Agricultural forecaster ABARES says this is due largely to drier and warmer than average seasonal conditions in Queensland and northern NSW cropping regions.

"The unfavourable seasonal conditions curtailed planting of dryland summer crops in the latter part of the planting window, lowered soil moisture levels and reduced yield prospects of dryland crops," the report found.

Looking ahead, the Bureau of Meteorology says it is more likely rainfall in those regions will be below average than above average, especially in Queensland.

The total area planted to summer crops is estimated to have fallen by 23 per cent in 2018-19 to around one million hectares.

Production of all the major summer crops is forecast to fall - cotton by 42 per cent, grain sorghum by nine per cent and rice by 83 per cent.

The ABARES report also showed winter crop production had dropped by 20 per cent in 2018-19 to 30.4 million tonnes.

This was a slightly better-than-expected result from previous forecasts, driven by higher production in WA.

Production of all the major winter crops has fallen - wheat by 19 per cent (to 17.3 million tonnes), barley by seven per cent (to 8.3 million tonnes) and canola by 41 per cent (to 2.2 million tonnes).

Australian Associated Press