Emergence and germination response of Sonchus oleraceus and Rapistrum rugosum to different temperatures and moisture stress regimes.

Sonchus oleraceus and Rapistrum rugosum are two rapidly emerging weeds of the northern grain region of Australia. To understand the ability of these weeds regarding their germination response to temperature and different soil moisture regimes, experiments were undertaken on the germination of these weeds at varying osmotic potential and temperature regimes. The experiment was conducted as a split‐plot design with alternating day/night temperature regimes (15/5, 20/10, 25/15 and 30/20°C) as a main plot and osmotic potential regimes (0.0, −0.1, −0.2, −0.4, −0.6, −0.8 and −1 MPa) as a subplot. At different temperature regimes, there was 65–91% germination of S. oleraceus in water (0 MPa). There was 0–4% germination at −0.8 MPa and no germination at −1.0 MPa. Osmotic potential values that can cause 50% reduction in germination of S. oleraceus based on a sigmoid regression model ranged from −0.38 to −0.48 MPa. There was 33–81% germination of R. rugosum in distilled water (0 MPa), 1–3% germination at −0.8 MPa and no germination at −1.0 MPa. Osmotic potential values that can cause 50% reduction in germination of R. rugosum based on a sigmoid model ranged from −0.26 to −0.54 MPa. Results of the study were related to the emergence pattern of weeds during field survey and soil moisture profiles estimated by the Australian Landscape Water Balance Model and explain the emergence of these weeds outside the normal seasonal window of prevalence as a response to changes in weather. [ABSTRACT FROM AUTHOR]