China has stuck by a forecast of a record corn crop, even while downgrading its estimate for its rice harvest, engraining a fresh divergence over forecasts for the harvest.

The country's grain think tank, the China National Grain and Oils Information Centre (CNGOIC), trimmed 700,000 tonnes from its estimate for rice production following the floods which killed more than 130 people and caused an estimated $12bn of damage in the south of the country.

However, the forecast for corn, which is produced largely in the north east and suffered a spell of dry weather in the spring, was left unchanged at 168.0m tonnes.

The estimate is more upbeat than those of many other analysts, including the US Department of Agriculture, which has pegged the harvest at 166.0m tonnes.

FO Licht, the German analysis group, on Monday put the harvest at 159.0m tonnes, noting that "hot conditions are stressing the crop in China".

Last month, the US Grains Council said after a tour of corn-growing regions that crops were "not as strong as normal", and that some 2-3% of the area intended for the grain had not been sown with other crops because of the adverse weather, although rain since has assuaged some fears for the crop.

Data questions

The varying assessments of the crop threaten to extend to 2010-11 a dispute still raging over the size of the last crop, which the CNGOIC has pegged at 164m tonnes, but which other observers see as being considerably lower.

US officials in Beijing have expressed concern over the reliability of Chinese data, saying that they may be swollen by a subsidy system which rewards regional authorities on the size of the harvest that they declare.

The size of China's corn harvest has become a key concern for grain investors since the country, the second biggest corn producer and consumer, earlier this year resumed significant exports for the first time in some 15 years, as domestic prices reached record levels in some regions.

Prices on China's Dalian exchange remain near their peaks, closing on Wednesday at 1,955 reminbi for September delivery, equivalent to $289 a tonne, or about $7.30 a bushel – nearly twice the Chicago price.

Wheat hopes 

The CNGOIC also restated China's wheat harvest at 115.10m tonnes.

The USDA last week raised its estimate of the crop to 114.5m tonnes, "based on data from Chinese provinces indicating higher estimated wheat area, and on a higher yield forecast following excellent late-season weather".