Technical annual report 2000-01
Dept. of Regional Development, Primary Industry, Fisheries and Resources technical annual report; Department of Regional Development, Primary Industry, Fisheries and Resources technical and annual report; Reports; PublicationNT; Technical bulletin (Northern Territory. Dept. of Primary Industry and Fisheries) ; no. 295
Made available via the Publications (Legal Deposit) Act 2004 (NT).
Agriculture -- Northern Territory -- Periodicals; Fisheries -- Northern Territory -- Periodicals
Dept. of Primary Industry and Fisheries
Technical bulletin (Northern Territory. Dept. of Primary Industry and Fisheries) ; no. 295
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Department of Primary Industry and Fisheries 178 PROJECT: Improving Rambutan Productivity Project Officers: C. Wicks, G. McMahon and G. Dunker Location: Various commercial Rambutan orchards and CPHRF Objective: To develop rootstock/scion combinations and pruning strategies that control flowering and tree size. To improve industry productivity by benchmarking nutrition standards. To improve grower knowledge and use of irrigation monitoring. The main focus of this project is on the benchmarking of nutrition standards and the uptake of irrigation monitoring systems. A system to improve/control flowering has been developed and was published in 2000. The development of pruning strategies to control tree size is the basis for a project currently being conducted in Queensland. There is an opportunity to conduct similar work in the NT. The development of rootstock/scion combinations was scheduled to finish after the 2000 season but an almost 100% fruit loss due to fertiliser burn in 2000 plus the death of trees resulting in poor replication has relegated this portion of the project to a minor priority. The flowering and tree size differences in 2000 were not significant. The other component of the project will improve our understanding of nutrient and irrigation management in rambutan, with particular emphasis on management during the fruit-filling stage. This will lead to improved yield and fruit quality with more efficient use of fertiliser and irrigation inputs and increased profitability. The project involves monitoring fertiliser and irrigation inputs on a number of commercial orchards in the Darwin rural area. The performance of orchards where regular fertigation is practised will be compared with those where fertiliser is applied conventionally. The irrigation-monitoring component is being used mainly as an extension tool to assist growers in the development of irrigation scheduling and monitoring. The project is being run in conjunction with the NT Rambutan Growers Group, a subgroup of the NT Horticultural Association. Each grower is contributing financially to the project as well as providing complete details of fertiliser and irrigation regimes used and tree yields. The growers meet at least four times a year with DPIF staff to discuss results. Method: Nutrition: Soil and leaf samples are taken quarterly from 14 commercial properties and CPHRF. The samples are analysed for a large number of different nutrients including leaf N, K, and Ca, and soil pH, Ca and Mg. When used in conjunction with grower-applied fertiliser inputs and tree response/growth, we can get a very good picture of rambutan nutritional requirements. Irrigation: Nine (of the 14) commercial properties and CPHRF are being monitored weekly for irrigation inputs, soil water status, temperature and RH, and tree status. This is being done using tensiometers and capacitance-based soil water detection devices to monitor soil water status; water meters are used to monitor irrigation inputs, electronic loggers to monitor temperature and RH, and visual assessment to monitor tree status. Results: To date there have been 12 rounds of soil and leaf sampling with the first occurring in June 1998 while the latest round was completed in February 2001. Data from these observations show that soil and leaf nutrient levels do not always correspond. For example, high soil zinc levels do not necessarily show sufficient levels of zinc in the leaf. This is due to the use of foliar sprays by some growers to supply the required trace elements while others use soil application.