Skeleton weed (Chondrilla juncea) in the Victorian Mallee. 5. Chemical fallowing

Abstract

Skeleton weed is difficult to control on cultivated fallows during the summer and experiments were commenced in 1963 on the use of short-term residual herbicides for chemically fallowing infested land for wheatgrowing. Rates and times of application of simazine mixtures, a picloram/2,4-D mixture, an atrazine/amiltrole mixture, and fenac were tested. Compared with cultivated fallows, chemical fallowing increased wheat yields in four years out of six. The yield responses were associated with increased soil nitrate and soil moisture at sowing, reflecting the improved weed control by herbicides, particularly during the summer period. The effects of toxic residues from simazine and atrazine on the wheat crop were influenced by rate and time of application, rainfall during the fallow period, and soil type.