To measure the loss of soil water attributed to summer weeds and to quantify the impact of summer weeds on lost production.

• Summer weeds use significatn amounts of stored soil water.
• The long-term impact of summer weeds amounts to a loss in production of 1t/ha in cereal yield in the southern Mallee.
• In a changed climate scenario, where our region is likely to receive more summer rain at the expense of spring rain, the impact of summer weeds on potential crop yield is likely to increase.