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Rural Industries Research & Development Corporation
Rambutan - Improving Yield and Quality
by Yan DiczbalisNovember 2002
RIRDC Publication No 02/136 RIRDC Project No DAQ-251A (Rambutan)
The rambutan (Nephelium lappaceum L.) is a tropical fruit and member of the Sapindaceae family closely related to the lychee and longan. The rambutan tree can grow to 10 m in height and up to 14 m in width.
The rambutan is native to west Malaysia and the island of Sumatra in Indonesia (Watson, 1984, Tindall 1994). The native environment of the rambutan is characterized by high rainfall (evenly distributed), high humidity, low evaporation rates and average minimum temperatures above 20 o C (Diczbalis et al. (1996).
Seedling rambutans were first introduced into Australia in the 1930’s and commercial plantings commenced in the 1970’s (Watson 1988). From the early 1970’s to 1988 fifty-one cultivars were imported into Australia and underwent preliminary evaluation at Kamerunga on the outskirts of Cairns (Watson, 1988). The rambutan industry in Australia is now located in the NT and north Queensland (Lim and Diczbalis 1998). The industry initially spread along the coast north and south of Cairns (Cooktown 16 o S to Tully 18 o S). Trees were introduced to the Northern Territory in the early 1980’s where a small but active industry is established in the rural areas near Darwin (12 o S). Current Australian plantings are reported to be in the vicinity of 40,000 trees and the annual production can range from 500 to 1000 tonnes is valued at a maximum of $4.5M (RTEGA 2002). The main commercial varieties in Australia include; R9, R134, R156(red), R162, R167, Binjai, Jitlee and Rongrien.
The Australian rambutan and longan industries, together with DPI, NT DPIF and RIRDC and other bodies have, over the last few years engaged in detailed assessments of industry research and development needs. Industry strategic plans have been developed for the rambutan industry (Anon 1997) and a commitment to support research has been made by the relevant organizations. The rambutan industry has identified nutrition and irrigation research as a priority issue.
The project aims were to; monitor changes in rambutan leaf and soil nutrient status over three seasons measure grower fertiliser inputs in relation to the above assess the effect of nutrient status on productivity monitor tree phenology in relation to climate and irrigation management quantify rambutan water/irrigation requirements.
This report details the findings of three years of study from July 1998 to May 2001. As a result of this project rambutan researchers, extension officers, growers and associated industry organizations are now able to access an improved understanding of the effect of nutrition on yield. Tentative leaf and soil standards were developed to use as a guide to fertiliser management.
The project was unable to identify any direct links between tree nutritional status, fertiliser inputs and yield. Its important to note that all commercial orchards surveyed had relatively high leaf nutrient status and no unfertilized trees were included in the study. This suggests that within the range of nutrient status observed other factors such as pruning practices and climate play a more important role in flowering and subsequent yield.
A guide to fertiliser requirements was developed using a nutrient budget approach where nutrient inputs are based on fruit production and removal and take into account additional nutrient loss via leaching, runoff and fixation.
As a result of the development of a nutrient budget, inputs can now be geared to production rather than based on an ad-hoc approach. This allows for potential savings on fertiliser inputs, however, more importantly the nutrient budget approach has the potential to reduce fertiliser loss and hence contamination of sub-soils and drainage systems.
Rambutan irrigation requirements during fruit filling were monitored at three sites. In north Queensland high rainfall, spread through out much of the year, negates the need for irrigation for much of the year. When low rainfall or dry conditions occur, observations suggest that evaporation rates based on work carried out in the Northern Territory be used. Hence irrigation requirements can be calculated using a simple evaporation based calculation; Irrigation Requirements = canopy area (m 2 ) * Evaporation Rate (mm/week) * Crop Factor Growers are advised to monitor the above irrigation input recommendations with readily available soil moisture sensing technology and where possible the addition of a water flow meter. These simple tools allow the orchard manager to fine tune irrigation inputs to their crop, season and soil type.
As an outcome of the project rambutan growers should be encouraged to monitor fertiliser inputs in conjunction with regular leaf and soil analysis and yield records. In this way fertiliser inputs can be geared more closely to nutrient outputs. The following key points should be included in a monitoring system; Develop fertiliser input worksheets that can be easily transferred to spread sheet software packages.
Use of the tentative leaf and soil standards as a guide to current fertiliser management strategy.
Develop a fertiliser management spreadsheet based on nutrient removal through fruit and other loss factors and encourage it use among industry members.
Use the nutrient budget to develop a fertiliser program for the season, based on yield projections.
Promote the use of fertigation to improve the application efficiency of fertiliser application.
Monitor rambutan yields in conjunction with fertiliser management records to validate the nutrient budget approach over a minimum of 5 seasons, to reduce the effects of climate and other management issues (eg. pruning) on yield.
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