Johannesburg - White corn in South Africa declined to a two- year low as the harvest of what may be the biggest crop in 33 years starts.

White corn slumped 2.9 percent to R1976.20 a metric ton by the midday close on the South African Futures Exchange, the lowest since May 7, 2012. The yellow type dropped 2.2 percent to R2094 a ton.

Local farmers may harvest 13.03 million tons of corn this season, 11 percent more than in 2013, the Crop Estimates Committee said on April 24. That would make it the biggest crop since 1981, according to the group. Cornmeal made out of the white variety is a staple food known locally as pap, while the yellow type is mainly used as animal feed.

“The size of this big crop that farmers are now starting to harvest is weighing more and more on the market,” Brink van Wyk, a trader at Pretoria-based BVG, said in an e-mailed response to questions. “So the weakness is not over and we should see prices going even lower over time.”

Stocks of both white and yellow corn may rise 16 percent to 1.27 million tons by the close of the marketing year that ends in April 2015, the Grain and Oilseeds Supply and Demand Estimates Committee said on April 25.

Wheat rose 1 percent to R4056 a ton, the highest since March 26.