So many communities depend on the sugar industry that it must not be allowed to become yesterday's crop. But if it doesn't change, it will.

That change, according to the leader of the collaborative Sugar Yield Decline Joint Venture project, Alan Garside, must include consideration of other crop species as rotations in the monoculture, cane farming system.

And the industry must stop seeing other species as a threat, because they can be very complementary to cane farming, providing disease breaks and residual soil nitrogen benefits to following cane crops as well as the additional income from the break crop itself.

Mr Garside spoke to more than 130 cane farmers at "Grains Research Updates for Cane Growers" in Mackay and Ayr last week.

The Grains Research and Development Corporation (GRDC) collaborated with the Joint Venture project to organise the Updates, in response to increased cane grower interest in planting grain crops ­ particularly legumes like peanuts and soybeans ­ in rotation with sugar cane.

"Yield decline has been a major concern to the sugar industry for more than 20 years, because there's been no yield increase since 1970," Dr Garside said.

"The loss of productivity of sugar cane growing soils has been caused by long term monoculture and the ways in which we have practised that monoculture.

"Between 1905 and 1970 there was a steady increase in sugar yield harvested per hectare but cropping systems changed in the 1960s and 1970s, with the introduction of mechanical harvesting and its heavy machinery, often driven indiscriminately over wet paddocks.

"The industry also expanded onto some of the poorer soils but one of the worst decisions was the removal of assignment restrictions designed to ensure sugar land was rotated regularly with fallow break crops like cowpea."

Dr Garside said when the percentage of sugar land required to be fallowed every year was reduced ­ from 25 per cent to 15 per cent in 1964, and from 15 per cent to zero in 1975 ­ plough out and replant became common practice, intensifying monoculture.

The collaborative Sugar Yield Decline Joint Venture project ­ set up to identify the reasons for, and to find solutions for, the problem of yield decline ­ had found monoculture had contributed to chemical, physical and biological degradation of cane farming soils.

Minimum tillage, controlled traffic and rotations were identified as potential answers to these soil problems.