fertilising and pesticide spraying would not arise. By use of drip irrigation for a coconut nursery the cost of production of seedling could be minimised. When drip irrigation system is used to coconut palms the water is supplied direct to the roots area of the palms and as a result the growth of weeds in the surrounding area could be reduced.

Soil and water management

The proper management of soil and water in coconut cultivated lands directly helps to improve the yield. It is not possible to use drip irrigation system to supply water requirements of all coconut lands in Sri Lanka.

If requirement of water is available within the coconut land drip irrigation system could be used to supply the water to the coconut land and good yield of coconut could be obtained. For purpose of soil and water management in coconut land it would be advisable to bury coconut husk, coir dust around coconut palm and grow cover crops, inter-cropping.

In case of coconut lands with slope water conservation devices should be adopted on the higher level of land in addition to that to construction of terraces drain, buns, and hedges would help to retain water to maximum within the coconut land. If the water management is carried out in this way, along with drip irrigation ill-effects of dry spells could be avoided. By conserving water within the coconut land the soil moisture could be retained and as a result increased yields of coconut could be expected continually.

Propagation of the system

The Coconut Cultivation Board has taken many steps to increase the yield and improve the productivity of coconut lands. The financial facilities for drip irrigation system are being provided through 'kappruka' loan scheme under Coconut Cultivation Board.

Loans are given for installation drip irrigation system in coconut lands with concessions on the interest at the land. The necessary information regarding instillation of drip irrigation system and required technical knowledge could be obtained from the head office of Coconut Cultivation Board and regional offices.

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