Let us spray - calculator says when, saves $$

Using an environmental model to help decide when to use herbicides could save more than 25 per cent of current expenditure on herbicides. Its developers claim even a 10 per cent use of the model could deliver million-dollar benefits each year to farmers.

The model, called HERBIRATE and developed by AGWEST researchers under a project supported by growers through the GRDC, predicts the performance of Roundup CT, Sprayseed 250, Hoegrass and Diuron/MCPA under various environmental conditions. This means a farmer can reduce herbicide rates when conditions are favourable or boost the rate when necessary to avoid failure. Either way the farmer saves money.

AGWEST researchers investigated the effect of a range of factors on herbicide performance and found that an early seasonal break followed by a warm dry spell made weeds particularly hard to kill. Herbicides performed worse on nitrogen-deficient plants.

How to know?

As rules of thumb to help decide whether they need to increase herbicide applications to deal with moisture or nitrogen stress, farmers can judge moisture stress from rainfall records and soil type, and can identify nitrogen stress from the yellowing of older leaves.

All herbicides responded in a similar manner to environmental stresses. Grasses were easier to kill at the two-leaf stage than at older or younger stages.

Program 3.3.3

Contact: Mr John Moore 08 9892 8476