In sorghum [Sorghum bicolor (L.) Moench], genotype‐by‐environment interaction effects on ontogeny can be caused by differing responses to temperature and photoperiod. We conducted glasshouse and field experiments to develop predictive models of ontogeny for old and new sorghum genotypes. New genotypes are considered better adapted to more tropical environments. In the glasshouse studies, 10 genotypes were grown at two temperatures (20 and 25 °C) and six planting dates (photoperiod 10 to 15 h). At photoperiods greater than about 13 h, duration of emergence to floral initiation (GS1) was lengthened about 5 d for all genotypes at both temperatures. Genotypes differed in duration of GS1 by up to 10 d at both temperatures. Hybrids responded like their earlier parent, indicating earliness to show some form of dominance. Photoperiod had little or no effect on duration of floral initiation to anthesis (GS2), and hybrids differed by about 3 d. Field experiments with 12 hybrids were conducted at sites in Australia and USA covering latitudes from 16 to 39 °C. Durations of GS1 and GS2 ranged from 17 to 128 d and 24 to 85 d, respectively. Daily rate of development was modeled using functions of air temperature and photoperiod. Development rate of all hybrids exhibited a curvilinear response to temperature in both phases. Old and new hybrids differed in their temperature responses in GS1 but were similar in GS2. New hybrids had slower rates of development at all temperatures, but the difference was greater at higher temperatures (>25 °C). All hybrids had similar short‐day photoperiodic response in GS1, with a critical photoperiod 13.2 h. The models were tested on a separate data set covering a similar broad range of environments and performed well.

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The principle role odours play in most resource-finding strategies is highlighted.

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We describe effects of a range of fallow and crop management practices on soil properties and crop growth in wheat and grain sorghum on a red-brown earth in south-west Queensland. Results from the first 4 years of the experiment, which commenced in 1983, have been published. This paper reports results from the next 6 years. No tillage (NT) and reduced tillage (RT), combined with stubble retention, resulted in better soil-water storage during fallow but less soil nitrate-nitrogen (N) at sowing than observed with more frequent and aggressive mechanical tillage treatments such as discing, and stubble removal. In drier growing seasons, when N application often resulted in yield reductions in wheat, NT and RT with stubble retention resulted in higher grain yields than other treatments in both crops. In a wetter growing season, when N application resulted in yield increases, wheat yields under NT and RT with stubble retention were lower than those of other treatments, even at the highest rate of N application, indicating that factors such as plant disease were also affecting yields. With stubble retention, average yields of 6 wheat crops were 12% higher under NT and reduced blade tillage, and average yields of 4 sorghum crops were 20-30% higher under NT, than other tillage treatments. Gypsum application resulted in an average yield increase of 15% in both crops under conventional disc tillage with stubble retention. In wheat, NT and RT with stubble retention were generally associated with lower grain protein concentration, and N application was necessary to maximise profitability of these practices.