Interference of Tapping Due to Rainfall and Effectiveness of Rainguards Under Different Rainfall Scenarios: A Case Study in the Dartonfield Rubber Estate
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Date
2015
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Uva Wellassa University of Sri Lanka
Abstract
Well distributed moderate rainfall is essential for good growth and production of rubber trees (Hevea brasiliensis). However, rainfall may be a limiting factor for tapping activity, as most of the rubber plantations of Sri Lanka are spreaded in the Wet Zone, where the annual rainfall is greater than 2500 mm. And thus an average of 35 % of potential yield of rubber is lost due to interference of rain. In this context, rainguards have been introduced to reduce the yield loss during rainy periods. Therefore, this research study was conducted to evaluate the rainfall interference on tapping and the effectiveness of rainguards under different rainfall scenarios, as a case study in the Dartonfield Rubber Estate, RRI, Agalawatta. Hence, rainfall distribution was identified with the help of annual rainfall, annual wet and dry days and average monthly rainfall. Further, trend analyses were done for different rainfall parameters using Mann — Kendal Test, Through, a regression analysis, the most important rainfall characteristics that affect tapping and the relationship of these characteristics with tapping were determined. Moreover, the economic benefits that can be obtained by fixing rainguards were also assessed. The results revealed that the average annual rainfall at Dartonfield is 4156 mm, together with more years having wet days above 200. Mostly during evenings and nights, rains have fallen in the whole year. Further, during April to November, there have been more than 18 rainy days. The trend analysis results revealed that, there were no any significant trends in annual rainfall, annual wet and dry days, monthly wet days, and maximum rainfall amount in a given year, number of wet days as per to different rainfall events, consecutive wet days as per four cropping seasons of rubber and as per four monsoon periods. However, a significant decreasing trend could be observed only for longest wet spell. The regression analysis results revealed that, under without rainguards situation, the significant rainfall characteristics affect tapping were total rainfall duration of previous day and intensity of rains fallen during 3.00 am to 9.00 am period. The significant rainfall characteristics affect tapping under rainguarded situation were highest intensity of rain and total rainfall duration on previous day. Further, the comparison done for checking the possibility of tapping under with and without rainguards revealed that, the tapping can be practiced on additional 28 rainy days by fixing rainguards, leading to an additional income of Rs. 1,19,365/ha according to the crepe rubber price of 13th September 2015. Moreover, the rainguard establishment cost can be recovered from the earnings of 6 tapping days.
Key words Different rainfall scenarios, Rainfall interference, Rainguards, Rubber Plantations, Tapping
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Palm and Latex Technology and Value Addition Degree Programme ( PLT)