A Simulation Model of Kenaf for Assisting Fibre Industry Planning in Northern Australia. V.* Impact of Different Crop Traits

The production potential of rainfed kenaf in the Northern Territory (NT) (latitude 12-15¦S.) has been assessed using a growth simulation model for the cultivar Guatemala 4. However, this raises the important question of how well-suited is this cultivar, and what are the likely yield gains which might be obtained by breeding or selecting a different cultivar. Answering these questions with conventional experimentation would be expensive, given the variable yield response among seasons associated with rainfall variability in the NT. Accordingly, the kenaf growth simulation model NTKENAF was used in conjunction with long-term climatic data for two sites in the NT to assess the value of different plant traits relative to Guatemala 4, that are potential selection criteria in plant breeding. Extending the duration from sowing to flowering resulted in relatively small gains in stem yield over Guatemala 4, but substantial yield losses were predicted by using an earlier flowering cultivar. Increasing the efficiency of water use (higher transpiration efficiency) greatly increased yield, and was the most risk-efficient crop improvement strategy. Unfortunately, the prospects for improving transpiration efficiency of kenaf by plant breeding remain uncertain. Increasing the amount of water available for crop growth by greater extent of soil water extraction had little effect on yield in this water-limited environment. Changing the yield potential of kenaf by altering the photosynthetic capacity (higher radiation use efficiency) was risk-efficient in some situations, but the mean yield change was relatively small. It is concluded from the simulation analysis, that the standard cultivar Guatemala 4 is well-suited to the NT environment.