Manipulating the seed bank to manage herbicide-resistant weeds

摘要

Weed control and farming system practices are being assessed for their ability to reduce the seed banks of weed species that have developed herbicide resistance. In six long-term field experiments in southern Queensland, we are testing a wide varietyof management practices to deplete soil seed banks of key annual weed species, such as wild oat, common sowthistle, liverseed grass, barnyard grass and awnless barnyard grass. Irrigation increased the emergence of all species with timing of irrigation being important. Higher stubble levels increased the emergence of larger seeded species including wild oat and awnless barnyard grass, but decreased the emergence of sow-thistle. Cultivation reduced emergence of sowthistle and summer grasses, but had little effect on wild oat emergence. The wild oat seed bank was reduced by up to 70% in the top 5 cm of soil either with or without cultivation. However, cultivation increased the number of wild oat seeds persisting below 5 cm. Data suggest that wetter environments will encourage a more rapid depletion of summer grasses and sowthistle through increased emergence. Similarly, maintaining crop residue may increase seed bank depletion of larger seeded species through increased emergence. Cultivation increases the persistence of all the target species and is not a favoured practice for rapid depletion of the seed bank.