Dry conditions in the main part of South Africa's maize belt have delayed crop plantings, threatening yields for the staple food and sending prices sharply higher, the farmers lobby group Grain South Africa said on Tuesday.

With the optimum planting window fast closing in the western part of the countries maize belt, which produces 60% of the crop, farmers have only planted around 5% of the area intended to plant, Jannie de Villiers, Grain SA's chief executive said.

"So far it's a very tough season and we are very uncertain if we will make all the hectares that we intend to plant. By this time of the year we would have preferred to have finished half of what we intended to plant in the west," he said.

"Even if we get good rains in the second part of December and they plant the full hectares, which at the moment I doubt we will be able to do, the yield could become average or below average."

The planting window in the western part of the country, including in the key maize-growing provinces of North West and parts of the Free State, runs from 15 November to mid December.

The eastern part of the maize belt, which produces around 40% of the country's maize, has planted around 90% of its crop, said de Villiers.

In its latest seasonal climate watch, the South African Weather Service said last month the country was likely to receive above-normal rainfall over the summer rainfall areas from December to February.

However, maize prices have hit the highest level since January 2017 amid concerns over potential yields.

The white maize futures contract due in March closed up 4.29% to R2 895 – close to an 11-month high.

In October, South Africa's official Crop Estimates Committee said farmers were expected to plant 2.448-million hectares of maize in the 2018/2019 season, up 6% from the 2.318 million hectares planted in the previous period.

The Agricultural Business Chamber (Agbiz) has forecast the crop yield at around 12.2-million tonnes in 2018/19 compared with the final maize crop of 12.9-million tonnes in 2017/18.

"If we don't get rainfall during the month of December given that we have not planted on the white maize areas of western side of South Africa then those estimates could change drastically," Wandile Sihlobo, an economist with Agbiz, said.