Weather to sow or not

Jim Egan heads a halt-million-dollar program to take some of the risk out of matching rainfall to planting decisions.

The odds of growing successful crops are set to improve by using data extracted from rainfall records.

Aimed at all districts in the Australian cereal belt, this $0.5 million project aims to minimise risk in cropping programs by providing farmers with 'yield probabilities' based on data from the rainfall recordings — some going back more than 100 years.

Researchers and farmers in five states are cooperating in this innovative program. Funding comes in part from growers through the GRDC. Jim Egan of the SA Research and Development Institute is at the helm.

"I can best illustrate the application of this work by quoting the strategy developed by Minnipa (SA) farmer, Alan Lymn," he said.

"If his farm doesn't receive 40 mm of rain between April 1 and June 15, Alan cuts back his cropping area and will even consider not sowing.

"In years where he gets between 40 mm and 100 mm he sows an average area — about half the farm. In years of more than 100 mm in this period he increases the cropping area.

Adjust cropping to early season rains

"This strategy was related to actual yields over 30 years at the Minnipa Research Centre and the indications are that real economic benefits accrue over a number of seasons by adjusting cropping programs depending on the early season rains," he said.

Mr Egan said the statistical work was done by Samsul Huda, now working with the University of Western Sydney at Hawkesbury.

The researchers looked at the probability of receiving critical amounts of rain in a given week, the likelihood of receiving opening rains during selected time periods, the length of dry spells at selected sites and the reliability and length of the rainy season.

The rainfall work is not predictive but helps farmers determine what real risks they might face.

Findings confirm what many farmers might have thought but, until the study, could not substantiate.

Rainfall data helps risk management

For instance, the analyses show that districts such as Cummins and Lock in South Australia experience very reliable rain patterns for good crop growth in more than seven years in 10.

However, for districts like Walpeup in " Victoria and Minnipa, Nundroo and Kimba in SA, the probability of experiencing a rainy season adequate for optimum crop growth is less than seven years in 10.

Mr Egan said that the 1993 season in SA with its generally late and erratic break was a good example of the data's potential usefulness.

"Those who had not sown by early July could have examined the data, and, depending on where they farm, decided whether to sow or not or whether to sow a reduced area on their better paddocks only. They could also have assessed their chances of breaking even given good later rains," he said.

Reduce planting in late season

"The biggest decisions, at least in the lower rainfall districts, are whether or not to sow or to decide how much to sow. Ideally, when the opening of the season is delayed, planting programs should be reduced. Plantings should be increased when the opening is early.

"Using this strategy farmers would minimise their losses in poor years and maximise their gains in good years. Such a risk management approach is essential for farmers to remain viable in low rainfall areas."

"At the end, rainfall and climale records will become more than just a topic of discussion in the pub." promised Mr Egan.