Reap winter crop dividends from summer weed management

Author: Sharon Watt | Date: 16 Jun 2014

Fallow weed management

Grain growers can reap a high return on investment from managing weeds in fallow between harvest and sowing of winter crops. That’s according to a new reference manual for grain growers and advisers in the southern and western grains regions of Australia. The Summer Fallow Weed Management manual, published by the Grains Research and Development Corporation (GRDC) demonstrates that the economic benefits of summer fallow weed management flow from extra amounts of high value water and nitrogen, crop establishment advantages and reduced issues with weed-vectored disease and insect pests.

John Cameron from ICAN, who co-authored the manual with Andrew Storrie of Agronomo, says weeds in summer fallows rob the next crop of vital sub-soil moisture and nutrients. “Very few weeds are needed before a significant amount of highly valuable soil water is lost,” Mr Cameron said. Stopping weed growth in the fallow can lead to yield increases in the following crop via several pathways. These include: increased plant-available water; a wider and more reliable sowing window; higher levels of plant available nitrogen; reduced levels of weed-vectored diseases and nematodes; reduced levels of rust inoculum via interruption of the green bridge; reduced levels of diseases vectored by aphids that build in numbers on summer weeds; and reduced weed physical impacts on crop establishment.

The comprehensive manual draws heavily on the data produced by the much acclaimed GRDC-funded Water Use Efficiency Project.  The manual provides essential information on the value of stored water, the effects of summer weeds on nitrogen, other weed effects on following crops, use of herbicides in the fallow and effective spray application. It also includes grower and researcher case studies and research data. The Summer Fallow Weed Management manual is available for viewing and downloading via the GRDC website at or hard copies can be ordered through the GRDC’s Ground Cover Direct, free phone 1800 11 00 44 or email


CAPTION: A crop in which summer fallow weeds were managed (left) and where no fallow weed management occurred (right).  Photo: Col McMaster, NSW DPI

More information

For further information

John Cameron, ICAN
02 9482 4930 or 0427 209 709


Sharon Watt, Porter Novelli
0409 675100 

GRDC Project Code ICN00012

Region South, North