Environmental factors influencing germination ecology of buttongrass ( <i>Dactyloctenium radulans</i> ) in eastern Australia

Abstract A series of laboratory experiments was conducted to evaluate the germination ecology of buttongrass [ Dactyloctenium radulans (R. Br.) P. Beauv.] for designing weed management practices in eastern Australia. Two populations (BG3 and BG4) were evaluated under varying temperature, light, salinity, water stress, residue cover, and burial depth conditions. Germination was completely inhibited at 15/5 C (alternating day/night temperature regime) but increased at high temperature regimes, reaching 90–92% at 30/20 C and remaining high (72–88%) at 35/25 C, indicating strong adaptation to warm climates. Both populations germinated well in light (12 h)/dark (12 h) conditions (87–93%), while BG3 showed a reduction (80%) in complete darkness (24 h) compared with light/dark conditions, suggesting weak positive photoblastic behaviour. Germination decreased progressively with increasing sodium chloride (NaCl) concentrations, with 50% inhibition at 40 mM NaCl, indicating moderate salt tolerance. Germination was reduced by 50% at osmotic potentials of -0.30 MPa and -0.25 MPa for BG3 and BG4 populations, respectively. Seedling emergence declined with increasing sorghum residue loads, dropping by &gt;80% at &gt;6 Mg ha -1 , and was completely inhibited at 8 cm burial depth. These results demonstrate that D. radulans is a thermophilic, light-responsive, shallow-emerging grass capable of germinating under moderate salinity and water stress conditions, enabling persistence in semi-arid and reduced-tillage systems. High residue retention and deep burial of seeds (≥8 cm) could significantly suppress emergence, providing ecologically sustainable management options. Future studies should quantify population-level physiological variations and integrate temperature, moisture, and residue interactions into predictive emergence models to guide region-specific weed management under changing climatic conditions.