The coconut palm produces nuts round the year. Moisture is essential for the absorption of nutrients by roots. Lack of sufficient moisture in the soil diminishes the production of nuts, especially in the plantations raised in the sandy and the sandy loam soils. The number of nuts is not controlled by flower number or pollination, but exclusively by the nutritional factors, chiefly water supply. Irrigation increases female flower production and reduces premature nut fall as well.
Though the coconut-growing areas in the coastal region get high rainfall, the rainy season is limited to just 4 or 5 months. Coconut palms experience moisture stress during the remaining months. Soil moisture stress leads to stunted growth, drooping of leaves, immature nut fall and decreased yield. Therefore, adequate supply of water is essential for its unrestricted growth. Mulching is an effective method of conserving soil moisture.
Irrigation methods in Coconut Palms
The commonly adopted irrigation methods in coconut farming include flooding, basin irrigation, sprinkler or perfo-sprays and drip irrigation.
Flood irrigation is an age-old method of irrigating crops and water is delivered to the field by a ditch, pipe, etc., and it flows over the ground. The method is being practised in certain areas of Tamil Nadu and East and West Godavari districts of Andhra Pradesh. Water loss is high in this method. It has been reported that a higher yield of coconut could be realized under flood irrigation than basin irrigation. However, there is considerable wastage of water under flood irrigation.
In Basin irrigation, water is applied in the basins in a 1.8 to 2.0 m radius around the palm which is the active root zone of coconut. Often irrigation channels are made at the centre of two rows of coconut and each basin is connected with this channel. In this method also there will be water loss due to deep percolation and surface evaporation. Application of water in the basin through a hosepipe is therefore recommended in order to reduce the water loss in transit.
In Sprinkler irrigation, water is distributed through pipes and is then sprayed into the air through sprinklers. Water breaks up into small water drops which fall to the ground. The sprinkler system must be designed to facilitate a uniform application of water. The Sprinkler irrigation system is most suited for inter or mixed cropping systems where the entire surface requires wetting.
The Drip irrigation system involves dripping water onto the soil at very low rates (2–20 litres/h) through small-diameter plastic pipes, fitted with outlets called emitters or drippers. Water is applied close to palms and only part of the soil where the roots grow is wetted. Water loss is limited. Drip irrigation is suited for widely spaced crops like coconut since it saves water, energy and labour. However, the limited size of the wetted soil volume has been identified as a cause for concern.
Water Requirements for Coconut Palm
Depending on the infrastructure available, the irrigation levels may differ. The water requirement increases over the years and varies with the seasons. The percentage of water to dry matter in a young palm is much greater than in an adult palm. Therefore, the water requirement of a young palm in proportion to its size is greater. This makes the young palm more susceptible to drought conditions.
For the young palm, for the first two years from planting, irrigate at the rate of 45 litres of water/seedling, once in 4 days during dry summer months. Each adult palm requires 55 to 120 litres of water every day. Since the availability of irrigation water is scanty, drip irrigation is often preferred for coconut farming, especially in areas where water is scarce. Drip irrigation is known to save about 30 – 40% of water with a 38% – 40% increase in yield compared to basin irrigation system. Further the system enables conserving soil and reducing the competition from weeds for water and nutrients. Water requirement for coconut with drip irrigation is 65 Liter per day during summer, 55 Litre per day between summers and monsoons and 45 Litres per day during monsoons. The rainwater will be sufficient during the monsoon.
Source:
1) Maheswarappa H.P. and Krishnakumar V, An overview on water management in coconut (Cocos nucifera), Indian Journal of Agronomy 64 (4):
431- 439 (December 2019)
2) Coconut, Coconut Development Board & ICAR-Central Plantation Crops Research Institute, Kasaragod 671 124, Kerala, https://coconutboard.gov.in/docs/coconut-english.pd
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