Lime improves control of wild radish and annual ryegrass in acid soils of Western Australia

摘要

Most sandy soils of Western Australia (WA) are acidic, which may influence the competitive ability of crops against weeds like wild radish (Rap-hanus raphanistrum L.) and annual ryegrass (Lolium rigidum Gaudin). We examined the effect of lime appliedto acidic soils on weed control and crop yield over four seasons at three locations (Eradu, Wongan Hills and Merredin) of the WA wheatbelt. All experiments were conducted in a split-plot design with lime in the main plots replicated four times and herbicides in the sub-plots. Limesand was applied in the first year (2010) on the soil surface and incorporated by sowing. Lime treatments increased soil pH by approximately one unit in the top soil (0 to 10 cm) but the sub-soil pH (20—30 cm) remained at or below 4.8. Lime treatments had no effect on the density of weeds in the first three years after application, but in the fourth year lime at 2.5 and 5.0 t ha~(-1) reduced the in-crop density of wild radish by 45% at Eradu and annual ryegrass by up to 60% at Merredin. Herbicides applied in the sub-plots increased barley grain yield by 54-58% in the fourth year (2013) after lime application at Merredin and Eradu. Lime applied to the soil surface can reduce weed density but it may take three to four years after application to show the effect.