The government's Crop Estimates Committee (CEC), which will provide its third production forecast for the 2018 crop on Wednesday, is seen pegging the harvest at 12.75 million tonnes, up from the 12.42 million tonnes it forecast in March.

Late rains, particularly in western growing areas, have helped yields after an unexpected onset of dry conditions in the key maize-growing provinces of North West and the Free State in January had raised concerns for farmers.

"Rain the past couple of weeks will add to confidence that the current crop expectation could be met and may even be exceeded," said trader and director at Riddermark Capital Warren Langridge.

The poll expects the harvest to consist of 6.51 million tonnes of the staple food white maize, a slight increase from 6.36 million in CEC's March estimates and 6.14 million tonnes of yellow maize which is used in the production of animal feed.

Maize prices have remained depressed with the white maize contract ending in April up 0.10 percent to 1,970 rand by 0823 GMT, 63 percent lower than its all time high of 5,350 rand scaled in January, 2016 when a severe drought hit yields and plantings.

Low maize prices have helped to ease inflation and food prices but have placed pressure on farmers' profits. Consumer price inflation slowed to its lowest rate of 3.8 percent in seven years on Wednesday.