Competition between wheat and two Emex species

Abstract

Wheat was grown with either of the cereal weeds Emex australis or E. spinosa in two replacement series at different nitrogen levels to determine the relative competitiveness of the two weeds with wheat. Other planting combinations, including a three-species mixture, allowed comparison between the two Emex species with and without wheat. The two Emex species were more competitive with wheat at high levels of nitrogen than at low levels. E. australis was more competitive with wheat than E. spinosa, regardless of the growth index considered, at all but the highest nitrogen level. The results suggest that, where the two species co-exist, E. australis will suppress E. spinosa. The relative weediness of the two Emex species with wheat is discussed. We conclude that whilst the presence of E. spinosa seeds may reduce grain acceptability, the presence of E. australis plants may reduce wheat yields more than that of E. spinosa.