Improving wheat simulation capabilities in Australia from a cropping systems perspective: water and nitrogen effects on spring wheat in a semi-arid environment

Systems approaches can help to evaluate and improve the agronomic and economic viability of nitrogen application in the frequently water-limited environments. This requires a sound understanding of crop physiological processes and well tested simulation models. Thus, this experiment on spring wheat aimed to better quantify water x nitrogen effects on wheat by deriving some key crop physiological parameters that have proven useful in simulating crop growth. For spring wheat grown in Northern Australia under four levels of nitrogen (0 to 360 kg N ha(-1)) and either entirely on stored soil moisture or under full irrigation, kernel yields ranged from 343 to 719 g m(-2). Yield increases were strongly associated with increases in kernel number (9150-19950 kernels m(-2)), indicating the sensitivity of this parameter to water and N availability. Total water extraction under a rain shelter was 240 mm with a maximum extraction depth of 1.5 m. A substantial amount of mineral nitrogen available deep in the profile (below 0.9 m) was taken up by the crop. This was the source of nitrogen uptake observed after anthesis. Under dry conditions this late uptake accounted for approximately 50% of total nitrogen uptake and resulted in high (>2%) kernel nitrogen percentages even when no nitrogen was applied,Anthesis LAI values under sub-optimal water supply were reduced by 63% and under sub-optimal nitrogen supply by 50%. Radiation use efficiency (RUE) based on total incident short-wave radiation was 1.34 g MJ(-1) and did not differ among treatments. The conservative nature of RUE was the result of the crop reducing leaf area rather than leaf nitrogen content (which would have affected photosynthetic activity) under these moderate levels of nitrogen limitation. The transpiration efficiency coefficient was also conservative and averaged 4.7 Pa in the dry treatments. Kernel nitrogen percentage varied from 2.08 to 2.42%. The study provides a data set and a basis to consider ways to improve simulation capabilities of water and nitrogen effects on spring wheat. (C) 1997 Elsevier Science B.V.

Environmental assisted fracture for 4340 steel in water and air of various humidities

This paper reports on measurements of crack growth by environmental assisted fracture (EAF) for 4340 steel in water and in air at various relative humidities. Of most interest is the observation of slow crack propagation in dry air. Fractographic analysis leads to the strong suggestion that this slow crack propagation is due to hydrogen cracking caused by internal hydrogen in solid solution inside the sample material.

The use of strategic visioning to enhance local tourism planning in periphery communities

Tourism has had a profound impact upon destinations worldwide, and although this impact has been positive for many destinations, there are numerous examples where tourism has adversely impacted upon the environment and social fabric of the destination community (Coccossis 1996; Murphy 1985). The negative impacts of tourism have been attributed, among other things, to inadequate or non-existent planning for development (Gunn 1994; Hall2000). This has led to increased calls for tourism planning to offset some of the negative impacts that tourism can have on the destination community. While a number of approaches have been advocated, a collaborative philosophy, based on the principles of sustainability, is more likely to result in acceptable and successful policies and programmes for tourism destinations (Farrell1986; Jamal & Getz 1995; Maitland 2002; Minca & Getz 1995). Such an approach focuses on cooperation and broader based participation in tourism planning and decision-making between stakeholders to lead to agreement on planning directions and goals, with one of the primary objectives of collaborative arrangements being to develop a strategic vision for a destination (Bramwell & Lane 2000). [Extract from introduction]