Germination of weed species (Avena fatua, Bromus catharticus, Chenopodium album and Phalaris minor) with implications for their dispersal and control

Climatic conditions for seed germination of four weed species, Avena fatua, Bromus catharticus, Chenopodium album and Phalaris minor, which occur commonly in cereal fields in the north of Saudi Arabia, were compared. Proportionately, most seeds of the two collected seed lots germinated during the first three weeks of the experiment, confirming an early response pattern. Overall, germination was higher in Bromus catharticus, Avena fatua and Phalaris minor than Chenopodium album. Compared to the other species, proportionately more Phalaris minor seeds germinated in the second period, indicating a higher propensity for slow germination. Germination in all species favoured alternating temperatures (10/20 degrees C or 5/25 degrees C) over a constant (15 degrees C), in a light/dark (16/8 h) regime. However, Avena fatua and Bromus catharticus seeds also showed significant germination in a dark only (24 h) regime, indicating light has less influence on their germination. Variation in germination between geographically separate seed collections of all four species was significant in some conditions, however, the general pattern was of similar responses between the two seed lots. Results determined that, in respect of interactions between temperature and light, the most important climatic condition for maximum seed germination, in all four weed species, is alternating temperatures. The outcomes of this study can lead to the expected timings of weed species' germination and dispersal in field conditions, and are used to make recommendations for practical weed control measures.