Effect of Irrigation on Establishment and Early Growth of Coconut (VAR.CRIC 60) in the Dry Zone of Sri Lanka

The vigour and growth of seedlings of CRIC60 cultivar of coconut were studied in different irrigation treatments during the drought period, in a sandy soil in the dry zone. Nine irrigation treatments including a control with no watering were tested. Larger number of casualties were observed in the control while none in the irrigated plots. The best irrigation treatments in order of response were 40 litres applied twice a week, two earthenware pots buried on either side of the seedlings and filling them twice a week (27 litres per week) and 20 litres applied twice a week. However, the relative efficiency between 40 litres and 20 litres suggest that application of 20 litres twice a week could be preferred considering the savings on cost and the use of water. If finances are not limiting burying of two earthenware pots on either side of the plant and filling twice a week could be preferred. INTRODUCTION The coconut palm requires adequate and continuous supply of soil moisture for its proper growth and productivity. Soil moisture very often is the limiting factor in growth in areas subjected to long dry spells or where rainfall is low and poorly distributed. In the dry zone of Sri Lanka, March to September is the dry period. Inadequate soil moisture in these areas is the major constraint in the establishment of seedlings. Thus in the absence of rain, the newly transplanted seedlings need water regularly, until they are established. Further, it is necessary to continue irrigation during the dry months for the first two or three years, depending on the environmental conditions (Menon and Pandalai, 19S8). In the absence of irrigation, the newly planted seedlings are subjected to severe moisture stress during dry months resulting in a setback in growth and a high field mortality in the dry zone. Thus it became necessary to study the requirement of water and frequency of application when the seedlings are planted in a dry zone. A field experiment was conducted in the Eastern Province of Sri Lanka to study the establishment and early growth of coconut seedlings under different irrigation treatments. Data available on the amount of water required by' coconut seedlings during dry months are limited. Therefore the irrigation treatments identified here were based on observations of Copeland (1921) and Nelliat (1968). On an argumentative extension of the work of Copeland, Nelliat suggested application of 11.25 1 of water per day to young palms. The treatments in this study are based on this work.