Impact of soil amelioration on weed ecology and control – WA (Book)

This book was published by the Department of Primary Industries and Regional Development (DPIRD) with funding from the Grains Research and Development Corporation (GRDC). It is designed for growers and advisers managing sandy soils in grain cropping systems. It reports findings from a research project that examined how soil amelioration techniques influence weed dynamics. The study focuses on common sandy soil constraints, including soil acidity, water repellence and compaction, and how practices such as soil inversion, deep ripping and soil mixing affect weed seed movement, burial and persistence. A review of previous research identified key gaps in understanding weed responses to changes in soil properties, the effects of tillage on seed distribution, and how best to manage weeds following amelioration. #

The study found that responses varied between weed species. Amelioration improved the growth of highly competitive species such as wild radish. With full soil inversion, most weed seeds were buried to around half the working depth, where they degraded over 1 to five years. Leaving seeds buried for longer than this provided little additional benefit, challenging the common ‘10-year inversion’ rule. The Weed Seed Wizard decision tool was shown to effectively model seed burial and reinfestation risk following inversion. In contrast, seed burial from deep ripping and soil mixing was highly variable depending on soil type, although deep ripping consistently placed some seeds at full working depth. #

The research also highlights the importance of weed management before and after amelioration. Fields with high weed burdens before treatment are likely to remain problematic. Full soil inversion can provide strong weed control, but ongoing management is needed to prevent reinfestation. Delayed sowing after amelioration can improve weed control, while break crops, herbicide-resistant crops and resistance testing are recommended where weed pressure is high. The work was conducted in Western Australian sandy soils but is relevant to other Australian grain-growing regions with similar soil constraints (PDF 3.1MB, 85 pages). #

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