A simulation model of kenaf for assisting fibre industry planning in northern Australia. IV. Analysis of climatic risk

Abstract

The establishment of a pulp and paper industry based on kenaf (Hibiscus cannabinus L.) in semi-arid northern Australia requires clear demonstration of the long-term production potential of kenaf in this region. Owing to the high rainfall variability both within and among seasons, it would be difficult to assess the potential of a new dryland industry from traditional experimentation. Accordingly, this study was undertaken to assess the climatic risks to dryland kenaf production in the Northern Territory (NT) using the kenaf simulation model NTKENAF, which has been developed and validated for this climatic zone. The kenaf model was run, using long-term historical weather data, to determine optimal sowing strategies and expected yields at four representative sites in the NT. In the NT, a codict existed between sowing early, with resulting long duration and high yield potential, but high probability of plant mortality, and sowing later, with more reliable plant population, but shorter duration and lower yields. A general recommendation over all sites was for a sowing window extending from the start of November to mid-December each year; lower yields were simulated for earlier sowing dates due to problems with crop establishment, and for later sowing dates due to crop growth extending past the end of the wet season in most years. However, in circumstances of high rainfall prior to November, there was a yield advantage at several sites from sowing early. Over the 100 years of climatic data for Katherine (14¦ 28'S.) and sowing when 30 mm rainfall occurred in a 5-day period after 1 November, simulated stem yields for kenaf ranged from 800 to 17200 kg ha-1, with a mean stem yield of 8673 kg ha-1 and coefficient of variation of 42%. At the higher rainfall site of Douglas Daly (13¦ 48'S.), over 21 seasons and using the same sowing criterion, stem yields ranged from 4490 to 19 200 kg ha-1, with a mean stem yield of 12 509 kg ha-1 and coefficient of variation of 27%. Simulated stem yields were higher at the wettest site of Adelaide River (13¦ 06'S.) and lowest at the driest site of Larrimah (15¦ 36'S.). In the planning of a potential kenaf industry in the northern Australia, this research study has provided the essential information of yield probability distributions for kenaf crops grown at selected sites in the NT.