With planting in Northern Australia beginning, CSD would like to share some information which may be relevant to those planting into soils with high temperatures.
CSD has previously conducted a lot of research into germination at low temperatures, as the Australian cotton industry expanded south into cooler climates. Current expansion in Northern Australia has prompted the investigation of germination at higher temperatures.
Figure 1: Photos showing the result of seeds germinated for 7 days at labelled temperature.
Seed was germinated using the standard method for between paper germination used by CSD for commercial testing at a range of constant temperatures from 15°C to 45°C. The seeds were then
assessed for germination using the standard protocol (40 mm, free of abnormalities) with 100 seeds assessed at 4 days and another 100 seeds assessed at 7 days (see Figure 1).
Figure 2: Germination (%) and biomass (g) for a range of temperatures after 4 days.
The results for the 4-day trials (Figure 2), indicate an optimal temperature range from 25-35°C with a substantial drop in germination percentage at both lower and higher temperatures.
Lower levels of germination were measured at 20°C and 40°C while there was no germination (to 40 mm) at 15°C, 18°C or 45°C.
Similar results were obtained from the 7-day trials (Figure 3) although the longer germination time allowed greater germination percentage at the lower temperatures (18°C and 20°C).
Germination percentage at 40°C decreased after 7 days compared to 4 days, due to high levels of necrosis in the hot and humid conditions. Again, there was no germination (to 40 mm) recorded at 15°C or 45°C.